在自定义控件中实现ICallbackEventHandler接口不经过回发而实现客户端回掉
Asp.Net2.0中新增了ICallbackEventHandler接口，用于指示控件可以作为服务器的回调事件的目标。
MSDN中的描述:
实现 ICallbackEventHandler 接口的控件的示例包括 GridView、DetailsView 和 TreeView 控件。当回调事件以实现了 ICallbackEventHandler 接口的控件为目标时，将把事件变量作为参数传递来调用 RaiseCallbackEvent 方法以处理该事件，并且GetCallbackResult 方法返回回调的结果。
ICallbackEventHandler成员有：
如下代码实现一个不经过回发而实现客户端回掉的CheckBox。
<![CDATA[//------------------------------------------------------------------------------<br />
// <copyright company="Meibo Wu www.AspxBoy.com"><br />
// Copyright (c) www.AspxBoy.com All rights reserved.<br />
// </copyright><br />
//------------------------------------------------------------------------------<br />
using System;<br />
using System.Drawing;<br />
using System.Collections;<br />
using System.ComponentModel;<br />
using System.Web;<br />
using System.Web.UI;<br />
using System.Web.UI.WebControls;<br />
namespace HBZ<br />
{<br />
///<br />
<summary>
/// A Asynchronous AutoPostback Checkbox Control<br />
/// </summary>
<p>[DefaultEvent("CheckedChanged")]<br />
[ControlValueProperty("Checked")]<br />
[DefaultProperty("Text")]<br />
public class AsynchronousCheckBox : WebControl, INamingContainer, ICallbackEventHandler<br />
{<br />
#region Delegates<br />
///<br />
<summary>
/// The delegate for the checked changed event<br />
/// </summary>
<p>///</p>
<param name="sender">
///</p>
<param name="e">
public delegate void CheckedChangedEventHander(object sender, CheckChangedEventArgs e);<br />
#endregion<br />
#region Events<br />
private static readonly object eventCheckedChanged;<br />
///<br />
<summary>
/// The checked changed event.<br />
/// </summary>
<p>public event CheckedChangedEventHander CheckedChanged<br />
{<br />
add<br />
{<br />
Events.AddHandler(eventCheckedChanged, value);<br />
}<br />
remove<br />
{<br />
Events.RemoveHandler(eventCheckedChanged, value);<br />
}<br />
}<br />
#endregion<br />
#region Constructors<br />
///<br />
<summary>
/// Static Constructor<br />
/// </summary>
<p>static AsynchronousCheckBox()<br />
{<br />
eventCheckedChanged = new object();<br />
}<br />
///<br />
<summary>
/// Constructor<br />
/// </summary>
<p>public AsynchronousCheckBox()<br />
: base(HtmlTextWriterTag.Input)<br />
{<br />
}<br />
#endregion<br />
#region Properties<br />
///<br />
<summary>
/// Gets or sets a value indicating whether the Lable Text<br />
/// </summary>
<p>[Description("Gets or sets a value indicating whether the Lable Text")]<br />
public virtual string Text<br />
{<br />
get<br />
{<br />
return (string)ViewState["Text"];<br />
}<br />
set<br />
{<br />
this.ViewState["Text"] = value;<br />
}<br />
}<br />
///<br />
<summary>
/// Gets or sets a value indicating whether the 'Client CallBack Script Name'<br />
/// </summary>
<p>[Description("Gets or sets a value indicating whether the 'Client CallBack Script function Name'")]<br />
public string ClientCallBackScript<br />
{<br />
get<br />
{<br />
object o = ViewState["ClientCallBackScript"];<br />
return o == null ? "null" : o.ToString();<br />
}<br />
set<br />
{<br />
ViewState["ClientCallBackScript"] = value;<br />
}<br />
}<br />
///<br />
<summary>
/// Gets or sets a value indicating whether the checkbox 's checked<br />
/// </summary>
<p>[Description("Gets or sets a value indicating whether the checkbox 's checked")]<br />
public bool Checked<br />
{<br />
get<br />
{<br />
object o = ViewState["Checked"];<br />
return o == null ? false : (bool)o;<br />
}<br />
set<br />
{<br />
ViewState["Checked"] = value;<br />
}<br />
}<br />
///<br />
<summary>
/// Gets or sets a value indicating whether the Text 's cssClass<br />
/// </summary>
<p>[Description("Gets or sets a value indicating whether the Text 's cssClass")]<br />
public string TextCss<br />
{<br />
get<br />
{<br />
return (string)ViewState["TextCss"];<br />
}<br />
set<br />
{<br />
ViewState["TextCss"] = value;<br />
}<br />
}<br />
///<br />
<summary>
/// Gets or sets a value indicating whether the Label 's position<br />
/// </summary>
<p>public virtual TextAlign TextAlign<br />
{<br />
get<br />
{<br />
object o = ViewState["TextAlign"];<br />
if (o != null)<br />
{<br />
return (TextAlign)o;<br />
}<br />
return TextAlign.Right;<br />
}<br />
set<br />
{<br />
if ((value <textalign.left> TextAlign.Right))<br />
{<br />
throw new ArgumentOutOfRangeException("value");<br />
}<br />
ViewState["TextAlign"] = value;<br />
}<br />
}<br />
#endregion<br />
#region Render Meghods<br />
///<br />
<summary>
///<br />
/// </summary>
<p>///</p>
<param name="writer">
protected override void Render(HtmlTextWriter writer)<br />
{<br />
if (TextAlign == TextAlign.Left)<br />
{<br />
RenderLabel(writer);<br />
base.Render(writer);<br />
}<br />
else<br />
{<br />
base.Render(writer);<br />
RenderLabel(writer);<br />
}<br />
}<br />
///<br />
<summary>
/// Render Label<br />
/// </summary>
<p>///</p>
<param name="writer">
private void RenderLabel(HtmlTextWriter writer)<br />
{<br />
if (string.IsNullOrEmpty(Text))<br />
{<br />
return;<br />
}<br />
writer.Write("<label writer.writeattribute clientid if textcss writer.write>");<br />
writer.Write(Text);<br />
writer.WriteEndTag("label");<br />
}<br />
///<br />
<summary>
/// Override the AddAttributesToRender method<br />
/// </summary>
<p>///</p>
<param name="writer">
protected override void AddAttributesToRender(HtmlTextWriter writer)<br />
{<br />
if (base.Page == null)<br />
{<br />
base.Page.VerifyRenderingInServerForm(this);<br />
}<br />
string callbackReference<br />
= Page.ClientScript.GetCallbackEventReference(this, "this.checked", ClientCallBackScript, null);<br />
writer.AddAttribute(HtmlTextWriterAttribute.Onclick, callbackReference);<br />
writer.AddAttribute(HtmlTextWriterAttribute.Type, "checkbox");<br />
if (Checked)<br />
{<br />
writer.AddAttribute(HtmlTextWriterAttribute.Checked, "checked");<br />
}<br />
if (!Enabled)<br />
{<br />
writer.AddAttribute(HtmlTextWriterAttribute.Disabled, "disabled");<br />
}<br />
if (!string.IsNullOrEmpty(ToolTip))<br />
{<br />
writer.AddAttribute(HtmlTextWriterAttribute.Title, ToolTip);<br />
}<br />
base.AddAttributesToRender(writer);<br />
}<br />
#endregion<br />
#region On Checked Changed<br />
///<br />
<summary>
/// Invoke the check changed event.<br />
/// </summary>
<p>///</p>
<param name="sender">
///</p>
<param name="e">
protected virtual void OnCheckedChanged(object sender, CheckChangedEventArgs e)<br />
{<br />
CheckedChangedEventHander hander = Events[eventCheckedChanged] as CheckedChangedEventHander;<br />
if (hander != null)<br />
{<br />
Checked = e.Checked;<br />
hander(this, e);<br />
}<br />
}<br />
#endregion<br />
#region ICallbackEventHandler Members<br />
///<br />
<summary>
/// Get the result of a client side callback.<br />
/// </summary>
<p>/// <returns>The callback result string.</returns><br />
public string GetCallbackResult()<br />
{<br />
return Checked.ToString();<br />
}<br />
///<br />
<summary>
/// Raise the client callback event<br />
/// </summary>
<p>///</p>
<param name="eventArgument">The event arguments.<br />
public void RaiseCallbackEvent(string eventArgument)<br />
{<br />
bool isChecked = Boolean.Parse(eventArgument);<br />
CheckChangedEventArgs args = new CheckChangedEventArgs(isChecked);<br />
OnCheckedChanged(this, args);<br />
}<br />
#endregion<br />
}<br />
}<br />
//------------------------------------------------------------------------------<br />
// <copyright company="Meibo Wu www.AspxBoy.com"><br />
// Copyright (c) www.AspxBoy.com All rights reserved.<br />
// </copyright><br />
//------------------------------------------------------------------------------<br />
using System;<br />
using System.Drawing;<br />
using System.Collections;<br />
using System.ComponentModel;<br />
using System.Web;<br />
using System.Web.UI;<br />
using System.Web.UI.WebControls;<br />
namespace HBZ<br />
{<br />
///<br />
<summary>
///<br />
/// </summary>
<p>public class CheckChangedEventArgs:EventArgs<br />
{<br />
///<br />
<summary>
///<br />
/// </summary>
<p>///</p>
<param name="_isChecked">
public CheckChangedEventArgs(bool _isChecked)<br />
{<br />
isChecked = _isChecked;<br />
}<br />
private bool isChecked = false;<br />
///<br />
<summary>
///<br />
/// </summary>
<p>public bool Checked<br />
{<br />
get<br />
{<br />
return isChecked;<br />
}<br />
}<br />
}<br />
}<br />
</label></textalign.left>]]> http://www.aspxboy.com/private/5504/default.aspx