通過MS Ajax可以擴展一個服務器端控件在客戶端呈現后的特性，使其界面更加友好。
        實例代碼:IScriptControl.rar
        一、創建網站，選擇asp.net AJAX-Enabled Web Site.
        二、向項目中添加一個類，使其派生自TextBox，并實現IScriptControl接口。如下代碼實例：

public class SampleTextBox : TextBox, IScriptControl

         三、這個控件我們將實現兩個屬性：
               HighlightCSSClass         控件得到焦點后的樣式。當控件得到焦點的時候使其能夠高亮顯示。
               NoHighlightCssClass     失去焦點的控件的樣式。

public string HighlightCssClass
        {
            get { return _highlightCssClass; }
            set { _highlightCssClass = value; }
        }

        public string NoHighlightCssClass
        {
            get { return _noHighlightCssClass; }
            set { _noHighlightCssClass = value; }
        }

        四、接口IScriptControl 的實現。
               GetScriptDescriptors()    返回一個包含控件客戶端實例的屬性和事件句柄的 ScriptDescriptor 類型的數組。
               GetScriptReferences()    返回一個包含控件客戶端 javaScript 代碼的ScriptReference 類型的數組。
               在這個實例中，我們用四個函數來實現這兩個函數。代碼入下：
PRotected virtual IEnumerable<ScriptReference> GetScriptReferences()
        {
            ScriptReference reference = new ScriptReference();
            reference.Path = ResolveClientUrl("SampleTextBox.js");

            return new ScriptReference[] { reference };
        }

        protected virtual IEnumerable<ScriptDescriptor> GetScriptDescriptors()
        {
            ScriptControlDescriptor descriptor = new ScriptControlDescriptor("Samples.SampleTextBox", this.ClientID);
            descriptor.AddProperty("highlightCssClass", this.HighlightCssClass);
            descriptor.AddProperty("nohighlightCssClass", this.NoHighlightCssClass);

            return new ScriptDescriptor[] { descriptor };
        }

        IEnumerable<ScriptReference> IScriptControl.GetScriptReferences()
        {
            return GetScriptReferences();
        }

        IEnumerable<ScriptDescriptor> IScriptControl.GetScriptDescriptors()
        {
            return GetScriptDescriptors();
        }        五、這冊控件。代碼比較簡單，所以就不再多加講述，入下：
protected override void OnPreRender(EventArgs e)
        {
            if (!this.DesignMode)
            {
                // Test for ScriptManager and register if it exists
                sm = ScriptManager.GetCurrent(Page);

                if (sm == null)
                    throw new HttpException("A ScriptManager control must exist on the current page.");

                sm.RegisterScriptControl(this);
            }

            base.OnPreRender(e);
        }

        protected override void Render(HtmlTextWriter writer)
        {
            if (!this.DesignMode)
                sm.RegisterScriptDescriptors(this);

            base.Render(writer);
        }
         六、下邊是我們新添加的類的完整代碼：
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Collections.Generic;

namespace TextBoxExtender
{
    /**//// <summary>
    /// SampleTextBox 的摘要說明
    /// </summary>
    public class SampleTextBox : TextBox, IScriptControl
    {
        private string _highlightCssClass;
        private string _noHighlightCssClass;
        private ScriptManager sm;

        public string HighlightCssClass
        {
            get { return _highlightCssClass; }
            set { _highlightCssClass = value; }
        }

        public string NoHighlightCssClass
        {
            get { return _noHighlightCssClass; }
            set { _noHighlightCssClass = value; }
        }

        protected override void OnPreRender(EventArgs e)
        {
            if (!this.DesignMode)
            {
                // Test for ScriptManager and register if it exists
                sm = ScriptManager.GetCurrent(Page);

                if (sm == null)
                    throw new HttpException("A ScriptManager control must exist on the current page.");

                sm.RegisterScriptControl(this);
            }

            base.OnPreRender(e);
        }

        protected override void Render(HtmlTextWriter writer)
        {
            if (!this.DesignMode)
                sm.RegisterScriptDescriptors(this);

            base.Render(writer);
        }

        protected virtual IEnumerable<ScriptReference> GetScriptReferences()
        {
            ScriptReference reference = new ScriptReference();
            reference.Path = ResolveClientUrl("SampleTextBox.js");

            return new ScriptReference[] { reference };
        }

        protected virtual IEnumerable<ScriptDescriptor> GetScriptDescriptors()
        {
            ScriptControlDescriptor descriptor = new ScriptControlDescriptor("Samples.SampleTextBox", this.ClientID);
            descriptor.AddProperty("highlightCssClass", this.HighlightCssClass);
            descriptor.AddProperty("nohighlightCssClass", this.NoHighlightCssClass);

            return new ScriptDescriptor[] { descriptor };
        }

        IEnumerable<ScriptReference> IScriptControl.GetScriptReferences()
        {
            return GetScriptReferences();
        }

        IEnumerable<ScriptDescriptor> IScriptControl.GetScriptDescriptors()
        {
            return GetScriptDescriptors();
        }
    }
}

         七、創建客戶端控件。為客戶端控件注冊一個命名空間，并實現各個屬性和事件：
// 為控件注冊命名控件
Type.registerNamespace('Samples');

//
// 定義控件的屬性
//
Samples.SampleTextBox = function(element) {
    Samples.SampleTextBox.initializeBase(this, [element]);

    this._highlightCssClass = null;
    this._nohighlightCssClass = null;
}

//
// 為控件創建屬性
//

Samples.SampleTextBox.prototype = {

    initialize : function() {
        Samples.SampleTextBox.callBaseMethod(this, 'initialize');
       
        this._onfocusHandler = Function.createDelegate(this, this._onFocus);
        this._onblurHandler = Function.createDelegate(this, this._onBlur);

        $addHandlers(this.get_element(),
                     { 'focus' : this._onFocus,
                       'blur' : this._onBlur },
                     this);
       
        this.get_element().className = this._nohighlightCssClass;
    },
   
    dispose : function() {
        $clearHandlers(this.get_element());
       
        Samples.SampleTextBox.callBaseMethod(this, 'dispose');
    },

    //
    // 事件委托
    //
   
    _onFocus : function(e) {
        if (this.get_element() && !this.get_element().disabled) {
            this.get_element().className = this._highlightCssClass;         
        }
    },
   
    _onBlur : function(e) {
        if (this.get_element() && !this.get_element().disabled) {
            this.get_element().className = this._nohighlightCssClass;         
        }
    },

    //
    // 控件屬性
    //
   
    get_highlightCssClass : function() {
        return this._highlightCssClass;
    },

    set_highlightCssClass : function(value) {
        if (this._highlightCssClass !== value) {
            this._highlightCssClass = value;
            this.raisePropertyChanged('highlightCssClass');
        }
    },
   
    get_nohighlightCssClass : function() {
        return this._nohighlightCssClass;
    },

    set_nohighlightCssClass : function(value) {
        if (this._nohighlightCssClass !== value) {
            this._nohighlightCssClass = value;
            this.raisePropertyChanged('nohighlightCssClass');
        }
    }
}

// Optional descriptor for JSON serialization.
Samples.SampleTextBox.descriptor = {
    properties: [   {name: 'highlightCssClass', type: String},
                    {name: 'nohighlightCssClass', type: String} ]
}

// Register the class as a type that inherits from Sys.UI.Control.
Samples.SampleTextBox.registerClass('Samples.SampleTextBox', Sys.UI.Control);

if (typeof(Sys) !== 'undefined') Sys.application.notifyScriptLoaded();

最后將如下代碼復制到Default.aspx頁面，用以測試空間：
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>
<%@ Register Namespace="TextBoxExtender" TagPrefix="sample" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "

<html xmlns="<head id="Head1" runat="server">
    <title>ASP.NET AJAX Control Sample</title>
    <style type="text/css">
    .LowLight
    {
        background-color:#EEEEEE;
    }
   
    .HighLight
    {
        background-color:Ivory;
    }
    </style>
</head>
<body>
    <form id="form1" runat="server">
        <asp:ScriptManager ID="ScriptManager1" runat="server" >
            <Scripts>
                <asp:ScriptReference Path="JScript.js" />
            </Scripts>
        </asp:ScriptManager>
        <div>
            <table border="0" cellpadding="2">
              <tr>
                <td><asp:Label runat="server" ID="Label1" AssociatedControlID="TextBox1">Name</asp:Label></td>
                <td><sample:SampleTextBox ID="TextBox1" runat="server" NoHighlightCssClass="LowLight" HighlightCssClass="HighLight" /></td>
              </tr>
              <tr>
                <td><asp:Label runat="server" ID="Label2" AssociatedControlID="TextBox2">Phone</asp:Label></td>
                <td><sample:SampleTextBox ID="TextBox2" runat="server" NoHighlightCssClass="LowLight" HighlightCssClass="HighLight" /></td>
              </tr>
              <tr>
                <td><asp:Label runat="server" ID="Label3" AssociatedControlID="TextBox3">E-mail</asp:Label></td>
                <td><sample:SampleTextBox ID="TextBox3" runat="server" NoHighlightCssClass="LowLight" HighlightCssClass="HighLight" /></td>
              </tr>
            </table>
           
            <asp:Button runat="server" ID="Button1" Text="Submit Form" />
        </div>
    </form>
</body>
</html>
http://www.49028c.com/hblynn/archive/2007/01/29/633619.html