如何在WPF中的代码中复制资源引用？

Question

在我的应用程序中,我有一个颜色资源.我有一个元素使用该颜色作为xaml中的动态资源.

  <Window x:Class="ResourcePlay.MainWindow"
          xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
          xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
          Title="MainWindow" Height="350" Width="425">
     <Window.Resources>
        <Color x:Key="MyColor">Red</Color>
     </Window.Resources>
     <Grid>
        <Rectangle VerticalAlignment="Top" Width="80" Height="80" Margin="10">
           <Rectangle.Fill>
              <SolidColorBrush x:Name="TopBrush" Color="{DynamicResource MyColor}"/>
           </Rectangle.Fill>
        </Rectangle>
        <Rectangle VerticalAlignment="Bottom" Width="80" Height="80" Margin="10">
           <Rectangle.Fill>
              <SolidColorBrush x:Name="BottomBrush"/>
           </Rectangle.Fill>
        </Rectangle>
     </Grid>
  </Window>

在代码中,我想复制此资源引用.

  using System.Windows;
  using System.Windows.Media;

  namespace ResourcePlay {
     public partial class MainWindow : Window {
        public MainWindow() {
           InitializeComponent();

           // I want to copy the resource reference, not the color.
           BottomBrush.Color = TopBrush.Color;

           // I'd really rather do something like this.
           var reference = TopBrush.GetResourceReference(SolidColorBrush.ColorProperty);
           BottomBrush.SetResourceReference(reference);

           // I want this to change the colors of both elements
           Resources["MyColor"] = Colors.Green;
        }
     }
  }

但是,SetResourceReference仅适用于FrameworkElements或FrameworkContentElements.SolidColorBrush只是一个Freezable.另外,我不知道如何在代码中获取资源引用.

有没有办法在WPF中执行此操作,以便两种颜色同时更改？在我的实际应用程序中,问题并不那么简单,所以我不能在xaml中添加第二个DynamicResource.

Answer 1

Il Vic建议使用反射.在此基础上,我能够为DependencyObject构建一些扩展方法来实现我想要的.我真的不喜欢在代码中使用反射,如果其他人知道更好的方法来实现它,我很乐意看到它.每当我尝试从后面的代码调试DynamicResources时,至少这将是有用的.

  public static class DependencyObjectExtensions
  {
     public static object GetDynamicResourceKey(this DependencyObject obj, DependencyProperty prop)
     {
        // get the value entry from the depencency object for the specified dependency property
        var dependencyObject = typeof(DependencyObject);
        var dependencyObject_LookupEntry = dependencyObject.GetMethod("LookupEntry", BindingFlags.NonPublic | BindingFlags.Instance);
        var entryIndex = dependencyObject_LookupEntry.Invoke(obj, new object[] { prop.GlobalIndex });
        var effectiveValueEntry_GetValueEntry = dependencyObject.GetMethod("GetValueEntry", BindingFlags.NonPublic | BindingFlags.Instance);
        var valueEntry = effectiveValueEntry_GetValueEntry.Invoke(obj, new object[] { entryIndex, prop, null, 0x10 });

        // look inside the value entry to find the ModifiedValue object
        var effectiveValueEntry = valueEntry.GetType();
        var effectiveValueEntry_Value = effectiveValueEntry.GetProperty("Value", BindingFlags.Instance | BindingFlags.NonPublic);
        var effectiveValueEntry_Value_Getter = effectiveValueEntry_Value.GetGetMethod(nonPublic: true);
        var rawEntry = effectiveValueEntry_Value_Getter.Invoke(valueEntry, new object[0]);

        // look inside the ModifiedValue object to find the ResourceReference
        var modifiedValue = rawEntry.GetType();
        var modifiedValue_BaseValue = modifiedValue.GetProperty("BaseValue", BindingFlags.Instance | BindingFlags.NonPublic);
        var modifiedValue_BaseValue_Getter = modifiedValue_BaseValue.GetGetMethod(nonPublic: true);
        var resourceReferenceValue = modifiedValue_BaseValue_Getter.Invoke(rawEntry, new object[0]);

        // check the ResourceReference for the original ResourceKey
        var resourceReference = resourceReferenceValue.GetType();
        var resourceReference_resourceKey = resourceReference.GetField("_resourceKey", BindingFlags.NonPublic | BindingFlags.Instance);
        var resourceKey = resourceReference_resourceKey.GetValue(resourceReferenceValue);

        return resourceKey;
     }

     public static void SetDynamicResourceKey(this DependencyObject obj, DependencyProperty prop, object resourceKey)
     {
        var dynamicResource = new DynamicResourceExtension(resourceKey);
        var resourceReferenceExpression = dynamicResource.ProvideValue(null);
        obj.SetValue(prop, resourceReferenceExpression);
     }
  }

第二种方法用于DynamicResourceExtension避免使用Activator的一些肮脏,但第一种方法感觉非常脆弱.

我可以在原始示例中使用这些方法,如下所示:

  public MainWindow() {
     InitializeComponent();

     var key = TopBrush.GetDynamicResourceKey(SolidColorBrush.ColorProperty);
     BottomBrush.SetDynamicResourceKey(SolidColorBrush.ColorProperty, key);

     Resources["MyColor"] = Colors.Green;
  }

这适用于任何DependencyProperty,前提是当我们尝试获取资源键时将其设置为DynamicResource.生产代码需要更多的技巧.