如何在 WPF 后面的代码中复制资源引用? [英] How do I duplicate a resource reference in code behind in WPF?
问题描述
在我的应用程序中，我有一个颜色资源.我有一个元素将该颜色用作 xaml 中的动态资源.
In my application, I have a color resources. I have one element that uses that color as a dynamic resource in xaml.
<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，我想复制这个资源引用.
In the code, I want to duplicate this resource reference.
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，我不知道如何在后面的代码中获取资源引用.
However, SetResourceReference only works for FrameworkElements or FrameworkContentElements. SolidColorBrush is just a Freezable. Also, I have no idea how to get a resource reference in code behind.
有没有办法在 WPF 中做到这一点，以便两种颜色同时改变?在我的实际应用中，问题并没有那么简单，所以我不能只在 xaml 中添加第二个 DynamicResource.
Is there a way to do this in WPF so that both of the colors change at the same time? In my real application, the problem isn't quite so simple, so I can't just add a second DynamicResource in xaml.
推荐答案
Il Vic 建议使用反射.对此进行扩展，我能够为 DependencyObject 构建一些可以执行我想要的扩展方法.我真的不喜欢在代码中使用反射，如果其他人知道实现这一点的更好方法，我很乐意看到它.至少，每当我尝试从背后的代码调试 DynamicResources 时，这都会有所帮助.
Il Vic suggested using reflection. Expanding on that, I was able to build some extension methods for DependencyObject that do what I want. I don't really like using reflection in code, and if someone else knows a better way to implement this, I'd love to see it. At least this will be helpful whenever I'm trying to debug DynamicResources from code behind.
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);
}
}
第二种方法使用 DynamicResourceExtension 来避免 Activator 的一些麻烦，但第一种方法感觉非常脆弱.
The second method uses DynamicResourceExtension to avoid some nastiness with Activator, but the first method feels incredibly brittle.
我可以在原始示例中使用这些方法，如下所示:
I can use these methods in my original example as follows:
public MainWindow() {
InitializeComponent();
var key = TopBrush.GetDynamicResourceKey(SolidColorBrush.ColorProperty);
BottomBrush.SetDynamicResourceKey(SolidColorBrush.ColorProperty, key);
Resources["MyColor"] = Colors.Green;
}
这将适用于任何 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.
This will work for any DependencyProperty, provided it is set to a DynamicResource when we try to get the resource key. A little more finesse would be needed for production code.
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