Use FindEntityType(Type) as appropriate

- Make FindEntityType(Type) return null for shared type entity type
- Add IModel.IsShared(Type) API
- Flow IEntityType info in places when availble rather than doing Type based loopup

Part of #9914

src/EFCore/DbContext.cs

@@ -304,6 +304,11 @@ private IEntityFinder Finder(Type type)
                     throw new InvalidOperationException(CoreStrings.InvalidSetTypeWeak(type.ShortDisplayName()));
                 }
 
+                if (Model.IsShared(type))
+                {
+                    throw new InvalidOperationException(CoreStrings.InvalidSetSharedType(type.ShortDisplayName()));
+                }
+
                 throw new InvalidOperationException(CoreStrings.InvalidSetType(type.ShortDisplayName()));
             }
 

src/EFCore/Extensions/EntityFrameworkServiceCollectionExtensions.cs

@@ -116,7 +116,7 @@ public static IServiceCollection AddDbContext<TContextService, TContextImplement
                 serviceCollection,
                 optionsAction == null
                     ? (Action<IServiceProvider, DbContextOptionsBuilder>)null
-                    : (p, b) => optionsAction.Invoke(b), contextLifetime, optionsLifetime);
+                    : (p, b) => optionsAction(b), contextLifetime, optionsLifetime);
 
         /// <summary>
         ///     <para>
@@ -672,7 +672,7 @@ public static IServiceCollection AddDbContextFactory<TContext, TFactory>(
                 serviceCollection,
                 optionsAction == null
                     ? (Action<IServiceProvider, DbContextOptionsBuilder>)null
-                    : (p, b) => optionsAction.Invoke(b),
+                    : (p, b) => optionsAction(b),
                 lifetime);
 
         /// <summary>

src/EFCore/Extensions/ModelExtensions.cs

@@ -22,7 +22,8 @@ public static class ModelExtensions
     {
         /// <summary>
         ///     Gets the entity that maps the given entity class. Returns <see langword="null" /> if no entity type with
-        ///     the given CLR type is found or the entity type has a defining navigation.
+        ///     the given CLR type is found or the given CLR type is being used by shared type entity type
+        ///     or the entity type has a defining navigation.
         /// </summary>
         /// <param name="model"> The model to find the entity type in. </param>
         /// <param name="type"> The type to find the corresponding entity type for. </param>
@@ -34,6 +35,7 @@ public static IEntityType FindEntityType([NotNull] this IModel model, [NotNull]
         /// <summary>
         ///     Gets the entity that maps the given entity class, where the class may be a proxy derived from the
         ///     actual entity type. Returns <see langword="null" /> if no entity type with the given CLR type is found
+        ///     or the given CLR type is being used by shared type entity type
         ///     or the entity type has a defining navigation.
         /// </summary>
         /// <param name="model"> The model to find the entity type in. </param>
@@ -119,6 +121,16 @@ public static bool HasEntityTypeWithDefiningNavigation([NotNull] this IModel mod
             => Check.NotNull(model, nameof(model)).AsModel()
                 .HasEntityTypeWithDefiningNavigation(Check.NotNull(name, nameof(name)));
 
+        /// <summary>
+        ///     Gets whether the CLR type is used by shared type entities in the model.
+        /// </summary>
+        /// <param name="model"> The model to find the entity type in. </param>
+        /// <param name="clrType"> The CLR type. </param>
+        /// <returns> Whether the CLR type is used by shared type entities in the model. </returns>
+        [DebuggerStepThrough]
+        public static bool IsShared([NotNull] this IModel model, [NotNull] Type clrType)
+            => Check.NotNull(model, nameof(model)).AsModel().IsShared(Check.NotNull(clrType, nameof(clrType)));
+
         /// <summary>
         ///     Gets the default change tracking strategy being used for entities in the model. This strategy indicates how the
         ///     context detects changes to properties for an instance of an entity type.

src/EFCore/Extensions/MutableModelExtensions.cs

@@ -18,7 +18,9 @@ namespace Microsoft.EntityFrameworkCore
     public static class MutableModelExtensions
     {
         /// <summary>
-        ///     Gets the entity that maps the given entity class. Returns <see langword="null" /> if no entity type with the given name is found.
+        ///     Gets the entity that maps the given entity class. Returns <see langword="null" /> if no entity type with
+        ///     the given CLR type is found or the given CLR type is being used by shared type entity type
+        ///     or the entity type has a defining navigation.
         /// </summary>
         /// <param name="model"> The model to find the entity type in. </param>
         /// <param name="type"> The type to find the corresponding entity type for. </param>

src/EFCore/Infrastructure/ModelValidator.cs

@@ -207,6 +207,7 @@ var isTargetWeakOrOwned
 
                     if (targetType?.IsValidEntityType() == true
                         && (isTargetWeakOrOwned
+                            || conventionModel.IsShared(targetType)
                             || conventionModel.FindEntityType(targetType) != null
                             || targetType.GetRuntimeProperties().Any(p => p.IsCandidateProperty())))
                     {

src/EFCore/Internal/EntityFinder.cs

@@ -29,7 +29,7 @@ public class EntityFinder<TEntity> : IEntityFinder<TEntity>
         private readonly IStateManager _stateManager;
         private readonly IDbSetSource _setSource;
         private readonly IDbSetCache _setCache;
-        private readonly IModel _model;
+        private readonly IEntityType _entityType;
         private readonly IQueryable<TEntity> _queryRoot;
 
         /// <summary>
@@ -47,7 +47,7 @@ public EntityFinder(
             _stateManager = stateManager;
             _setSource = setSource;
             _setCache = setCache;
-            _model = entityType.Model;
+            _entityType = entityType;
             _queryRoot = (IQueryable<TEntity>)BuildQueryRoot(entityType);
         }
 
@@ -274,7 +274,7 @@ private static IReadOnlyList<IProperty> GetLoadProperties(INavigation navigation
 
         private TEntity FindTracked(object[] keyValues, out IReadOnlyList<IProperty> keyProperties)
         {
-            var key = _model.FindEntityType(typeof(TEntity)).FindPrimaryKey();
+            var key = _entityType.FindPrimaryKey();
             keyProperties = key.Properties;
 
             if (keyProperties.Count != keyValues.Length)

src/EFCore/Internal/InternalDbSet.cs

@@ -74,6 +74,11 @@ private IEntityType EntityType
                         throw new InvalidOperationException(CoreStrings.InvalidSetTypeWeak(typeof(TEntity).ShortDisplayName()));
                     }
 
+                    if (_context.Model.IsShared(typeof(TEntity)))
+                    {
+                        throw new InvalidOperationException(CoreStrings.InvalidSetSharedType(typeof(TEntity).ShortDisplayName()));
+                    }
+
                     throw new InvalidOperationException(CoreStrings.InvalidSetType(typeof(TEntity).ShortDisplayName()));
                 }
 

src/EFCore/Metadata/Conventions/BackingFieldConvention.cs

@@ -87,29 +87,31 @@ private FieldInfo GetFieldToSet(IConventionPropertyBase propertyBase)
                 return null;
             }
 
-            var type = propertyBase.DeclaringType.ClrType;
+            var entityType = (IConventionEntityType)propertyBase.DeclaringType;
+            var type = entityType.ClrType;
+            var baseTypes = entityType.GetAllBaseTypes().ToArray();
             while (type != null)
             {
-                var fieldInfo = TryMatchFieldName(propertyBase, type);
+                var fieldInfo = TryMatchFieldName(propertyBase, entityType, type);
                 if (fieldInfo != null
                     && (propertyBase.PropertyInfo != null || propertyBase.Name == fieldInfo.GetSimpleMemberName()))
                 {
                     return fieldInfo;
                 }
 
                 type = type.BaseType;
+                entityType = baseTypes.FirstOrDefault(et => et.ClrType == type);
+
             }
 
             return null;
         }
 
-        private static FieldInfo TryMatchFieldName(IConventionPropertyBase propertyBase, Type entityClrType)
+        private static FieldInfo TryMatchFieldName(IConventionPropertyBase propertyBase, IConventionEntityType entityType, Type entityClrType)
         {
-            var model = propertyBase.DeclaringType.Model;
             var propertyName = propertyBase.Name;
 
             IReadOnlyDictionary<string, FieldInfo> fields;
-            var entityType = model.FindEntityType(entityClrType);
             if (entityType == null)
             {
                 var newFields = new Dictionary<string, FieldInfo>(StringComparer.Ordinal);

src/EFCore/Metadata/Conventions/BaseTypeDiscoveryConvention.cs

@@ -34,6 +34,7 @@ public virtual void ProcessEntityTypeAdded(
             var entityType = entityTypeBuilder.Metadata;
             var clrType = entityType.ClrType;
             if (clrType == null
+                || entityType.HasSharedClrType
                 || entityType.HasDefiningNavigation()
                 || entityType.FindDeclaredOwnership() != null
                 || entityType.Model.FindIsOwnedConfigurationSource(clrType) != null)

src/EFCore/Metadata/Conventions/DerivedTypeDiscoveryConvention.cs

@@ -35,7 +35,10 @@ public virtual void ProcessEntityTypeAdded(
             var entityType = entityTypeBuilder.Metadata;
             var clrType = entityType.ClrType;
             if (clrType == null
-                || entityType.HasDefiningNavigation())
+                || entityType.HasSharedClrType
+                || entityType.HasDefiningNavigation()
+                || entityType.FindDeclaredOwnership() != null
+                || entityType.Model.FindIsOwnedConfigurationSource(clrType) != null)
             {
                 return;
             }

src/EFCore/Metadata/IConventionModel.cs

@@ -50,7 +50,13 @@ public interface IConventionModel : IModel, IConventionAnnotatable
         IConventionEntityType AddEntityType([NotNull] Type clrType, bool fromDataAnnotation = false);
 
         /// <summary>
-        ///     Adds an entity type to the model.
+        ///     <para>
+        ///         Adds a shared type entity type to the model.
+        ///     </para>
+        ///     <para>
+        ///         Shared type entity type is an entity type which can share CLR type with other types in the model but has
+        ///         a unique name and always identified by the name.
+        ///     </para>
         /// </summary>
         /// <param name="name"> The name of the entity to be added. </param>
         /// <param name="clrType"> The CLR class that is used to represent instances of the entity type. </param>
@@ -88,6 +94,7 @@ IConventionEntityType AddEntityType(
 
         /// <summary>
         ///     Gets the entity with the given name. Returns <see langword="null" /> if no entity type with the given name is found
+        ///     or the given CLR type is being used by shared type entity type
         ///     or the entity type has a defining navigation.
         /// </summary>
         /// <param name="name"> The name of the entity type to find. </param>
@@ -136,10 +143,10 @@ IConventionEntityType FindEntityType(
         string RemoveIgnored([NotNull] string typeName);
 
         /// <summary>
-        ///     Gets whether the CLR type is used by shared entities in the model.
+        ///     Gets whether the CLR type is used by shared type entities in the model.
         /// </summary>
         /// <param name="clrType"> The CLR type. </param>
-        /// <returns> Whether the CLR type is used by shared entities in the model. </returns>
+        /// <returns> Whether the CLR type is used by shared type entities in the model. </returns>
         bool IsShared([NotNull] Type clrType);
 
         /// <summary>

src/EFCore/Metadata/IModel.cs

@@ -32,6 +32,7 @@ public interface IModel : IAnnotatable
 
         /// <summary>
         ///     Gets the entity type with the given name. Returns null if no entity type with the given name is found
+        ///     or the given CLR type is being used by shared type entity type
         ///     or the entity type has a defining navigation.
         /// </summary>
         /// <param name="name"> The name of the entity type to find. </param>

src/EFCore/Metadata/IMutableModel.cs

@@ -42,7 +42,13 @@ public interface IMutableModel : IModel, IMutableAnnotatable
         IMutableEntityType AddEntityType([NotNull] Type clrType);
 
         /// <summary>
-        ///     Adds an entity type to the model.
+        ///     <para>
+        ///         Adds a shared type entity type to the model.
+        ///     </para>
+        ///     <para>
+        ///         Shared type entity type is an entity type which can share CLR type with other types in the model but has
+        ///         a unique name and always identified by the name.
+        ///     </para>
         /// </summary>
         /// <param name="name"> The name of the entity to be added. </param>
         /// <param name="clrType"> The CLR class that is used to represent instances of the entity type. </param>
@@ -75,6 +81,7 @@ IMutableEntityType AddEntityType(
 
         /// <summary>
         ///     Gets the entity with the given name. Returns <see langword="null" /> if no entity type with the given name is found
+        ///     or the given CLR type is being used by shared type entity type
         ///     or the entity type has a defining navigation.
         /// </summary>
         /// <param name="name"> The name of the entity type to find. </param>

src/EFCore/Metadata/Internal/Model.cs

@@ -230,6 +230,11 @@ private EntityType AddEntityType(EntityType entityType)
 
                 if (entityType.HasSharedClrType)
                 {
+                    if (_entityTypes.Any(et => !et.Value.HasSharedClrType && et.Value.ClrType == entityType.ClrType))
+                    {
+                        throw new InvalidOperationException(CoreStrings.ClashingNonSharedType(entityType.DisplayName()));
+                    }
+
                     _sharedEntityClrTypes.Add(entityType.ClrType);
                 }
                 else if (_sharedEntityClrTypes.Contains(entityType.ClrType))
@@ -249,15 +254,7 @@ private EntityType AddEntityType(EntityType entityType)
         ///     any release. You should only use it directly in your code with extreme caution and knowing that
         ///     doing so can result in application failures when updating to a new Entity Framework Core release.
         /// </summary>
-        public virtual EntityType FindEntityType([NotNull] Type type)
-        {
-            if (_sharedEntityClrTypes.Contains(type))
-            {
-                throw new InvalidOperationException(CoreStrings.CannotFindEntityWithClrTypeWhenShared(type.DisplayName()));
-            }
-
-            return FindEntityType(GetDisplayName(type));
-        }
+        public virtual EntityType FindEntityType([NotNull] Type type) => FindEntityType(GetDisplayName(type));
 
         /// <summary>
         ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
@@ -714,6 +711,15 @@ private string AddIgnored(
 
             _ignoredTypeNames[name] = configurationSource;
 
+            if (type == null)
+            {
+                // This is to populate Type for convention when removing shared type entity type
+                type = _entityTypes.TryGetValue(name, out var existingEntityType)
+                    && existingEntityType.HasSharedClrType
+                    ? existingEntityType.ClrType
+                    : null;
+            }
+
             return ConventionDispatcher.OnEntityTypeIgnored(Builder, name, type);
         }