sl下的两种跨线程访问方式

Deployment.Current.Dispatcher.BeginInvoke(() =>
{

     //do something
});

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;

using System.IO;
using System.Threading;

namespace SilverlightApplication1
{
    public partial class MainPage : UserControl
    {
        SynchronizationContext syn;

        public MainPage()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, RoutedEventArgs e)
        {
            syn = SynchronizationContext.Current;

            string url = "http://www.baidu.com/";
            HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(url);
            request.BeginGetResponse(new AsyncCallback(a), request);
        }

        private void a(IAsyncResult ia)
        {
            HttpWebRequest r = (HttpWebRequest)ia.AsyncState;
            HttpWebResponse s = (HttpWebResponse)r.EndGetResponse(ia);
            string str = "";
            using (StreamReader sr =new StreamReader(s.GetResponseStream()))
            {
                str = sr.ReadToEnd();
            }
            syn.Post(getText, str);
        }

        private void getText(object text)
        {
            textBox1.Text = text.ToString();
        }

    }
}