修改select 的selectedValue或者selectedIndex或者两者，在服务器端还是默认的选择项，想想可能与元素的selected有关，试了一下，果然如此。
aspx代码如此:
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>无标题页</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:TextBox ID="txtTest" runat="server"></asp:TextBox>
<asp:DropDownList ID="ddlTest" runat="server">
<asp:ListItem Text="1" Value="1" Selected="true"></asp:ListItem>
<asp:ListItem Text="2" Value="1" ></asp:ListItem>
<asp:ListItem Text="3" Value="1"></asp:ListItem>
<asp:ListItem Text="4" Value="4"></asp:ListItem>
<asp:ListItem Text="5" Value="5"></asp:ListItem>
<asp:ListItem Text="6" Value="6"></asp:ListItem>
</asp:DropDownList>
<script type="text/C#" runat="server">
private void foo()
{
btnReturn.Click += new EventHandler(btnReturn_Click);
}
</script>
<script type="text/javascript">
var txt = document.getElementById("<%=txtTest.ClientID %>");
txt.value = "asdfsdf";
var ddl =document.getElementById("<%=ddlTest.ClientID %>");
ddlSelByValue( ddl,1,0);
function ddlSelByIndex( ddl, index )
{
var selIndex = -1;
// check
if( ddl.length < 1 )
{
return;
}
if( index >= ddl.length )
{
return;
}
for(var i=0;i<ddl.length;i++)
{
if( ddl[i].selected == true )
{
selIndex =i;
break;
}
}
if( selIndex != -1 )
{
ddl[selIndex].selected = false;
}
ddl[index].selected = true;
}
function ddlSelByValue( ddl , value ,order)
{
// check
if( ddl == undefined )
{
return;
}
if( value == undefined)
{
return;
}
if ( order == undefined )
{
order = 0;
}
if( order < 0 )
{
return;
}
var selIndex = -1;
var index4Value =[];
// get current selectedIndex and indexs for match the input value
for(var i=0;i<ddl.length;i++)
{
if( ddl[i].selected == true )
{
selIndex =i;
}
if( ddl[i].value == value )
{
index4Value.push(i);
}
}
// process
if( index4Value == undefined || index4Value.length < 1 )
{
return;
}
if( order >= index4Value.length )
{
return;
}
if( selIndex != -1 && selIndex == index4Value[order])
{
return;
}
ddl[ selIndex ].selected = false;
ddl[ index4Value[order] ].selected = true;
}
</script>
<asp:Button ID="btnReturn" runat="server" Text="return" OnClick="btnReturn_Click" />
</div>
</form>
</body>
</html>
CS代码如下：
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void btnReturn_Click(object sender, EventArgs e)
{
this.Request.SaveAs("c:\\a.txt", true);
}
}
打开C:\a.txt,我们将会看到以下内容：
POST /WebSite1/Default.aspx HTTP/1.1
Cache-Control: no-cache
Connection: Keep-Alive
Content-Length: 254
Content-Type: application/x-www-form-urlencoded
Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, application/msword, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/x-ms-application, application/x-ms-xbap, application/vnd.ms-xpsdocument, application/xaml+xml, */*
Accept-Encoding: gzip, deflate
Accept-Language: zh-cn
Host: localhost:1230
Referer: http://localhost:1230/WebSite1/Default.aspx
User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 2.0.50727; .NET CLR 3.0.04506.648; .NET CLR 3.5.21022)
__VIEWSTATE=%2FwEPDwUKLTgxOTUxNjU1N2RkD74GTaa7YkYEXnEtKp8fUvs%2Fo10%3D&txtTest=asdfsdf&ddlTest=6&btnReturn=return&__EVENTVALIDATION=%2FwEWCQK6tuK0AwL9h%2FmcCQKK6%2BCJCAKK6%2BCJCAKK6%2BCJCAKJ6%2BCJCAKO6%2BCJCAKP6%2BCJCAL02tCyAsYjRYHRHKh5VciUq%2FsNDu9bmDaK
__ViewState以前是头部信息，__ViewState及其后面是控件的值，我们可以看到ddlTest=6，6为Value值，如果我们选择第二项或第三项，这个值永远是1,那么在服务器端，ddlTest.SelectedItem永远是第一个。
