1.关于委托的BeginInvoke和EndInvoke方法
.NET Framework 允许您异步调用任何方法。为此，应定义与您要调用的方法具有相同签名的委托；公共语言运行库会自动使用适当的签名为该委托定义 BeginInvoke 和 EndInvoke 方法。
例如：
namespace carydemo2
{
public class CaryAsync
{
public string LongtimeOperation(int data, out int threadId)
{
Console.WriteLine("Long time operation begin");
data = data + 123;
Thread.Sleep(500);
threadId = Thread.CurrentThread.ManagedThreadId;
return String.Format("Data:{0}.", data.ToString());
}
}
public delegate string CaryAsyncCaller(int data, out int threadId);
public class CaryTest
{
private static int threadId;
public static void
{
CaryAsync ca = new CaryAsync();
CaryAsyncCaller caller = new CaryAsyncCaller(ca.LongtimeOperation);
IAsyncResult result = caller.BeginInvoke(3000, out threadId, null, null);
Thread.Sleep(0);
Console.WriteLine("Main thread :{0}", Thread.CurrentThread.ManagedThreadId);
result.AsyncWaitHandle.WaitOne();
while (result.IsCompleted == false)
{
Thread.Sleep(10);
}
string returnValue = caller.EndInvoke(out threadId, result);
Console.WriteLine("The caller thread: {0}, Data :\"{1}\".", threadId, returnValue);
}
}
}
调用你可以使用 BeginInvoke 返回的 IAsyncResult 的 AsyncWaitHandle 属性来获取 WaitHandle。异步调用完成时会发出 WaitHandle 信号，而您可以通过调用 WaitOne 方法等待它。这样你就可以在异步调用完成之前或之后，在通过调用 EndInvoke 检索结果之前，还可以执行其他处理。
可以使用由 BeginInvoke 返回的 IAsyncResult 的 IsCompleted 属性来发现异步调用何时完成。
还可以在调用完成时执行回调方法，代码如下：
public class CaryTest
{
private static int threadId;
public static void
{
CaryAsync ca = new CaryAsync();
CaryAsyncCaller caller = new CaryAsyncCaller(ca.LongtimeOperation);
IAsyncResult result = caller.BeginInvoke(3000, out threadId, new AsyncCallback(CaryCallBack), caller);
Console.ReadLine();
}
static void CaryCallBack(IAsyncResult ar)
{
CaryAsyncCaller caller = (CaryAsyncCaller)ar.AsyncState;
string returnValue = caller.EndInvoke(out threadId, ar);
Console.WriteLine("The caller thread:{0},return value\"{1}\"", threadId, returnValue);
}
}
2.IAsyncResult接口：它表示异步操作的状态.该接口定义了4个公用属性，如下：
AsyncState 获取用户定义的对象，它限定或包含关于异步操作的信息。
AsyncWaitHandle 获取用于等待异步操作完成的 WaitHandle。
CompletedSynchronously 获取异步操作是否同步完成的指示。
IsCompleted 获取异步操作是否已完成的指示。
IAsyncResult 接口由包含可异步操作的方法的类实现。它是启动异步操作的方法的返回类型，如 FileStream.BeginRead，也是结束异步操作的方法的第三个参数的类型，如 FileStream.EndRead。当异步操作完成时，IAsyncResult 对象也将传递给由 AsyncCallback 委托调用的方法。
支持 IAsyncResult 接口的对象存储异步操作的状态信息，并提供同步对象以允许线程在操作完成时终止。
3. AsyncCallback 委托
引用在异步操作完成时调用的回调方法。AsyncCallback 引用的事件处理程序包含完成客户端异步任务的程序逻辑。AsyncCallback 使用 IAsyncResult 接口获取异步操作的状态。
下面为例子：
namespace carydemo1
{
public class AsyncResult : System.IAsyncResult
{
public object AsyncState
{
get; set;
}
System.Threading.WaitHandle asyncWaitHandle = new AutoResetEvent(false);
public System.Threading.WaitHandle AsyncWaitHandle
{
get { return asyncWaitHandle; }
}
public bool CompletedSynchronously
{
get; set;
}
public bool IsCompleted
{
get;
set;
}
public int Data
{
set;get;
}
}
class TestClass
{
AsyncCallback asyncCallback;
AsyncResult asyncResult;
public TestClass()
{
asyncCallback = new AsyncCallback(callback);
asyncResult = new AsyncResult();
}
void callback(IAsyncResult asyncResult)
{
AsyncResult temp = asyncResult as AsyncResult;
((AutoResetEvent)temp.AsyncWaitHandle).Set();
}
public AsyncResult AsyncMethod(int value, object asyncState)
{
Console.WriteLine("Start...");
this.asyncResult.AsyncState = asyncState;
this.asyncResult.Data = value;
Thread t = new Thread(new ThreadStart(myThread));
t.Start();
return this.asyncResult;
}
void myThread()
{
Console.WriteLine("begin ");
for (int i = 0; i < 3; i++)
{
Console.WriteLine(i);
asyncResult.Data = asyncResult.Data + i;
Thread.Sleep(500);
}
Console.WriteLine("end...");
asyncCallback(this.asyncResult);
}
}
class Program
{
static void
{
TestClass obj = new TestClass();
AsyncResult r = obj.AsyncMethod(50, null);
r.AsyncWaitHandle.WaitOne();
System.Console.WriteLine(r.Data);
System.Console.WriteLine("完成");
System.Console.Read();
}
}
}
