来自森大科技官方博客 http://www.cnsendblog.com/index.php/?p=104
<%@ Page Language="C#" MasterPageFile="~/MasterPage.master" Theme="style" AutoEventWireup="true"
CodeFile="r_Balance.aspx.cs"
Inherits="Report_r_Balance" %>
<asp:Content
ID="content" ContentPlaceHolderID="MainContent"
runat="server">
<form id="form1"
runat="server">
<div>
<table class="topTable" cellspacing="0"
cellpadding="0" border="0">
<tbody>
<tr class="title">
<td>
<asp:Label ID="lbPagename"
runat="server" SkinID="title" Text="余额统计"></asp:Label>
</td>
</tr>
<tr class="butt">
<td>
<asp:ImageButton ID="btnPrint"
runat="server" SkinID="b_print"
OnClick="btnPrint_Click" />
<asp:ImageButton ID="btnExport"
runat="server" SkinID="b_export"
OnClick="btnExport_Click" />
</td>
</tr>
</tbody>
</table>
<!--结束功能条-->
<table border="1" style="font: 宋体;
font-size: 12px;">
<tr>
<td align="center" style="width: 256px; height:
15px;">
卡号*</td>
<td colspan="1" style="width: 233px; height: 15px">
<asp:TextBox ID="txtc_printno"
runat="server"></asp:TextBox></td>
<td colspan="1" style="height: 24px; font-size: 14px;
font-family: 宋体; width: 180px;"
align="center">
<asp:ImageButton ID="nSearch"
runat="server" AlternateText="查询"
ImageAlign="Middle"
ImageUrl="~/images/go.gif" OnClick="nSearch_Click" />
</td>
</tr>
</table>
....
生成的HTML代码：
<form
name="aspnetForm" method="post"
action="r_Balance.aspx" id="aspnetForm">
<table
class="topTable" cellspacing="0" cellpadding="0"
border="0">
<tbody>
<tr class="title">
<td>
<span id="ctl00_MainContent_lbPagename"
style="display:inline-block;color:#F2F3F9;border-style:None;font-family:宋体;font-size:13px;height:22px;">余额统计</span>
</td>
</tr>
<tr class="butt">
<td>
<input type="image" name="ctl00$MainContent$btnPrint"
id="ctl00_MainContent_btnPrint"
src="../App_Themes/style/images/b_print.jpg" align="middle"
onclick="return np();"
style="border-style:Ridge;border-width:0px;" />
<input type="image" name="ctl00$MainContent$btnExport"
id="ctl00_MainContent_btnExport" src="../App_Themes/style/images/b_export.jpg"
align="middle" style="border-style:Ridge;border-width:0px;"
/>
</td>
</tr>
</tbody>
</table>
<!--结束功能条-->
<table border="1" style="font: 宋体;
font-size: 12px;">
<tr>
<td align="center" style="width: 256px; height:
15px;">
卡号*</td>
<td colspan="1" style="width: 233px; height: 15px">
<input name="ctl00$MainContent$txtc_printno"
type="text" id="ctl00_MainContent_txtc_printno"
style="width:120px;height:16px;font-size:12px;font-family:宋体;color:DimGray;border-width:1px;border-style:Solid;border-color:#C4CAE6;"
/></td>
<td colspan="1" style="height: 24px; font-size: 14px;
font-family: 宋体; width: 180px;"
align="center">
<input type="image" name="ctl00$MainContent$nSearch"
id="ctl00_MainContent_nSearch" src="../images/go.gif"
alt="查询" align="middle"
onclick="return nselect();" style="border-width:0px;" />
</td>
</tr>
</table>
注意：
1.源文件控件和元素ID和生成HTML文件的ID不一致。在生成的HTML中原ASP控件ID加了ctl00_MainContent_前缀，其他元素加了ctl00$MainContent$前缀。原变form1为aspnetForm这是因为aspx页面的控件是母板页的ContentPlaceHolder
控件下的子控件,所以控件ID会变
2.<system.Web><xhtmlConformance
mode="Transitional|Legacy|Strict" />在其中选择
Transitional、Strict则产生自动前缀。ctl00.选择 Legacy|则产生自动前缀_ctl0.
3.后台Request.Form["txtc_name"]键值需要改变，必须变为Request.Form["ctl00$MainContent$txtc_name"]才能收到页面输入值
4.至于为什么，只能说这是.NET机制问题。。。
原文地址：https://www.cnblogs.com/cnsend/p/9955712.html