如何在運行時使用DynamicResourceExtension和IValueConverter設置顏色？

Question

我有一個枚舉：

public enum SignalColor
{
    None,
    Signal01A,
    Signal02A
 }

和LightTheme.xaml：

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                >
<ResourceDictionary.MergedDictionaries>
    <ResourceDictionary Source="../Colors.xaml"/>
</ResourceDictionary.MergedDictionaries>
<!--Signal colors-->
<SolidColorBrush x:Key="Signal01ABrush" Color="#8bc34a"/>
<SolidColorBrush x:Key="Signal01BBrush" Color="#5b9914"/>
</ResourceDictionary>

我有SignalColorSelector控件來選擇顏色

<c:SignalColorSelector Name="Test" Grid.Column="0" AllowsTransparent="True" SelectedColor="Signal02A"></c:SignalColorSelector>
<c:SignalColorSelector Name="ChooseColor" Grid.Column="1" Header="Choose a color" SelectedColor="Signal01A"></c:SignalColorSelector>

如何創建從MarkupExtension派生並實現IValueConverter的SignalColorToBrushConverter類？ 在Convert方法中，該值應為SignalColor類型。 如果它是SignalColor.None，則返回DependencyProperty.UnsetValue。 否則，使用DynamicResourceExtension返回相應的信號顏色筆刷 。

編輯1我創建了SignalColorToBrushConverter類：

 public class SignalColorToBrushConverter : MarkupExtension, IValueConverter
{
    private static DynamicResourceExtension dynamicResource = new DynamicResourceExtension();

    public SignalColorToBrushConverter()
    {
    }

    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        return this;
    }

    public object Convert(object value, Type tagertType, object parameter, System.Globalization.CultureInfo culture)
    {
        if (value == null)
            return null;

        SignalColor signalColor = (SignalColor)Enum.Parse(typeof(SignalColor), value.ToString());

        switch (signalColor)
        {
            case SignalColor.None:
                return DependencyProperty.UnsetValue;
            case SignalColor.Signal01A:
                dynamicResource.ResourceKey = "Signal01ABrush";
                break;
            case SignalColor.Signal01B:
                dynamicResource.ResourceKey = "Signal01BBrush";
                break;
            case SignalColor.Signal02A:
                dynamicResource.ResourceKey = "Signal02ABrush";
                break;
            case SignalColor.Signal02B:
                dynamicResource.ResourceKey = "Signal02BBrush";
                break;
        }

        try
        {
            return Application.Current.FindResource(dynamicResource.ResourceKey);
        }
        catch (ResourceReferenceKeyNotFoundException)
        {
            return DependencyProperty.UnsetValue;
        }
    }

然后，使用它：

 <TextBlock Text="Choose a color" Width="100" FontWeight="Bold" HorizontalAlignment="Left"
                                   Foreground="{Binding Path=SelectedColor, Converter={v:SignalColorToBrushConverter}, ElementName=ChooseColor}"/>

Answer 1

您可以創建如下所示的擴展標記

public class SignalColorExtension : MarkupExtension
{
    public SignalColor IncomingSignalColor
    {
        get;
        set;
    }

    public SignalColorExtension() { }

    public SignalColorExtension(string color)
    {
        SignalColor outColor;
        if (! SignalColor.TryParse(color,true,out outColor))
            IncomingSignalColor = SignalColor.None;
    }
    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        var target = serviceProvider.GetService(typeof(IProvideValueTarget)) as IProvideValueTarget;
        var host = target.TargetObject as FrameworkElement;

        if (host != null && IncomingSignalColor != SignalColor.None)
        {
            var colorResourse = host.TryFindResource(IncomingSignalColor.ToString());
            return colorResourse;
        }
        return DependencyProperty.UnsetValue;
    }
}

並使用TargetObject上的find Resource查找顏色（如果它們與dynamicresource標記一樣存在）。 然后，您可以像下面那樣使用標記：

<Grid Background="{sigColor:SignalColor Signal01A}" >

其中sigColor是標記擴展所在的程序集的命名空間。