如何在WPF中应用多个样式

计算标记扩展的输出

要计算标记扩展的输出,我们需要覆盖MarkupExtension中名为"ProvideValue"的方法.从此方法返回的值将在标记扩展的目标中设置.

我开始为Style创建一个扩展方法,它知道如何合并两个样式.这种方法的代码非常简单:

public static void Merge(this Style style1, Style style2)
{
    if (style1 == null)
    {
        throw new ArgumentNullException("style1");
    }
    if (style2 == null)
    {
        throw new ArgumentNullException("style2");
    }

    if (style1.TargetType.IsAssignableFrom(style2.TargetType))
    {
        style1.TargetType = style2.TargetType;
    }

    if (style2.BasedOn != null)
    {
        Merge(style1, style2.BasedOn);
    }

    foreach (SetterBase currentSetter in style2.Setters)
    {
        style1.Setters.Add(currentSetter);
    }

    foreach (TriggerBase currentTrigger in style2.Triggers)
    {
        style1.Triggers.Add(currentTrigger);
    }

    // This code is only needed when using DynamicResources.
    foreach (object key in style2.Resources.Keys)
    {
        style1.Resources[key] = style2.Resources[key];
    }
}

style1.Merge(style2);

public MultiStyleExtension(params Style[] styles)
{
}

Style currentStyle = new StaticResourceExtension(currentResourceKey).ProvideValue(serviceProvider) as Style;

public override object ProvideValue(IServiceProvider serviceProvider)
{
    Style resultStyle = new Style();

    foreach (string currentResourceKey in resourceKeys)
    {
        Style currentStyle = new StaticResourceExtension(currentResourceKey).ProvideValue(serviceProvider) as Style;

        if (currentStyle == null)
        {
            throw new InvalidOperationException("Could not find style with resource key " + currentResourceKey + ".");
        }

        resultStyle.Merge(currentStyle);
    }
    return resultStyle;
}