Code:
/ DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Core / System / Windows / Media / UniqueEventHelper.cs / 1 / UniqueEventHelper.cs
using System; using System.Collections; using System.Diagnostics; namespace System.Windows.Media { ////// Aids in making events unique. i.e. you register the same function for /// the same event twice, but it will only be called once for each time /// the event is invoked. /// /// UniqueEventHelper should only be accessed from the UI thread so that /// handlers that throw exceptions will crash the app, making the developer /// aware of the problem. /// internal class UniqueEventHelperwhere TEventArgs : EventArgs { /// /// Add the handler to the list of handlers associated with this event. /// If the handler has already been added, we simply increment the ref /// count. That way if this same handler has already been added, it /// won't be invoked multiple times when the event is raised. /// internal void AddEvent(EventHandlerhandler) { if (handler == null) { throw new System.ArgumentNullException("handler"); } EnsureEventTable(); if (_htDelegates[handler] == null) { _htDelegates.Add(handler, 1); } else { int refCount = (int)_htDelegates[handler] + 1; _htDelegates[handler] = refCount; } } /// /// Removed the handler from the list of handlers associated with this /// event. If the handler has been added multiple times (more times than /// it has been removed), we simply decrement its ref count. /// internal void RemoveEvent(EventHandlerhandler) { if (handler == null) { throw new System.ArgumentNullException("handler"); } EnsureEventTable(); if (_htDelegates[handler] != null) { int refCount = (int)_htDelegates[handler]; if (refCount == 1) { _htDelegates.Remove(handler); } else { _htDelegates[handler] = refCount - 1; } } } /// /// Enumerates all the keys in the hashtable, which must be EventHandlers, /// and invokes them. /// /// The sender for the callback. /// The args object to be sent by the delegate internal void InvokeEvents(object sender, TEventArgs args) { Debug.Assert((sender != null), "Sender is null"); if (_htDelegates != null) { Hashtable htDelegates = (Hashtable)_htDelegates.Clone(); foreach (EventHandlerhandler in htDelegates.Keys) { Debug.Assert((handler != null), "Event handler is null"); handler(sender, args); } } } /// /// Clones the event helper /// internal UniqueEventHelperClone() { UniqueEventHelper ueh = new UniqueEventHelper (); if (_htDelegates != null) { ueh._htDelegates = (Hashtable)_htDelegates.Clone(); } return ueh; } /// /// Ensures Hashtable is created so that event handlers can be added/removed /// private void EnsureEventTable() { if (_htDelegates == null) { _htDelegates = new Hashtable(); } } private Hashtable _htDelegates; } // internal class UniqueEventHelper { ////// Add the handler to the list of handlers associated with this event. /// If the handler has already been added, we simply increment the ref /// count. That way if this same handler has already been added, it /// won't be invoked multiple times when the event is raised. /// internal void AddEvent(EventHandler handler) { if (handler == null) { throw new System.ArgumentNullException("handler"); } EnsureEventTable(); if (_htDelegates[handler] == null) { _htDelegates.Add(handler, 1); } else { int refCount = (int)_htDelegates[handler] + 1; _htDelegates[handler] = refCount; } } ////// Removed the handler from the list of handlers associated with this /// event. If the handler has been added multiple times (more times than /// it has been removed), we simply decrement its ref count. /// internal void RemoveEvent(EventHandler handler) { if (handler == null) { throw new System.ArgumentNullException("handler"); } EnsureEventTable(); if (_htDelegates[handler] != null) { int refCount = (int)_htDelegates[handler]; if (refCount == 1) { _htDelegates.Remove(handler); } else { _htDelegates[handler] = refCount - 1; } } } ////// Enumerates all the keys in the hashtable, which must be EventHandlers, /// and invokes them. /// /// The sender for the callback. /// The args object to be sent by the delegate internal void InvokeEvents(object sender, EventArgs args) { Debug.Assert((sender != null), "Sender is null"); if (_htDelegates != null) { Hashtable htDelegates = (Hashtable)_htDelegates.Clone(); foreach (EventHandler handler in htDelegates.Keys) { Debug.Assert((handler != null), "Event handler is null"); handler(sender, args); } } } ////// Clones the event helper /// internal UniqueEventHelper Clone() { UniqueEventHelper ueh = new UniqueEventHelper(); if (_htDelegates != null) { ueh._htDelegates = (Hashtable)_htDelegates.Clone(); } return ueh; } ////// Ensures Hashtable is created so that event handlers can be added/removed /// private void EnsureEventTable() { if (_htDelegates == null) { _htDelegates = new Hashtable(); } } private Hashtable _htDelegates; } } // 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
- MsmqInputChannelListenerBase.cs
- UnauthorizedAccessException.cs
- HtmlWindow.cs
- Button.cs
- PropertyRef.cs
- SerTrace.cs
- ToolStripRenderEventArgs.cs
- CodeGotoStatement.cs
- FileLogRecordStream.cs
- UnsafeMethods.cs
- SoapReflectionImporter.cs
- HostedNamedPipeTransportManager.cs
- WebHttpBindingCollectionElement.cs
- GetPageCompletedEventArgs.cs
- GreenMethods.cs
- SqlClientPermission.cs
- WebPartEditVerb.cs
- EventlogProvider.cs
- TextRangeBase.cs
- validationstate.cs
- _FixedSizeReader.cs
- ListBindingHelper.cs
- FrameworkTextComposition.cs
- WorkflowInstanceTerminatedRecord.cs
- Queue.cs
- UInt64Storage.cs
- RenderData.cs
- SettingsProviderCollection.cs
- AssemblyInfo.cs
- DbProviderFactoriesConfigurationHandler.cs
- CompositeScriptReferenceEventArgs.cs
- XmlSecureResolver.cs
- UDPClient.cs
- EnumValidator.cs
- OletxVolatileEnlistment.cs
- VectorValueSerializer.cs
- DataRow.cs
- ArrayExtension.cs
- QueryStringConverter.cs
- CommonObjectSecurity.cs
- TraceProvider.cs
- Figure.cs
- BoolExpression.cs
- ProxyWebPartManagerDesigner.cs
- RecordBuilder.cs
- MarginsConverter.cs
- XmlTextEncoder.cs
- Size3DConverter.cs
- Math.cs
- XmlSerializer.cs
- ServiceModelSecurityTokenTypes.cs
- SettingsPropertyCollection.cs
- Version.cs
- SafeNativeMethodsMilCoreApi.cs
- AndCondition.cs
- StyleConverter.cs
- PagesSection.cs
- CellParaClient.cs
- RawStylusActions.cs
- MsmqInputChannelBase.cs
- DataSourceCache.cs
- ButtonBase.cs
- WebPartConnectionsCancelVerb.cs
- TextUtf8RawTextWriter.cs
- VirtualPathUtility.cs
- SingleObjectCollection.cs
- TdsParameterSetter.cs
- FontStyleConverter.cs
- ProcessInputEventArgs.cs
- Html32TextWriter.cs
- ProtectedProviderSettings.cs
- AttachedAnnotation.cs
- DataConnectionHelper.cs
- VideoDrawing.cs
- JoinElimination.cs
- DocumentXPathNavigator.cs
- BooleanProjectedSlot.cs
- HashMembershipCondition.cs
- XmlMtomWriter.cs
- ArgumentNullException.cs
- BlurEffect.cs
- WindowsIdentity.cs
- Selector.cs
- SendKeys.cs
- ParserHooks.cs
- TextRangeAdaptor.cs
- DocumentSequenceHighlightLayer.cs
- CodeConditionStatement.cs
- TabletCollection.cs
- MessageHeader.cs
- SrgsRule.cs
- Validator.cs
- _ShellExpression.cs
- StdValidatorsAndConverters.cs
- WorkflowEnvironment.cs
- ExtensionDataObject.cs
- HideDisabledControlAdapter.cs
- ServiceModelStringsVersion1.cs
- WorkItem.cs
- _CacheStreams.cs