自定义控件学习笔记（五）－－比较客户提交数据和之前数据
1。要点
1）重写RaisePostDataChangedEvent方法
2）当LoadPostData返回true的时候触发RaisePostDataChangedEvent
3）在RaisePostDataChangedEvent里写当LoadPostData为true的时候，应该如何应对客户
usingSystem;usingSystem.Web.UI;usingSystem.Collections.Specialized;namespaceTestCustomControl
...{
publicclassCompareDataChange:Control,IPostBackDataHandler
...{publicstringText...{get...{if(ViewState["myText"]!=null)...{stringtext=(string)ViewState["myText"];returntext;
}else...{return"";}}set...{ViewState["myText"]=value;}}publiceventEventHandlerTextChanged;protectedoverridevoidRender(HtmlTextWriterwriter)...{writer.WriteBeginTag("input");writer.WriteAttribute("name",UniqueID);if(ID!=null)...{writer.WriteAttribute("id",ClientID);}if(Text.Length>0)...{writer.WriteAttribute("value",Text);}writer.Write(HtmlTextWriter.TagRightChar);writer.WriteEndTag("input");}publicboolLoadPostData(stringpostDataKey,NameValueCollectionpostCollection)...{//先用户修改文字并回传后，text被修改（Render）之前引发此事件。//流程：render－》显示－》用户修改－》LoadPostData－》（RaisePostDataChangedEvent）－》Render（第二次）stringtemp=Text;Text=postCollection[postDataKey];if(temp!=Text)returntrue;//引发RaisePostDataChangedEventelsereturnfalse;}publicvoidRaisePostDataChangedEvent()...{if(TextChanged!=null)//指客户端使用控件时候，写入了（OnTextChanged="MethodName"),否则则认为用户没有处理此事件...{TextChanged(this,newEventArgs());}}}
}
3。用法
前台：
<%...@PageLanguage="C#"AutoEventWireup="true"CodeFile="CompareDataChange.aspx.cs"Inherits="TestCustomControl_First_CompareDataChange"%><%...@RegisterAssembly="CompareDataChange"TagPrefix="Surance"Namespace="TestCustomControl"%><!DOCTYPEhtmlPUBLIC"-//W3C//DTDXHTML1.0Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><htmlxmlns="http://www.w3.org/1999/xhtml"><headrunat="server"><title>无标题页</title></head><body><formid="form1"runat="server"><div><Surance:CompareDataChangeID="C1"runat="server"Text="TypeSomethingDiffernt"OnTextChanged="C1_TextChanged"/><asp:ButtonID="Button1"runat="server"Text="Click"/></div></form></body></html>
后台：
protectedvoidC1_TextChanged(objectsender,EventArgse)...{Response.Write("Texthaschaged");}
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