利用MS AJAX 扩展服务器端控件

通过MS Ajax可以扩展一个服务器端控件在客户端呈现后的特性，使其界面更加友好。
        实例代码:IScriptControl.rar
        一、创建网站，选择ASP.NET AJAX-Enabled Web Site.
        二、向项目中添加一个类，使其派生自TextBox，并实现IScriptControl接口。如下代码实例：

public class SampleTextBox : TextBox, IScriptControl

         三、这个控件我们将实现两个属性：
               HighlightCSSClass         控件得到焦点后的样式。当控件得到焦点的时候使其能够高亮显示。
               NoHighlightCssClass     失去焦点的控件的样式。

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

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

        四、接口IScriptControl 的实现。
               GetScriptDescriptors()    返回一个包含控件客户端实例的属性和事件句柄的 ScriptDescriptor 类型的数组。
               GetScriptReferences()    返回一个包含控件客户端 javascript 代码的ScriptReference 类型的数组。
               在这个实例中，我们用四个函数来实现这两个函数。代码入下：
protected virtual IEnumerable<ScriptReference> GetScriptReferences()
        {
            ScriptReference reference = new ScriptReference();
            reference.Path = ResolveClientUrl("SampleTextBox.js");

            return new ScriptReference { descriptor };
        }

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

        IEnumerable<ScriptDescriptor> IScriptControl.GetScriptDescriptors()
        {
            return GetScriptDescriptors();
        }        五、这册控件。代码比较简单，所以就不再多加讲述，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、下边是我们新添加的类的完整代码：
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 的摘要说明
    /// </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 { descriptor };
        }

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

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

         七、创建客户端控件。为客户端控件注册一个命名空间，并实现各个属性和事件：
// 为控件注册命名控件
Type.registerNamespace("Samples");

//
// 定义控件的属性
//
Samples.SampleTextBox = function(element) {
    Samples.SampleTextBox.initializeBase(this, );

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

//
// 为控件创建属性
//

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

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