Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Data.Entity/System/Data/Objects/Internal/NullEntityWrapper.cs

@@ -0,0 +1,207 @@
+//---------------------------------------------------------------------
+// <copyright file="NullEntityWrapper.cs" company="Microsoft">
+//      Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>
+//
+// @owner       [....]
+// @backupOwner [....]
+//---------------------------------------------------------------------
+namespace System.Data.Objects.Internal
+{
+    using System.Data.Metadata.Edm;
+    using System.Data.Objects.DataClasses;
+    using System.Diagnostics;
+
+    /// <summary>
+    /// Defines an entity wrapper that wraps an entity with a null value.
+    /// This is a singleton class for which the same instance is always returned
+    /// any time a wrapper around a null entity is requested.  Objects of this
+    /// type are immutable and mutable to allow this behavior to work correctly.
+    /// </summary>
+    internal class NullEntityWrapper : IEntityWrapper
+    {
+        private static IEntityWrapper s_nullWrapper = new NullEntityWrapper();
+
+        // Private constructor prevents anyone else from creating an instance
+        private NullEntityWrapper()
+        {
+        }
+
+        /// <summary>
+        /// The single instance of this class.
+        /// </summary>
+        internal static IEntityWrapper NullWrapper
+        {
+            get { return s_nullWrapper; }
+        }
+
+        public RelationshipManager RelationshipManager
+        {
+            get
+            {
+                Debug.Fail("Cannot access RelationshipManager from null wrapper.");
+                return null;
+            }
+        }
+
+        public bool OwnsRelationshipManager
+        {
+            get
+            {
+                Debug.Fail("Cannot access RelationshipManager from null wrapper.");
+                return false;
+            }
+        }
+
+        public object Entity
+        {
+            get { return null; }
+        }
+
+        public EntityEntry ObjectStateEntry
+        {
+            get { return null; }
+            set { }
+        }
+
+        public void CollectionAdd(RelatedEnd relatedEnd, object value)
+        {
+            Debug.Fail("Cannot modify collection from null wrapper.");
+        }
+
+        public bool CollectionRemove(RelatedEnd relatedEnd, object value)
+        {
+            Debug.Fail("Cannot modify collection from null wrapper.");
+            return false;
+        }
+
+        public EntityKey EntityKey
+        {
+            get
+            {
+                Debug.Fail("Cannot access EntityKey from null wrapper.");
+                return null;
+            }
+            set
+            {
+                Debug.Fail("Cannot access EntityKey from null wrapper.");
+            }
+        }
+
+        public EntityKey GetEntityKeyFromEntity()
+        {
+            Debug.Assert(false, "Method on NullEntityWrapper should not be called");
+            return null;
+        }
+
+        public ObjectContext Context
+        {
+            get
+            {
+                Debug.Fail("Cannot access Context from null wrapper.");
+                return null;
+            }
+            set
+            {
+                Debug.Fail("Cannot access Context from null wrapper.");
+            }
+        }
+
+        public MergeOption MergeOption
+        {
+            get
+            {
+                Debug.Fail("Cannot access MergeOption from null wrapper.");
+                return MergeOption.NoTracking;
+            }
+        }
+
+        public void AttachContext(ObjectContext context, EntitySet entitySet, MergeOption mergeOption)
+        {
+            Debug.Fail("Cannot access Context from null wrapper.");
+        }
+
+        public void ResetContext(ObjectContext context, EntitySet entitySet, MergeOption mergeOption)
+        {
+            Debug.Fail("Cannot access Context from null wrapper.");
+        }
+
+        public void DetachContext()
+        {
+            Debug.Fail("Cannot access Context from null wrapper.");
+        }
+
+        public void SetChangeTracker(IEntityChangeTracker changeTracker)
+        {
+            Debug.Fail("Cannot access ChangeTracker from null wrapper.");
+        }
+
+        public void TakeSnapshot(EntityEntry entry)
+        {
+            Debug.Fail("Cannot take snapshot of using null wrapper.");
+        }
+
+        public void TakeSnapshotOfRelationships(EntityEntry entry)
+        {
+            Debug.Fail("Cannot take snapshot using null wrapper.");
+        }
+
+        public Type IdentityType
+        {
+            get
+            {
+                Debug.Fail("Cannot access IdentityType from null wrapper.");
+                return null;
+            }
+        }
+
+        public void EnsureCollectionNotNull(RelatedEnd relatedEnd)
+        {
+            Debug.Fail("Cannot modify collection from null wrapper.");
+        }
+
+        public object GetNavigationPropertyValue(RelatedEnd relatedEnd)
+        {
+            Debug.Fail("Cannot access property using null wrapper.");
+            return null;
+        }
+
+        public void SetNavigationPropertyValue(RelatedEnd relatedEnd, object value)
+        {
+            Debug.Fail("Cannot access property using null wrapper.");
+        }
+
+        public void RemoveNavigationPropertyValue(RelatedEnd relatedEnd, object value)
+        {
+            Debug.Fail("Cannot access property using null wrapper.");
+        }
+
+        public void SetCurrentValue(EntityEntry entry, StateManagerMemberMetadata member, int ordinal, object target, object value)
+        {
+            Debug.Fail("Cannot set a value onto a null entity.");
+        }
+
+        public bool InitializingProxyRelatedEnds
+        {
+            get
+            { 
+                Debug.Fail("Cannot access flag on null wrapper.");
+                return false;
+            }
+            set
+            {
+                Debug.Fail("Cannot access flag on null wrapper.");
+            }
+        }
+
+        public void UpdateCurrentValueRecord(object value, EntityEntry entry)
+        {
+            Debug.Fail("Cannot UpdateCurrentValueRecord on a null entity."); 
+        }
+
+        public bool RequiresRelationshipChangeTracking
+        {
+            get { return false; }
+        }
+    }
+}