关于webservice的异步调用简单实例

下面，我们就以异步调用一个webservice?为例作说明。
这是一个webservice

????<WebMethod(Description:="试验")>?_
????Public?Function?delCurTable(ByVal?tbName?As?String)?As?Boolean
????????Try
????????????Return?True
????????Catch?ex?As?Exception
????????????Return?False
????????End?Try
????End?Function

关于这个webservice的同步调用方法，我就不做说明了
异步调用：
?Private?a?As?vbwebservice.DataManage'定义一个webservice变量
??Dim?ar?As?IAsyncResult
public?sub?Callback1(byval?ar?as?IAsyncResult)
''这里可以不写任何代码
'这里的代码在调用方运行结束后，开始运行
end?sub

#region?"异步调用"
private?sub?btnStart_Click()
dim?cb?as?asyncallback=new?asyncallback(address(me.callback1))
ar=a.begindelcurtable("zdf",cb,a)
end?sub

private?sub?btnEnd_Click()
if?ar?is?nothing?then
exit?sub
end?if
if??ar.IsCompleted?Then
dim?m?as?boolean=a.enddelcurtable(ar)
messagebox.show(m.tostring)
end?if
end?sub
#end?region
注意：“返回异步调用的结果一次只能调用一次，如果想再执行一遍，就必须重新执行一遍begin的方法”
以上是vb.net的用法，下面是c#的用法
CWebService.DataManage??a;
??System.IAsyncResult?ar;
??private?void?Form1_Load(object?sender,?System.EventArgs?e)
??{
???a=new?CWebService.DataManage();
??}

??
??public?void?CallBack1(System.IAsyncResult?ar)
??{
??}

??private?void?btnStart_Click(object?sender,?System.EventArgs?e)
??{
???System.AsyncCallback?cb=new?AsyncCallback(this.CallBack1);
???ar=a.BegindelCurTable("zhang",a);
??}

??private?void?btnEnd_Click(object?sender,?System.EventArgs?e) ??{ ???if(ar==null) ???{ ????MessageBox.Show("null"); ????return?; ???} ???if(ar.IsCompleted?) ???{ ????bool?m=a.EnddelCurTable(ar); ????MessageBox.Show(m.ToString()); ???} ???else ???{ ????MessageBox.Show("为完成"); ???} ??}