SnapshotChangeTrackingStrategy.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / DataEntity / System / Data / Objects / Internal / SnapshotChangeTrackingStrategy.cs / 1305376 / SnapshotChangeTrackingStrategy.cs
                        

                        
                            using System; 
using System.Collections.Generic;
using System.Text;
using System.Data.Objects.DataClasses;
 
namespace System.Data.Objects.Internal
{ 
    ///  
    /// Implementation of the change tracking strategy for entities that require snapshot change tracking.
    /// These are typically entities that do not implement IEntityWithChangeTracker. 
    /// 
    internal sealed class SnapshotChangeTrackingStrategy : IChangeTrackingStrategy
    {
        private static SnapshotChangeTrackingStrategy _instance = new SnapshotChangeTrackingStrategy(); 

        ///  
        /// Returns the single static instance of this class; a single instance is all that is needed 
        /// because the class is stateless.
        ///  
        public static SnapshotChangeTrackingStrategy Instance
        {
            get
            { 
                return _instance;
            } 
        } 

        // Private constructor to help prevent additional instances being created. 
        private SnapshotChangeTrackingStrategy()
        {
        }
 
        // See IChangeTrackingStrategy documentation
        public void SetChangeTracker(IEntityChangeTracker changeTracker) 
        { 
            // Nothing to do when using snapshots for change tracking
        } 

        // See IChangeTrackingStrategy documentation
        public void TakeSnapshot(EntityEntry entry)
        { 
            if (entry != null)
            { 
                entry.TakeSnapshot(false); 
            }
        } 

        // See IChangeTrackingStrategy documentation
        public void SetCurrentValue(EntityEntry entry, StateManagerMemberMetadata member, int ordinal, object target, object value)
        { 
            // If the target is the entity, then this is a change to a member on the entity itself rather than
            // a change to some complex type hanging off the entity.  In this case we can use the change tracking 
            // API in the normal way. 
            if (Object.ReferenceEquals(target, entry.Entity))
            { 
                // equivalent of EntityObject.ReportPropertyChanging()
                ((IEntityChangeTracker)entry).EntityMemberChanging(member.CLayerName);
                member.SetValue(target, value);
                // equivalent of EntityObject.ReportPropertyChanged() 
                ((IEntityChangeTracker)entry).EntityMemberChanged(member.CLayerName);
 
                if (member.IsComplex) 
                {
                    // This is required because the OSE contains a separate cache of user objects for 
                    // complex objects such that original values can be looked up correctly.
                    entry.UpdateComplexObjectSnapshot(member, target, ordinal, value);
                }
            } 
            else
            { 
                // Must be a complex type.  We would like to do this: 
                // ((IEntityChangeTracker)entry).EntityComplexMemberChanging(topLevelMember.CLayerName, target, member.CLayerName);
                // ((IEntityChangeTracker)entry).EntityComplexMemberChanged(topLevelMember.CLayerName, target, member.CLayerName); 
                //
                // However, we have no way of getting the topLevelMember.CLayerName.  This is because the value record does not
                // contain any reference to its parent.  (In non-POCO, ComplexObject takes care of this.)
                // Therefore, in this case we are going to just call a localized DetectChanges to make sure that changes in the 
                // complex types are found.
                // 
                // Note that this case only happens when the entity is POCO and complex types are set through the CurrentValues 
                // object.  This is probably not a very common pattern.
                member.SetValue(target, value); 
                if (entry.State != EntityState.Added)
                {
                    // Entry is not Detached - checked in ValidateState() in EntityEntry.SetCurrentEntityValue
                    entry.DetectChangesInProperties(true); 
                }
            } 
        } 

        // See IChangeTrackingStrategy documentation 
        public void UpdateCurrentValueRecord(object value, EntityEntry entry)
        {
            // No change tracker, but may or may not be a proxy
            entry.UpdateRecordWithoutSetModified(value, entry.CurrentValues); 
            entry.DetectChangesInProperties(false);
        } 
    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.

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