浅述WinForm多线程编程与Control.Invoke的应用
VS2008、C#3.0
在WinForm开发中,我们通常不希望当窗体上点了某个按钮执行某个业务的时候,窗体就被卡死了,直到该业务执行完毕后才缓过来。一个最直接的方法便是使用多线程。多线程编程的方式在WinForm开发中必不可少。
本文介绍在WinForm开发中如何使用多线程,以及在线程中如何通过Control.Invoke方法返回窗体主线程执行相关操作。
-. WinForm多线程编程
1. new Thread()
新开一个线程,执行一个方法,没有参数传递:
private void DoWork() {
Thread t = new Thread(new ThreadStart(this.DoSomething));
t.Start();
}
private void DoSomething() {
MessageBox.Show("thread start");
}
新开一个线程,执行一个方法,并传递参数:
private void DoWork() {
Thread t = new Thread(new ParameterizedThreadStart(this.DoSomething));
t.Start("guozhijian");
}
private void DoSomething(object o) {
MessageBox.Show(o.ToString());
}
参数定义为object类型。
2. ThreadPool
众所周知,新开一个线程代价是很高昂的,如果我们每个操作都新开一个线程,那么太浪费了,于是,下面使用线程池。
无参数传递:
private void DoWork() {
ThreadPool.QueueUserWorkItem(new WaitCallback(this.DoSomething));
}
private void DoSomething(object o) {
MessageBox.Show("thread start");
}
有参数传递:
private void DoWork() {
ThreadPool.QueueUserWorkItem(new WaitCallback(this.DoSomething), "guozhijian");
}
private void DoSomething(object o) {
MessageBox.Show(o.ToString());
}
使用匿名方法更灵活:
private void DoWork() {
string name = "guozhijian";
ThreadPool.QueueUserWorkItem(new WaitCallback(delegate(object o){
MessageBox.Show(name);
}));
}
在匿名代码段里面可以直接访问局部变量,不用在关心参数传递的问题
二. Invoke
1. this.Invoke
现在,在业务线程里面执行完毕,要改变窗体控件的值了,此时,如果直接通过this得到控件的句柄,然后对它进行操作是会抛异常的,.Net WinForm Application里面是不允许这样的操作的。这是,可以调用Invoke方法
2.Invoke方法签名:
object Control.Invoke(Delegate Method)
object Control.Invoke(Delegate Method, params object[] args)
3.使用自定义委托
private void DoWork() {
WaitCallback wc = new WaitCallback(this.DoSomething);
ThreadPool.QueueUserWorkItem(wc, "Guozhijian");
}
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private delegate void MyInvokeDelegate(string name);
private void DoSomething(object o) {
this.Invoke(new MyInvokeDelegate(this.ChangeText), o.ToString());
}
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private void ChangeText(string name) {
this.textBox1.Text = name;
}
哦,太麻烦了,难道我每次都要定义一个委托啊,这样可不行。
4.使用System.Action:
private void DoWork() {
WaitCallback wc = new WaitCallback(this.DoSomething);
ThreadPool.QueueUserWorkItem(wc, "Guozhijian");
}
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private void DoSomething(object o) {
this.Invoke(new Action<string>(this.ChangeText), o.ToString());
}
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private void ChangeText(string name) {
this.textBox1.Text = name;
}
本例传递一个参数,System.Action有很多个重载,可以无参数(非泛型),而最多可以有四个参数,同样采用匿名方法,不使用泛型形式的System.Action,如下:
private void DoWork() {
WaitCallback wc = new WaitCallback(this.DoSomething);
ThreadPool.QueueUserWorkItem(wc, "Guozhijian");
}
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private void DoSomething(object o) {
this.Invoke(new Action(delegate() {
this.textBox1.Text = o.ToString();
}));
}
5.使用System.Func
如果Invoke调用主窗体操作之后,还希望在调用完得到一个返回值:
private void DoWork() {
WaitCallback wc = new WaitCallback(this.DoSomething);
ThreadPool.QueueUserWorkItem(wc, "Guozhijian");
}
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private void DoSomething(object o) {
System.Func<string, int> f = new Func<string, int>(this.GetId);
object result = this.Invoke(f,o.ToString());
MessageBox.Show(result.ToString());
}
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private int GetId(string name) {
this.textBox1.Text = name;
if (name == "Guozhijian") {
return 999;
}
else {
return 0;
}
}
result的值为 999。
System.Func同样有很多泛形重载,这里不赘述。
6.关于Invoke的拥有者:Control
本文例中都是用this来引用,这里this替换为窗体任何一个控件的句柄都是OK的,因为Control.Invoke含义是将方法委托给拥有该Control的线程去执行。
在WinForm开发中,我们通常不希望当窗体上点了某个按钮执行某个业务的时候,窗体就被卡死了,直到该业务执行完毕后才缓过来。一个最直接的方法便是使用多线程。多线程编程的方式在WinForm开发中必不可少。
本文介绍在WinForm开发中如何使用多线程,以及在线程中如何通过Control.Invoke方法返回窗体主线程执行相关操作。
-. WinForm多线程编程
1. new Thread()
新开一个线程,执行一个方法,没有参数传递:
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新开一个线程,执行一个方法,并传递参数:
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2. ThreadPool
众所周知,新开一个线程代价是很高昂的,如果我们每个操作都新开一个线程,那么太浪费了,于是,下面使用线程池。
无参数传递:
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二. Invoke
1. this.Invoke
现在,在业务线程里面执行完毕,要改变窗体控件的值了,此时,如果直接通过this得到控件的句柄,然后对它进行操作是会抛异常的,.Net WinForm Application里面是不允许这样的操作的。这是,可以调用Invoke方法
2.Invoke方法签名:
object Control.Invoke(Delegate Method)
object Control.Invoke(Delegate Method, params object[] args)
3.使用自定义委托
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4.使用System.Action:
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5.使用System.Func
如果Invoke调用主窗体操作之后,还希望在调用完得到一个返回值:
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result的值为 999。
System.Func同样有很多泛形重载,这里不赘述。
6.关于Invoke的拥有者:Control
本文例中都是用this来引用,这里this替换为窗体任何一个控件的句柄都是OK的,因为Control.Invoke含义是将方法委托给拥有该Control的线程去执行。
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