Silverlight中跨线程访问的问题

在silverlight中跨线程访问，不像在winform里有controls.invoke

在里面一般的情况下使用的是Dispather.BeginInvoke

但是本人还发现，用AsyncOperator或者AsynchronazationContext也可以实现上下文的转换

代码如下

 

<UserControl x:Class="SilverlightChat.Page"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    Width="400" Height="300">
    <Grid x:Name="LayoutRoot" Background="White">
        <Grid.RowDefinitions>
            <RowDefinition Height="80" />
            <RowDefinition Height="80" />
        </Grid.RowDefinitions>
        <TextBlock x:Name="tblTest" Text="not loaded yet" VerticalAlignment="Center" HorizontalAlignment="Center" Grid.Row="0" />
        <Button x:Name="btnTest" Content="ClickMe" Height="30" Width="50" Click="btnTest_Click" Grid.Row="1" />
    </Grid>
</UserControl>

 

using System.Windows.Controls;
using System.Threading;
using System.ComponentModel;

namespace SilverlightChat
{
    public partial class Page : UserControl
    {
        //private SynchronizationContext currentContext;
        private AsyncOperation asyncOper;


        public Page()
        {
            InitializeComponent();
            asyncOper = AsyncOperationManager.CreateOperation(null);
            //this.currentContext = SynchronizationContext.Current;
        }

        private void btnTest_Click(object sender, System.Windows.RoutedEventArgs e)
        {
            Thread t = new Thread(new ThreadStart(AcrossThread));
            t.Start();
        }

        private void AcrossThread()
        {
            asyncOper.Post(result =>
            {
                tblTest.Text = "HasChanged";
            }, null);
            //currentContext.Post(result =>
            //{
            //    tblTest.Text = "HasChanged";
            //}, null);
        }
    }
}

 

从而达到跨线程访问UI的目的

想请问达人。。后面两种访问具体在什么时候才会用的到。。