如何在Xamarin中创建ResourceDictionary？

<Application xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="YourAppName.App">
    <Application.Resources>
        <ResourceDictionary>
            <!-- 在这里添加资源 -->
        </ResourceDictionary>
    </Application.Resources>
</Application>

<Application.Resources>
    <ResourceDictionary>
        <Style x:Key="ButtonStyle" TargetType="Button">
            <Setter Property="BackgroundColor" Value="Blue" />
            <Setter Property="TextColor" Value="White" />
        </Style>
        <Color x:Key="PrimaryColor">#FF0000</Color>
        <x:String x:Key="WelcomeMessage">Welcome to Xamarin Forms!</x:String>
    </ResourceDictionary>
</Application.Resources>

<Button Style="{StaticResource ButtonStyle}" Text="{StaticResource WelcomeMessage}" BackgroundColor="{StaticResource PrimaryColor}" />