QueueUserWorkItem()的用法

[stevenjin]

在创建线程池时，QueueUserWorkItem()方法将一个任务项排列到线程池中，原型如下：
public static bool QueueUserWorkItem(WaitCallback callBack,object state)
其中，callback表示线程池执行任务时要调用的委托，state表示包含状态的对象，该对象将在线程执行任务时传递给委托。返回值true表明方法调用成功了，false表示调用失败。在MSDN的示例里，我看到了一个new，被搞晕了，它在这里干嘛的呀？这句代码如下：
if (ThreadPool.QueueUserWorkItem(new WaitCallback(ThreadProc), ti))

完整代码如下：
// This example shows how to create an object containing task
// information, and pass that object to a task queued for
// execution by the thread pool.
using System;
using System.Threading;

// TaskInfo holds state information for a task that will be
// executed by a ThreadPool thread.
public class TaskInfo {
// State information for the task. These members
// can be implemented as read-only properties, read/write
// properties with validation, and so on, as required.
public string Boilerplate;
public int Value;

// Public constructor provides an easy way to supply all
// the information needed for the task.
public TaskInfo(string text, int number) {
Boilerplate = text;
Value = number;
}
}

public class Example {
public static void Main() {
// Create an object containing the information needed
// for the task.
TaskInfo ti = new TaskInfo("This report displays the number {0}.", 42);

// Queue the task and data.
if (ThreadPool.QueueUserWorkItem(new WaitCallback(ThreadProc), ti)) {
Console.WriteLine("Main thread does some work, then sleeps.");

// If you comment out the Sleep, the main thread exits before
// the ThreadPool task has a chance to run. ThreadPool uses
// background threads, which do not keep the application
// running. (This is a simple example of a race condition.)
Thread.Sleep(1000);

Console.WriteLine("Main thread exits.");
}
else {
Console.WriteLine("Unable to queue ThreadPool request.");
}
}

// The thread procedure performs the independent task, in this case
// formatting and printing a very simple report.
//
static void ThreadProc(Object stateInfo) {
TaskInfo ti = (TaskInfo) stateInfo;
Console.WriteLine(ti.Boilerplate, ti.Value);
}
}

[witer666]

可以NEW一个构造函数

[gomoku]

[Quote=引用楼主 stevenjin 的帖子:]
我看到了一个new，被搞晕了，它在这里干嘛的呀？这句代码如下：
if (ThreadPool.QueueUserWorkItem(new WaitCallback(ThreadProc), ti))
[/Quote]

The normal way to create a delegate.

//If you write code like this:
ThreadPool.QueueUserWorkItem( ThreadProc, ti));

//Actually the compiler understands it and silently changes it to:
ThreadPool.QueueUserWorkItem(new WaitCallback(ThreadProc), ti));

[xuwen861209]

WaitCallback是一个委托，new的作用是建立一个WaitCallback类型的委托实例，参数ThreadProc是线程启动时需要进行处理的方法。