NullEntityWrapper.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / DataEntity / System / Data / Objects / Internal / NullEntityWrapper.cs / 1305376 / NullEntityWrapper.cs
                        
                        
                            //---------------------------------------------------------------------- 
// 
//      Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// 
// @owner       [....]
// @backupOwner [....] 
//--------------------------------------------------------------------- 
using System.Collections;
using System.Data.Objects.DataClasses; 
using System.Data.Entity;
using System.Data.Metadata.Edm;
using System.Diagnostics;
 
namespace System.Data.Objects.Internal
{ 
    ///  
    /// 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.
    /// 
    internal class NullEntityWrapper : IEntityWrapper 
    {
        private static IEntityWrapper s_nullWrapper = new NullEntityWrapper(); 
 
        // Private constructor prevents anyone else from creating an instance
        private NullEntityWrapper() 
        {
        }

        ///  
        /// The single instance of this class.
        ///  
        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; } 
        }
 
        public bool RequiresComplexChangeTracking
        {
            get { return false; }
        } 

        public bool RequiresScalarChangeTracking 
        { 
            get { return false; }
        } 

        public bool RequiresAnyChangeTracking
        {
            get { return false; } 
        }
    } 
} 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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NullEntityWrapper.cs source code in C# .NET

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