a) IAsycResult interface
IAsyncResult stores relative asynchronouse invoking information,including the following
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property type comments
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AsyncState Object additional data invoking method
AsyncWaitHandle System.Treading.WaitHandle to wait synchronouse object until OP finished.
CompletedSynchronously bool
IsCompleted bool operation has finished or not?
Invoking BeginInvoke() of delegate wll return an ISyncResult reference, and the same applies to BeginXXX().
ii. Simple sample about Threads executing synchronousely and asynchronousely
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Runtime.Remoting.Messaging;
namespace MyThread
{
public class ThreadUnits
{
public static string ThreadDescription(Thread thread)
{
StringBuilder sb = new StringBuilder(100);
if (thread.Name != null && thread.Name != "")
{
sb.Append(thread.Name);
sb.Append(", ");
}
sb.Append("hash: ");
sb.Append(thread.GetHashCode());
sb.Append(", pool:");
sb.Append(thread.IsThreadPoolThread);
sb.Append(", backgrnd");
sb.Append(thread.IsBackground);
sb.Append(", state");
sb.Append(thread.ThreadState);
return sb.ToString();
}
public static void DisplayThreadInfo(string context)
{
string output = "\n" + context + "\n" + ThreadDescription(Thread.CurrentThread);
Console.WriteLine(output);
}
}
public class DataRetriever
{
public string GetAddress(string name)
{
ThreadUnits.DisplayThreadInfo("In GetAddress...");
//simulate waiting to get results off database servers.
Thread.Sleep(1000);
if (name == "Simon")
return "Simon lives in Lancaster";
else if (name == "Wrox Press")
return "Wrox Press lives in Acocks Green";
else
return name + "is not in database
}
public delegate string GetAddressDelegate(string name);
public void GetAddressSync(string name)
{
try
{
GetAddressDelegate dc = new GetAddressDelegate(this.GetAddress);
string result = dc(name);
Console.WriteLine("\n Sync:" + result);
}
catch (Exception ex)
{
Console.WriteLine("\nSync: a problem occurred:" + ex.Message);
}
}
//BeginInvoke和EndInvoke显式调用，不用回调函数
public void GetAddressAsyncWait(string name)
{
GetAddressDelegate dc = new GetAddressDelegate(this.GetAddress);
IAsyncResult ar = dc.BeginInvoke(name, null, null);
//此处没有利用回调函数 AsyncCallBack,因此用EndInvoker显式关闭
/*
Main Thread can do other work now。。。。
*/
try
{
string result = dc.EndInvoke(ar);
Console.WriteLine("\nAsync waiting:" + result);
}
catch (Exception ex)
{
Console.WriteLine("\nAsync Waiting, a problem occurred:" + ex.Message);
}
}
public void GetResultsOnCallback(IAsyncResult ar)
{
GetAddressDelegate del = (GetAddressDelegate)((AsyncResult)ar).AsyncDelegate;
//AsyncResult comf from : System.Runtime.remoting.message;
//especial notes: IAsyncResult ->System.Threading;
// AsyncResult ->System.Runtime.Remoting.message;
try
{
string result;
result = del.EndInvoke(ar);
Console.WriteLine("\nOn CallBack :result is " + result);
}
catch (Exception ex)
{
Console.WriteLine("On Callback, problem occurred: "+ex.Message);
}
}
//BeginInvoke之后，利用回调函数返回结果
public void GetAddressAsync(string name)
{
GetAddressDelegate dc = new GetAddressDelegate(this.GetAddress);
AsyncCallback cb = new AsyncCallback(this.GetResultsOnCallback);
IAsyncResult ar = dc.BeginInvoke(name, cb, null);
}
}
public class EntryPoint
{
public static void Main()
{
Thread.CurrentThread.Name = "Main Thread";
DataRetriever dr = new DataRetriever();
//Synchronization
dr.GetAddressSync("Simon");
dr.GetAddressSync("Wrox Press");
dr.GetAddressSync("Herengang");
//Asynchronization without callback
dr.GetAddressAsync("Simon");
dr.GetAddressAsync("Herengang");
dr.GetAddressAsync("Wrox Press");
//Asynchronization with callback
dr.GetAddressAsyncWait("Simon");
dr.GetAddressAsyncWait("Wrox Press");
dr.GetAddressAsyncWait("Herengang");
Console.WriteLine("thread finished");
Console.Read();
}
}
}
if everything goes well, you will see the following window:
