Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Shared / MS / Internal / WeakReferenceList.cs / 1305600 / WeakReferenceList.cs
using System; using System.Collections; using System.Diagnostics; #if WINDOWS_BASE using MS.Internal.WindowsBase; #elif PRESENTATION_CORE using MS.Internal.PresentationCore; #elif PRESENTATIONFRAMEWORK using MS.Internal.PresentationFramework; #elif DRT using MS.Internal.Drt; #else #error Attempt to use FriendAccessAllowedAttribute from an unknown assembly. using MS.Internal.YourAssemblyName; #endif namespace MS.Internal { ////// This is a Cached ThreadSafe ArrayList of WeakReferences. /// - When the "List" property is requested a readonly reference to the /// list is returned and a reference to the readonly list is cached. /// - If the "List" is requested again, the same cached reference is returned. /// - When the list is modified, if a readonly reference is present in the /// cache then the list is copied before it is modified and the readonly list is /// released from the cache. /// [FriendAccessAllowed] internal class WeakReferenceList : CopyOnWriteList, IEnumerable { public WeakReferenceList():base(null) { } public WeakReferenceList(object syncRoot):base(syncRoot) { } public WeakReferenceListEnumerator GetEnumerator() { return new WeakReferenceListEnumerator(List); } IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); } public bool Contains(object item) { Debug.Assert(null != item, "WeakReferenceList.Contains() should not be passed null."); lock (base.SyncRoot) { int index = FindWeakReference(item); // If the object is already on the list then // return true if (index >= 0) return true; return false; } } public int Count { get { int count = 0; lock (base.SyncRoot) { count = base.LiveList.Count; } return count; } } ////// Add a weak reference to the List. /// Returns true if successfully added. /// Returns false if object is already on the list. /// public override bool Add(object obj) { Debug.Assert(null!=obj, "WeakReferenceList.Add() should not be passed null."); return Add(obj, false /*skipFind*/); } //Will insert a new WeakREference into the list. //The object bein inserted MUST be unique as there is no check for it. public bool Add(object obj, bool skipFind) { Debug.Assert(null!=obj, "WeakReferenceList.Add() should not be passed null."); lock(base.SyncRoot) { if (!skipFind && FindWeakReference(obj) >= 0) { return false; } return base.Internal_Add(new WeakReference(obj)); } } ////// Remove a weak reference to the List. /// Returns true if successfully added. /// Returns false if object is already on the list. /// public override bool Remove(object obj) { Debug.Assert(null!=obj, "WeakReferenceList.Remove() should not be passed null."); lock(base.SyncRoot) { int index = FindWeakReference(obj); // If the object is not on the list then // we are done. (return false) if(index < 0) return false; return base.RemoveAt(index); } } ////// Insert a weak reference into the List. /// Returns true if successfully inserted. /// Returns false if object is already on the list. /// public bool Insert(int index, object obj) { Debug.Assert(null!=obj, "WeakReferenceList.Add() should not be passed null."); lock(base.SyncRoot) { int existingIndex = FindWeakReference(obj); // If the object is already on the list then // we are done. (return false) if(existingIndex >= 0) return false; return base.Internal_Insert(index, new WeakReference(obj)); } } ////// Find an object on the List. /// Also cleans up dead weakreferences. /// private int FindWeakReference(object obj) { // syncRoot Lock MUST be held by the caller. // Search the LiveList looking for the object, also remove any // dead references.we find. These two operations are combinded // to prevent having to walk the list twice. // // We use the "LiveList" to avoid snapping a Clone everytime we // Change something. // To do this correctly you need to understand how the base class // virtualizes the Copy On Write. ArrayList list = base.LiveList; int foundItem = -1; for(int i = 0; i < list.Count; i++) { WeakReference weakRef = (WeakReference) list[i]; if(weakRef.IsAlive) { if(obj == weakRef.Target) foundItem = i; } else { // Removing dead refs should not invalidate "foundItem" above. // Call the base RemoveAt to preserve the Copy on Write // virtualization. ie. list.RemoveAt(i) would be WRONG! // The RemoveAt call might Clone the LiveList (the first // time only) so we should get a new reference to it. base.RemoveAt(i); list = base.LiveList; // Also the ArrayList will copy-up to fill the Removed element // so back up and do the same index again. i -= 1; } } return foundItem; } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007. // Copyright (c) Microsoft Corporation. All rights reserved.
Link Menu
This book is available now!
Buy at Amazon US or
Buy at Amazon UK
- MulticastNotSupportedException.cs
- DragDrop.cs
- XmlSchemaRedefine.cs
- BamlResourceDeserializer.cs
- XsdValidatingReader.cs
- XmlTypeAttribute.cs
- ClientRoleProvider.cs
- SqlInternalConnectionTds.cs
- LifetimeServices.cs
- SynchronousChannel.cs
- _ChunkParse.cs
- DropShadowEffect.cs
- Model3D.cs
- BindingExpression.cs
- XPathItem.cs
- XmlTypeMapping.cs
- NonClientArea.cs
- EntityDataSourceMemberPath.cs
- ProfilePropertySettings.cs
- MimeTypeMapper.cs
- SqlUserDefinedAggregateAttribute.cs
- FileCodeGroup.cs
- EntityDataReader.cs
- WhitespaceSignificantCollectionAttribute.cs
- PositiveTimeSpanValidatorAttribute.cs
- RootProjectionNode.cs
- QueryExecutionOption.cs
- HeaderedContentControl.cs
- QilInvokeEarlyBound.cs
- CategoryValueConverter.cs
- ParentUndoUnit.cs
- TCEAdapterGenerator.cs
- DataGridViewLinkColumn.cs
- EventEntry.cs
- DefaultIfEmptyQueryOperator.cs
- RecoverInstanceLocksCommand.cs
- PartialTrustVisibleAssembly.cs
- ReadOnlyDictionary.cs
- CharUnicodeInfo.cs
- AttributeEmitter.cs
- EncoderParameters.cs
- TdsParserSafeHandles.cs
- ZipIOBlockManager.cs
- MsmqProcessProtocolHandler.cs
- BlockCollection.cs
- EventManager.cs
- HttpProfileGroupBase.cs
- ExpressionBuilderCollection.cs
- ScriptReference.cs
- ETagAttribute.cs
- DictionaryBase.cs
- AudienceUriMode.cs
- SchemaTableOptionalColumn.cs
- InfoCardMasterKey.cs
- EntityViewGenerationAttribute.cs
- TextParagraph.cs
- StrokeSerializer.cs
- Utilities.cs
- TypefaceMetricsCache.cs
- graph.cs
- ButtonRenderer.cs
- DispatcherHooks.cs
- XmlObjectSerializerWriteContextComplexJson.cs
- DefaultEventAttribute.cs
- FileDialog_Vista_Interop.cs
- ReturnValue.cs
- XomlDesignerLoader.cs
- XmlSchemaComplexType.cs
- TextBox.cs
- ComponentChangedEvent.cs
- TransformerInfo.cs
- MDIClient.cs
- OrderedDictionaryStateHelper.cs
- StaticSiteMapProvider.cs
- CodeSubDirectory.cs
- TextServicesPropertyRanges.cs
- AssertUtility.cs
- HttpCacheVaryByContentEncodings.cs
- BamlResourceSerializer.cs
- DispatchChannelSink.cs
- InvalidEnumArgumentException.cs
- ParseChildrenAsPropertiesAttribute.cs
- CodeMethodInvokeExpression.cs
- IfJoinedCondition.cs
- AttributeUsageAttribute.cs
- AnonymousIdentificationSection.cs
- _StreamFramer.cs
- InvalidContentTypeException.cs
- PngBitmapEncoder.cs
- ResourceCodeDomSerializer.cs
- WindowsFormsHost.cs
- ApplicationBuildProvider.cs
- GZipStream.cs
- TemplateAction.cs
- DynamicPropertyReader.cs
- SchemaNamespaceManager.cs
- DeferredSelectedIndexReference.cs
- StringFormat.cs
- ControlPropertyNameConverter.cs
- DictionaryKeyPropertyAttribute.cs