由于asp2.0提供了異步頁的支持使異步調用WebService的性能有了真正的提升。
使用異步頁，首先要設置Async="true"，異步頁是在PRerender和PrerenderComplete事件間加入Begin，end異步方法實現的，Begin和End方法屬于不同的線程。
WS異步頁的實現有兩種方式：
1、使用等待方法實現異步
通用類，封裝了WS
/**//// <summary>
        /// 使用等待方法實現異步
        /// </summary>
        /// <param name="name"></param>
        /// <returns></returns>
        private Account account;
        private string username;
        public Account Account
        {
            get { return account; }
            set { account = value; }
        }
        public string Username
        {
            get { return username; }
            set { username = value; }
        }
        public IAsyncResult BeginAsyncGetAccount(object sender, EventArgs e, AsyncCallback cb, object state)
        {
          
            return vb.BeginGetAccountbyName(username,cb,state);
        }
        public void EndAsyncGetAccount(IAsyncResult ar)
        {
            account = vb.EndGetAccountbyName(ar);
        }

          /**//// <summary>
        /// 使用事件驅動的異步
        /// </summary>
        /// <param name="username"></param>
        public void GetAccountCompleted(Object source, VB.GetAccountbyNameCompletedEventArgs e)
        {
            account = e.Result;
        }
        public void AsGetAccount(string username)
        {
                      vb.GetAccountbyNameCompleted += new GetAccountbyNameCompletedEventHandler(GetAccountCompleted);
            vb.GetAccountbyNameAsync(username）
           
        }調用方法
 protected void Page_Load(object sender, EventArgs e)
    {
        this.PreRenderComplete += new EventHandler(Page_PreRenderComplete);
        b.Username = "dinghao";
      
        AddOnPreRenderCompleteAsync(b.BeginAsyncGetAccount, b.EndAsyncGetAccount);
    }
    protected void Page_PreRenderComplete(object sender, EventArgs e)
    {
        //異步調用結束
        VB.Account a = b.Account;
        AccountIf ai = new AccountIf(a);
        ais[0] = ai;
        GridView1.DataSource = ais;
        GridView1.DataBind();
    }由于AddOnPreRenderCompleteAsync的兩個委托都是Void類型，所以在通用類中要加入有返回值的屬性如：Account供主調方法使用，另外委托中沒有異步方法的參數信息，要加入參數的屬性如：Username
2、事件驅動的異步（2.0新增）
調用方法：
protected void Page_Load(object sender, EventArgs e)
    {
        this.PreRenderComplete += new EventHandler(Page_PreRenderComplete);
        b.AsGetAccount("dinghao");
    
    }
    protected void Page_PreRenderComplete(object sender, EventArgs e)
    {
        //異步調用結束
        VB.Account a = b.Account;
        AccountIf ai = new AccountIf(a);
        ais[0] = ai;
        GridView1.DataSource = ais;
        GridView1.DataBind();
    }這種調用方式，用的是*Completed事件，在*Async完成時觸發，這種調用方式可以
省去Account，Username屬性，用起來比較簡單

http://bluewater.VEVb.com/archive/2006/06/20/430758.html