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
- FSWPathEditor.cs
- BufferAllocator.cs
- WebPartDescription.cs
- HitTestFilterBehavior.cs
- QuaternionRotation3D.cs
- FileDialog.cs
- ScalarConstant.cs
- BindingSource.cs
- TheQuery.cs
- FileDialog.cs
- ClientTarget.cs
- ParameterModifier.cs
- EnvironmentPermission.cs
- TreeNodeConverter.cs
- Vars.cs
- LineGeometry.cs
- MimeMapping.cs
- OpCopier.cs
- DbParameterCollection.cs
- ColorMatrix.cs
- QueryOutputWriter.cs
- AnnotationComponentManager.cs
- DynamicMethod.cs
- formatstringdialog.cs
- ViewStateModeByIdAttribute.cs
- DateTimeConverter2.cs
- DesignerActionItem.cs
- NameValueCollection.cs
- DbCommandTree.cs
- PropertyMap.cs
- ContentFileHelper.cs
- ExpressionEditorAttribute.cs
- SafeEventLogWriteHandle.cs
- _Connection.cs
- Propagator.Evaluator.cs
- OledbConnectionStringbuilder.cs
- DirectoryRedirect.cs
- FromRequest.cs
- JsonGlobals.cs
- UserControlBuildProvider.cs
- CodeObject.cs
- DropDownList.cs
- AnimationClockResource.cs
- SafeRightsManagementEnvironmentHandle.cs
- RegexReplacement.cs
- Object.cs
- CodeDelegateInvokeExpression.cs
- Font.cs
- CatalogZone.cs
- OdbcInfoMessageEvent.cs
- XmlSerializableServices.cs
- XmlQueryOutput.cs
- CatalogPart.cs
- M3DUtil.cs
- CircleHotSpot.cs
- WebPartDesigner.cs
- Subset.cs
- DataTablePropertyDescriptor.cs
- _FtpControlStream.cs
- Util.cs
- SAPIEngineTypes.cs
- XmlTextWriter.cs
- DropTarget.cs
- ComEventsMethod.cs
- FixedSOMLineCollection.cs
- CustomErrorsSectionWrapper.cs
- DispatcherProcessingDisabled.cs
- TextProperties.cs
- Int16AnimationUsingKeyFrames.cs
- List.cs
- ComponentEditorPage.cs
- AnimationTimeline.cs
- WebPartEventArgs.cs
- MimeBasePart.cs
- WebPartAuthorizationEventArgs.cs
- PrinterResolution.cs
- documentsequencetextcontainer.cs
- PageCanvasSize.cs
- Column.cs
- PointHitTestParameters.cs
- EncryptedData.cs
- LinqDataSourceDisposeEventArgs.cs
- EventWaitHandle.cs
- HeaderedContentControl.cs
- QueryExpr.cs
- SecurityMode.cs
- TagPrefixInfo.cs
- CaseInsensitiveComparer.cs
- ExpandCollapsePattern.cs
- XmlSchemaParticle.cs
- EmptyControlCollection.cs
- HttpServerUtilityWrapper.cs
- WebZoneDesigner.cs
- RequestCachePolicy.cs
- GACMembershipCondition.cs
- ResourceDisplayNameAttribute.cs
- Brush.cs
- AutomationIdentifierGuids.cs
- CaseInsensitiveOrdinalStringComparer.cs
- SqlDependencyListener.cs