Code:
/ DotNET / DotNET / 8.0 / untmp / WIN_WINDOWS / lh_tools_devdiv_wpf / Windows / wcp / Framework / MS / Internal / Ink / StrokeCollectionDefaultValueFactory.cs / 1 / StrokeCollectionDefaultValueFactory.cs
//---------------------------------------------------------------------------- // //// Copyright (C) Microsoft Corporation. All rights reserved. // // // Description: DefaultValueFactory for StrokeCollection // // History: // 2006/01/24 : [....] - Created // //--------------------------------------------------------------------------- using System; using System.Diagnostics; using System.Windows; using System.Windows.Controls; using System.Windows.Ink; namespace MS.Internal.Ink { internal class StrokeCollectionDefaultValueFactory : DefaultValueFactory { internal StrokeCollectionDefaultValueFactory() { } ////// Returns an "immutable" default value. Since we can't make the default value /// read only we'll return a new one every time. /// internal override object DefaultValue { get { return new StrokeCollection(); } } ////// Creates a mutable default value /// internal override object CreateDefaultValue(DependencyObject owner, DependencyProperty property) { Debug.Assert(property.PropertyType == typeof(StrokeCollection), string.Format(System.Globalization.CultureInfo.InvariantCulture, "The DependencyProperty {0} has to be type of StrokeCollection.", property)); // Instantiate our default value instance. StrokeCollection defaultValue = new StrokeCollection(); // Add event handlers for tracking the changes on the default value instance. StrokeCollectionDefaultPromoter promoter = new StrokeCollectionDefaultPromoter(owner, property); defaultValue.StrokesChanged += new StrokeCollectionChangedEventHandler(promoter.OnStrokeCollectionChanged); defaultValue.PropertyDataChanged += new PropertyDataChangedEventHandler(promoter.OnStrokeCollectionChanged ); return defaultValue; } /// /// A tracking class which monitors any changes on StrokeCollection /// private class StrokeCollectionDefaultPromoter { ////// Constructor /// /// /// internal StrokeCollectionDefaultPromoter(DependencyObject owner, DependencyProperty property) { _owner = owner; _dependencyProperty = property; } ////// A handler for both AttributeChanged and PropertyDataChanged. /// /// /// internal void OnStrokeCollectionChanged(object sender, TEventArgs e) { StrokeCollection value = (StrokeCollection)sender; // The current instance will be promoted to the local value other than the default value. // Then we could just remove our handlers to stop tracking. value.StrokesChanged -= new StrokeCollectionChangedEventHandler(OnStrokeCollectionChanged ); value.PropertyDataChanged -= new PropertyDataChangedEventHandler(OnStrokeCollectionChanged ); // if ( _owner.ReadLocalValue(_dependencyProperty) == DependencyProperty.UnsetValue ) { // Promote the instance to the local value. _owner.SetValue(_dependencyProperty, value); } // Remove this value from the DefaultValue cache so we stop // handing it out as the default value now that it has changed. PropertyMetadata metadata = _dependencyProperty.GetMetadata(_owner.DependencyObjectType); metadata.ClearCachedDefaultValue(_owner, _dependencyProperty); } private readonly DependencyObject _owner; private readonly DependencyProperty _dependencyProperty; } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007. // Copyright (c) Microsoft Corporation. All rights reserved.
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