1 using System;
 2 using System.Collections.Generic;
 3 using System.Linq;
 4 using System.Threading;
 5 using System.Web;
 6 using System.Web.Services;
 7 
 8 namespace WFasy
 9 {
10     /// <summary>
11     /// AsyWeb 的摘要说明
12     /// </summary>
13     [WebService(Namespace = "http://tempuri.org/")]
14     [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
15     [System.ComponentModel.ToolboxItem(false)]
16     // 若要允许使用 ASP.NET AJAX 从脚本中调用此 Web 服务，请取消注释以下行。 
17     // [System.Web.Script.Services.ScriptService]
18     public class AsyWeb : System.Web.Services.WebService
19     {
20 
21         [WebMethod(Description="模拟服务等待，返回输入字符的前三位")]
22         public string AsynchronousCall(string code)
23         {
24             // 线程sleep5秒，模拟服务请求等待。
25             Thread.Sleep(5000);
26             if (code.Length >= 3)
27                 return code.Substring(0, 3);
28             return "***";
29         }
30     }
31 }

 1 using System;
 2 using System.Collections.Generic;
 3 using System.ComponentModel;
 4 using System.Data;
 5 using System.Drawing;
 6 using System.Linq;
 7 using System.Text;
 8 using System.Threading.Tasks;
 9 using System.Windows.Forms;
10 
11 namespace WFAsyC
12 {
13     public partial class form : Form
14     {
15         public form()
16         {
17             InitializeComponent();
18         }
19 
20         private void btnSure_Click(object sender, EventArgs e)
21         {
22             string inString = txtIn.Text;
23             string outString = txtOut.Text;
24 
25             WS.AsyWebSoapClient ws = new WS.AsyWebSoapClient();
26 
27             // 在调用服务前，应注册调用完成事件，即“回调方法”
28             // 一定要在异步调用前注册
29             ws.AsynchronousCallCompleted += ws_AsynchronousCallCompleted;
30 
31             // 我们之前用这个方法调用服务
32             // ws.AsynchronousCall(txtIn.Text);
33             // 异步调用时用Asyn
34             ws.AsynchronousCallAsync(txtIn.Text);
35         }
36 
37         /// <summary>
38         /// 调用成功后触发此事件
39         /// </summary>
40         /// <param name="sender">object</param>
41         /// <param name="e">EventArgs</param>
42         void ws_AsynchronousCallCompleted(object sender, WS.AsynchronousCallCompletedEventArgs e)
43         {
44             if (e.Error == null)
45             {
46                 // 若调用服务没有异常
47                 txtOut.Text = e.Result;
48             }
49             else
50             {
51                 txtOut.Text = "服务端出现异常！";
52             }
53         }
54     }
55 }