其实原理很简单，就是判断回传过来的数据是否跟原来相等，不相等返回true，则执行RaisePostDataChangeEvent方法。控件的全部代码如下：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Text;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace HenllyeeControls
{
[DefaultProperty("Text"),
ParseChildren(true,"Text"),
DefaultEvent("TextChanged"),
ControlBuilder(typeof(HenllyeeTextBuider))]
public class HenllyeeText:WebControl,IPostBackDataHandler
{
Properties#region Properties
[PersistenceMode(PersistenceMode.EncodedInnerDefaultProperty),
DefaultValue(""),
Category("Behavior"),
Description("文本内容")]
public string Text
{
get
{
return this.ViewState["Text"] == null ? String.Empty : (string)this.ViewState["Text"];
}
set
{
this.ViewState["Text"] = value;
}
}
#endregion
Events#region Events
private static object _objEvent;
[Category("Action")]
public event EventHandler TextChanged
{
add
{
this.Events.AddHandler(_objEvent, value);
}
remove
{
this.Events.RemoveHandler(_objEvent, value);
}
}
#endregion
Render#region Render
protected override HtmlTextWriterTag TagKey
{
get
{
return HtmlTextWriterTag.Input;
}
}
protected override void AddAttributesToRender(HtmlTextWriter writer)
{
base.AddAttributesToRender(writer);

if (Page != null)
{
Page.VerifyRenderingInServerForm(this);
}
writer.AddAttribute(HtmlTextWriterAttribute.Type, "text");
writer.AddAttribute(HtmlTextWriterAttribute.Name, this.UniqueID);
if (!Enabled)
{
writer.AddAttribute(HtmlTextWriterAttribute.Disabled, "disabled");
}
writer.AddAttribute(HtmlTextWriterAttribute.Value, this.Text);
}
protected override void AddParsedSubObject(object obj)
{
if (!(obj is Literal))
return;
base.AddParsedSubObject(obj);
}
#endregion
IPostBackData#region IPostBackData
public bool LoadPostData(string postKey, System.Collections.Specialized.NameValueCollection valueCollection)
{
string postData = valueCollection[postKey].ToString();
string strText = this.Text;
if (strText.Equals(postData, StringComparison.Ordinal))
return false;
this.Text = postData;
return true;
}
public void RaisePostDataChangedEvent()
{
EventHandler handler = (EventHandler)Events[_objEvent];
if (handler != null)
{
handler(this, EventArgs.Empty);
}
}
#endregion
}
public class HenllyeeTextBuider : ControlBuilder
{
public override bool AllowWhitespaceLiterals()
{
return false;
}
public override bool HtmlDecodeLiterals()
{
return true;
}
}
}

我们新建一个页面中，添加刚才的控件，跟一个Button可是发现能支持数据回传了。