理解SynchronizationContext，如何在Winform里面跨线程访问UI控件

public partial class Form1 : Form
    {

        SynchronizationContext sc = null;
        public Form1()
        {

            InitializeComponent();
            sc = SynchronizationContext.Current;
            this.Load += Form1_Load;
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            Thread thread = new Thread((object state) =>
            {
                int id = Thread.CurrentThread.ManagedThreadId;

                for (int i = 0; i < 1000; i++)
                {
                    Thread.Sleep(10);
                    sc.Post(UpdateUI, "line " + i.ToString());
                }
            });
            thread.Start();
        }


        /// <summary>
        /// This method is executed on the main UI thread.
        /// </summary>
        private void UpdateUI(object state)
        {
            int id = Thread.CurrentThread.ManagedThreadId;
            SendLogMessage("UpdateUI thread:" + id);
            string text = state as string;
            SendLogMessage(text);
        }

        /// <summary>
        /// UI线程回调方法,访问控件刷新显示
        /// </summary>
        /// <param name="message">消息内容</param>
        private void LogMessageBack(object message)
        {
            rbxMessageInfo.AppendText(DateTime.Now + "->" + message.ToString() + Environment.NewLine);
        }

        /// <summary>
        /// 交给UI线程去排队显示消息
        /// </summary>
        /// <param name="message"></param>
        private void SendLogMessage(string message)
        {
            sc.Post(LogMessageBack, message);
        }
    }

protected internal static System.AsyncCallback SyncCallback(System.AsyncCallback callback)
		{
			System.Threading.SynchronizationContext sc = System.Threading.SynchronizationContext.Current;
			if (sc == null)
			{
				return callback;
			}
			return delegate(System.IAsyncResult asyncResult)
			{
				sc.Post(delegate(object result)
				{
					callback((System.IAsyncResult)result);
				}, asyncResult);
			};
		}
		protected void DataAction(Action action)
		{
			try
			{
				action();
			}
			catch (System.Exception ex)
			{
				OperateLog.OpExcpLog(string.Format("[{0}][{1}]功能操作执行异常，异常原因：{2}", action.Method.GetType().FullName, action.Method.Name, ex.Message));
				System.Windows.Forms.MessageBox.Show(EESException.getException(ex).Message, "异常警告", System.Windows.Forms.MessageBoxButtons.OK, System.Windows.Forms.MessageBoxIcon.Hand);
			}
		}
		protected void BeginAction(MethodDelegate action, object obj, params object[] args)
		{
			EForm.AsyncRequest asyncRequest = new EForm.AsyncRequest(action, obj, args, System.Threading.SynchronizationContext.Current);
			this.inAsyncAction = null;
			this.OnBeginAction(asyncRequest);
			System.Threading.ThreadPool.QueueUserWorkItem(new System.Threading.WaitCallback(this.OnWaitCallback), asyncRequest);
		}
		protected void BeginAction(object proxy, string command, params object[] args)
		{
			MethodDelegate action = FastInvoke.CreateMethodDelegate(proxy.GetType().GetMethod(command));
			this.BeginAction(action, proxy, args);
		}
		protected void BeginActionWithToolTip(MethodDelegate action, object obj, string toolTip, params object[] args)
		{
			EForm.AsyncRequest asyncRequest = new EForm.AsyncRequest(action, obj, args, System.Threading.SynchronizationContext.Current, toolTip);
			this.inAsyncAction = null;
			this.OnBeginAction(asyncRequest);
			System.Threading.ThreadPool.QueueUserWorkItem(new System.Threading.WaitCallback(this.OnWaitCallback), asyncRequest);
		}
		protected void BeginActionWithToolTip(object proxy, string command, string toolTip, params object[] args)
		{
			MethodDelegate action = FastInvoke.CreateMethodDelegate(proxy.GetType().GetMethod(command));
			this.BeginAction(action, proxy, new object[]
			{
				toolTip,
				args
			});
		}
		protected virtual void OnBeginAction(EForm.AsyncRequest context)
		{
			if (this.waitingForm.Visible)
			{
				throw new EESException("后台正在执行，请稍候……");
			}
			this.waitingForm.Message = context.ToolTip;
			this.waitingForm.Show();
		}
		protected virtual void OnEndAction(EForm.AsyncResponse context)
		{
			this.waitingForm.Visible = false;
		}
		private void OnWaitCallback(object state)
		{
			EForm.AsyncRequest asyncRequest = (EForm.AsyncRequest)state;
			object result = null;
			System.Exception exception = null;
			try
			{
				result = asyncRequest.Method(asyncRequest.Obj, asyncRequest.Args);
			}
			catch (System.Exception ex)
			{
				exception = ex;
			}
			EForm.AsyncResponse state2 = new EForm.AsyncResponse(asyncRequest.Method, result, asyncRequest.Args, exception);
			System.Threading.SynchronizationContext context = asyncRequest.Context;
			if (context != null)
			{
				context.Post(new System.Threading.SendOrPostCallback(this.OnSendOrPostCallback), state2);
			}
		}
		private void OnSendOrPostCallback(object state)
		{
			EForm.AsyncResponse asyncResponse = (EForm.AsyncResponse)state;
			this.OnEndAction(asyncResponse);
			if (asyncResponse.Exception != null)
			{
				System.Windows.Forms.MessageBox.Show(EESException.getException(asyncResponse.Exception).Message);
				return;
			}
			this.OnActionComplete(asyncResponse);
		}
		protected virtual void OnActionComplete(EForm.AsyncResponse context)
		{
		}