如何在Windows中交叉引用MergedDictionaries？

Question

WPF文档 on MergedDictionaries建议，如果在XAML中加载两个ResourceDictionaries，则第二个加载的ResourceDictionaries将能够引用第一个ResourceDictionaries。Windows电话文档 on MergedDictionaries没有说明这一点，但我假设同样的规则也适用。但是，以下内容在我的Windows App.xaml中不起作用，

<ResourceDictionary.MergedDictionaries>
    <ResourceDictionary Source="View/ThemeDictionaries/LightThemeResourceDictionary.xaml"/>
    <ResourceDictionary Source="View/ThemeDictionaries/MainResourceDictionary.xaml"/>
</ResourceDictionary.MergedDictionaries>

调试说，MainResourceDictionary行不能引用在LightThemeResourceDictionary中定义的SubTitleTextColor --我检查了引用的拼写。

这种类型的加载在Windows中是不可能的吗？我该怎么处理呢？

Answer 1

基于Silverlight资源文档 (比WPF更适用)，这个场景将无法工作。有两种方法可以解决这个问题：

• 将第一个字典合并到第二个字典中，而不是应用程序的字典。
• 创建一个附加属性，该属性具有一个List<ResourceDictionary>，该属性将手动将它们合并为一个巨大的ResourceDictionary，并将应用程序的资源设置为它。

Answer 2

感谢Abe的帮助，不过最后我还是选择了一个“解析器”类，该类作为合并字典包括在适当的主题字典中。原因超出了原来问题的范围：

1. 您可以在初始化阶段在App.xaml.cs中加载适当的字典，而不必在以后根据用户的选择以编程方式覆盖资源(在默认主题中合并之前，比如启动时的光照，如果用户选择了Dark，那么稍后在黑暗主题中合并)
2. 最重要的是，如果您以后重写主题资源，那么在初始化时定义的引用覆盖资源的其他资源不会改变！

代码是基于这个博客作者的想法的。

ThemeResourceDictionaryResolver.cs

using System;
using System.IO;
using System.Windows;
using System.Windows.Markup;
using System.Windows.Resources;
using System.IO.IsolatedStorage;

namespace YourAppName.View
{
    public enum ApplicationTheme 
    {
        Dark,
        Light
    }

    public class ThemeResourceDictionaryResolver : ResourceDictionary
    {
        public ThemeResourceDictionaryResolver() : base()
        {
            ApplicationTheme theme;
            if (System.ComponentModel.DesignerProperties.IsInDesignTool)
            {
                // Set here which dictionary you want to be loaded in Blend
                theme = ApplicationTheme.Light;
            }
            else
            {
                ApplicationTheme theme;
                if (!IsolatedStorage.ApplicationSettings.TryGetValue("ApplicationTheme", out theme))
                {
                    // The 'standard' way to get the global phone theme
                    Visibility darkBGVisibility = (Visibility)Application.Current.Resources["PhoneDarkThemeVisibility"];
                    theme = (darkBGVisibility == Visibility.Visible) ? ApplicationTheme.Dark : ApplicationTheme.Light;
                }
            }
            // Change the URI string as appropriate - this way refers to the Dictionaries 
            // which are set to 'Build: Page'. I couldn't get to work when set to Build as
            // Content and using the simpler URI scheme.
            Uri uri = new Uri(string.Format("YouAppName;component/View/Themes/{0}ThemeResourceDictionary.xaml", theme), UriKind.RelativeOrAbsolute);
            ResourceDictionary res = this.LoadXaml<ResourceDictionary>(uri);
            this.MergedDictionaries.Add(res);
        }


        // For some reason a simple ResourceDictionary() { Source = uri }; does not work, 
        // need to use this instead
        T LoadXaml<T>(Uri uri)
        {
            StreamResourceInfo info = Application.GetResourceStream(uri);
            if (info != null)
            {
                using (StreamReader reader = new StreamReader(info.Stream))
                {
                    return (T)XamlReader.Load(reader.ReadToEnd());
                }
            }
            return default(T);
        }

    }
}

MainResourceDictionary.xaml

...

<ResourceDictionary.MergedDictionaries>
    <views:ThemeResourceDictionaryResolver />
</ResourceDictionary.MergedDictionaries>

<!-- StaticResources that refer to the theme StaticResources can go here -->

...

App.xaml

...

<ResourceDictionary.MergedDictionaries>
    <ResourceDictionary Source="View/Themes/MainResourceDictionary.xaml" />
</ResourceDictionary.MergedDictionaries>

...