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　　　　　　　　　　　　　　　　　　　　多线程更新processbar或输出后台更新前端控件

   背景

　　　　在用Windows Form编程时候，我们通常会遇到如此问题：

           1. 后台更新大量处理数据过程。

           2.需要把后台的Log输出到前端，以监控运行状态。

           3. 如果运行大量处理过程，前端会出现白屏状态，这样对用户不友好。

         针对此，我们需求创建多线程来处理后台。用多线程调用处理，按平常处理，是不能更新主线程的控件的，需要做特殊处理。

   代码程序如下：

       using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Threading;namespace TestWinForm
{
    public partial class Form1 : Form
    {
        delegate void SetValueCallback(int value);public Form1()
        {
            InitializeComponent();
        }private void btnRun_Click(object sender, EventArgs e)
        {
            Thread t = new Thread(new ThreadStart(Foo));
            t.Start();
        }private void Foo()
        {
            for (int i = 1; i <= 100; i++)
            {
                Thread.Sleep(100);
                SetProcessBarValue(i);
                SetLabelValue(i);
            }
        }private void SetLabelValue(int value)
        {
            // InvokeRequired required compares the thread ID of the
            // calling thread to the thread ID of the creating thread.
            // If these threads are different, it returns true.
            if (this.lblStatus.InvokeRequired)
            {
                SetValueCallback d = new SetValueCallback(SetLabelValue);
                this.Invoke(d, new object[] { value });
            }
            else
            {
                this.lblStatus.Text = value.ToString()+'%';
            }
        }private void SetProcessBarValue(int value)
        {
            // InvokeRequired required compares the thread ID of the
            // calling thread to the thread ID of the creating thread.
            // If these threads are different, it returns true.
            if (this.prbStatus.InvokeRequired)
            {
                SetValueCallback d = new SetValueCallback(SetProcessBarValue);
                this.Invoke(d, new object[] { value });
            }
            else
            {
                this.prbStatus.Value = value;
            }
        }
    }
}