diff --git a/framework/src/Volo.Abp.Http.Abstractions/Volo.Abp.Http.Abstractions.csproj b/framework/src/Volo.Abp.Http.Abstractions/Volo.Abp.Http.Abstractions.csproj
index 332c803147..adbc783c15 100644
--- a/framework/src/Volo.Abp.Http.Abstractions/Volo.Abp.Http.Abstractions.csproj
+++ b/framework/src/Volo.Abp.Http.Abstractions/Volo.Abp.Http.Abstractions.csproj
@@ -5,6 +5,8 @@
 
   <PropertyGroup>
     <TargetFrameworks>netstandard2.0;netstandard2.1;net7.0</TargetFrameworks>
+    <Nullable>enable</Nullable>
+    <WarningsAsErrors>Nullable</WarningsAsErrors>
     <AssemblyName>Volo.Abp.Http.Abstractions</AssemblyName>
     <PackageId>Volo.Abp.Http.Abstractions</PackageId>
     <AssetTargetFallback>$(AssetTargetFallback);portable-net45+win8+wp8+wpa81;</AssetTargetFallback>
diff --git a/framework/src/Volo.Abp.Http.Abstractions/Volo/Abp/Http/ClientProxyExceptionEventData.cs b/framework/src/Volo.Abp.Http.Abstractions/Volo/Abp/Http/ClientProxyExceptionEventData.cs
index 1bc17c7b65..029556c00e 100644
--- a/framework/src/Volo.Abp.Http.Abstractions/Volo/Abp/Http/ClientProxyExceptionEventData.cs
+++ b/framework/src/Volo.Abp.Http.Abstractions/Volo/Abp/Http/ClientProxyExceptionEventData.cs
@@ -4,5 +4,5 @@ public class ClientProxyExceptionEventData
 {
     public int? StatusCode { get; set; }
 
-    public string ReasonPhrase { get; set; }
+    public string? ReasonPhrase { get; set; }
 }
diff --git a/framework/src/Volo.Abp.Http.Client.Dapr/Volo.Abp.Http.Client.Dapr.csproj b/framework/src/Volo.Abp.Http.Client.Dapr/Volo.Abp.Http.Client.Dapr.csproj
index 0d22e68b97..1fd0b7b07b 100644
--- a/framework/src/Volo.Abp.Http.Client.Dapr/Volo.Abp.Http.Client.Dapr.csproj
+++ b/framework/src/Volo.Abp.Http.Client.Dapr/Volo.Abp.Http.Client.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.Http.Client.Dapr/Volo/Abp/Http/Client/Dapr/AbpInvocationHandler.cs b/framework/src/Volo.Abp.Http.Client.Dapr/Volo/Abp/Http/Client/Dapr/AbpInvocationHandler.cs
index 9ebfb5665d..4a17c3b67a 100644
--- a/framework/src/Volo.Abp.Http.Client.Dapr/Volo/Abp/Http/Client/Dapr/AbpInvocationHandler.cs
+++ b/framework/src/Volo.Abp.Http.Client.Dapr/Volo/Abp/Http/Client/Dapr/AbpInvocationHandler.cs
@@ -12,7 +12,7 @@ public class AbpInvocationHandler : InvocationHandler, ITransientDependency
     {
         if (!daprOptions.Value.HttpEndpoint.IsNullOrWhiteSpace())
         {
-            DaprEndpoint = daprOptions.Value.HttpEndpoint;
+            DaprEndpoint = daprOptions.Value.HttpEndpoint!;
         }
     }
 }
diff --git a/framework/src/Volo.Abp.Http.Client.IdentityModel.MauiBlazor/Volo.Abp.Http.Client.IdentityModel.MauiBlazor.csproj b/framework/src/Volo.Abp.Http.Client.IdentityModel.MauiBlazor/Volo.Abp.Http.Client.IdentityModel.MauiBlazor.csproj
index 671fd3db2d..4a92cc975d 100644
--- a/framework/src/Volo.Abp.Http.Client.IdentityModel.MauiBlazor/Volo.Abp.Http.Client.IdentityModel.MauiBlazor.csproj
+++ b/framework/src/Volo.Abp.Http.Client.IdentityModel.MauiBlazor/Volo.Abp.Http.Client.IdentityModel.MauiBlazor.csproj
@@ -5,6 +5,8 @@
 
     <PropertyGroup>
         <TargetFramework>net7.0</TargetFramework>
+        <Nullable>enable</Nullable>
+        <WarningsAsErrors>Nullable</WarningsAsErrors>
         <PackageId>Volo.Abp.Http.Client.IdentityModel.MauiBlazor</PackageId>
         <AssetTargetFallback>$(AssetTargetFallback);portable-net45+win8+wp8+wpa81;</AssetTargetFallback>
         <GenerateAssemblyConfigurationAttribute>false</GenerateAssemblyConfigurationAttribute>
diff --git a/framework/src/Volo.Abp.Http.Client.IdentityModel.MauiBlazor/Volo/Abp/Http/Client/IdentityModel/MauiBlazor/MauiBlazorAbpAccessTokenProvider.cs b/framework/src/Volo.Abp.Http.Client.IdentityModel.MauiBlazor/Volo/Abp/Http/Client/IdentityModel/MauiBlazor/MauiBlazorAbpAccessTokenProvider.cs
index 8afbcbafed..3f923aa9bb 100644
--- a/framework/src/Volo.Abp.Http.Client.IdentityModel.MauiBlazor/Volo/Abp/Http/Client/IdentityModel/MauiBlazor/MauiBlazorAbpAccessTokenProvider.cs
+++ b/framework/src/Volo.Abp.Http.Client.IdentityModel.MauiBlazor/Volo/Abp/Http/Client/IdentityModel/MauiBlazor/MauiBlazorAbpAccessTokenProvider.cs
@@ -7,7 +7,7 @@ namespace Volo.Abp.Http.Client.IdentityModel.MauiBlazor;
 [Dependency(ReplaceServices = true)]
 public class MauiBlazorAbpAccessTokenProvider : IAbpAccessTokenProvider, ITransientDependency
 {
-    public virtual Task<string> GetTokenAsync()
+    public virtual Task<string?> GetTokenAsync()
     {
         return Task.FromResult(null as string);
     }
diff --git a/framework/src/Volo.Abp.Http.Client.IdentityModel.Web/Volo.Abp.Http.Client.IdentityModel.Web.csproj b/framework/src/Volo.Abp.Http.Client.IdentityModel.Web/Volo.Abp.Http.Client.IdentityModel.Web.csproj
index 4fc1525e59..05d1a14ef8 100644
--- a/framework/src/Volo.Abp.Http.Client.IdentityModel.Web/Volo.Abp.Http.Client.IdentityModel.Web.csproj
+++ b/framework/src/Volo.Abp.Http.Client.IdentityModel.Web/Volo.Abp.Http.Client.IdentityModel.Web.csproj
@@ -5,6 +5,8 @@
 
   <PropertyGroup>
     <TargetFramework>net7.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <WarningsAsErrors>Nullable</WarningsAsErrors>
     <AssemblyName>Volo.Abp.Http.Client.IdentityModel.Web</AssemblyName>
     <PackageId>Volo.Abp.Http.Client.IdentityModel.Web</PackageId>
     <AssetTargetFallback>$(AssetTargetFallback);portable-net45+win8+wp8+wpa81;</AssetTargetFallback>
diff --git a/framework/src/Volo.Abp.Http.Client.IdentityModel.Web/Volo/Abp/Http/Client/IdentityModel/Web/HttpContextAbpAccessTokenProvider.cs b/framework/src/Volo.Abp.Http.Client.IdentityModel.Web/Volo/Abp/Http/Client/IdentityModel/Web/HttpContextAbpAccessTokenProvider.cs
index 97d88bd3b0..5044513438 100644
--- a/framework/src/Volo.Abp.Http.Client.IdentityModel.Web/Volo/Abp/Http/Client/IdentityModel/Web/HttpContextAbpAccessTokenProvider.cs
+++ b/framework/src/Volo.Abp.Http.Client.IdentityModel.Web/Volo/Abp/Http/Client/IdentityModel/Web/HttpContextAbpAccessTokenProvider.cs
@@ -16,7 +16,7 @@ public class HttpContextAbpAccessTokenProvider : IAbpAccessTokenProvider, ITrans
         HttpContextAccessor = httpContextAccessor;
     }
 
-    public virtual async Task<string> GetTokenAsync()
+    public virtual async Task<string?> GetTokenAsync()
     {
         var httpContext = HttpContextAccessor?.HttpContext;
         if (httpContext == null)
diff --git a/framework/src/Volo.Abp.Http.Client.IdentityModel.WebAssembly/Volo.Abp.Http.Client.IdentityModel.WebAssembly.csproj b/framework/src/Volo.Abp.Http.Client.IdentityModel.WebAssembly/Volo.Abp.Http.Client.IdentityModel.WebAssembly.csproj
index e98f5d92ff..42d60909bc 100644
--- a/framework/src/Volo.Abp.Http.Client.IdentityModel.WebAssembly/Volo.Abp.Http.Client.IdentityModel.WebAssembly.csproj
+++ b/framework/src/Volo.Abp.Http.Client.IdentityModel.WebAssembly/Volo.Abp.Http.Client.IdentityModel.WebAssembly.csproj
@@ -5,6 +5,8 @@
 
     <PropertyGroup>
         <TargetFramework>net7.0</TargetFramework>
+        <Nullable>enable</Nullable>
+        <WarningsAsErrors>Nullable</WarningsAsErrors>
         <AssemblyName>Volo.Abp.Http.Client.IdentityModel.WebAssembly</AssemblyName>
         <PackageId>Volo.Abp.Http.Client.IdentityModel.WebAssembly</PackageId>
         <AssetTargetFallback>$(AssetTargetFallback);portable-net45+win8+wp8+wpa81;</AssetTargetFallback>
diff --git a/framework/src/Volo.Abp.Http.Client.IdentityModel.WebAssembly/Volo/Abp/Http/Client/IdentityModel/WebAssembly/WebAssemblyAbpAccessTokenProvider.cs b/framework/src/Volo.Abp.Http.Client.IdentityModel.WebAssembly/Volo/Abp/Http/Client/IdentityModel/WebAssembly/WebAssemblyAbpAccessTokenProvider.cs
index d0a68cdb7c..137787820b 100644
--- a/framework/src/Volo.Abp.Http.Client.IdentityModel.WebAssembly/Volo/Abp/Http/Client/IdentityModel/WebAssembly/WebAssemblyAbpAccessTokenProvider.cs
+++ b/framework/src/Volo.Abp.Http.Client.IdentityModel.WebAssembly/Volo/Abp/Http/Client/IdentityModel/WebAssembly/WebAssemblyAbpAccessTokenProvider.cs
@@ -8,14 +8,14 @@ namespace Volo.Abp.Http.Client.IdentityModel.WebAssembly;
 [Dependency(ReplaceServices = true)]
 public class WebAssemblyAbpAccessTokenProvider : IAbpAccessTokenProvider, ITransientDependency
 {
-    protected IAccessTokenProvider AccessTokenProvider { get; }
+    protected IAccessTokenProvider? AccessTokenProvider { get; }
 
     public WebAssemblyAbpAccessTokenProvider(IAccessTokenProvider accessTokenProvider)
     {
         AccessTokenProvider = accessTokenProvider;
     }
 
-    public virtual async Task<string> GetTokenAsync()
+    public virtual async Task<string?> GetTokenAsync()
     {
         if (AccessTokenProvider == null)
         {
diff --git a/framework/src/Volo.Abp.Http.Client.IdentityModel/Volo.Abp.Http.Client.IdentityModel.csproj b/framework/src/Volo.Abp.Http.Client.IdentityModel/Volo.Abp.Http.Client.IdentityModel.csproj
index 083e987d49..3e791a1e69 100644
--- a/framework/src/Volo.Abp.Http.Client.IdentityModel/Volo.Abp.Http.Client.IdentityModel.csproj
+++ b/framework/src/Volo.Abp.Http.Client.IdentityModel/Volo.Abp.Http.Client.IdentityModel.csproj
@@ -5,6 +5,8 @@
 
   <PropertyGroup>
     <TargetFrameworks>netstandard2.0;netstandard2.1;net7.0</TargetFrameworks>
+    <Nullable>enable</Nullable>
+    <WarningsAsErrors>Nullable</WarningsAsErrors>
     <AssemblyName>Volo.Abp.Http.Client.IdentityModel</AssemblyName>
     <PackageId>Volo.Abp.Http.Client.IdentityModel</PackageId>
     <AssetTargetFallback>$(AssetTargetFallback);portable-net45+win8+wp8+wpa81;</AssetTargetFallback>
diff --git a/framework/src/Volo.Abp.Http.Client.IdentityModel/Volo/Abp/Http/Client/RemoteServiceConfigurationExtensions.cs b/framework/src/Volo.Abp.Http.Client.IdentityModel/Volo/Abp/Http/Client/RemoteServiceConfigurationExtensions.cs
index 417875619b..58c4b71078 100644
--- a/framework/src/Volo.Abp.Http.Client.IdentityModel/Volo/Abp/Http/Client/RemoteServiceConfigurationExtensions.cs
+++ b/framework/src/Volo.Abp.Http.Client.IdentityModel/Volo/Abp/Http/Client/RemoteServiceConfigurationExtensions.cs
@@ -8,8 +8,7 @@ public static class RemoteServiceConfigurationExtensions
     public const string IdentityClientName = "IdentityClient";
     public const string UseCurrentAccessTokenName = "UseCurrentAccessToken";
 
-    [CanBeNull]
-    public static string GetIdentityClient([NotNull] this RemoteServiceConfiguration configuration)
+    public static string? GetIdentityClient([NotNull] this RemoteServiceConfiguration configuration)
     {
         Check.NotNullOrEmpty(configuration, nameof(configuration));
 
diff --git a/framework/src/Volo.Abp.Http.Client.Web/Volo.Abp.Http.Client.Web.csproj b/framework/src/Volo.Abp.Http.Client.Web/Volo.Abp.Http.Client.Web.csproj
index 68bbbd1157..63da778ecd 100644
--- a/framework/src/Volo.Abp.Http.Client.Web/Volo.Abp.Http.Client.Web.csproj
+++ b/framework/src/Volo.Abp.Http.Client.Web/Volo.Abp.Http.Client.Web.csproj
@@ -5,6 +5,8 @@
 
     <PropertyGroup>
         <TargetFramework>net7.0</TargetFramework>
+        <Nullable>enable</Nullable>
+        <WarningsAsErrors>Nullable</WarningsAsErrors>
         <AssemblyName>Volo.Abp.Http.Client.Web</AssemblyName>
         <PackageId>Volo.Abp.Http.Client.Web</PackageId>
         <AssetTargetFallback>$(AssetTargetFallback);portable-net45+win8+wp8+wpa81;</AssetTargetFallback>
diff --git a/framework/src/Volo.Abp.Http.Client.Web/Volo/Abp/Http/Client/Web/Conventions/AbpHttpClientProxyServiceConvention.cs b/framework/src/Volo.Abp.Http.Client.Web/Volo/Abp/Http/Client/Web/Conventions/AbpHttpClientProxyServiceConvention.cs
index 49080939c2..a7a2aad343 100644
--- a/framework/src/Volo.Abp.Http.Client.Web/Volo/Abp/Http/Client/Web/Conventions/AbpHttpClientProxyServiceConvention.cs
+++ b/framework/src/Volo.Abp.Http.Client.Web/Volo/Abp/Http/Client/Web/Conventions/AbpHttpClientProxyServiceConvention.cs
@@ -69,7 +69,7 @@ public class AbpHttpClientProxyServiceConvention : AbpServiceConvention
             if (controllerApiDescription != null &&
                 !controllerApiDescription.ControllerGroupName.IsNullOrWhiteSpace())
             {
-                controller.ControllerName = controllerApiDescription.ControllerGroupName;
+                controller.ControllerName = controllerApiDescription.ControllerGroupName!;
             }
 
             ConfigureClientProxySelector(controller);
@@ -115,7 +115,7 @@ public class AbpHttpClientProxyServiceConvention : AbpServiceConvention
         {
             var selector = controller.Selectors.FirstOrDefault();
             selector?.EndpointMetadata.Add(new AreaAttribute(moduleApiDescription.RootPath));
-            controller.RouteValues.Add(new KeyValuePair<string, string>("area", moduleApiDescription.RootPath));
+            controller.RouteValues.Add(new KeyValuePair<string, string?>("area", moduleApiDescription.RootPath));
         }
 
         var controllerType = controller.ControllerType.AsType();
@@ -163,7 +163,7 @@ public class AbpHttpClientProxyServiceConvention : AbpServiceConvention
                 var abpServiceSelectorModel = new SelectorModel
                 {
                     AttributeRouteModel = new AttributeRouteModel(new RouteAttribute(template: actionApiDescriptionModel.Url)),
-                    ActionConstraints = { new HttpMethodActionConstraint(new[] { actionApiDescriptionModel.HttpMethod }) }
+                    ActionConstraints = { new HttpMethodActionConstraint(new[] { actionApiDescriptionModel.HttpMethod! }) }
                 };
 
                 action.Selectors.Add(abpServiceSelectorModel);
@@ -190,7 +190,7 @@ public class AbpHttpClientProxyServiceConvention : AbpServiceConvention
 
                     if (!selector.ActionConstraints.OfType<HttpMethodActionConstraint>().Any())
                     {
-                        selector.ActionConstraints.Add(new HttpMethodActionConstraint(new[] { httpMethod }));
+                        selector.ActionConstraints.Add(new HttpMethodActionConstraint(new[] { httpMethod! }));
                     }
                 }
             }
@@ -226,7 +226,7 @@ public class AbpHttpClientProxyServiceConvention : AbpServiceConvention
         }
     }
 
-    protected virtual ModuleApiDescriptionModel FindModuleApiDescriptionModel(ControllerModel controller)
+    protected virtual ModuleApiDescriptionModel? FindModuleApiDescriptionModel(ControllerModel controller)
     {
         var appServiceType = FindAppServiceInterfaceType(controller);
         if (appServiceType == null)
@@ -246,7 +246,7 @@ public class AbpHttpClientProxyServiceConvention : AbpServiceConvention
         return null;
     }
 
-    protected virtual ControllerApiDescriptionModel FindControllerApiDescriptionModel(ControllerModel controller)
+    protected virtual ControllerApiDescriptionModel? FindControllerApiDescriptionModel(ControllerModel controller)
     {
         var appServiceType = FindAppServiceInterfaceType(controller);
         if (appServiceType == null)
@@ -266,7 +266,7 @@ public class AbpHttpClientProxyServiceConvention : AbpServiceConvention
         return null;
     }
 
-    protected virtual ActionApiDescriptionModel FindActionApiDescriptionModel(ControllerModel controller, ActionModel action)
+    protected virtual ActionApiDescriptionModel? FindActionApiDescriptionModel(ControllerModel controller, ActionModel action)
     {
         var appServiceType = FindAppServiceInterfaceType(controller);
         if (appServiceType == null)
@@ -285,7 +285,7 @@ public class AbpHttpClientProxyServiceConvention : AbpServiceConvention
             return null;
         }
 
-        if (actionApiDescriptionModel.ImplementFrom.StartsWith("Volo.Abp.Application.Services"))
+        if (actionApiDescriptionModel.ImplementFrom!.StartsWith("Volo.Abp.Application.Services"))
         {
             return actionApiDescriptionModel;
         }
@@ -298,7 +298,7 @@ public class AbpHttpClientProxyServiceConvention : AbpServiceConvention
         return null;
     }
 
-    protected virtual Type FindAppServiceInterfaceType(ControllerModel controller)
+    protected virtual Type? FindAppServiceInterfaceType(ControllerModel controller)
     {
         return controller.ControllerType.GetInterfaces()
             .FirstOrDefault(type => !type.IsGenericType &&
diff --git a/framework/src/Volo.Abp.IdentityModel/Volo.Abp.IdentityModel.csproj b/framework/src/Volo.Abp.IdentityModel/Volo.Abp.IdentityModel.csproj
index a707f58b9c..b0c2b3e567 100644
--- a/framework/src/Volo.Abp.IdentityModel/Volo.Abp.IdentityModel.csproj
+++ b/framework/src/Volo.Abp.IdentityModel/Volo.Abp.IdentityModel.csproj
@@ -5,6 +5,8 @@
 
   <PropertyGroup>
     <TargetFrameworks>netstandard2.0;netstandard2.1;net7.0</TargetFrameworks>
+    <Nullable>enable</Nullable>
+    <WarningsAsErrors>Nullable</WarningsAsErrors>
     <AssemblyName>Volo.Abp.IdentityModel</AssemblyName>
     <PackageId>Volo.Abp.IdentityModel</PackageId>
     <AssetTargetFallback>$(AssetTargetFallback);portable-net45+win8+wp8+wpa81;</AssetTargetFallback>
diff --git a/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/AbpIdentityClientOptions.cs b/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/AbpIdentityClientOptions.cs
index 364d2dc2ea..62fc21a5fa 100644
--- a/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/AbpIdentityClientOptions.cs
+++ b/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/AbpIdentityClientOptions.cs
@@ -14,7 +14,7 @@ public class AbpIdentityClientOptions
         IdentityClients = new IdentityClientConfigurationDictionary();
     }
 
-    public IdentityClientConfiguration GetClientConfiguration(ICurrentTenant currentTenant, string identityClientName = null)
+    public IdentityClientConfiguration? GetClientConfiguration(ICurrentTenant currentTenant, string? identityClientName = null)
     {
         if (identityClientName.IsNullOrWhiteSpace())
         {
@@ -35,7 +35,7 @@ public class AbpIdentityClientOptions
             }
         }
 
-        return IdentityClients.GetOrDefault(identityClientName) ??
+        return IdentityClients.GetOrDefault(identityClientName!) ??
                IdentityClients.Default;
     }
 }
diff --git a/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IIdentityModelAuthenticationService.cs b/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IIdentityModelAuthenticationService.cs
index fee1a032fb..8a5902bdbf 100644
--- a/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IIdentityModelAuthenticationService.cs
+++ b/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IIdentityModelAuthenticationService.cs
@@ -9,7 +9,7 @@ public interface IIdentityModelAuthenticationService
 {
     Task<bool> TryAuthenticateAsync(
         [NotNull] HttpClient client,
-        string identityClientName = null);
+        string? identityClientName = null);
 
     Task<string> GetAccessTokenAsync(
         IdentityClientConfiguration configuration);
diff --git a/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IdentityClientConfiguration.cs b/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IdentityClientConfiguration.cs
index 8faf3225ab..011e40b4b3 100644
--- a/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IdentityClientConfiguration.cs
+++ b/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IdentityClientConfiguration.cs
@@ -5,14 +5,14 @@ using IdentityModel;
 
 namespace Volo.Abp.IdentityModel;
 
-public class IdentityClientConfiguration : Dictionary<string, string>
+public class IdentityClientConfiguration : Dictionary<string, string?>
 {
     /// <summary>
     /// Possible values: "client_credentials" or "password".
     /// Default value: "client_credentials".
     /// </summary>
     public string GrantType {
-        get => this.GetOrDefault(nameof(GrantType));
+        get => this.GetOrDefault(nameof(GrantType))!;
         set => this[nameof(GrantType)] = value;
     }
 
@@ -20,7 +20,7 @@ public class IdentityClientConfiguration : Dictionary<string, string>
     /// Client Id.
     /// </summary>
     public string ClientId {
-        get => this.GetOrDefault(nameof(ClientId));
+        get => this.GetOrDefault(nameof(ClientId))!;
         set => this[nameof(ClientId)] = value;
     }
 
@@ -28,7 +28,7 @@ public class IdentityClientConfiguration : Dictionary<string, string>
     /// Client secret (as plain text - without hashed).
     /// </summary>
     public string ClientSecret {
-        get => this.GetOrDefault(nameof(ClientSecret));
+        get => this.GetOrDefault(nameof(ClientSecret))!;
         set => this[nameof(ClientSecret)] = value;
     }
 
@@ -36,7 +36,7 @@ public class IdentityClientConfiguration : Dictionary<string, string>
     /// User name.
     /// Valid only if <see cref="GrantType"/> is "password".
     /// </summary>
-    public string UserName {
+    public string? UserName {
         get => this.GetOrDefault(nameof(UserName));
         set => this[nameof(UserName)] = value;
     }
@@ -45,7 +45,7 @@ public class IdentityClientConfiguration : Dictionary<string, string>
     /// Password of the <see cref="UserName"/>.
     /// Valid only if <see cref="GrantType"/> is "password".
     /// </summary>
-    public string UserPassword {
+    public string? UserPassword {
         get => this.GetOrDefault(nameof(UserPassword));
         set => this[nameof(UserPassword)] = value;
     }
@@ -54,7 +54,7 @@ public class IdentityClientConfiguration : Dictionary<string, string>
     /// Authority.
     /// </summary>
     public string Authority {
-        get => this.GetOrDefault(nameof(Authority));
+        get => this.GetOrDefault(nameof(Authority))!;
         set => this[nameof(Authority)] = value;
     }
 
@@ -62,7 +62,7 @@ public class IdentityClientConfiguration : Dictionary<string, string>
     /// Scope.
     /// </summary>
     public string Scope {
-        get => this.GetOrDefault(nameof(Scope));
+        get => this.GetOrDefault(nameof(Scope))!;
         set => this[nameof(Scope)] = value;
     }
 
@@ -113,8 +113,8 @@ public class IdentityClientConfiguration : Dictionary<string, string>
         string clientId,
         string clientSecret,
         string grantType = OidcConstants.GrantTypes.ClientCredentials,
-        string userName = null,
-        string userPassword = null,
+        string? userName = null,
+        string? userPassword = null,
         bool requireHttps = true,
         int cacheAbsoluteExpiration = 60 * 30,
         bool validateIssuerName = true,
diff --git a/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IdentityClientConfigurationDictionary.cs b/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IdentityClientConfigurationDictionary.cs
index e8c42fe390..4993cfa462 100644
--- a/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IdentityClientConfigurationDictionary.cs
+++ b/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IdentityClientConfigurationDictionary.cs
@@ -2,11 +2,11 @@
 
 namespace Volo.Abp.IdentityModel;
 
-public class IdentityClientConfigurationDictionary : Dictionary<string, IdentityClientConfiguration>
+public class IdentityClientConfigurationDictionary : Dictionary<string, IdentityClientConfiguration?>
 {
     public const string DefaultName = "Default";
 
-    public IdentityClientConfiguration Default {
+    public IdentityClientConfiguration? Default {
         get => this.GetOrDefault(DefaultName);
         set => this[DefaultName] = value;
     }
diff --git a/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IdentityModelAuthenticationService.cs b/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IdentityModelAuthenticationService.cs
index 6f5f8eda95..4354d83735 100644
--- a/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IdentityModelAuthenticationService.cs
+++ b/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IdentityModelAuthenticationService.cs
@@ -54,7 +54,7 @@ public class IdentityModelAuthenticationService : IIdentityModelAuthenticationSe
 
     public async Task<bool> TryAuthenticateAsync(
         [NotNull] HttpClient client,
-        string identityClientName = null)
+        string? identityClientName = null)
     {
         var accessToken = await GetAccessTokenOrNullAsync(identityClientName);
         if (accessToken == null)
@@ -66,7 +66,7 @@ public class IdentityModelAuthenticationService : IIdentityModelAuthenticationSe
         return true;
     }
 
-    protected virtual async Task<string> GetAccessTokenOrNullAsync(string identityClientName)
+    protected virtual async Task<string?> GetAccessTokenOrNullAsync(string? identityClientName)
     {
         var configuration = ClientOptions.GetClientConfiguration(CurrentTenant, identityClientName);
         if (configuration == null)
diff --git a/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IdentityModelDiscoveryDocumentCacheItem.cs b/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IdentityModelDiscoveryDocumentCacheItem.cs
index 0fbf50d020..6cabe5d9b9 100644
--- a/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IdentityModelDiscoveryDocumentCacheItem.cs
+++ b/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IdentityModelDiscoveryDocumentCacheItem.cs
@@ -7,9 +7,9 @@ namespace Volo.Abp.IdentityModel;
 [IgnoreMultiTenancy]
 public class IdentityModelDiscoveryDocumentCacheItem
 {
-    public string TokenEndpoint { get; set; }
+    public string TokenEndpoint { get; set; } = default!;
 
-    public string DeviceAuthorizationEndpoint { get; set; }
+    public string DeviceAuthorizationEndpoint { get; set; } = default!;
 
     public IdentityModelDiscoveryDocumentCacheItem()
     {
diff --git a/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IdentityModelHttpRequestMessageOptions.cs b/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IdentityModelHttpRequestMessageOptions.cs
index d72cc9682e..78b2a342f4 100644
--- a/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IdentityModelHttpRequestMessageOptions.cs
+++ b/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IdentityModelHttpRequestMessageOptions.cs
@@ -5,5 +5,5 @@ namespace Volo.Abp.IdentityModel;
 
 public class IdentityModelHttpRequestMessageOptions
 {
-    public Action<HttpRequestMessage> ConfigureHttpRequestMessage { get; set; }
+    public Action<HttpRequestMessage>? ConfigureHttpRequestMessage { get; set; }
 }
diff --git a/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IdentityModelTokenCacheItem.cs b/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IdentityModelTokenCacheItem.cs
index 2a164a23e6..72beed1577 100644
--- a/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IdentityModelTokenCacheItem.cs
+++ b/framework/src/Volo.Abp.IdentityModel/Volo/Abp/IdentityModel/IdentityModelTokenCacheItem.cs
@@ -7,7 +7,7 @@ namespace Volo.Abp.IdentityModel;
 [Serializable]
 public class IdentityModelTokenCacheItem
 {
-    public string AccessToken { get; set; }
+    public string AccessToken { get; set; } = default!;
 
     public IdentityModelTokenCacheItem()
     {