ThreadPool..::.QueueUserWorkItem 方法 (WaitCallback, Object)

參考 MSDN  http://msdn.microsoft.com/zh-tw/library/4yd16hza.aspx

// 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);
}
}
///////////////////////
當執行此敘述 if (ThreadPool.QueueUserWorkItem(new WaitCallback(ThreadProc), ti
ti會一起傳送到 ThreadProc(Object stateInfo) 裡面的
stateInfo
因此 在
ThreadProc(Object stateInfo)中  需要轉換 Object 為 TaskInfo 型態再轉存一次