线程操作UI界面的方法

以前一般都是用BeginInvoke来刷新UI界面，
现在采用 SynchronizationContext 来刷新，写起来清楚多了。

SynchronizationContext synchronizationContext;

private void TongbuShuju(List layers)
{
synchronizationContext = SynchronizationContext.Current;
Thread thread = new Thread(() => TongbuShuju(layers, synchronizationContext));
thread.Start();
}
public void TongbuShuju(List layers, SynchronizationContext uiContext)
{
string errorMsg = string.Format("开始同步图层：【{0}】", "测试1");
uiContext.Send(AppendTxtMsg, errorMsg);
}
public void AppendTxtMsg(Object state)
{
txtResult.Text += string.Format("{0}{1}", state, System.Environment.NewLine);
}