ASP.NET 2.0 Client Callback浅析

1public interface ICallbackEventHandler
2{
3   string GetCallbackResult();
4   void RaiseCallbackEvent(string eventArgument);
5}

public string GetCallbackEventReference (
Control control,
string argument,
string clientCallback,
string context,
string clientErrorCallback,
bool useAsync
)

1public class MyControl : WebControl, ICallbackEventHandler
2    {
3        private const string Script1 = "function onCallbackComplete(result){ \n" +
4                "   var element = document.getElementById('%ID%'); \n" +
5                "   if(element != null) \n" +
6                "       element.innerHTML = result;} \n";
7
8        private const string Script2 = "function onCallbackError(){ \n" +
9                "   var element = document.getElementById('%ID%'); \n" +
10                "   if(element != null) \n" +
11                "       element.innerHTML = 'error';} \n";
12
13        public string GetCallbackResult()
14        {
15            return "Callback result";
16        }
17
18        public void RaiseCallbackEvent(string eventArgument)
19        {
20        }
21
22        public override void RenderBeginTag(HtmlTextWriter writer)
23        {
24            writer.AddAttribute(HtmlTextWriterAttribute.Onclick, "DoClientCallBack()");
25            base.RenderBeginTag(writer);
26            writer.Write("My Callback control");
27        }
28
29        protected override void OnPreRender(EventArgs e)
30        {
31            //Define callback references.
32            string callbackRef = this.Page.ClientScript.GetCallbackEventReference(
33                this, "", "onCallbackComplete", null, "onCallbackError", true);
34
35            // Register script blocks will perform call to the server.
36            this.Page.ClientScript.RegisterClientScriptBlock(
37                this.GetType(), "DoClientCallBack",
38                "function DoClientCallBack() { " + callbackRef + "} \n", true
39            );
40
41            // Register other scripts
42            this.Page.ClientScript.RegisterClientScriptBlock(
43                this.GetType(), "onCallbackComplete", 
44                Script1.Replace("%ID%", this.ClientID), true);
45            this.Page.ClientScript.RegisterClientScriptBlock(
46                this.GetType(), "onCallbackError", 
47                Script2.Replace("%ID%", this.ClientID), true); 
48
49            base.OnPreRender(e);
50        }