ThreadPool的QueueUserWorkItem 方法 (WaitCallback)和QueueUserWorkItem 方法 (WaitCallback, Object)

注：要使用此方法都需要引入應用：using System.Threading;//引入應用

參數意義：將要執行的方法排入隊列以便執行，WaitCallback，即表示將要執行的方法；Object，包含方法所用數據的對象。如果將方法成功排入隊列，則為 true；否則為 false。

一、下面是ThreadPool.QueueUserWorkItem 方法 (WaitCallback)的示例代碼：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;//引入應用

namespace QueueUserWorkItem_WaitCallback_
{
    class Program
    {
        static void Main(string[] args)
        {
            // Queue the task.
            ThreadPool.QueueUserWorkItem(new WaitCallback(ThreadProc));

            Console.WriteLine("Main thread does some work, then sleeps.");
            // If you comment out the Sleep, the main thread exits before
            // the thread pool task runs.  The thread pool 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.");
        }

        // This thread procedure performs the task.
        static void ThreadProc(Object stateInfo)
        {
            // No state object was passed to QueueUserWorkItem, so 
            // stateInfo is null.
            Console.WriteLine("Hello from the thread pool.");
        }
    }
}

運行以上代碼后：

二、下面是ThreadPool.QueueUserWorkItem 方法 (WaitCallback, Object)的示例代碼：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;

namespace QueueUserWorkItem__WaitCallback__Object_
{
    //將方法排入隊列以便執行，並指定包含該方法所用數據的對象。 此方法在有線程池線程變得可用時執行。
    /*
     * 
     * public static bool QueueUserWorkItem(WaitCallback callBack,Object state)
     * 
     * 
     * callBack  類型：System.Threading.WaitCallback
     * WaitCallback ，它表示要執行的方法。
     * 
     * 
     * state     類型：System.Object
     * 包含方法所用數據的對象。
     * 
     * 
     * 返回值    類型：System.Boolean
     * 如果此方法成功排隊，則為 true；如果無法將該工作項排隊，則引發 NotSupportedException。
     * 
     * 
     * 注：如果回調方法需要復雜數據，可以定義包含這些數據的類。
     * 
     */
    class Program
    {
        static void Main(string[] args)
        {
            // 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.
            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.");
        }

        // 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);
        }
    }

    // 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;
        }
    }
}

運行以上代碼后：