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//---------------------------------------------------------------------
// <copyright file="NullEntityWrapper.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
//
// @owner Microsoft
// @backupOwner Microsoft
//---------------------------------------------------------------------
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; }
}
}
}
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