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。如下代码实现一个不经过回发而实现客户端回掉的CheckBox。
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[//------------------------------------------------------------------------------
// <copyright company="Meibo Wu www.AspxBoy.com">
// Copyright (c) www.AspxBoy.com All rights reserved.
// </copyright>
//------------------------------------------------------------------------------
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace HBZ
{
/// <summary>
/// A Asynchronous AutoPostback Checkbox Control
/// </summary>
[DefaultEvent("CheckedChanged")]
[ControlValueProperty("Checked")]
[DefaultProperty("Text")]
public class AsynchronousCheckBox : WebControl, INamingContainer, ICallbackEventHandler
{
#region Delegates
/// <summary>
/// The delegate for the checked changed event
/// </summary>
///
<param name="sender"></param>
///
<param name="e"></param>
public delegate void CheckedChangedEventHander(object sender, CheckChangedEventArgs e);
#endregion
#region Events
private static readonly object eventCheckedChanged;
/// <summary>
/// The checked changed event.
/// </summary>
public event CheckedChangedEventHander CheckedChanged
{
add
{
Events.AddHandler(eventCheckedChanged, value);
}
remove
{
Events.RemoveHandler(eventCheckedChanged, value);
}
}
#endregion
#region Constructors
/// <summary>
/// Static Constructor
/// </summary>
static AsynchronousCheckBox()
{
eventCheckedChanged = new object();
}
/// <summary>
/// Constructor
/// </summary>
public AsynchronousCheckBox()
: base(HtmlTextWriterTag.Input)
{
}
#endregion
#region Properties
/// <summary>
/// Gets or sets a value indicating whether the Lable Text
/// </summary>
[Description("Gets or sets a value indicating whether the Lable Text")]
public virtual string Text
{
get
{
return (string)ViewState["Text"];
}
set
{
this.ViewState["Text"] = value;
}
}
/// <summary>
/// Gets or sets a value indicating whether the 'Client CallBack Script Name'
/// </summary>
[Description("Gets or sets a value indicating whether the 'Client CallBack Script function Name'")]
public string ClientCallBackScript
{
get
{
object o = ViewState["ClientCallBackScript"];
return o == null ? "null" : o.ToString();
}
set
{
ViewState["ClientCallBackScript"] = value;
}
}
/// <summary>
/// Gets or sets a value indicating whether the checkbox 's checked
/// </summary>
[Description("Gets or sets a value indicating whether the checkbox 's checked")]
public bool Checked
{
get
{
object o = ViewState["Checked"];
return o == null ? false : (bool)o;
}
set
{
ViewState["Checked"] = value;
}
}
/// <summary>
/// Gets or sets a value indicating whether the Text 's cssClass
/// </summary>
[Description("Gets or sets a value indicating whether the Text 's cssClass")]
public string TextCss
{
get
{
return (string)ViewState["TextCss"];
}
set
{
ViewState["TextCss"] = value;
}
}
/// <summary>
/// Gets or sets a value indicating whether the Label 's position
/// </summary>
public virtual TextAlign TextAlign
{
get
{
object o = ViewState["TextAlign"];
if (o != null)
{
return (TextAlign)o;
}
return TextAlign.Right;
}
set
{
if ((value <textalign.left) || (value > TextAlign.Right))
{
throw new ArgumentOutOfRangeException("value");
}
ViewState["TextAlign"] = value;
}
}
#endregion
#region Render Meghods
/// <summary>
///
/// </summary>
///
<param name="writer"></param>
protected override void Render(HtmlTextWriter writer)
{
if (TextAlign == TextAlign.Left)
{
RenderLabel(writer);
base.Render(writer);
}
else
{
base.Render(writer);
RenderLabel(writer);
}
}
/// <summary>
/// Render Label
/// </summary>
///
<param name="writer"></param>
private void RenderLabel(HtmlTextWriter writer)
{
if (string.IsNullOrEmpty(Text))
{
return;
}
writer.Write("<label");
writer.WriteAttribute("for", ClientID);
if (!string.IsNullOrEmpty(TextCss))
{
writer.WriteAttribute("class", TextCss);
}
writer.Write(">");
writer.Write(Text);
writer.WriteEndTag("label");
}
/// <summary>
/// Override the AddAttributesToRender method
/// </summary>
///
<param name="writer"></param>
protected override void AddAttributesToRender(HtmlTextWriter writer)
{
if (base.Page == null)
{
base.Page.VerifyRenderingInServerForm(this);
}
string callbackReference
= Page.ClientScript.GetCallbackEventReference(this, "this.checked", ClientCallBackScript, null);
writer.AddAttribute(HtmlTextWriterAttribute.Onclick, callbackReference);
writer.AddAttribute(HtmlTextWriterAttribute.Type, "checkbox");
if (Checked)
{
writer.AddAttribute(HtmlTextWriterAttribute.Checked, "checked");
}
if (!Enabled)
{
writer.AddAttribute(HtmlTextWriterAttribute.Disabled, "disabled");
}
if (!string.IsNullOrEmpty(ToolTip))
{
writer.AddAttribute(HtmlTextWriterAttribute.Title, ToolTip);
}
base.AddAttributesToRender(writer);
}
#endregion
#region On Checked Changed
/// <summary>
/// Invoke the check changed event.
/// </summary>
///
<param name="sender"></param>
///
<param name="e"></param>
protected virtual void OnCheckedChanged(object sender, CheckChangedEventArgs e)
{
CheckedChangedEventHander hander = Events[eventCheckedChanged] as CheckedChangedEventHander;
if (hander != null)
{
Checked = e.Checked;
hander(this, e);
}
}
#endregion
#region ICallbackEventHandler Members
/// <summary>
/// Get the result of a client side callback.
/// </summary>
/// <returns>The callback result string.</returns>
public string GetCallbackResult()
{
return Checked.ToString();
}
/// <summary>
/// Raise the client callback event
/// </summary>
///
<param name="eventArgument">The event arguments.</param>
public void RaiseCallbackEvent(string eventArgument)
{
bool isChecked = Boolean.Parse(eventArgument);
CheckChangedEventArgs args = new CheckChangedEventArgs(isChecked);
OnCheckedChanged(this, args);
}
#endregion
}
}
//------------------------------------------------------------------------------
// <copyright company="Meibo Wu www.AspxBoy.com">
// Copyright (c) www.AspxBoy.com All rights reserved.
// </copyright>
//------------------------------------------------------------------------------
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace HBZ
{
/// <summary>
///
/// </summary>
public class CheckChangedEventArgs:EventArgs
{
/// <summary>
///
/// </summary>
///
<param name="_isChecked"></param>
public CheckChangedEventArgs(bool _isChecked)
{
isChecked = _isChecked;
}
private bool isChecked = false;
/// <summary>
///
/// </summary>
public bool Checked
{
get
{
return isChecked;
}
}
}
}
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