diff --git a/framework/src/Volo.Abp.MemoryDb/Microsoft/Extensions/DependencyInjection/AbpMemoryDbServiceCollectionExtensions.cs b/framework/src/Volo.Abp.MemoryDb/Microsoft/Extensions/DependencyInjection/AbpMemoryDbServiceCollectionExtensions.cs
index 0f06706180..d14d8d657e 100644
--- a/framework/src/Volo.Abp.MemoryDb/Microsoft/Extensions/DependencyInjection/AbpMemoryDbServiceCollectionExtensions.cs
+++ b/framework/src/Volo.Abp.MemoryDb/Microsoft/Extensions/DependencyInjection/AbpMemoryDbServiceCollectionExtensions.cs
@@ -7,7 +7,7 @@ namespace Microsoft.Extensions.DependencyInjection;
 
 public static class AbpMemoryDbServiceCollectionExtensions
 {
-    public static IServiceCollection AddMemoryDbContext<TMemoryDbContext>(this IServiceCollection services, Action<IAbpMemoryDbContextRegistrationOptionsBuilder> optionsBuilder = null)
+    public static IServiceCollection AddMemoryDbContext<TMemoryDbContext>(this IServiceCollection services, Action<IAbpMemoryDbContextRegistrationOptionsBuilder>? optionsBuilder = null)
         where TMemoryDbContext : MemoryDbContext
     {
         var options = new AbpMemoryDbContextRegistrationOptions(typeof(TMemoryDbContext), services);
diff --git a/framework/src/Volo.Abp.MemoryDb/Volo.Abp.MemoryDb.csproj b/framework/src/Volo.Abp.MemoryDb/Volo.Abp.MemoryDb.csproj
index 07ddca1d7a..5f4f78a5db 100644
--- a/framework/src/Volo.Abp.MemoryDb/Volo.Abp.MemoryDb.csproj
+++ b/framework/src/Volo.Abp.MemoryDb/Volo.Abp.MemoryDb.csproj
@@ -5,6 +5,8 @@
 
   <PropertyGroup>
     <TargetFrameworks>netstandard2.0;netstandard2.1;net7.0</TargetFrameworks>
+    <Nullable>enable</Nullable>
+    <WarningsAsErrors>Nullable</WarningsAsErrors>
     <AssemblyName>Volo.Abp.MemoryDb</AssemblyName>
     <PackageId>Volo.Abp.MemoryDb</PackageId>
     <AssetTargetFallback>$(AssetTargetFallback);portable-net45+win8+wp8+wpa81;</AssetTargetFallback>
diff --git a/framework/src/Volo.Abp.MemoryDb/Volo/Abp/Domain/Repositories/MemoryDb/MemoryDatabase.cs b/framework/src/Volo.Abp.MemoryDb/Volo/Abp/Domain/Repositories/MemoryDb/MemoryDatabase.cs
index c3103e20f2..a38aeec1b2 100644
--- a/framework/src/Volo.Abp.MemoryDb/Volo/Abp/Domain/Repositories/MemoryDb/MemoryDatabase.cs
+++ b/framework/src/Volo.Abp.MemoryDb/Volo/Abp/Domain/Repositories/MemoryDb/MemoryDatabase.cs
@@ -25,9 +25,9 @@ public class MemoryDatabase : IMemoryDatabase, ITransientDependency
     public IMemoryDatabaseCollection<TEntity> Collection<TEntity>()
         where TEntity : class, IEntity
     {
-        return _sets.GetOrAdd(typeof(TEntity),
+        return (_sets.GetOrAdd(typeof(TEntity),
                 _ => _serviceProvider.GetRequiredService<IMemoryDatabaseCollection<TEntity>>()) as
-            IMemoryDatabaseCollection<TEntity>;
+            IMemoryDatabaseCollection<TEntity>)!;
     }
 
     public TKey GenerateNextId<TEntity, TKey>()
diff --git a/framework/src/Volo.Abp.MemoryDb/Volo/Abp/Domain/Repositories/MemoryDb/MemoryDbRepository.cs b/framework/src/Volo.Abp.MemoryDb/Volo/Abp/Domain/Repositories/MemoryDb/MemoryDbRepository.cs
index 39b2247a61..186edd7d33 100644
--- a/framework/src/Volo.Abp.MemoryDb/Volo/Abp/Domain/Repositories/MemoryDb/MemoryDbRepository.cs
+++ b/framework/src/Volo.Abp.MemoryDb/Volo/Abp/Domain/Repositories/MemoryDb/MemoryDbRepository.cs
@@ -192,7 +192,7 @@ public class MemoryDbRepository<TMemoryDbContext, TEntity> : RepositoryBase<TEnt
         TriggerDomainEvents(entity);
     }
 
-    public override async Task<TEntity> FindAsync(
+    public override async Task<TEntity?> FindAsync(
         Expression<Func<TEntity, bool>> predicate,
         bool includeDetails = true,
         CancellationToken cancellationToken = default)
@@ -340,14 +340,14 @@ public class MemoryDbRepository<TMemoryDbContext, TEntity, TKey> : MemoryDbRepos
         return entity;
     }
 
-    public virtual async Task<TEntity> FindAsync(TKey id, bool includeDetails = true, CancellationToken cancellationToken = default)
+    public virtual async Task<TEntity?> FindAsync(TKey id, bool includeDetails = true, CancellationToken cancellationToken = default)
     {
-        return (await GetQueryableAsync()).FirstOrDefault(e => e.Id.Equals(id));
+        return (await GetQueryableAsync()).FirstOrDefault(e => e.Id!.Equals(id));
     }
 
     public virtual async Task DeleteAsync(TKey id, bool autoSave = false, CancellationToken cancellationToken = default)
     {
-        await DeleteAsync(x => x.Id.Equals(id), autoSave, cancellationToken);
+        await DeleteAsync(x => x.Id!.Equals(id), autoSave, cancellationToken);
     }
 
     public virtual async Task DeleteManyAsync(IEnumerable<TKey> ids, bool autoSave = false, CancellationToken cancellationToken = default)
diff --git a/framework/src/Volo.Abp.MemoryDb/Volo/Abp/Domain/Repositories/MemoryDb/Utf8JsonMemoryDbSerializer.cs b/framework/src/Volo.Abp.MemoryDb/Volo/Abp/Domain/Repositories/MemoryDb/Utf8JsonMemoryDbSerializer.cs
index deff9658fb..1a901820f3 100644
--- a/framework/src/Volo.Abp.MemoryDb/Volo/Abp/Domain/Repositories/MemoryDb/Utf8JsonMemoryDbSerializer.cs
+++ b/framework/src/Volo.Abp.MemoryDb/Volo/Abp/Domain/Repositories/MemoryDb/Utf8JsonMemoryDbSerializer.cs
@@ -21,6 +21,6 @@ public class Utf8JsonMemoryDbSerializer : IMemoryDbSerializer, ITransientDepende
 
     public object Deserialize(byte[] value, Type type)
     {
-        return JsonSerializer.Deserialize(value, type, Options.JsonSerializerOptions);
+        return JsonSerializer.Deserialize(value, type, Options.JsonSerializerOptions)!;
     }
 }
diff --git a/framework/src/Volo.Abp.MemoryDb/Volo/Abp/MemoryDb/DependencyInjection/MemoryDbRepositoryRegistrar.cs b/framework/src/Volo.Abp.MemoryDb/Volo/Abp/MemoryDb/DependencyInjection/MemoryDbRepositoryRegistrar.cs
index d746c65acf..21fddd50d2 100644
--- a/framework/src/Volo.Abp.MemoryDb/Volo/Abp/MemoryDb/DependencyInjection/MemoryDbRepositoryRegistrar.cs
+++ b/framework/src/Volo.Abp.MemoryDb/Volo/Abp/MemoryDb/DependencyInjection/MemoryDbRepositoryRegistrar.cs
@@ -14,7 +14,7 @@ public class MemoryDbRepositoryRegistrar : RepositoryRegistrarBase<AbpMemoryDbCo
 
     protected override IEnumerable<Type> GetEntityTypes(Type dbContextType)
     {
-        var memoryDbContext = (MemoryDbContext)Activator.CreateInstance(dbContextType);
+        var memoryDbContext = (MemoryDbContext)Activator.CreateInstance(dbContextType)!;
         return memoryDbContext.GetEntityTypes();
     }