110 lines
4.1 KiB
C#
110 lines
4.1 KiB
C#
namespace AntDesignWPF.Controls
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{
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using System;
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using System.ComponentModel;
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using System.Windows;
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using System.Windows.Data;
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/// <summary>
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///依赖属性描述符的 AddValueChanged 会导致内存泄漏，如您所知。
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///因此，如此处所述，您可以创建自定义类 PropertyChangeNotifier 来监听
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///到任何依赖属性更改。
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///此类利用绑定使用弱引用来管理关联的事实
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///因此，该类不会对属性更改它的对象进行 root 权限。它还使用一个 WeakReference
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///以维护对它正在监视其属性的对象的引用，而无需对该对象进行 root 设置。
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///通过这种方式，您可以维护这些对象的集合，以便可以取消挂钩属性
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///稍后更改，而不必担心该集合会对您正在监视其值的对象进行 root。
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///完整的实现可以在这里找到：http://agsmith.wordpress.com/2008/04/07/propertydescriptor-addvaluechanged-alternative/
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/// </summary>
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internal sealed class PropertyChangeNotifier : DependencyObject, IDisposable
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{
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private WeakReference _propertySource;
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public PropertyChangeNotifier(DependencyObject propertySource, string path)
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: this(propertySource, new PropertyPath(path))
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{
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}
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public PropertyChangeNotifier(DependencyObject propertySource, DependencyProperty property)
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: this(propertySource, new PropertyPath(property))
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{
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}
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public PropertyChangeNotifier(DependencyObject propertySource, PropertyPath property)
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{
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if (null == propertySource)
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{
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throw new ArgumentNullException(nameof(propertySource));
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}
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if (null == property)
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{
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throw new ArgumentNullException(nameof(property));
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}
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this._propertySource = new WeakReference(propertySource);
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var binding = new Binding();
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binding.Path = property;
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binding.Mode = BindingMode.OneWay;
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binding.Source = propertySource;
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BindingOperations.SetBinding(this, ValueProperty, binding);
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}
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public DependencyObject PropertySource
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{
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get
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{
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try
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{
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// note, it is possible that accessing the target property
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// will result in an exception so i’ve wrapped this check
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// in a try catch
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return this._propertySource.IsAlive
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? this._propertySource.Target as DependencyObject
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: null;
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}
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catch
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{
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return null;
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}
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}
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}
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/// <summary>
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/// Identifies the <see cref="Value"/> dependency property
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/// </summary>
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public static readonly DependencyProperty ValueProperty
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= DependencyProperty.Register("Value", typeof(object), typeof(PropertyChangeNotifier),
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new FrameworkPropertyMetadata(null, new PropertyChangedCallback(OnPropertyChanged)));
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/// <summary>
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/// Returns/sets the value of the property
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/// </summary>
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/// <seealso cref="ValueProperty"/>
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[Description("Returns/sets the value of the property")]
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[Category("Behavior")]
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[Bindable(true)]
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public object Value
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{
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get { return (object)this.GetValue(ValueProperty); }
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set { this.SetValue(ValueProperty, value); }
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}
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private static void OnPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
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{
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var notifier = (PropertyChangeNotifier)d;
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if (notifier.RaiseValueChanged)
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{
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notifier.ValueChanged?.Invoke(notifier.PropertySource, EventArgs.Empty);
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}
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}
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public event EventHandler ValueChanged;
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public bool RaiseValueChanged { get; set; } = true;
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public void Dispose()
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{
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BindingOperations.ClearBinding(this, ValueProperty);
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}
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}
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}
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