具有自定义背景颜色的MetroDialog

Question

我想显示带有自定义背景颜色的MetroDialog，以显示错误消息。

我尝试使用属性CustomResourceDictionary没有运气：

显示讯息的功能：

public static async Task<MessageDialogResult> DialogOK(string title, string message)
{
    MetroDialogSettings settings = new MetroDialogSettings();
    settings.CustomResourceDictionary = new ResourceDictionary { Source = new Uri("pack://application:,,,/MyApp;component/Resources/ErrorDialogRD.xaml") };
    var result = await mainWindow.ShowMessageAsync(title, message, MessageDialogStyle.Affirmative, settings );
    return result;
}

资源字典：

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:Dialogs="clr-namespace:MahApps.Metro.Controls.Dialogs;assembly=MahApps.Metro">
    <Style TargetType="{x:Type Dialogs:BaseMetroDialog}">
        <Setter Property="Background" Value="Red" />
    </Style>
</ResourceDictionary>

我错过了什么？ ：）