c# winform编程之多线程ui界面资源修改总结篇

单线程的winfom程序中，设置一个控件的值是很easy的事情，直接 this.TextBox1.value = "Hello World!";就搞定了，但是如果在一个新线程中这么做，比如:
private void btnSet_Click(object sender, EventArgs e)
{   
    Thread t = new Thread(new ParameterizedThreadStart(SetTextBoxValue));
    //当然也可以用匿名委托写成Thread t = new Thread(SetTextBoxValue);
    t.Start("Hello World");
}


void SetTextBoxValue(object obj)
{
    this.textBox1.Text = obj.ToString();
}

运行时，会报出一个无情的错误：
线程间操作无效: 从不是创建控件“textBox1”的线程访问它。

究其原因，winform中的UI控件不是线程安全的，如果可以随意在任何线程中改变其值，你创建一个线程，我创建一个线程，大家都来抢着更改"TextBox1"的值，没有任何秩序的话，天下大乱...

解决办法:
1.掩耳盗铃法（Control.CheckForIllegalCrossThreadCalls = false;）--仅Winform有效
using System;
using System.Threading;
using System.Windows.Forms;

namespace ThreadTest
{
    public partial class Form1 : Form
    {       

        public Form1()
        {
            InitializeComponent();
            Control.CheckForIllegalCrossThreadCalls = false;//这一行是关键     
        }
      

        private void btnSet_Click(object sender, EventArgs e)
        {          
            Thread t = new Thread(new ParameterizedThreadStart(SetTextBoxValue));
            t.Start("Hello World");
        }


        void SetTextBoxValue(object obj)
        {
            this.textBox1.Text = obj.ToString();
        }       
    }
}

设置Control.CheckForIllegalCrossThreadCalls为false,相当于不检测线程之间的冲突，允许各路线程随便乱搞，当然最终TextBox1的值到底是啥难以预料，只有天知道，不过这也是最省力的办法

2.利用委托调用--最常见的办法（仅WinForm有效）
using System;
using System.Threading;
using System.Windows.Forms;

namespace ThreadTest
{
    public partial class Form1 : Form
    {
        delegate void D(object obj);

        public Form1()
        {
            InitializeComponent();           
        }
      

        private void btnSet_Click(object sender, EventArgs e)
        {          
            Thread t = new Thread(new ParameterizedThreadStart(SetTextBoxValue));
            t.Start("Hello World");
        }


        void SetTextBoxValue(object obj)
        {
            if (textBox1.InvokeRequired)
            {
                D d = new D(DelegateSetValue);
                textBox1.Invoke(d,obj);

            }
            else
            {
                this.textBox1.Text = obj.ToString();
            }
        }


        void DelegateSetValue(object obj)
        {
            this.textBox1.Text = obj.ToString();
        }
    }
}

3.利用SynchronizationContext上下文 -- 最神秘的方法(Winform/Silverlight能用)

之所以说它神秘，是因为msdn官方对它的解释据说也是不清不楚
using System;
using System.Threading;
using System.Windows.Forms;

namespace ThreadTest
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();           
        }      

        private void btnSet_Click(object sender, EventArgs e)
        {
            Thread t = new Thread(new ParameterizedThreadStart(Run));
            MyPram _p = new MyPram() { context = SynchronizationContext.Current, parm = "Hello World" };
            t.Start(_p);
        }

        void Run(object obj)
        {
            MyPram p = obj as MyPram;
            p.context.Post(SetTextValue, p.parm);
        }


        void SetTextValue(object obj)
        {
            this.textBox1.Text = obj.ToString();
        }
    }


    public class MyPram
    {
        public SynchronizationContext context { set; get; }
        public object parm { set; get; }
    }
}

4.利用BackgroundWorker --最偷懒的办法(Winform/Silverlight通用)

BackgroundWorker会在主线程之外，另开一个后台线程，我们可以把一些处理放在后台线程中处理，完成之后，后台线程会把结果传递给主线程，同时结束自己。
using System;
using System.ComponentModel;
using System.Windows.Forms;

namespace ThreadTest
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();           
        }      

        private void btnSet_Click(object sender, EventArgs e)
        {
            //MessageBox.Show(Thread.CurrentThread.ManagedThreadId.ToString());
            using (BackgroundWorker bw = new BackgroundWorker())
            {
                bw.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bw_RunWorkerCompleted);
                bw.DoWork += new DoWorkEventHandler(bw_DoWork);
                bw.RunWorkerAsync("Hello World");
            }
        }

        void bw_DoWork(object sender, DoWorkEventArgs e)
        {
            //MessageBox.Show(Thread.CurrentThread.ManagedThreadId.ToString());
            e.Result = e.Argument;//这里只是简单的把参数当做结果返回，当然您也可以在这里做复杂的处理后，再返回自己想要的结果(这里的操作是在另一个线程上完成的)
        }

        void bw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            //这时后台线程已经完成，并返回了主线程，所以可以直接使用UI控件了
            this.textBox1.Text = e.Result.ToString();
            //MessageBox.Show(Thread.CurrentThread.ManagedThreadId.ToString());
        }      
    }   
}

5.Dispatcher.BeginInvoke--Silverlight的独门秘籍
代码
using System.Threading;
using System.Windows.Controls;
using System.Windows.Input;

namespace ThreadTest
{
    public partial class MainPage : UserControl
    {
        public MainPage()
        {
            InitializeComponent();
        }

        private void LayoutRoot_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            Thread t = new Thread(SetTextValue);
            t.Start("Hello World");
        }

        void SetTextValue(object text)
        {
            this.Dispatcher.BeginInvoke(() => { this.txt.Text = text.ToString(); });           
        }
    }
}