Add GetDbSets and fix error details of incorrect Entity type full name

src/EFCore/DbContext.cs

@@ -16,6 +16,7 @@
 using Microsoft.EntityFrameworkCore.Infrastructure;
 using Microsoft.EntityFrameworkCore.Internal;
 using Microsoft.EntityFrameworkCore.Metadata;
+using Microsoft.EntityFrameworkCore.Metadata.Internal;
 using Microsoft.EntityFrameworkCore.Query;
 using Microsoft.EntityFrameworkCore.Utilities;
 using Microsoft.Extensions.DependencyInjection;
@@ -138,7 +139,8 @@ public virtual ChangeTracker ChangeTracker
         /// </summary>
         public virtual IModel Model
         {
-            [DebuggerStepThrough] get => DbContextDependencies.Model;
+            [DebuggerStepThrough]
+            get => DbContextDependencies.Model;
         }
 
         /// <summary>
@@ -311,7 +313,16 @@ private IEntityFinder Finder(Type type)
                     throw new InvalidOperationException(CoreStrings.InvalidSetSharedType(type.ShortDisplayName()));
                 }
 
-                throw new InvalidOperationException(CoreStrings.InvalidSetType(type.ShortDisplayName()));
+                var findSameTypeName = Model.FindSameTypeNameWithDifferentNamespace(type);
+                //if the same name exists in your entity types we will show you the full namespace of the type
+                if (!string.IsNullOrEmpty(findSameTypeName))
+                {
+                    throw new InvalidOperationException(CoreStrings.InvalidSetSameTypeWithDifferentNamespace(type.DisplayName(), findSameTypeName));
+                }
+                else
+                {
+                    throw new InvalidOperationException(CoreStrings.InvalidSetType(type.ShortDisplayName()));
+                }
             }
 
             if (entityType.FindPrimaryKey() == null)

src/EFCore/Internal/InternalDbSet.cs

@@ -14,6 +14,7 @@
 using Microsoft.EntityFrameworkCore.Diagnostics;
 using Microsoft.EntityFrameworkCore.Infrastructure;
 using Microsoft.EntityFrameworkCore.Metadata;
+using Microsoft.EntityFrameworkCore.Metadata.Internal;
 using Microsoft.EntityFrameworkCore.Query.Internal;
 using Microsoft.EntityFrameworkCore.Utilities;
 
@@ -81,7 +82,16 @@ public override IEntityType EntityType
                         throw new InvalidOperationException(CoreStrings.InvalidSetSharedType(typeof(TEntity).ShortDisplayName()));
                     }
 
-                    throw new InvalidOperationException(CoreStrings.InvalidSetType(typeof(TEntity).ShortDisplayName()));
+                    var findSameTypeName = _context.Model.FindSameTypeNameWithDifferentNamespace(typeof(TEntity));
+                    //if the same name exists in your entity types we will show you the full namespace of the type
+                    if (!string.IsNullOrEmpty(findSameTypeName))
+                    {
+                        throw new InvalidOperationException(CoreStrings.InvalidSetSameTypeWithDifferentNamespace(typeof(TEntity).DisplayName(), findSameTypeName));
+                    }
+                    else
+                    {
+                        throw new InvalidOperationException(CoreStrings.InvalidSetType(typeof(TEntity).ShortDisplayName()));
+                    }
                 }
 
                 if (_entityType.IsOwned())

src/EFCore/Metadata/Internal/EntityTypeExtensions.cs

@@ -404,5 +404,31 @@ public static IProperty CheckPropertyBelongsToType([NotNull] this IEntityType en
         /// </summary>
         public static EntityType AsEntityType([NotNull] this IEntityType entityType, [NotNull] [CallerMemberName] string methodName = "")
             => MetadataExtensions.AsConcreteMetadataType<IEntityType, EntityType>(entityType, methodName);
+
+
+
+        /// <summary>
+        ///     Try to find the name of the type that has a different namespace from your entity types
+        /// </summary>
+        /// <param name="model">
+        ///     model Of your context to find entities
+        /// </param>
+        /// <param name="type">
+        ///     A Type that you think have a different namespace and exists in your entity types
+        /// </param>
+        /// <returns>
+        ///     the name with different namespace found
+        /// </returns>
+        public static string? FindSameTypeNameWithDifferentNamespace([NotNull] this IModel model, [NotNull] Type type)
+        {
+            //try to find the same name of the entity with type to throw a specific exception
+            return model.GetEntityTypes()
+                //check the short names are equals because the namespaces are not equaled we need to check just names are equals
+                .Where(x => x.ClrType.DisplayName(false) == type.DisplayName(false))
+                //select the full name of type because we need to show the developer a type with the full name
+                .Select(x => x.ClrType.DisplayName())
+                //select one of them to show the developer
+                .FirstOrDefault();
+        }
     }
 }

src/EFCore/Properties/CoreStrings.resx

@@ -611,6 +611,9 @@
   <data name="InvalidSetType" xml:space="preserve">
     <value>Cannot create a DbSet for '{typeName}' because this type is not included in the model for the context.</value>
   </data>
+  <data name="InvalidSetSameTypeWithDifferentNamespace" xml:space="preserve">
+    <value>Cannot create a DbSet for '{typeName}' because this type is not included in the model for the context. However the model contains an entity type with the same name in a different namespace: '{entityTypeName}'.</value>
+  </data>
   <data name="InvalidSetTypeOwned" xml:space="preserve">
     <value>Cannot create a DbSet for '{typeName}' because it is configured as an owned entity type and must be accessed through its owning entity type '{ownerType}'.</value>
   </data>

test/EFCore.Specification.Tests/FindTestBase.cs

@@ -5,6 +5,7 @@
 using System.ComponentModel.DataAnnotations.Schema;
 using System.Threading.Tasks;
 using Microsoft.EntityFrameworkCore.Diagnostics;
+using Microsoft.EntityFrameworkCore.Infrastructure;
 using Microsoft.EntityFrameworkCore.TestUtilities;
 using Xunit;
 
@@ -300,11 +301,22 @@ public virtual void Throws_for_bad_type_for_composite_key()
         public virtual void Throws_for_bad_entity_type()
         {
             using var context = CreateContext();
+
             Assert.Equal(
                 CoreStrings.InvalidSetType(nameof(Random)),
                 Assert.Throws<InvalidOperationException>(() => Find<Random>(context, 77)).Message);
         }
 
+        [ConditionalFact]
+        public virtual void Throws_for_bad_entity_type_with_different_namespace()
+        {
+            using var context = CreateContext();
+
+            Assert.Equal(
+                CoreStrings.InvalidSetSameTypeWithDifferentNamespace(typeof(Microsoft.EntityFrameworkCore.DifferentNamespace.ShadowKey).DisplayName(), typeof(ShadowKey).DisplayName()),
+                Assert.Throws<InvalidOperationException>(() => Find<Microsoft.EntityFrameworkCore.DifferentNamespace.ShadowKey>(context, 77)).Message);
+        }
+
         [ConditionalFact]
         public virtual async Task Find_int_key_tracked_async()
         {
@@ -580,6 +592,17 @@ public virtual async Task Throws_for_bad_entity_type_async()
                 (await Assert.ThrowsAsync<InvalidOperationException>(() => FindAsync<Random>(context, 77).AsTask())).Message);
         }
 
+        [ConditionalFact]
+        public virtual async Task Throws_for_bad_entity_type_with_different_namespace_async()
+        {
+            using var context = CreateContext();
+
+            Assert.Equal(
+                CoreStrings.InvalidSetSameTypeWithDifferentNamespace(typeof(Microsoft.EntityFrameworkCore.DifferentNamespace.ShadowKey).DisplayName(), typeof(ShadowKey).DisplayName()),
+                (await Assert.ThrowsAsync<InvalidOperationException>(() => FindAsync<Microsoft.EntityFrameworkCore.DifferentNamespace.ShadowKey>(context, 77).AsTask())).Message);
+        }
+
+
         protected class BaseType
         {
             [DatabaseGenerated(DatabaseGeneratedOption.None)]
@@ -677,3 +700,12 @@ protected override void Seed(PoolableDbContext context)
         }
     }
 }
+
+
+namespace Microsoft.EntityFrameworkCore.DifferentNamespace
+{
+    internal class ShadowKey
+    {
+        public string Foo { get; set; }
+    }
+}

test/EFCore.Tests/DbContextServicesTest.cs

@@ -3671,3 +3671,24 @@ public DerivedContext2(DbContextOptions<DerivedContext2> options)
         }
     }
 }
+
+namespace Microsoft.EntityFrameworkCore.DifferentNamespace
+{
+    internal class Category
+    {
+        public int Id { get; set; }
+        public string Name { get; set; }
+
+        public List<Product> Products { get; set; }
+    }
+
+    internal class Product
+    {
+        public int Id { get; set; }
+        public string Name { get; set; }
+        public decimal Price { get; set; }
+
+        public int CategoryId { get; set; }
+        public Category Category { get; set; }
+    }
+}

test/EFCore.Tests/DbContextTest.cs

@@ -35,9 +35,19 @@ public void Set_throws_for_type_not_in_model()
 
             using var context = new DbContext(optionsBuilder.Options);
             var ex = Assert.Throws<InvalidOperationException>(() => context.Set<Category>().Local);
+
             Assert.Equal(CoreStrings.InvalidSetType(nameof(Category)), ex.Message);
         }
 
+        [ConditionalFact]
+        public void Set_throws_for_type_not_in_model_same_type_with_different_namespace()
+        {
+            using var context = new EarlyLearningCenter();
+            var ex = Assert.Throws<InvalidOperationException>(() => context.Set<Microsoft.EntityFrameworkCore.DifferentNamespace.Category>().Local);
+
+            Assert.Equal(CoreStrings.InvalidSetSameTypeWithDifferentNamespace(typeof(Microsoft.EntityFrameworkCore.DifferentNamespace.Category).DisplayName(), typeof(Category).DisplayName()), ex.Message);
+        }
+
         [ConditionalFact]
         public void Local_calls_DetectChanges()
         {

test/EFCore.Tests/DbSetTest.cs

@@ -212,6 +212,7 @@ public void Use_of_LocalView_throws_if_context_is_disposed()
         public void Using_ignored_entity_that_has_DbSet_on_context_throws_appropriately()
         {
             using var context = new IgnoredCntext();
+
             Assert.Equal(
                 CoreStrings.InvalidSetType(nameof(IgnoredEntity)),
                 Assert.Throws<InvalidOperationException>(() => context.Ignored.ToList()).Message);