diff --git a/framework/src/Volo.Abp.Auditing.Contracts/Volo/Abp/Auditing/IDeletionAuditedObject.cs b/framework/src/Volo.Abp.Auditing.Contracts/Volo/Abp/Auditing/IDeletionAuditedObject.cs
index a7be0c29a1..afec5e4e5f 100644
--- a/framework/src/Volo.Abp.Auditing.Contracts/Volo/Abp/Auditing/IDeletionAuditedObject.cs
+++ b/framework/src/Volo.Abp.Auditing.Contracts/Volo/Abp/Auditing/IDeletionAuditedObject.cs
@@ -22,5 +22,5 @@ public interface IDeletionAuditedObject<TUser> : IDeletionAuditedObject
     /// <summary>
     /// Reference to the deleter user.
     /// </summary>
-    TUser Deleter { get; }
+    TUser? Deleter { get; }
 }
diff --git a/framework/src/Volo.Abp.Auditing.Contracts/Volo/Abp/Auditing/IMayHaveCreator.cs b/framework/src/Volo.Abp.Auditing.Contracts/Volo/Abp/Auditing/IMayHaveCreator.cs
index 25748f5af9..78989e16d2 100644
--- a/framework/src/Volo.Abp.Auditing.Contracts/Volo/Abp/Auditing/IMayHaveCreator.cs
+++ b/framework/src/Volo.Abp.Auditing.Contracts/Volo/Abp/Auditing/IMayHaveCreator.cs
@@ -8,8 +8,7 @@ public interface IMayHaveCreator<TCreator>
     /// <summary>
     /// Reference to the creator.
     /// </summary>
-    [CanBeNull]
-    TCreator Creator { get; }
+    TCreator? Creator { get; }
 }
 
 /// <summary>
diff --git a/framework/src/Volo.Abp.Auditing.Contracts/Volo/Abp/Auditing/IModificationAuditedObject.cs b/framework/src/Volo.Abp.Auditing.Contracts/Volo/Abp/Auditing/IModificationAuditedObject.cs
index 48f26b6299..a82e1452e8 100644
--- a/framework/src/Volo.Abp.Auditing.Contracts/Volo/Abp/Auditing/IModificationAuditedObject.cs
+++ b/framework/src/Volo.Abp.Auditing.Contracts/Volo/Abp/Auditing/IModificationAuditedObject.cs
@@ -22,5 +22,5 @@ public interface IModificationAuditedObject<TUser> : IModificationAuditedObject
     /// <summary>
     /// Reference to the last modifier user of this entity.
     /// </summary>
-    TUser LastModifier { get; }
+    TUser? LastModifier { get; }
 }
diff --git a/framework/src/Volo.Abp.BlazoriseUI/Components/ObjectExtending/LookupExtensionProperty.razor b/framework/src/Volo.Abp.BlazoriseUI/Components/ObjectExtending/LookupExtensionProperty.razor
index 7c32549d51..ecdae979f2 100644
--- a/framework/src/Volo.Abp.BlazoriseUI/Components/ObjectExtending/LookupExtensionProperty.razor
+++ b/framework/src/Volo.Abp.BlazoriseUI/Components/ObjectExtending/LookupExtensionProperty.razor
@@ -9,7 +9,7 @@
     <Autocomplete Data="@lookupItems"
                   TItem="SelectItem<object>"
                   TValue="object"
-                  TextField="item => item?.Text"
+                  TextField="item => item?.Text!"
                   ValueField="item => item?.Value"
                   SelectedValue="@SelectedValue"
                   SelectedValueChanged="@SelectedValueChanged"
diff --git a/framework/src/Volo.Abp.Dapper/Volo.Abp.Dapper.csproj b/framework/src/Volo.Abp.Dapper/Volo.Abp.Dapper.csproj
index e4236d697c..e42eca0d2b 100644
--- a/framework/src/Volo.Abp.Dapper/Volo.Abp.Dapper.csproj
+++ b/framework/src/Volo.Abp.Dapper/Volo.Abp.Dapper.csproj
@@ -5,6 +5,8 @@
 
   <PropertyGroup>
     <TargetFramework>net7.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <WarningsAsErrors>Nullable</WarningsAsErrors>
     <AssemblyName>Volo.Abp.Dapper</AssemblyName>
     <PackageId>Volo.Abp.Dapper</PackageId>
     <AssetTargetFallback>$(AssetTargetFallback);portable-net45+win8+wp8+wpa81;</AssetTargetFallback>
diff --git a/framework/src/Volo.Abp.Dapper/Volo/Abp/Domain/Repositories/Dapper/DapperRepository.cs b/framework/src/Volo.Abp.Dapper/Volo/Abp/Domain/Repositories/Dapper/DapperRepository.cs
index b9f061b9aa..fda89ab61d 100644
--- a/framework/src/Volo.Abp.Dapper/Volo/Abp/Domain/Repositories/Dapper/DapperRepository.cs
+++ b/framework/src/Volo.Abp.Dapper/Volo/Abp/Domain/Repositories/Dapper/DapperRepository.cs
@@ -16,7 +16,7 @@ namespace Volo.Abp.Domain.Repositories.Dapper;
 public class DapperRepository<TDbContext> : IDapperRepository, IUnitOfWorkEnabled
     where TDbContext : IEfCoreDbContext
 {
-    public IAbpLazyServiceProvider LazyServiceProvider { get; set; }
+    public IAbpLazyServiceProvider LazyServiceProvider { get; set; } = default!;
 
     public IDataFilter DataFilter => LazyServiceProvider.LazyGetRequiredService<IDataFilter>();
 
@@ -39,9 +39,9 @@ public class DapperRepository<TDbContext> : IDapperRepository, IUnitOfWorkEnable
     public virtual async Task<IDbConnection> GetDbConnectionAsync() => (await _dbContextProvider.GetDbContextAsync()).Database.GetDbConnection();
 
     [Obsolete("Use GetDbTransactionAsync method.")]
-    public IDbTransaction DbTransaction => _dbContextProvider.GetDbContext().Database.CurrentTransaction?.GetDbTransaction();
+    public IDbTransaction? DbTransaction => _dbContextProvider.GetDbContext().Database.CurrentTransaction?.GetDbTransaction();
 
-    public virtual async Task<IDbTransaction> GetDbTransactionAsync() => (await _dbContextProvider.GetDbContextAsync()).Database.CurrentTransaction?.GetDbTransaction();
+    public virtual async Task<IDbTransaction?> GetDbTransactionAsync() => (await _dbContextProvider.GetDbContextAsync()).Database.CurrentTransaction?.GetDbTransaction();
 
     protected virtual CancellationToken GetCancellationToken(CancellationToken preferredValue = default)
     {
diff --git a/framework/src/Volo.Abp.Dapper/Volo/Abp/Domain/Repositories/Dapper/IDapperRepository.cs b/framework/src/Volo.Abp.Dapper/Volo/Abp/Domain/Repositories/Dapper/IDapperRepository.cs
index e5e8fa4c54..5a22e65e00 100644
--- a/framework/src/Volo.Abp.Dapper/Volo/Abp/Domain/Repositories/Dapper/IDapperRepository.cs
+++ b/framework/src/Volo.Abp.Dapper/Volo/Abp/Domain/Repositories/Dapper/IDapperRepository.cs
@@ -12,7 +12,7 @@ public interface IDapperRepository
     Task<IDbConnection> GetDbConnectionAsync();
 
     [Obsolete("Use GetDbTransactionAsync method.")]
-    IDbTransaction DbTransaction { get; }
+    IDbTransaction? DbTransaction { get; }
 
-    Task<IDbTransaction> GetDbTransactionAsync();
+    Task<IDbTransaction?> GetDbTransactionAsync();
 }
diff --git a/framework/src/Volo.Abp.Dapr/Volo.Abp.Dapr.csproj b/framework/src/Volo.Abp.Dapr/Volo.Abp.Dapr.csproj
index f21af371bb..1b952e34cc 100644
--- a/framework/src/Volo.Abp.Dapr/Volo.Abp.Dapr.csproj
+++ b/framework/src/Volo.Abp.Dapr/Volo.Abp.Dapr.csproj
@@ -5,6 +5,8 @@
 
     <PropertyGroup>
         <TargetFramework>net7.0</TargetFramework>
+        <Nullable>enable</Nullable>
+        <WarningsAsErrors>Nullable</WarningsAsErrors>
         <RootNamespace />
     </PropertyGroup>
 
diff --git a/framework/src/Volo.Abp.Dapr/Volo/Abp/Dapr/AbpDaprClientFactory.cs b/framework/src/Volo.Abp.Dapr/Volo/Abp/Dapr/AbpDaprClientFactory.cs
index aa14bbe7f2..43e9dbc953 100644
--- a/framework/src/Volo.Abp.Dapr/Volo/Abp/Dapr/AbpDaprClientFactory.cs
+++ b/framework/src/Volo.Abp.Dapr/Volo/Abp/Dapr/AbpDaprClientFactory.cs
@@ -24,7 +24,7 @@ public class AbpDaprClientFactory : IAbpDaprClientFactory, ISingletonDependency
         JsonSerializerOptions = CreateJsonSerializerOptions(systemTextJsonSerializerOptions.Value);
     }
 
-    public virtual DaprClient Create(Action<DaprClientBuilder> builderAction = null)
+    public virtual DaprClient Create(Action<DaprClientBuilder>? builderAction = null)
     {
         var builder = new DaprClientBuilder()
             .UseJsonSerializationOptions(JsonSerializerOptions);
@@ -51,9 +51,9 @@ public class AbpDaprClientFactory : IAbpDaprClientFactory, ISingletonDependency
     }
 
     public virtual HttpClient CreateHttpClient(
-        string appId = null,
-        string daprEndpoint = null,
-        string daprApiToken = null)
+        string? appId = null,
+        string? daprEndpoint = null,
+        string? daprApiToken = null)
     {
         if(daprEndpoint.IsNullOrWhiteSpace() &&
            !DaprOptions.HttpEndpoint.IsNullOrWhiteSpace())
diff --git a/framework/src/Volo.Abp.Dapr/Volo/Abp/Dapr/AbpDaprModule.cs b/framework/src/Volo.Abp.Dapr/Volo/Abp/Dapr/AbpDaprModule.cs
index 4153ae2ec1..e1ca4bb0db 100644
--- a/framework/src/Volo.Abp.Dapr/Volo/Abp/Dapr/AbpDaprModule.cs
+++ b/framework/src/Volo.Abp.Dapr/Volo/Abp/Dapr/AbpDaprModule.cs
@@ -33,14 +33,14 @@ public class AbpDaprModule : AbpModule
                 var confEnv = configuration["DAPR_API_TOKEN"];
                 if (!confEnv.IsNullOrWhiteSpace())
                 {
-                    options.DaprApiToken = confEnv;
+                    options.DaprApiToken = confEnv!;
                 }
                 else
                 {
                     var env = Environment.GetEnvironmentVariable("DAPR_API_TOKEN");
                     if (!env.IsNullOrWhiteSpace())
                     {
-                        options.DaprApiToken = env;
+                        options.DaprApiToken = env!;
                     }
                 }
             }
@@ -50,14 +50,14 @@ public class AbpDaprModule : AbpModule
                 var confEnv = configuration["APP_API_TOKEN"];
                 if (!confEnv.IsNullOrWhiteSpace())
                 {
-                    options.AppApiToken = confEnv;
+                    options.AppApiToken = confEnv!;
                 }
                 else
                 {
                     var env = Environment.GetEnvironmentVariable("APP_API_TOKEN");
                     if (!env.IsNullOrWhiteSpace())
                     {
-                        options.AppApiToken = env;
+                        options.AppApiToken = env!;
                     }
                 }
             }
diff --git a/framework/src/Volo.Abp.Dapr/Volo/Abp/Dapr/AbpDaprOptions.cs b/framework/src/Volo.Abp.Dapr/Volo/Abp/Dapr/AbpDaprOptions.cs
index 7ac19ad31c..f436f35147 100644
--- a/framework/src/Volo.Abp.Dapr/Volo/Abp/Dapr/AbpDaprOptions.cs
+++ b/framework/src/Volo.Abp.Dapr/Volo/Abp/Dapr/AbpDaprOptions.cs
@@ -2,11 +2,11 @@
 
 public class AbpDaprOptions
 {
-    public string HttpEndpoint { get; set; }
+    public string? HttpEndpoint { get; set; }
 
-    public string GrpcEndpoint { get; set; }
+    public string? GrpcEndpoint { get; set; }
     
-    public string DaprApiToken { get; set; }
+    public string? DaprApiToken { get; set; }
     
-    public string AppApiToken { get; set; }
+    public string? AppApiToken { get; set; }
 }
\ No newline at end of file
diff --git a/framework/src/Volo.Abp.Dapr/Volo/Abp/Dapr/DaprApiTokenProvider.cs b/framework/src/Volo.Abp.Dapr/Volo/Abp/Dapr/DaprApiTokenProvider.cs
index 10dd3913ed..c38f36bf10 100644
--- a/framework/src/Volo.Abp.Dapr/Volo/Abp/Dapr/DaprApiTokenProvider.cs
+++ b/framework/src/Volo.Abp.Dapr/Volo/Abp/Dapr/DaprApiTokenProvider.cs
@@ -12,12 +12,12 @@ public class DaprApiTokenProvider : IDaprApiTokenProvider, ISingletonDependency
         Options = options.Value;
     }
 
-    public virtual string GetDaprApiToken()
+    public virtual string? GetDaprApiToken()
     {
         return Options.DaprApiToken;
     }
 
-    public virtual string GetAppApiToken()
+    public virtual string? GetAppApiToken()
     {
         return Options.AppApiToken;
     }
diff --git a/framework/src/Volo.Abp.Dapr/Volo/Abp/Dapr/IAbpDaprClientFactory.cs b/framework/src/Volo.Abp.Dapr/Volo/Abp/Dapr/IAbpDaprClientFactory.cs
index 65c4e76b7e..bbf074af6c 100644
--- a/framework/src/Volo.Abp.Dapr/Volo/Abp/Dapr/IAbpDaprClientFactory.cs
+++ b/framework/src/Volo.Abp.Dapr/Volo/Abp/Dapr/IAbpDaprClientFactory.cs
@@ -6,11 +6,11 @@ namespace Volo.Abp.Dapr;
 
 public interface IAbpDaprClientFactory
 {
-    DaprClient Create(Action<DaprClientBuilder> builderAction = null);
+    DaprClient Create(Action<DaprClientBuilder>? builderAction = null);
 
     HttpClient CreateHttpClient(
-        string appId = null,
-        string daprEndpoint = null,
-        string daprApiToken = null
+        string? appId = null,
+        string? daprEndpoint = null,
+        string? daprApiToken = null
     );
 }
diff --git a/framework/src/Volo.Abp.Dapr/Volo/Abp/Dapr/IDaprApiTokenProvider.cs b/framework/src/Volo.Abp.Dapr/Volo/Abp/Dapr/IDaprApiTokenProvider.cs
index 60f2195596..5e153ba2ea 100644
--- a/framework/src/Volo.Abp.Dapr/Volo/Abp/Dapr/IDaprApiTokenProvider.cs
+++ b/framework/src/Volo.Abp.Dapr/Volo/Abp/Dapr/IDaprApiTokenProvider.cs
@@ -2,7 +2,7 @@ namespace Volo.Abp.Dapr;
 
 public interface IDaprApiTokenProvider
 {
-    string GetDaprApiToken();
+    string? GetDaprApiToken();
 
-    string GetAppApiToken();
+    string? GetAppApiToken();
 }
diff --git a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo.Abp.Ddd.Application.Contracts.csproj b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo.Abp.Ddd.Application.Contracts.csproj
index ae01d66fd0..891a4b8a33 100644
--- a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo.Abp.Ddd.Application.Contracts.csproj
+++ b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo.Abp.Ddd.Application.Contracts.csproj
@@ -5,6 +5,8 @@
 
   <PropertyGroup>
     <TargetFrameworks>netstandard2.0;netstandard2.1;net7.0</TargetFrameworks>
+    <Nullable>enable</Nullable>
+    <WarningsAsErrors>Nullable</WarningsAsErrors>
     <AssemblyName>Volo.Abp.Ddd.Application.Contracts</AssemblyName>
     <PackageId>Volo.Abp.Ddd.Application.Contracts</PackageId>
     <AssetTargetFallback>$(AssetTargetFallback);portable-net45+win8+wp8+wpa81;</AssetTargetFallback>
diff --git a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/AuditedEntityWithUserDto.cs b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/AuditedEntityWithUserDto.cs
index 992abc68fe..dfdbb10590 100644
--- a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/AuditedEntityWithUserDto.cs
+++ b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/AuditedEntityWithUserDto.cs
@@ -12,10 +12,10 @@ namespace Volo.Abp.Application.Dtos;
 public abstract class AuditedEntityWithUserDto<TUserDto> : AuditedEntityDto, IAuditedObject<TUserDto>
 {
     /// <inheritdoc />
-    public TUserDto Creator { get; set; }
+    public TUserDto? Creator { get; set; }
 
     /// <inheritdoc />
-    public TUserDto LastModifier { get; set; }
+    public TUserDto? LastModifier { get; set; }
 }
 
 /// <summary>
@@ -28,8 +28,8 @@ public abstract class AuditedEntityWithUserDto<TUserDto> : AuditedEntityDto, IAu
 public abstract class AuditedEntityWithUserDto<TPrimaryKey, TUserDto> : AuditedEntityDto<TPrimaryKey>, IAuditedObject<TUserDto>
 {
     /// <inheritdoc />
-    public TUserDto Creator { get; set; }
+    public TUserDto? Creator { get; set; }
 
     /// <inheritdoc />
-    public TUserDto LastModifier { get; set; }
+    public TUserDto? LastModifier { get; set; }
 }
diff --git a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/CreationAuditedEntityWithUserDto.cs b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/CreationAuditedEntityWithUserDto.cs
index e566e8852b..241944bb69 100644
--- a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/CreationAuditedEntityWithUserDto.cs
+++ b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/CreationAuditedEntityWithUserDto.cs
@@ -11,7 +11,7 @@ namespace Volo.Abp.Application.Dtos;
 [Serializable]
 public abstract class CreationAuditedEntityWithUserDto<TUserDto> : CreationAuditedEntityDto, ICreationAuditedObject<TUserDto>
 {
-    public TUserDto Creator { get; set; }
+    public TUserDto? Creator { get; set; }
 }
 
 /// <summary>
@@ -23,5 +23,5 @@ public abstract class CreationAuditedEntityWithUserDto<TUserDto> : CreationAudit
 [Serializable]
 public abstract class CreationAuditedEntityWithUserDto<TPrimaryKey, TUserDto> : CreationAuditedEntityDto<TPrimaryKey>, ICreationAuditedObject<TUserDto>
 {
-    public TUserDto Creator { get; set; }
+    public TUserDto? Creator { get; set; }
 }
diff --git a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/EntityDto.cs b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/EntityDto.cs
index a205549695..656e63b0d5 100644
--- a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/EntityDto.cs
+++ b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/EntityDto.cs
@@ -17,7 +17,7 @@ public abstract class EntityDto<TKey> : EntityDto, IEntityDto<TKey>
     /// <summary>
     /// Id of the entity.
     /// </summary>
-    public TKey Id { get; set; }
+    public TKey Id { get; set; } = default!;
 
     public override string ToString()
     {
diff --git a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/ExtensibleAuditedEntityWithUserDto.cs b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/ExtensibleAuditedEntityWithUserDto.cs
index 5f6fd28628..212dcfd807 100644
--- a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/ExtensibleAuditedEntityWithUserDto.cs
+++ b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/ExtensibleAuditedEntityWithUserDto.cs
@@ -15,10 +15,10 @@ namespace Volo.Abp.Application.Dtos;
 public abstract class ExtensibleAuditedEntityWithUserDto<TPrimaryKey, TUserDto> : ExtensibleAuditedEntityDto<TPrimaryKey>, IAuditedObject<TUserDto>
 {
     /// <inheritdoc />
-    public TUserDto Creator { get; set; }
+    public TUserDto? Creator { get; set; }
 
     /// <inheritdoc />
-    public TUserDto LastModifier { get; set; }
+    public TUserDto? LastModifier { get; set; }
 
     protected ExtensibleAuditedEntityWithUserDto()
         : this(true)
@@ -44,10 +44,10 @@ public abstract class ExtensibleAuditedEntityWithUserDto<TUserDto> : ExtensibleA
     IAuditedObject<TUserDto>
 {
     /// <inheritdoc />
-    public TUserDto Creator { get; set; }
+    public TUserDto? Creator { get; set; }
 
     /// <inheritdoc />
-    public TUserDto LastModifier { get; set; }
+    public TUserDto? LastModifier { get; set; }
 
     protected ExtensibleAuditedEntityWithUserDto()
         : this(true)
diff --git a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/ExtensibleCreationAuditedEntityWithUserDto.cs b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/ExtensibleCreationAuditedEntityWithUserDto.cs
index 3ea1be97ab..21677718cb 100644
--- a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/ExtensibleCreationAuditedEntityWithUserDto.cs
+++ b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/ExtensibleCreationAuditedEntityWithUserDto.cs
@@ -14,7 +14,7 @@ namespace Volo.Abp.Application.Dtos;
 [Serializable]
 public abstract class ExtensibleCreationAuditedEntityWithUserDto<TPrimaryKey, TUserDto> : ExtensibleCreationAuditedEntityDto<TPrimaryKey>, ICreationAuditedObject<TUserDto>
 {
-    public TUserDto Creator { get; set; }
+    public TUserDto? Creator { get; set; }
 
     protected ExtensibleCreationAuditedEntityWithUserDto()
         : this(true)
@@ -39,7 +39,7 @@ public abstract class ExtensibleCreationAuditedEntityWithUserDto<TPrimaryKey, TU
 public abstract class ExtensibleCreationAuditedEntityWithUserDto<TUserDto> : ExtensibleCreationAuditedEntityDto,
     ICreationAuditedObject<TUserDto>
 {
-    public TUserDto Creator { get; set; }
+    public TUserDto? Creator { get; set; }
 
     protected ExtensibleCreationAuditedEntityWithUserDto()
         : this(true)
diff --git a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/ExtensibleEntityDto.cs b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/ExtensibleEntityDto.cs
index 1af46a3287..9687af0cf7 100644
--- a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/ExtensibleEntityDto.cs
+++ b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/ExtensibleEntityDto.cs
@@ -9,7 +9,7 @@ public abstract class ExtensibleEntityDto<TKey> : ExtensibleObject, IEntityDto<T
     /// <summary>
     /// Id of the entity.
     /// </summary>
-    public TKey Id { get; set; }
+    public TKey Id { get; set; } = default!;
 
     protected ExtensibleEntityDto()
         : this(true)
diff --git a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/ExtensibleFullAuditedEntityWithUserDto.cs b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/ExtensibleFullAuditedEntityWithUserDto.cs
index 018a84cd7a..9793774a47 100644
--- a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/ExtensibleFullAuditedEntityWithUserDto.cs
+++ b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/ExtensibleFullAuditedEntityWithUserDto.cs
@@ -15,13 +15,13 @@ namespace Volo.Abp.Application.Dtos;
 public abstract class ExtensibleFullAuditedEntityWithUserDto<TPrimaryKey, TUserDto> : ExtensibleFullAuditedEntityDto<TPrimaryKey>, IFullAuditedObject<TUserDto>
 {
     /// <inheritdoc />
-    public TUserDto Creator { get; set; }
+    public TUserDto? Creator { get; set; }
 
     /// <inheritdoc />
-    public TUserDto LastModifier { get; set; }
+    public TUserDto? LastModifier { get; set; }
 
     /// <inheritdoc />
-    public TUserDto Deleter { get; set; }
+    public TUserDto? Deleter { get; set; }
 
     protected ExtensibleFullAuditedEntityWithUserDto()
         : this(true)
@@ -47,13 +47,13 @@ public abstract class ExtensibleFullAuditedEntityWithUserDto<TUserDto> : Extensi
     IFullAuditedObject<TUserDto>
 {
     /// <inheritdoc />
-    public TUserDto Creator { get; set; }
+    public TUserDto? Creator { get; set; }
 
     /// <inheritdoc />
-    public TUserDto LastModifier { get; set; }
+    public TUserDto? LastModifier { get; set; }
 
     /// <inheritdoc />
-    public TUserDto Deleter { get; set; }
+    public TUserDto? Deleter { get; set; }
 
     protected ExtensibleFullAuditedEntityWithUserDto()
         : this(true)
diff --git a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/FullAuditedEntityWithUserDto.cs b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/FullAuditedEntityWithUserDto.cs
index 0575c348b4..c9941d9127 100644
--- a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/FullAuditedEntityWithUserDto.cs
+++ b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/FullAuditedEntityWithUserDto.cs
@@ -12,13 +12,13 @@ namespace Volo.Abp.Application.Dtos;
 public abstract class FullAuditedEntityWithUserDto<TUserDto> : FullAuditedEntityDto, IFullAuditedObject<TUserDto>
 {
     /// <inheritdoc />
-    public TUserDto Creator { get; set; }
+    public TUserDto? Creator { get; set; }
 
     /// <inheritdoc />
-    public TUserDto LastModifier { get; set; }
+    public TUserDto? LastModifier { get; set; }
 
     /// <inheritdoc />
-    public TUserDto Deleter { get; set; }
+    public TUserDto? Deleter { get; set; }
 }
 
 /// <summary>
@@ -31,11 +31,11 @@ public abstract class FullAuditedEntityWithUserDto<TUserDto> : FullAuditedEntity
 public abstract class FullAuditedEntityWithUserDto<TPrimaryKey, TUserDto> : FullAuditedEntityDto<TPrimaryKey>, IFullAuditedObject<TUserDto>
 {
     /// <inheritdoc />
-    public TUserDto Creator { get; set; }
+    public TUserDto? Creator { get; set; }
 
     /// <inheritdoc />
-    public TUserDto LastModifier { get; set; }
+    public TUserDto? LastModifier { get; set; }
 
     /// <inheritdoc />
-    public TUserDto Deleter { get; set; }
+    public TUserDto? Deleter { get; set; }
 }
diff --git a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/ISortedResultRequest.cs b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/ISortedResultRequest.cs
index 0f0a4fe90f..b27c3bf99d 100644
--- a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/ISortedResultRequest.cs
+++ b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/ISortedResultRequest.cs
@@ -16,5 +16,5 @@ public interface ISortedResultRequest
     /// "Name DESC"
     /// "Name ASC, Age DESC"
     /// </example>
-    string Sorting { get; set; }
+    string? Sorting { get; set; }
 }
diff --git a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/LimitedResultRequestDto.cs b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/LimitedResultRequestDto.cs
index d72f7b0a77..646eb4d45e 100644
--- a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/LimitedResultRequestDto.cs
+++ b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/LimitedResultRequestDto.cs
@@ -42,7 +42,7 @@ public class LimitedResultRequestDto : ILimitedResultRequest, IValidatableObject
                     "MaxResultCountExceededExceptionMessage",
                     nameof(MaxResultCount),
                     MaxMaxResultCount,
-                    typeof(LimitedResultRequestDto).FullName,
+                    typeof(LimitedResultRequestDto).FullName!,
                     nameof(MaxMaxResultCount)
                 ],
                 new[] { nameof(MaxResultCount) });
@@ -90,7 +90,7 @@ public class ExtensibleLimitedResultRequestDto : ExtensibleEntityDto, ILimitedRe
                     "MaxResultCountExceededExceptionMessage",
                     nameof(MaxResultCount),
                     MaxMaxResultCount,
-                    typeof(ExtensibleLimitedResultRequestDto).FullName,
+                    typeof(ExtensibleLimitedResultRequestDto).FullName!,
                     nameof(MaxMaxResultCount)
                 ],
                 new[] { nameof(MaxResultCount) });
diff --git a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/ListResultDto.cs b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/ListResultDto.cs
index 361b27faac..56937e7049 100644
--- a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/ListResultDto.cs
+++ b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/ListResultDto.cs
@@ -13,7 +13,7 @@ public class ListResultDto<T> : IListResult<T>
         get { return _items ?? (_items = new List<T>()); }
         set { _items = value; }
     }
-    private IReadOnlyList<T> _items;
+    private IReadOnlyList<T>? _items;
 
     /// <summary>
     /// Creates a new <see cref="ListResultDto{T}"/> object.
@@ -42,7 +42,7 @@ public class ExtensibleListResultDto<T> : ExtensibleObject, IListResult<T>
         get { return _items ?? (_items = new List<T>()); }
         set { _items = value; }
     }
-    private IReadOnlyList<T> _items;
+    private IReadOnlyList<T>? _items;
 
     /// <summary>
     /// Creates a new <see cref="ListResultDto{T}"/> object.
diff --git a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/PagedAndSortedResultRequestDto.cs b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/PagedAndSortedResultRequestDto.cs
index 229178adbf..8a9b62bb60 100644
--- a/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/PagedAndSortedResultRequestDto.cs
+++ b/framework/src/Volo.Abp.Ddd.Application.Contracts/Volo/Abp/Application/Dtos/PagedAndSortedResultRequestDto.cs
@@ -8,7 +8,7 @@ namespace Volo.Abp.Application.Dtos;
 [Serializable]
 public class PagedAndSortedResultRequestDto : PagedResultRequestDto, IPagedAndSortedResultRequest
 {
-    public virtual string Sorting { get; set; }
+    public virtual string? Sorting { get; set; }
 }
 
 /// <summary>
@@ -17,5 +17,5 @@ public class PagedAndSortedResultRequestDto : PagedResultRequestDto, IPagedAndSo
 [Serializable]
 public class ExtensiblePagedAndSortedResultRequestDto : ExtensiblePagedResultRequestDto, IPagedAndSortedResultRequest
 {
-    public virtual string Sorting { get; set; }
+    public virtual string? Sorting { get; set; }
 }
diff --git a/framework/src/Volo.Abp.Ddd.Application/Volo.Abp.Ddd.Application.csproj b/framework/src/Volo.Abp.Ddd.Application/Volo.Abp.Ddd.Application.csproj
index fc0586ce8e..03351adb7f 100644
--- a/framework/src/Volo.Abp.Ddd.Application/Volo.Abp.Ddd.Application.csproj
+++ b/framework/src/Volo.Abp.Ddd.Application/Volo.Abp.Ddd.Application.csproj
@@ -5,6 +5,8 @@
 
   <PropertyGroup>
     <TargetFrameworks>netstandard2.0;netstandard2.1;net7.0</TargetFrameworks>
+    <Nullable>enable</Nullable>
+    <WarningsAsErrors>Nullable</WarningsAsErrors>
     <AssemblyName>Volo.Abp.Ddd.Application</AssemblyName>
     <PackageId>Volo.Abp.Ddd.Application</PackageId>
     <AssetTargetFallback>$(AssetTargetFallback);portable-net45+win8+wp8+wpa81;</AssetTargetFallback>
diff --git a/framework/src/Volo.Abp.Ddd.Application/Volo/Abp/Application/Services/AbstractKeyCrudAppService.cs b/framework/src/Volo.Abp.Ddd.Application/Volo/Abp/Application/Services/AbstractKeyCrudAppService.cs
index 6b6ad975d7..b3a2af6663 100644
--- a/framework/src/Volo.Abp.Ddd.Application/Volo/Abp/Application/Services/AbstractKeyCrudAppService.cs
+++ b/framework/src/Volo.Abp.Ddd.Application/Volo/Abp/Application/Services/AbstractKeyCrudAppService.cs
@@ -70,11 +70,11 @@ public abstract class AbstractKeyCrudAppService<TEntity, TGetOutputDto, TGetList
 {
     protected IRepository<TEntity> Repository { get; }
 
-    protected virtual string CreatePolicyName { get; set; }
+    protected virtual string? CreatePolicyName { get; set; }
 
-    protected virtual string UpdatePolicyName { get; set; }
+    protected virtual string? UpdatePolicyName { get; set; }
 
-    protected virtual string DeletePolicyName { get; set; }
+    protected virtual string? DeletePolicyName { get; set; }
 
     protected AbstractKeyCrudAppService(IRepository<TEntity> repository)
         : base(repository)
diff --git a/framework/src/Volo.Abp.Ddd.Application/Volo/Abp/Application/Services/AbstractKeyReadOnlyAppService.cs b/framework/src/Volo.Abp.Ddd.Application/Volo/Abp/Application/Services/AbstractKeyReadOnlyAppService.cs
index e56e3ff042..8602792701 100644
--- a/framework/src/Volo.Abp.Ddd.Application/Volo/Abp/Application/Services/AbstractKeyReadOnlyAppService.cs
+++ b/framework/src/Volo.Abp.Ddd.Application/Volo/Abp/Application/Services/AbstractKeyReadOnlyAppService.cs
@@ -40,9 +40,9 @@ public abstract class AbstractKeyReadOnlyAppService<TEntity, TGetOutputDto, TGet
 {
     protected IReadOnlyRepository<TEntity> ReadOnlyRepository { get; }
 
-    protected virtual string GetPolicyName { get; set; }
+    protected virtual string? GetPolicyName { get; set; }
 
-    protected virtual string GetListPolicyName { get; set; }
+    protected virtual string? GetListPolicyName { get; set; }
 
     protected AbstractKeyReadOnlyAppService(IReadOnlyRepository<TEntity> repository)
     {
@@ -107,7 +107,7 @@ public abstract class AbstractKeyReadOnlyAppService<TEntity, TGetOutputDto, TGet
         {
             if (!sortInput.Sorting.IsNullOrWhiteSpace())
             {
-                return query.OrderBy(sortInput.Sorting);
+                return query.OrderBy(sortInput.Sorting!);
             }
         }
 
diff --git a/framework/src/Volo.Abp.Ddd.Application/Volo/Abp/Application/Services/ApplicationService.cs b/framework/src/Volo.Abp.Ddd.Application/Volo/Abp/Application/Services/ApplicationService.cs
index b24e4b2900..ba82e5bdc2 100644
--- a/framework/src/Volo.Abp.Ddd.Application/Volo/Abp/Application/Services/ApplicationService.cs
+++ b/framework/src/Volo.Abp.Ddd.Application/Volo/Abp/Application/Services/ApplicationService.cs
@@ -36,10 +36,10 @@ public abstract class ApplicationService :
     IGlobalFeatureCheckingEnabled,
     ITransientDependency
 {
-    public IAbpLazyServiceProvider LazyServiceProvider { get; set; }
+    public IAbpLazyServiceProvider LazyServiceProvider { get; set; } = default!;
 
     [Obsolete("Use LazyServiceProvider instead.")]
-    public IServiceProvider ServiceProvider { get; set; }
+    public IServiceProvider ServiceProvider { get; set; } = default!;
 
     public static string[] CommonPostfixes { get; set; } = { "AppService", "ApplicationService", "IntService", "IntegrationService", "Service" };
 
@@ -49,7 +49,7 @@ public abstract class ApplicationService :
 
     protected IAsyncQueryableExecuter AsyncExecuter => LazyServiceProvider.LazyGetRequiredService<IAsyncQueryableExecuter>();
 
-    protected Type ObjectMapperContext { get; set; }
+    protected Type? ObjectMapperContext { get; set; }
     protected IObjectMapper ObjectMapper => LazyServiceProvider.LazyGetService<IObjectMapper>(provider =>
         ObjectMapperContext == null
             ? provider.GetRequiredService<IObjectMapper>()
@@ -85,34 +85,34 @@ public abstract class ApplicationService :
             return _localizer;
         }
     }
-    private IStringLocalizer _localizer;
+    private IStringLocalizer? _localizer;
 
-    protected Type LocalizationResource {
+    protected Type? LocalizationResource {
         get => _localizationResource;
         set {
             _localizationResource = value;
             _localizer = null;
         }
     }
-    private Type _localizationResource = typeof(DefaultResource);
+    private Type? _localizationResource = typeof(DefaultResource);
 
-    protected IUnitOfWork CurrentUnitOfWork => UnitOfWorkManager?.Current;
+    protected IUnitOfWork? CurrentUnitOfWork => UnitOfWorkManager?.Current;
 
-    protected ILogger Logger => LazyServiceProvider.LazyGetService<ILogger>(provider => LoggerFactory?.CreateLogger(GetType().FullName) ?? NullLogger.Instance);
+    protected ILogger Logger => LazyServiceProvider.LazyGetService<ILogger>(provider => LoggerFactory?.CreateLogger(GetType().FullName!) ?? NullLogger.Instance);
 
     /// <summary>
     /// Checks for given <paramref name="policyName"/>.
     /// Throws <see cref="AbpAuthorizationException"/> if given policy has not been granted.
     /// </summary>
     /// <param name="policyName">The policy name. This method does nothing if given <paramref name="policyName"/> is null or empty.</param>
-    protected virtual async Task CheckPolicyAsync([CanBeNull] string policyName)
+    protected virtual async Task CheckPolicyAsync(string? policyName)
     {
         if (string.IsNullOrEmpty(policyName))
         {
             return;
         }
 
-        await AuthorizationService.CheckAsync(policyName);
+        await AuthorizationService.CheckAsync(policyName!);
     }
 
     protected virtual IStringLocalizer CreateLocalizer()
diff --git a/framework/src/Volo.Abp.Ddd.Domain.Shared/Volo.Abp.Ddd.Domain.Shared.csproj b/framework/src/Volo.Abp.Ddd.Domain.Shared/Volo.Abp.Ddd.Domain.Shared.csproj
index 2972ef23c1..efc808fdc7 100644
--- a/framework/src/Volo.Abp.Ddd.Domain.Shared/Volo.Abp.Ddd.Domain.Shared.csproj
+++ b/framework/src/Volo.Abp.Ddd.Domain.Shared/Volo.Abp.Ddd.Domain.Shared.csproj
@@ -5,6 +5,8 @@
 
     <PropertyGroup>
         <TargetFrameworks>netstandard2.0;netstandard2.1;net7.0</TargetFrameworks>
+        <Nullable>enable</Nullable>
+        <WarningsAsErrors>Nullable</WarningsAsErrors>
         <AssemblyName>Volo.Abp.Ddd.Domain.Shared</AssemblyName>
         <PackageId>Volo.Abp.Ddd.Domain.Shared</PackageId>
         <AssetTargetFallback>$(AssetTargetFallback);portable-net45+win8+wp8+wpa81;</AssetTargetFallback>
diff --git a/framework/src/Volo.Abp.Ddd.Domain.Shared/Volo/Abp/Domain/Entities/Events/Distributed/EntityEto.cs b/framework/src/Volo.Abp.Ddd.Domain.Shared/Volo/Abp/Domain/Entities/Events/Distributed/EntityEto.cs
index 8a2983b076..88e71f2e9f 100644
--- a/framework/src/Volo.Abp.Ddd.Domain.Shared/Volo/Abp/Domain/Entities/Events/Distributed/EntityEto.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain.Shared/Volo/Abp/Domain/Entities/Events/Distributed/EntityEto.cs
@@ -5,9 +5,9 @@ namespace Volo.Abp.Domain.Entities.Events.Distributed;
 [Serializable]
 public class EntityEto : EtoBase
 {
-    public string EntityType { get; set; }
+    public string EntityType { get; set; } = default!;
 
-    public string KeysAsString { get; set; }
+    public string KeysAsString { get; set; } = default!;
 
     public EntityEto()
     {
@@ -23,5 +23,5 @@ public class EntityEto : EtoBase
 
 public abstract class EntityEto<TKey> : IEntityEto<TKey>
 {
-    public TKey Id { get; set; }
+    public TKey Id { get; set; } = default!;
 }
\ No newline at end of file
diff --git a/framework/src/Volo.Abp.Ddd.Domain.Shared/Volo/Abp/Domain/Entities/Events/Distributed/EtoMappingDictionary.cs b/framework/src/Volo.Abp.Ddd.Domain.Shared/Volo/Abp/Domain/Entities/Events/Distributed/EtoMappingDictionary.cs
index bb9e362ac2..f62ccfd872 100644
--- a/framework/src/Volo.Abp.Ddd.Domain.Shared/Volo/Abp/Domain/Entities/Events/Distributed/EtoMappingDictionary.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain.Shared/Volo/Abp/Domain/Entities/Events/Distributed/EtoMappingDictionary.cs
@@ -5,7 +5,7 @@ namespace Volo.Abp.Domain.Entities.Events.Distributed;
 
 public class EtoMappingDictionary : Dictionary<Type, EtoMappingDictionaryItem>
 {
-    public void Add<TEntity, TEntityEto>(Type objectMappingContextType = null)
+    public void Add<TEntity, TEntityEto>(Type? objectMappingContextType = null)
     {
         this[typeof(TEntity)] = new EtoMappingDictionaryItem(typeof(TEntityEto), objectMappingContextType);
     }
diff --git a/framework/src/Volo.Abp.Ddd.Domain.Shared/Volo/Abp/Domain/Entities/Events/Distributed/EtoMappingDictionaryItem.cs b/framework/src/Volo.Abp.Ddd.Domain.Shared/Volo/Abp/Domain/Entities/Events/Distributed/EtoMappingDictionaryItem.cs
index a6065e1d5f..c250e6daae 100644
--- a/framework/src/Volo.Abp.Ddd.Domain.Shared/Volo/Abp/Domain/Entities/Events/Distributed/EtoMappingDictionaryItem.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain.Shared/Volo/Abp/Domain/Entities/Events/Distributed/EtoMappingDictionaryItem.cs
@@ -6,9 +6,9 @@ public class EtoMappingDictionaryItem
 {
     public Type EtoType { get; }
 
-    public Type ObjectMappingContextType { get; }
+    public Type? ObjectMappingContextType { get; }
 
-    public EtoMappingDictionaryItem(Type etoType, Type objectMappingContextType = null)
+    public EtoMappingDictionaryItem(Type etoType, Type? objectMappingContextType = null)
     {
         EtoType = etoType;
         ObjectMappingContextType = objectMappingContextType;
diff --git a/framework/src/Volo.Abp.Ddd.Domain.Shared/Volo/Abp/Domain/Entities/Events/Distributed/IEntityToEtoMapper.cs b/framework/src/Volo.Abp.Ddd.Domain.Shared/Volo/Abp/Domain/Entities/Events/Distributed/IEntityToEtoMapper.cs
index 6f0ea7a880..67406fd0d4 100644
--- a/framework/src/Volo.Abp.Ddd.Domain.Shared/Volo/Abp/Domain/Entities/Events/Distributed/IEntityToEtoMapper.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain.Shared/Volo/Abp/Domain/Entities/Events/Distributed/IEntityToEtoMapper.cs
@@ -4,6 +4,5 @@ namespace Volo.Abp.Domain.Entities.Events.Distributed;
 
 public interface IEntityToEtoMapper
 {
-    [CanBeNull]
-    object Map(object entityObj);
+    object? Map(object entityObj);
 }
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo.Abp.Ddd.Domain.csproj b/framework/src/Volo.Abp.Ddd.Domain/Volo.Abp.Ddd.Domain.csproj
index c15f7c96a8..5130c57f12 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo.Abp.Ddd.Domain.csproj
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo.Abp.Ddd.Domain.csproj
@@ -5,6 +5,8 @@
 
   <PropertyGroup>
     <TargetFrameworks>netstandard2.0;netstandard2.1;net7.0</TargetFrameworks>
+    <Nullable>enable</Nullable>
+    <WarningsAsErrors>Nullable</WarningsAsErrors>
     <AssemblyName>Volo.Abp.Ddd.Domain</AssemblyName>
     <PackageId>Volo.Abp.Ddd.Domain</PackageId>
     <AssetTargetFallback>$(AssetTargetFallback);portable-net45+win8+wp8+wpa81;</AssetTargetFallback>
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/DependencyInjection/AbpCommonDbContextRegistrationOptions.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/DependencyInjection/AbpCommonDbContextRegistrationOptions.cs
index bc50368645..8342451056 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/DependencyInjection/AbpCommonDbContextRegistrationOptions.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/DependencyInjection/AbpCommonDbContextRegistrationOptions.cs
@@ -16,13 +16,13 @@ public abstract class AbpCommonDbContextRegistrationOptions : IAbpCommonDbContex
 
     public IServiceCollection Services { get; }
 
-    public Dictionary<MultiTenantDbContextType, Type> ReplacedDbContextTypes { get; }
+    public Dictionary<MultiTenantDbContextType, Type?> ReplacedDbContextTypes { get; }
 
     public Type DefaultRepositoryDbContextType { get; protected set; }
 
-    public Type DefaultRepositoryImplementationType { get; private set; }
+    public Type? DefaultRepositoryImplementationType { get; private set; }
 
-    public Type DefaultRepositoryImplementationTypeWithoutKey { get; private set; }
+    public Type? DefaultRepositoryImplementationTypeWithoutKey { get; private set; }
 
     public bool RegisterDefaultRepositories { get; private set; }
 
@@ -40,7 +40,7 @@ public abstract class AbpCommonDbContextRegistrationOptions : IAbpCommonDbContex
         Services = services;
         DefaultRepositoryDbContextType = originalDbContextType;
         CustomRepositories = new Dictionary<Type, Type>();
-        ReplacedDbContextTypes = new Dictionary<MultiTenantDbContextType, Type>();
+        ReplacedDbContextTypes = new Dictionary<MultiTenantDbContextType, Type?>();
         SpecifiedDefaultRepositories = new List<Type>();
     }
 
@@ -54,7 +54,7 @@ public abstract class AbpCommonDbContextRegistrationOptions : IAbpCommonDbContex
         return ReplaceDbContext(typeof(TOtherDbContext), typeof(TTargetDbContext), multiTenancySides);
     }
 
-    public IAbpCommonDbContextRegistrationOptionsBuilder ReplaceDbContext(Type otherDbContextType, Type targetDbContextType = null, MultiTenancySides multiTenancySides = MultiTenancySides.Both)
+    public IAbpCommonDbContextRegistrationOptionsBuilder ReplaceDbContext(Type otherDbContextType, Type? targetDbContextType = null, MultiTenancySides multiTenancySides = MultiTenancySides.Both)
     {
         if (!otherDbContextType.IsAssignableFrom(OriginalDbContextType))
         {
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/DependencyInjection/IAbpCommonDbContextRegistrationOptionsBuilder.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/DependencyInjection/IAbpCommonDbContextRegistrationOptionsBuilder.cs
index 58a82bf77d..ee580332a8 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/DependencyInjection/IAbpCommonDbContextRegistrationOptionsBuilder.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/DependencyInjection/IAbpCommonDbContextRegistrationOptionsBuilder.cs
@@ -90,5 +90,5 @@ public interface IAbpCommonDbContextRegistrationOptionsBuilder
     /// <param name="otherDbContextType">The DbContext type to be replaced</param>
     /// <param name="targetDbContextType">The target DbContext type (optional, used this DbContext type if not provided)</param>
     /// <param name="multiTenancySides">MultiTenancy side</param>
-    IAbpCommonDbContextRegistrationOptionsBuilder ReplaceDbContext(Type otherDbContextType, Type targetDbContextType = null, MultiTenancySides multiTenancySides = MultiTenancySides.Both);
+    IAbpCommonDbContextRegistrationOptionsBuilder ReplaceDbContext(Type otherDbContextType, Type? targetDbContextType = null, MultiTenancySides multiTenancySides = MultiTenancySides.Both);
 }
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/DependencyInjection/MultiTenantDbContextType.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/DependencyInjection/MultiTenantDbContextType.cs
index ff0d74608a..b015b9204a 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/DependencyInjection/MultiTenantDbContextType.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/DependencyInjection/MultiTenantDbContextType.cs
@@ -15,7 +15,7 @@ public class MultiTenantDbContextType
         MultiTenancySide = multiTenancySide;
     }
 
-    public override bool Equals(object obj)
+    public override bool Equals(object? obj)
     {
         var other = obj as MultiTenantDbContextType;
 
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Auditing/AuditedAggregateRootWithUser.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Auditing/AuditedAggregateRootWithUser.cs
index ebb573579b..f38c21d2fe 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Auditing/AuditedAggregateRootWithUser.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Auditing/AuditedAggregateRootWithUser.cs
@@ -12,10 +12,10 @@ public abstract class AuditedAggregateRootWithUser<TUser> : AuditedAggregateRoot
     where TUser : IEntity<Guid>
 {
     /// <inheritdoc />
-    public virtual TUser Creator { get; protected set; }
+    public virtual TUser? Creator { get; protected set; }
 
     /// <inheritdoc />
-    public virtual TUser LastModifier { get; set; }
+    public virtual TUser? LastModifier { get; set; }
 }
 
 /// <summary>
@@ -28,10 +28,10 @@ public abstract class AuditedAggregateRootWithUser<TKey, TUser> : AuditedAggrega
     where TUser : IEntity<Guid>
 {
     /// <inheritdoc />
-    public virtual TUser Creator { get; protected set; }
+    public virtual TUser? Creator { get; protected set; }
 
     /// <inheritdoc />
-    public virtual TUser LastModifier { get; set; }
+    public virtual TUser? LastModifier { get; set; }
 
     protected AuditedAggregateRootWithUser()
     {
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Auditing/AuditedEntityWithUser.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Auditing/AuditedEntityWithUser.cs
index 99b9b66303..3f8598d348 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Auditing/AuditedEntityWithUser.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Auditing/AuditedEntityWithUser.cs
@@ -12,10 +12,10 @@ public abstract class AuditedEntityWithUser<TUser> : AuditedEntity, IAuditedObje
     where TUser : IEntity<Guid>
 {
     /// <inheritdoc />
-    public virtual TUser Creator { get; protected set; }
+    public virtual TUser? Creator { get; protected set; }
 
     /// <inheritdoc />
-    public virtual TUser LastModifier { get; set; }
+    public virtual TUser? LastModifier { get; set; }
 }
 
 /// <summary>
@@ -28,10 +28,10 @@ public abstract class AuditedEntityWithUser<TKey, TUser> : AuditedEntity<TKey>,
     where TUser : IEntity<Guid>
 {
     /// <inheritdoc />
-    public virtual TUser Creator { get; protected set; }
+    public virtual TUser? Creator { get; protected set; }
 
     /// <inheritdoc />
-    public virtual TUser LastModifier { get; set; }
+    public virtual TUser? LastModifier { get; set; }
 
     protected AuditedEntityWithUser()
     {
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Auditing/CreationAuditedAggregateRootWithUser.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Auditing/CreationAuditedAggregateRootWithUser.cs
index 73da9d2026..4407a93de8 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Auditing/CreationAuditedAggregateRootWithUser.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Auditing/CreationAuditedAggregateRootWithUser.cs
@@ -11,7 +11,7 @@ namespace Volo.Abp.Domain.Entities.Auditing;
 public abstract class CreationAuditedAggregateRootWithUser<TUser> : CreationAuditedAggregateRoot, ICreationAuditedObject<TUser>
 {
     /// <inheritdoc />
-    public virtual TUser Creator { get; protected set; }
+    public virtual TUser? Creator { get; protected set; }
 }
 
 /// <summary>
@@ -23,7 +23,7 @@ public abstract class CreationAuditedAggregateRootWithUser<TUser> : CreationAudi
 public abstract class CreationAuditedAggregateRootWithUser<TKey, TUser> : CreationAuditedAggregateRoot<TKey>, ICreationAuditedObject<TUser>
 {
     /// <inheritdoc />
-    public virtual TUser Creator { get; protected set; }
+    public virtual TUser? Creator { get; protected set; }
 
     protected CreationAuditedAggregateRootWithUser()
     {
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Auditing/CreationAuditedEntityWithUser.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Auditing/CreationAuditedEntityWithUser.cs
index 203967fb89..635bb06183 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Auditing/CreationAuditedEntityWithUser.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Auditing/CreationAuditedEntityWithUser.cs
@@ -11,7 +11,7 @@ namespace Volo.Abp.Domain.Entities.Auditing;
 public abstract class CreationAuditedEntityWithUser<TUser> : CreationAuditedEntity, ICreationAuditedObject<TUser>
 {
     /// <inheritdoc />
-    public virtual TUser Creator { get; protected set; }
+    public virtual TUser? Creator { get; protected set; }
 }
 
 /// <summary>
@@ -23,7 +23,7 @@ public abstract class CreationAuditedEntityWithUser<TUser> : CreationAuditedEnti
 public abstract class CreationAuditedEntityWithUser<TKey, TUser> : CreationAuditedEntity<TKey>, ICreationAuditedObject<TUser>
 {
     /// <inheritdoc />
-    public virtual TUser Creator { get; protected set; }
+    public virtual TUser? Creator { get; protected set; }
 
     protected CreationAuditedEntityWithUser()
     {
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Auditing/FullAuditedAggregateRootWithUser.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Auditing/FullAuditedAggregateRootWithUser.cs
index 918270088e..af8f196f00 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Auditing/FullAuditedAggregateRootWithUser.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Auditing/FullAuditedAggregateRootWithUser.cs
@@ -12,13 +12,13 @@ public abstract class FullAuditedAggregateRootWithUser<TUser> : FullAuditedAggre
     where TUser : IEntity<Guid>
 {
     /// <inheritdoc />
-    public virtual TUser Deleter { get; set; }
+    public virtual TUser? Deleter { get; set; }
 
     /// <inheritdoc />
-    public virtual TUser Creator { get; protected set; }
+    public virtual TUser? Creator { get; protected set; }
 
     /// <inheritdoc />
-    public virtual TUser LastModifier { get; set; }
+    public virtual TUser? LastModifier { get; set; }
 }
 
 /// <summary>
@@ -31,13 +31,13 @@ public abstract class FullAuditedAggregateRootWithUser<TKey, TUser> : FullAudite
     where TUser : IEntity<Guid>
 {
     /// <inheritdoc />
-    public virtual TUser Deleter { get; set; }
+    public virtual TUser? Deleter { get; set; }
 
     /// <inheritdoc />
-    public virtual TUser Creator { get; protected set; }
+    public virtual TUser? Creator { get; protected set; }
 
     /// <inheritdoc />
-    public virtual TUser LastModifier { get; set; }
+    public virtual TUser? LastModifier { get; set; }
 
     protected FullAuditedAggregateRootWithUser()
     {
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Auditing/FullAuditedEntityWithUser.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Auditing/FullAuditedEntityWithUser.cs
index 1f4886f4c0..834b106d95 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Auditing/FullAuditedEntityWithUser.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Auditing/FullAuditedEntityWithUser.cs
@@ -12,13 +12,13 @@ public abstract class FullAuditedEntityWithUser<TUser> : FullAuditedEntity, IFul
     where TUser : IEntity<Guid>
 {
     /// <inheritdoc />
-    public virtual TUser Deleter { get; set; }
+    public virtual TUser? Deleter { get; set; }
 
     /// <inheritdoc />
-    public virtual TUser Creator { get; protected set; }
+    public virtual TUser? Creator { get; protected set; }
 
     /// <inheritdoc />
-    public virtual TUser LastModifier { get; set; }
+    public virtual TUser? LastModifier { get; set; }
 }
 
 /// <summary>
@@ -31,13 +31,13 @@ public abstract class FullAuditedEntityWithUser<TKey, TUser> : FullAuditedEntity
     where TUser : IEntity<Guid>
 {
     /// <inheritdoc />
-    public virtual TUser Deleter { get; set; }
+    public virtual TUser? Deleter { get; set; }
 
     /// <inheritdoc />
-    public virtual TUser Creator { get; protected set; }
+    public virtual TUser? Creator { get; protected set; }
 
     /// <inheritdoc />
-    public virtual TUser LastModifier { get; set; }
+    public virtual TUser? LastModifier { get; set; }
 
     protected FullAuditedEntityWithUser()
     {
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Caching/EntityCacheBase.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Caching/EntityCacheBase.cs
index 7e5b17b687..2cb2b2c32b 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Caching/EntityCacheBase.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Caching/EntityCacheBase.cs
@@ -27,23 +27,23 @@ public abstract class EntityCacheBase<TEntity, TEntityCacheItem, TKey> :
         UnitOfWorkManager = unitOfWorkManager;
     }
     
-    public virtual async Task<TEntityCacheItem> FindAsync(TKey id)
+    public virtual async Task<TEntityCacheItem?> FindAsync(TKey id)
     {
         return await Cache.GetOrAddAsync(
             id,
-            async () => MapToCacheItem(await Repository.FindAsync(id))
+            async () => MapToCacheItem(await Repository.FindAsync(id))!
         );
     }
 
     public virtual async Task<TEntityCacheItem> GetAsync(TKey id)
     {
-        return await Cache.GetOrAddAsync(
+        return (await Cache.GetOrAddAsync(
             id,
-            async () => MapToCacheItem(await Repository.GetAsync(id))
-        );
+            async () => MapToCacheItem(await Repository.GetAsync(id))!
+        ))!;
     }
 
-    protected abstract TEntityCacheItem MapToCacheItem(TEntity entity);
+    protected abstract TEntityCacheItem? MapToCacheItem(TEntity? entity);
     
     public async Task HandleEventAsync(EntityChangedEventData<TEntity> eventData)
     {
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Caching/EntityCacheServiceCollectionExtensions.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Caching/EntityCacheServiceCollectionExtensions.cs
index bf7ceac45c..c208c7b107 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Caching/EntityCacheServiceCollectionExtensions.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Caching/EntityCacheServiceCollectionExtensions.cs
@@ -13,7 +13,7 @@ public static class EntityCacheServiceCollectionExtensions
 {
     public static IServiceCollection AddEntityCache<TEntity, TKey>(
         this IServiceCollection services,
-        [CanBeNull] DistributedCacheEntryOptions cacheOptions = null)
+        DistributedCacheEntryOptions? cacheOptions = null)
         where TEntity : Entity<TKey>
     {
         services
@@ -39,7 +39,7 @@ public static class EntityCacheServiceCollectionExtensions
 
     public static IServiceCollection AddEntityCache<TEntity, TEntityCacheItem, TKey>(
         this IServiceCollection services,
-        [CanBeNull] DistributedCacheEntryOptions cacheOptions = null)
+        DistributedCacheEntryOptions? cacheOptions = null)
         where TEntity : Entity<TKey>
         where TEntityCacheItem : class
     {
@@ -61,7 +61,7 @@ public static class EntityCacheServiceCollectionExtensions
 
     public static IServiceCollection AddEntityCache<TObjectMapperContext, TEntity, TEntityCacheItem, TKey>(
         this IServiceCollection services,
-        [CanBeNull] DistributedCacheEntryOptions cacheOptions = null)
+        DistributedCacheEntryOptions? cacheOptions = null)
         where TEntity : Entity<TKey>
         where TEntityCacheItem : class
     {
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Caching/EntityCacheWithObjectMapper.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Caching/EntityCacheWithObjectMapper.cs
index 727df63ea7..a37ad49b1e 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Caching/EntityCacheWithObjectMapper.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Caching/EntityCacheWithObjectMapper.cs
@@ -23,7 +23,7 @@ public class EntityCacheWithObjectMapper<TEntity, TEntityCacheItem, TKey> :
         ObjectMapper = objectMapper;
     }
 
-    protected override TEntityCacheItem MapToCacheItem(TEntity entity)
+    protected override TEntityCacheItem? MapToCacheItem(TEntity? entity)
     {
         if (entity == null)
         {
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Caching/EntityCacheWithoutCacheItem.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Caching/EntityCacheWithoutCacheItem.cs
index c81f3e5e9e..0f300a7f28 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Caching/EntityCacheWithoutCacheItem.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Caching/EntityCacheWithoutCacheItem.cs
@@ -16,7 +16,7 @@ public class EntityCacheWithoutCacheItem<TEntity, TKey> :
     {
     }
 
-    protected override TEntity MapToCacheItem(TEntity entity)
+    protected override TEntity? MapToCacheItem(TEntity? entity)
     {
         return entity;
     }
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Caching/IEntityCache.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Caching/IEntityCache.cs
index 84f4486c65..bd8ba80a63 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Caching/IEntityCache.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Caching/IEntityCache.cs
@@ -10,8 +10,7 @@ public interface IEntityCache<TEntityCacheItem, in TKey>
     /// Gets the entity with given <paramref name="id"/>,
     /// or returns null if the entity was not found.
     /// </summary>
-    [ItemCanBeNull] 
-    Task<TEntityCacheItem> FindAsync(TKey id);
+    Task<TEntityCacheItem?> FindAsync(TKey id);
  
     /// <summary>
     /// Gets the entity with given <paramref name="id"/>,
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Entity.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Entity.cs
index 54ebd01d1e..9e52d1abfd 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Entity.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Entity.cs
@@ -18,7 +18,7 @@ public abstract class Entity : IEntity
         return $"[ENTITY: {GetType().Name}] Keys = {GetKeys().JoinAsString(", ")}";
     }
 
-    public abstract object[] GetKeys();
+    public abstract object?[] GetKeys();
 
     public bool EntityEquals(IEntity other)
     {
@@ -31,7 +31,7 @@ public abstract class Entity : IEntity
 public abstract class Entity<TKey> : Entity, IEntity<TKey>
 {
     /// <inheritdoc/>
-    public virtual TKey Id { get; protected set; }
+    public virtual TKey Id { get; protected set; } = default!;
 
     protected Entity()
     {
@@ -43,9 +43,9 @@ public abstract class Entity<TKey> : Entity, IEntity<TKey>
         Id = id;
     }
 
-    public override object[] GetKeys()
+    public override object?[] GetKeys()
     {
-        return new object[] { Id };
+        return new object?[] { Id };
     }
 
     /// <inheritdoc/>
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/EntityHelper.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/EntityHelper.cs
index f7a4f27e5f..584807fac5 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/EntityHelper.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/EntityHelper.cs
@@ -25,7 +25,7 @@ public static class EntityHelper
         return typeof(IMultiTenant).IsAssignableFrom(type);
     }
 
-    public static bool EntityEquals(IEntity entity1, IEntity entity2)
+    public static bool EntityEquals(IEntity? entity1, IEntity? entity2)
     {
         if (entity1 == null || entity2 == null)
         {
@@ -131,7 +131,7 @@ public static class EntityHelper
         return IsValueObjectPredicate(type);
     }
 
-    public static bool IsValueObject(object obj)
+    public static bool IsValueObject(object? obj)
     {
         return obj != null && IsValueObject(obj.GetType());
     }
@@ -161,7 +161,7 @@ public static class EntityHelper
 
     public static bool HasDefaultId<TKey>(IEntity<TKey> entity)
     {
-        if (EqualityComparer<TKey>.Default.Equals(entity.Id, default))
+        if (EqualityComparer<TKey>.Default.Equals(entity.Id, default!))
         {
             return true;
         }
@@ -180,7 +180,7 @@ public static class EntityHelper
         return false;
     }
 
-    private static bool IsDefaultKeyValue(object value)
+    private static bool IsDefaultKeyValue(object? value)
     {
         if (value == null)
         {
@@ -222,8 +222,7 @@ public static class EntityHelper
     /// Tries to find the primary key type of the given entity type.
     /// May return null if given type does not implement <see cref="IEntity{TKey}"/>
     /// </summary>
-    [CanBeNull]
-    public static Type FindPrimaryKeyType<TEntity>()
+    public static Type? FindPrimaryKeyType<TEntity>()
         where TEntity : IEntity
     {
         return FindPrimaryKeyType(typeof(TEntity));
@@ -233,8 +232,7 @@ public static class EntityHelper
     /// Tries to find the primary key type of the given entity type.
     /// May return null if given type does not implement <see cref="IEntity{TKey}"/>
     /// </summary>
-    [CanBeNull]
-    public static Type FindPrimaryKeyType([NotNull] Type entityType)
+    public static Type? FindPrimaryKeyType([NotNull] Type entityType)
     {
         if (!typeof(IEntity).IsAssignableFrom(entityType))
         {
@@ -260,7 +258,7 @@ public static class EntityHelper
         var lambdaParam = Expression.Parameter(typeof(TEntity));
         var leftExpression = Expression.PropertyOrField(lambdaParam, "Id");
         var idValue = Convert.ChangeType(id, typeof(TKey));
-        Expression<Func<object>> closure = () => idValue;
+        Expression<Func<object?>> closure = () => idValue;
         var rightExpression = Expression.Convert(closure.Body, leftExpression.Type);
         var lambdaBody = Expression.Equal(leftExpression, rightExpression);
         return Expression.Lambda<Func<TEntity, bool>>(lambdaBody, lambdaParam);
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Events/Distributed/EntitySynchronizer.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Events/Distributed/EntitySynchronizer.cs
index b971acc25f..5640c427c2 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Events/Distributed/EntitySynchronizer.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Events/Distributed/EntitySynchronizer.cs
@@ -22,7 +22,7 @@ public abstract class EntitySynchronizer<TEntity, TKey, TSourceEntityEto> :
         Repository = repository;
     }
 
-    protected override Task<TEntity> FindLocalEntityAsync(TSourceEntityEto eto)
+    protected override Task<TEntity?> FindLocalEntityAsync(TSourceEntityEto eto)
     {
         return Repository.FindAsync(eto.Id);
     }
@@ -154,10 +154,9 @@ public abstract class EntitySynchronizer<TEntity, TSourceEntityEto> :
         return true;
     }
 
-    [ItemCanBeNull]
-    protected abstract Task<TEntity> FindLocalEntityAsync(TSourceEntityEto eto);
+    protected abstract Task<TEntity?> FindLocalEntityAsync(TSourceEntityEto eto);
 
-    protected virtual Task<bool> IsEtoNewerAsync(TSourceEntityEto eto, [CanBeNull] TEntity localEntity)
+    protected virtual Task<bool> IsEtoNewerAsync(TSourceEntityEto eto, TEntity? localEntity)
     {
         if (localEntity is IHasEntityVersion versionedLocalEntity && eto is IHasEntityVersion versionedEto)
         {
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Events/Distributed/EntityToEtoMapper.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Events/Distributed/EntityToEtoMapper.cs
index b9d5911375..cab3fe4614 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Events/Distributed/EntityToEtoMapper.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Events/Distributed/EntityToEtoMapper.cs
@@ -21,7 +21,7 @@ public class EntityToEtoMapper : IEntityToEtoMapper, ITransientDependency
         Options = options.Value;
     }
 
-    public object Map(object entityObj)
+    public object? Map(object entityObj)
     {
         Check.NotNull(entityObj, nameof(entityObj));
 
@@ -36,7 +36,7 @@ public class EntityToEtoMapper : IEntityToEtoMapper, ITransientDependency
         if (etoMappingItem == null)
         {
             var keys = entity.GetKeys().JoinAsString(",");
-            return new EntityEto(entityType.FullName, keys);
+            return new EntityEto(entityType.FullName!, keys);
         }
 
         using (var scope = HybridServiceScopeFactory.CreateScope())
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Events/EntityChangeEventHelper.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Events/EntityChangeEventHelper.cs
index 20556f16ff..44eb5c058a 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Events/EntityChangeEventHelper.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Events/EntityChangeEventHelper.cs
@@ -133,7 +133,7 @@ public class EntityChangeEventHelper : IEntityChangeEventHelper, ITransientDepen
     {
         var entityType = ProxyHelper.UnProxy(entityOrEto).GetType();
         var eventType = genericEventType.MakeGenericType(entityType);
-        var eventData = Activator.CreateInstance(eventType, entityOrEto);
+        var eventData = Activator.CreateInstance(eventType, entityOrEto)!;
         var currentUow = UnitOfWorkManager.Current;
 
         if (currentUow == null)
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Events/EntityEventData.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Events/EntityEventData.cs
index c2845da60e..b295f22f4e 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Events/EntityEventData.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/Events/EntityEventData.cs
@@ -27,7 +27,7 @@ public class EntityEventData<TEntity> : IEventDataWithInheritableGenericArgument
 
     public virtual object[] GetConstructorArgs()
     {
-        return new object[] { Entity };
+        return new object[] { Entity! };
     }
 
     public virtual bool IsMultiTenant(out Guid? tenantId)
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/IEntity.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/IEntity.cs
index 7f4d425df2..1df1b75696 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/IEntity.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/IEntity.cs
@@ -10,7 +10,7 @@ public interface IEntity
     /// Returns an array of ordered keys for this entity.
     /// </summary>
     /// <returns></returns>
-    object[] GetKeys();
+    object?[] GetKeys();
 }
 
 /// <summary>
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/BasicRepositoryBase.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/BasicRepositoryBase.cs
index 8a87f9c391..0d86045eea 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/BasicRepositoryBase.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/BasicRepositoryBase.cs
@@ -20,9 +20,9 @@ public abstract class BasicRepositoryBase<TEntity> :
     IUnitOfWorkEnabled
     where TEntity : class, IEntity
 {
-    public IAbpLazyServiceProvider LazyServiceProvider { get; set; }
+    public IAbpLazyServiceProvider LazyServiceProvider { get; set; } = default!;
 
-    public IServiceProvider ServiceProvider { get; set; }
+    public IServiceProvider ServiceProvider { get; set; } = default!;
 
     public IDataFilter DataFilter => LazyServiceProvider.LazyGetRequiredService<IDataFilter>();
 
@@ -123,7 +123,7 @@ public abstract class BasicRepositoryBase<TEntity, TKey> : BasicRepositoryBase<T
         return entity;
     }
 
-    public abstract Task<TEntity> FindAsync(TKey id, bool includeDetails = true, CancellationToken cancellationToken = default);
+    public abstract Task<TEntity?> FindAsync(TKey id, bool includeDetails = true, CancellationToken cancellationToken = default);
 
     public virtual async Task DeleteAsync(TKey id, bool autoSave = false, CancellationToken cancellationToken = default)
     {
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/IReadOnlyBasicRepository.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/IReadOnlyBasicRepository.cs
index 6d447552f9..0736685709 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/IReadOnlyBasicRepository.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/IReadOnlyBasicRepository.cs
@@ -51,5 +51,5 @@ public interface IReadOnlyBasicRepository<TEntity, TKey> : IReadOnlyBasicReposit
     /// <param name="includeDetails">Set true to include all children of this entity</param>
     /// <param name="cancellationToken">A <see cref="T:System.Threading.CancellationToken" /> to observe while waiting for the task to complete.</param>
     /// <returns>Entity or null</returns>
-    Task<TEntity> FindAsync(TKey id, bool includeDetails = true, CancellationToken cancellationToken = default);
+    Task<TEntity?> FindAsync(TKey id, bool includeDetails = true, CancellationToken cancellationToken = default);
 }
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/IRepository.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/IRepository.cs
index da915626a8..3c7ae81875 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/IRepository.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/IRepository.cs
@@ -28,7 +28,7 @@ public interface IRepository<TEntity> : IReadOnlyRepository<TEntity>, IBasicRepo
     /// <param name="predicate">A condition to find the entity</param>
     /// <param name="includeDetails">Set true to include all children of this entity</param>
     /// <param name="cancellationToken">A <see cref="T:System.Threading.CancellationToken" /> to observe while waiting for the task to complete.</param>
-    Task<TEntity> FindAsync(
+    Task<TEntity?> FindAsync(
         [NotNull] Expression<Func<TEntity, bool>> predicate,
         bool includeDetails = true,
         CancellationToken cancellationToken = default
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/RepositoryAsyncExtensions.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/RepositoryAsyncExtensions.cs
index 304f9ea0bd..2115d00200 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/RepositoryAsyncExtensions.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/RepositoryAsyncExtensions.cs
@@ -120,7 +120,7 @@ public static class RepositoryAsyncExtensions
         return await repository.AsyncExecuter.FirstAsync(queryable, predicate, cancellationToken);
     }
 
-    public static async Task<T> FirstOrDefaultAsync<T>(
+    public static async Task<T?> FirstOrDefaultAsync<T>(
         [NotNull] this IReadOnlyRepository<T> repository,
         CancellationToken cancellationToken = default)
         where T : class, IEntity
@@ -129,7 +129,7 @@ public static class RepositoryAsyncExtensions
         return await repository.AsyncExecuter.FirstOrDefaultAsync(queryable, cancellationToken);
     }
 
-    public static async Task<T> FirstOrDefaultAsync<T>(
+    public static async Task<T?> FirstOrDefaultAsync<T>(
         [NotNull] this IReadOnlyRepository<T> repository,
         [NotNull] Expression<Func<T, bool>> predicate,
         CancellationToken cancellationToken = default)
@@ -162,7 +162,7 @@ public static class RepositoryAsyncExtensions
         return await repository.AsyncExecuter.LastAsync(queryable, predicate, cancellationToken);
     }
 
-    public static async Task<T> LastOrDefaultAsync<T>(
+    public static async Task<T?> LastOrDefaultAsync<T>(
         [NotNull] this IReadOnlyRepository<T> repository,
         CancellationToken cancellationToken = default)
         where T : class, IEntity
@@ -171,7 +171,7 @@ public static class RepositoryAsyncExtensions
         return await repository.AsyncExecuter.LastOrDefaultAsync(queryable, cancellationToken);
     }
 
-    public static async Task<T> LastOrDefaultAsync<T>(
+    public static async Task<T?> LastOrDefaultAsync<T>(
         [NotNull] this IReadOnlyRepository<T> repository,
         [NotNull] Expression<Func<T, bool>> predicate,
         CancellationToken cancellationToken = default)
@@ -204,7 +204,7 @@ public static class RepositoryAsyncExtensions
         return await repository.AsyncExecuter.SingleAsync(queryable, predicate, cancellationToken);
     }
 
-    public static async Task<T> SingleOrDefaultAsync<T>(
+    public static async Task<T?> SingleOrDefaultAsync<T>(
         [NotNull] this IReadOnlyRepository<T> repository,
         CancellationToken cancellationToken = default)
         where T : class, IEntity
@@ -213,7 +213,7 @@ public static class RepositoryAsyncExtensions
         return await repository.AsyncExecuter.SingleOrDefaultAsync(queryable, cancellationToken);
     }
 
-    public static async Task<T> SingleOrDefaultAsync<T>(
+    public static async Task<T?> SingleOrDefaultAsync<T>(
         [NotNull] this IReadOnlyRepository<T> repository,
         [NotNull] Expression<Func<T, bool>> predicate,
         CancellationToken cancellationToken = default)
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/RepositoryBase.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/RepositoryBase.cs
index d843584fc4..eb2457f8c8 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/RepositoryBase.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/RepositoryBase.cs
@@ -41,7 +41,7 @@ public abstract class RepositoryBase<TEntity> : BasicRepositoryBase<TEntity>, IR
 
     public abstract Task<IQueryable<TEntity>> GetQueryableAsync();
 
-    public abstract Task<TEntity> FindAsync(
+    public abstract Task<TEntity?> FindAsync(
         Expression<Func<TEntity, bool>> predicate,
         bool includeDetails = true,
         CancellationToken cancellationToken = default);
@@ -76,13 +76,13 @@ public abstract class RepositoryBase<TEntity> : BasicRepositoryBase<TEntity>, IR
     {
         if (typeof(ISoftDelete).IsAssignableFrom(typeof(TOtherEntity)))
         {
-            query = (TQueryable)query.WhereIf(DataFilter.IsEnabled<ISoftDelete>(), e => ((ISoftDelete)e).IsDeleted == false);
+            query = (TQueryable)query.WhereIf(DataFilter.IsEnabled<ISoftDelete>(), e => ((ISoftDelete)e!).IsDeleted == false);
         }
 
         if (typeof(IMultiTenant).IsAssignableFrom(typeof(TOtherEntity)))
         {
             var tenantId = CurrentTenant.Id;
-            query = (TQueryable)query.WhereIf(DataFilter.IsEnabled<IMultiTenant>(), e => ((IMultiTenant)e).TenantId == tenantId);
+            query = (TQueryable)query.WhereIf(DataFilter.IsEnabled<IMultiTenant>(), e => ((IMultiTenant)e!).TenantId == tenantId);
         }
 
         return query;
@@ -94,7 +94,7 @@ public abstract class RepositoryBase<TEntity, TKey> : RepositoryBase<TEntity>, I
 {
     public abstract Task<TEntity> GetAsync(TKey id, bool includeDetails = true, CancellationToken cancellationToken = default);
 
-    public abstract Task<TEntity> FindAsync(TKey id, bool includeDetails = true, CancellationToken cancellationToken = default);
+    public abstract Task<TEntity?> FindAsync(TKey id, bool includeDetails = true, CancellationToken cancellationToken = default);
 
     public virtual async Task DeleteAsync(TKey id, bool autoSave = false, CancellationToken cancellationToken = default)
     {
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/RepositoryExtensions.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/RepositoryExtensions.cs
index 379203f46a..cbebf62196 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/RepositoryExtensions.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/RepositoryExtensions.cs
@@ -54,7 +54,7 @@ public static class RepositoryExtensions
     )
        where TEntity : class, IEntity<TKey>
     {
-        if (!await repository.AnyAsync(x => x.Id.Equals(id), cancellationToken))
+        if (!await repository.AnyAsync(x => x.Id!.Equals(id), cancellationToken))
         {
             throw new EntityNotFoundException(typeof(TEntity), id);
         }
@@ -87,7 +87,7 @@ public static class RepositoryExtensions
         {
             using (var uow = uowManager.Begin())
             {
-                await HardDeleteWithUnitOfWorkAsync(repository, predicate, autoSave, cancellationToken, uowManager.Current);
+                await HardDeleteWithUnitOfWorkAsync(repository, predicate, autoSave, cancellationToken, uowManager.Current!);
                 await uow.CompleteAsync(cancellationToken);
             }
         }
@@ -111,7 +111,7 @@ public static class RepositoryExtensions
         {
             using (var uow = uowManager.Begin())
             {
-                await HardDeleteWithUnitOfWorkAsync(repository, entities, autoSave, cancellationToken, uowManager.Current);
+                await HardDeleteWithUnitOfWorkAsync(repository, entities, autoSave, cancellationToken, uowManager.Current!);
                 await uow.CompleteAsync(cancellationToken);
             }
         }
@@ -135,7 +135,7 @@ public static class RepositoryExtensions
         {
             using (var uow = uowManager.Begin())
             {
-                await HardDeleteWithUnitOfWorkAsync(repository, entity, autoSave, cancellationToken, uowManager.Current);
+                await HardDeleteWithUnitOfWorkAsync(repository, entity, autoSave, cancellationToken, uowManager.Current!);
                 await uow.CompleteAsync(cancellationToken);
             }
         }
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/RepositoryRegistrarBase.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/RepositoryRegistrarBase.cs
index 320aed8312..d162f2ffea 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/RepositoryRegistrarBase.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Repositories/RepositoryRegistrarBase.cs
@@ -75,12 +75,12 @@ public abstract class RepositoryRegistrarBase<TOptions>
         if (primaryKeyType == null)
         {
             return Options.SpecifiedDefaultRepositoryTypes
-                ? Options.DefaultRepositoryImplementationTypeWithoutKey.MakeGenericType(entityType)
+                ? Options.DefaultRepositoryImplementationTypeWithoutKey!.MakeGenericType(entityType)
                 : GetRepositoryType(Options.DefaultRepositoryDbContextType, entityType);
         }
 
         return Options.SpecifiedDefaultRepositoryTypes
-            ? Options.DefaultRepositoryImplementationType.MakeGenericType(entityType, primaryKeyType)
+            ? Options.DefaultRepositoryImplementationType!.MakeGenericType(entityType, primaryKeyType)
             : GetRepositoryType(Options.DefaultRepositoryDbContextType, entityType, primaryKeyType);
     }
 
diff --git a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Services/DomainService.cs b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Services/DomainService.cs
index 32cf42409c..b36b32eafd 100644
--- a/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Services/DomainService.cs
+++ b/framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Services/DomainService.cs
@@ -11,10 +11,10 @@ namespace Volo.Abp.Domain.Services;
 
 public abstract class DomainService : IDomainService
 {
-    public IAbpLazyServiceProvider LazyServiceProvider { get; set; }
+    public IAbpLazyServiceProvider LazyServiceProvider { get; set; } = default!;
 
     [Obsolete("Use LazyServiceProvider instead.")]
-    public IServiceProvider ServiceProvider { get; set; }
+    public IServiceProvider ServiceProvider { get; set; } = default!;
 
     protected IClock Clock => LazyServiceProvider.LazyGetRequiredService<IClock>();
 
@@ -26,5 +26,5 @@ public abstract class DomainService : IDomainService
 
     protected IAsyncQueryableExecuter AsyncExecuter => LazyServiceProvider.LazyGetRequiredService<IAsyncQueryableExecuter>();
 
-    protected ILogger Logger => LazyServiceProvider.LazyGetService<ILogger>(provider => LoggerFactory?.CreateLogger(GetType().FullName) ?? NullLogger.Instance);
+    protected ILogger Logger => LazyServiceProvider.LazyGetService<ILogger>(provider => LoggerFactory?.CreateLogger(GetType().FullName!) ?? NullLogger.Instance);
 }
diff --git a/framework/src/Volo.Abp.DistributedLocking.Abstractions/Volo.Abp.DistributedLocking.Abstractions.csproj b/framework/src/Volo.Abp.DistributedLocking.Abstractions/Volo.Abp.DistributedLocking.Abstractions.csproj
index 7e01d295e7..e53f5b718c 100644
--- a/framework/src/Volo.Abp.DistributedLocking.Abstractions/Volo.Abp.DistributedLocking.Abstractions.csproj
+++ b/framework/src/Volo.Abp.DistributedLocking.Abstractions/Volo.Abp.DistributedLocking.Abstractions.csproj
@@ -5,6 +5,8 @@
 
     <PropertyGroup>
         <TargetFrameworks>netstandard2.0;netstandard2.1;net7.0</TargetFrameworks>
+        <Nullable>enable</Nullable>
+        <WarningsAsErrors>Nullable</WarningsAsErrors>
         <AssemblyName>Volo.Abp.DistributedLocking.Abstractions</AssemblyName>
         <PackageId>Volo.Abp.DistributedLocking.Abstractions</PackageId>
         <AssetTargetFallback>$(AssetTargetFallback);portable-net45+win8+wp8+wpa81;</AssetTargetFallback>
diff --git a/framework/src/Volo.Abp.DistributedLocking.Abstractions/Volo/Abp/DistributedLocking/IAbpDistributedLock.cs b/framework/src/Volo.Abp.DistributedLocking.Abstractions/Volo/Abp/DistributedLocking/IAbpDistributedLock.cs
index 754ae807f8..1d1b5e01db 100644
--- a/framework/src/Volo.Abp.DistributedLocking.Abstractions/Volo/Abp/DistributedLocking/IAbpDistributedLock.cs
+++ b/framework/src/Volo.Abp.DistributedLocking.Abstractions/Volo/Abp/DistributedLocking/IAbpDistributedLock.cs
@@ -16,8 +16,7 @@ public interface IAbpDistributedLock
     /// <param name="name">The name of the lock</param>
     /// <param name="timeout">How long to wait before giving up on the acquisition attempt. Defaults to 0</param>
     /// <param name="cancellationToken">Cancellation token</param>
-    [ItemCanBeNull]
-    Task<IAbpDistributedLockHandle> TryAcquireAsync(
+    Task<IAbpDistributedLockHandle?> TryAcquireAsync(
         [NotNull] string name,
         TimeSpan timeout = default,
         CancellationToken cancellationToken = default
diff --git a/framework/src/Volo.Abp.DistributedLocking.Abstractions/Volo/Abp/DistributedLocking/LocalAbpDistributedLock.cs b/framework/src/Volo.Abp.DistributedLocking.Abstractions/Volo/Abp/DistributedLocking/LocalAbpDistributedLock.cs
index 490f024d36..58d67e1caf 100644
--- a/framework/src/Volo.Abp.DistributedLocking.Abstractions/Volo/Abp/DistributedLocking/LocalAbpDistributedLock.cs
+++ b/framework/src/Volo.Abp.DistributedLocking.Abstractions/Volo/Abp/DistributedLocking/LocalAbpDistributedLock.cs
@@ -22,7 +22,7 @@ public class LocalAbpDistributedLock : IAbpDistributedLock, ISingletonDependency
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public async Task<IAbpDistributedLockHandle> TryAcquireAsync(
+    public async Task<IAbpDistributedLockHandle?> TryAcquireAsync(
         string name,
         TimeSpan timeout = default,
         CancellationToken cancellationToken = default)
diff --git a/framework/src/Volo.Abp.DistributedLocking.Dapr/Volo.Abp.DistributedLocking.Dapr.csproj b/framework/src/Volo.Abp.DistributedLocking.Dapr/Volo.Abp.DistributedLocking.Dapr.csproj
index 79d39eedf0..a0ddaac22e 100644
--- a/framework/src/Volo.Abp.DistributedLocking.Dapr/Volo.Abp.DistributedLocking.Dapr.csproj
+++ b/framework/src/Volo.Abp.DistributedLocking.Dapr/Volo.Abp.DistributedLocking.Dapr.csproj
@@ -5,6 +5,8 @@
 
     <PropertyGroup>
         <TargetFramework>net7.0</TargetFramework>
+        <Nullable>enable</Nullable>
+        <WarningsAsErrors>Nullable</WarningsAsErrors>
         <RootNamespace />
     </PropertyGroup>
 
diff --git a/framework/src/Volo.Abp.DistributedLocking.Dapr/Volo/Abp/DistributedLocking/Dapr/AbpDistributedLockDaprOptions.cs b/framework/src/Volo.Abp.DistributedLocking.Dapr/Volo/Abp/DistributedLocking/Dapr/AbpDistributedLockDaprOptions.cs
index a51ed8ede7..b4572441d3 100644
--- a/framework/src/Volo.Abp.DistributedLocking.Dapr/Volo/Abp/DistributedLocking/Dapr/AbpDistributedLockDaprOptions.cs
+++ b/framework/src/Volo.Abp.DistributedLocking.Dapr/Volo/Abp/DistributedLocking/Dapr/AbpDistributedLockDaprOptions.cs
@@ -4,7 +4,7 @@ namespace Volo.Abp.DistributedLocking.Dapr;
 
 public class AbpDistributedLockDaprOptions
 {
-    public string StoreName { get; set; }
+    public string StoreName { get; set; } = default!;
 
     public string? Owner { get; set; }
 
diff --git a/framework/src/Volo.Abp.DistributedLocking.Dapr/Volo/Abp/DistributedLocking/Dapr/DaprAbpDistributedLock.cs b/framework/src/Volo.Abp.DistributedLocking.Dapr/Volo/Abp/DistributedLocking/Dapr/DaprAbpDistributedLock.cs
index 974c6461a6..100fece989 100644
--- a/framework/src/Volo.Abp.DistributedLocking.Dapr/Volo/Abp/DistributedLocking/Dapr/DaprAbpDistributedLock.cs
+++ b/framework/src/Volo.Abp.DistributedLocking.Dapr/Volo/Abp/DistributedLocking/Dapr/DaprAbpDistributedLock.cs
@@ -24,7 +24,7 @@ public class DaprAbpDistributedLock : IAbpDistributedLock, ITransientDependency
         DistributedLockDaprOptions = distributedLockDaprOptions.Value;
     }
 
-    public async Task<IAbpDistributedLockHandle> TryAcquireAsync(
+    public async Task<IAbpDistributedLockHandle?> TryAcquireAsync(
         string name,
         TimeSpan timeout = default,
         CancellationToken cancellationToken = default)
diff --git a/framework/src/Volo.Abp.DistributedLocking/Volo.Abp.DistributedLocking.csproj b/framework/src/Volo.Abp.DistributedLocking/Volo.Abp.DistributedLocking.csproj
index ae9f960917..8abd0873bd 100644
--- a/framework/src/Volo.Abp.DistributedLocking/Volo.Abp.DistributedLocking.csproj
+++ b/framework/src/Volo.Abp.DistributedLocking/Volo.Abp.DistributedLocking.csproj
@@ -5,6 +5,8 @@
 
     <PropertyGroup>
         <TargetFrameworks>netstandard2.0;netstandard2.1;net7.0</TargetFrameworks>
+        <Nullable>enable</Nullable>
+        <WarningsAsErrors>Nullable</WarningsAsErrors>
         <AssemblyName>Volo.Abp.DistributedLocking</AssemblyName>
         <PackageId>Volo.Abp.DistributedLocking</PackageId>
         <AssetTargetFallback>$(AssetTargetFallback);portable-net45+win8+wp8+wpa81;</AssetTargetFallback>
diff --git a/framework/src/Volo.Abp.DistributedLocking/Volo/Abp/DistributedLocking/MedallionAbpDistributedLock.cs b/framework/src/Volo.Abp.DistributedLocking/Volo/Abp/DistributedLocking/MedallionAbpDistributedLock.cs
index 0defc5a75f..2d9d07b45a 100644
--- a/framework/src/Volo.Abp.DistributedLocking/Volo/Abp/DistributedLocking/MedallionAbpDistributedLock.cs
+++ b/framework/src/Volo.Abp.DistributedLocking/Volo/Abp/DistributedLocking/MedallionAbpDistributedLock.cs
@@ -25,7 +25,7 @@ public class MedallionAbpDistributedLock : IAbpDistributedLock, ITransientDepend
         DistributedLockKeyNormalizer = distributedLockKeyNormalizer;
     }
 
-    public async Task<IAbpDistributedLockHandle> TryAcquireAsync(
+    public async Task<IAbpDistributedLockHandle?> TryAcquireAsync(
         string name,
         TimeSpan timeout = default,
         CancellationToken cancellationToken = default)
diff --git a/framework/src/Volo.Abp.Threading/Volo/Abp/Linq/AsyncQueryableExecuter.cs b/framework/src/Volo.Abp.Threading/Volo/Abp/Linq/AsyncQueryableExecuter.cs
index 108d3bb595..a6b9fb7949 100644
--- a/framework/src/Volo.Abp.Threading/Volo/Abp/Linq/AsyncQueryableExecuter.cs
+++ b/framework/src/Volo.Abp.Threading/Volo/Abp/Linq/AsyncQueryableExecuter.cs
@@ -209,7 +209,7 @@ public class AsyncQueryableExecuter : IAsyncQueryableExecuter, ISingletonDepende
         return Task.FromResult(queryable.SingleOrDefault(predicate))!;
     }
 
-    public Task<T?> MinAsync<T>(IQueryable<T> queryable, CancellationToken cancellationToken = default)
+    public Task<T> MinAsync<T>(IQueryable<T> queryable, CancellationToken cancellationToken = default)
     {
         var provider = FindProvider(queryable);
         
@@ -221,7 +221,7 @@ public class AsyncQueryableExecuter : IAsyncQueryableExecuter, ISingletonDepende
         return Task.FromResult(queryable.Min())!;
     }
 
-    public Task<TResult?> MinAsync<T, TResult>(IQueryable<T> queryable, Expression<Func<T, TResult>> selector, CancellationToken cancellationToken = default)
+    public Task<TResult> MinAsync<T, TResult>(IQueryable<T> queryable, Expression<Func<T, TResult>> selector, CancellationToken cancellationToken = default)
     {
         var provider = FindProvider(queryable);
         
@@ -233,7 +233,7 @@ public class AsyncQueryableExecuter : IAsyncQueryableExecuter, ISingletonDepende
         return Task.FromResult(queryable.Min(selector))!;
     }
 
-    public Task<T?> MaxAsync<T>(IQueryable<T> queryable, CancellationToken cancellationToken = default)
+    public Task<T> MaxAsync<T>(IQueryable<T> queryable, CancellationToken cancellationToken = default)
     {
         var provider = FindProvider(queryable);
         
@@ -245,7 +245,7 @@ public class AsyncQueryableExecuter : IAsyncQueryableExecuter, ISingletonDepende
         return Task.FromResult(queryable.Max())!;
     }
 
-    public Task<TResult?> MaxAsync<T, TResult>(IQueryable<T> queryable, Expression<Func<T, TResult>> selector, CancellationToken cancellationToken = default)
+    public Task<TResult> MaxAsync<T, TResult>(IQueryable<T> queryable, Expression<Func<T, TResult>> selector, CancellationToken cancellationToken = default)
     {
         var provider = FindProvider(queryable);
         
diff --git a/framework/src/Volo.Abp.Threading/Volo/Abp/Linq/IAsyncQueryableExecuter.cs b/framework/src/Volo.Abp.Threading/Volo/Abp/Linq/IAsyncQueryableExecuter.cs
index 2bea6c4604..4ee0666f4c 100644
--- a/framework/src/Volo.Abp.Threading/Volo/Abp/Linq/IAsyncQueryableExecuter.cs
+++ b/framework/src/Volo.Abp.Threading/Volo/Abp/Linq/IAsyncQueryableExecuter.cs
@@ -137,12 +137,12 @@ public interface IAsyncQueryableExecuter
 
     #region Min
 
-    Task<T?> MinAsync<T>(
+    Task<T> MinAsync<T>(
         [NotNull] IQueryable<T> queryable,
         CancellationToken cancellationToken = default);
 
 
-    Task<TResult?> MinAsync<T, TResult>(
+    Task<TResult> MinAsync<T, TResult>(
         [NotNull] IQueryable<T> queryable,
         [NotNull] Expression<Func<T, TResult>> selector,
         CancellationToken cancellationToken = default);
@@ -151,12 +151,12 @@ public interface IAsyncQueryableExecuter
 
     #region Max
 
-    Task<T?> MaxAsync<T>(
+    Task<T> MaxAsync<T>(
         [NotNull] IQueryable<T> queryable,
         CancellationToken cancellationToken = default);
 
 
-    Task<TResult?> MaxAsync<T, TResult>(
+    Task<TResult> MaxAsync<T, TResult>(
         [NotNull] IQueryable<T> queryable,
         [NotNull] Expression<Func<T, TResult>> selector,
         CancellationToken cancellationToken = default);
diff --git a/framework/src/Volo.Abp.Threading/Volo/Abp/Linq/IAsyncQueryableProvider.cs b/framework/src/Volo.Abp.Threading/Volo/Abp/Linq/IAsyncQueryableProvider.cs
index 3f38553ac5..3239fde6d6 100644
--- a/framework/src/Volo.Abp.Threading/Volo/Abp/Linq/IAsyncQueryableProvider.cs
+++ b/framework/src/Volo.Abp.Threading/Volo/Abp/Linq/IAsyncQueryableProvider.cs
@@ -139,12 +139,12 @@ public interface IAsyncQueryableProvider
 
     #region Min
 
-    Task<T?> MinAsync<T>(
+    Task<T> MinAsync<T>(
         [NotNull] IQueryable<T> queryable,
         CancellationToken cancellationToken = default);
 
 
-    Task<TResult?> MinAsync<T, TResult>(
+    Task<TResult> MinAsync<T, TResult>(
         [NotNull] IQueryable<T> queryable,
         [NotNull] Expression<Func<T, TResult>> selector,
         CancellationToken cancellationToken = default);
@@ -153,12 +153,12 @@ public interface IAsyncQueryableProvider
 
     #region Max
 
-    Task<T?> MaxAsync<T>(
+    Task<T> MaxAsync<T>(
         [NotNull] IQueryable<T> queryable,
         CancellationToken cancellationToken = default);
 
 
-    Task<TResult?> MaxAsync<T, TResult>(
+    Task<TResult> MaxAsync<T, TResult>(
         [NotNull] IQueryable<T> queryable,
         [NotNull] Expression<Func<T, TResult>> selector,
         CancellationToken cancellationToken = default);