注意：SqlCommand异步操作的特别之处在于线程并不依赖于CLR线程池，而是由Windows内部提供，这比使用异步委托更有效率。但如果需要使用回调函数的时候，回调函数的线程依然是来自于CLR线程池的工作者线程。

 1     class Program
 2     {
 3         //把Asynchronous Processing设置为true 4         static string connectionString = "Data Source=LESLIE-PC;Initial Catalog=Business;“+ 5                                          "Integrated Security=True;Asynchronous Processing=true";
 6
 7         static void Main(string[] args)
 8         {
 9             //把CLR线程池最大线程数设置为100010             ThreadPool.SetMaxThreads(1000, 1000);
11             ThreadPoolMessage("Start");
12
13             //使用WAITFOR DELAY命令来虚拟操作14             SqlConnection connection = new SqlConnection(connectionString);
15             SqlCommand command = new SqlCommand("WAITFOR DELAY '0:0:3';", connection);
16             connection.Open();
17
18             //启动异步SqlCommand操作，利用轮询方式监测操作19             IAsyncResult result = command.BeginExecuteNonQuery();
20             ThreadPoolMessage("BeginRead");
21             while (!result.AsyncWaitHandle.WaitOne(500))
22                 Console.WriteLine("Main thread do work........");
23
24             //结束异步SqlCommand25             int count= command.EndExecuteNonQuery(result);
26             ThreadPoolMessage("\nCompleted");
27             Console.ReadKey();
28         }
29
30         //显示线程池现状31         static void ThreadPoolMessage(string data)
32         {
33             int a, b;
34             ThreadPool.GetAvailableThreads(out a, out b);
35             string message = string.Format("{0}\n  CurrentThreadId is {1}\n  "+
36                    "WorkerThreads is:{2}  CompletionPortThreads is :{3}\n",
37                    data, Thread.CurrentThread.ManagedThreadId, a.ToString(), b.ToString());
38             Console.WriteLine(message);
39         }
40     }

     class Program{//把Asynchronous Processing设置为true         static string connectionString = "Data Source=LESLIE-PC;Initial Catalog=Business;”+“Integrated Security=True;Asynchronous Processing=true";static void Main(string[] args){//把CLR线程池最大线程数设置为1000             ThreadPool.SetMaxThreads(1000, 1000);ThreadPoolMessage("Start");//使用WAITFOR DELAY命令来虚拟操作             SqlConnection connection = new SqlConnection(connectionString);SqlCommand command = new SqlCommand("WAITFOR DELAY '0:0:3';", connection);connection.Open();//启动异步SqlCommand操作，并把SqlCommand对象传递到回调函数             IAsyncResult result = command.BeginExecuteNonQuery(new AsyncCallback(AsyncCallbackMethod),command);Console.ReadKey();}static void AsyncCallbackMethod(IAsyncResult result){Thread.Sleep(200);ThreadPoolMessage("AsyncCallback");SqlCommand command = (SqlCommand)result.AsyncState;int count=command.EndExecuteNonQuery(result);command.Connection.Close();}//显示线程池现状         static void ThreadPoolMessage(string data){int a, b;ThreadPool.GetAvailableThreads(out a, out b);string message = string.Format("{0}\n  CurrentThreadId is {1}\n  "+"WorkerThreads is:{2}  CompletionPortThreads is :{3}\n",data, Thread.CurrentThread.ManagedThreadId, a.ToString(), b.ToString());Console.WriteLine(message);}}