asp.net服务器端取js弹出层中dropdownlist的选中值？？？
我用了一个js的弹出层，里面放了一个dropdownlist控件，为什么每次我都不能取到选中的当前值，服务器端取到的都是原来的值。有什么解决方案吗？
asp.net前台代码（弹出层的div）：
<div id="test" style="display:none; text-align:center ">
          
<asp:DropDownList ID="ddlCategory" runat="server" >

</asp:DropDownList>
<asp:LinkButton ID="LinkButton2" runat="server" onclick="LinkButton2_Click" Text="转移"></asp:LinkButton>
</div>
cs页面代码：
if (!IsPostBack)
{
BindDataToDDL();
}
protected void BindDataToDDL()
{
绑定数据到dropdownlist....
}
protected void LinkButton2_Click(object sender, EventArgs e)
{
string test = ddlCategory.SelectedValue.ToString()
}
页面首次加载的时候的值是“6”，后来我选择了别的，为什么取到的值还是“6”？？、！


js弹出层代码：

popWin("将选择的供应商转移分类", div, 200, 60);

function popWin(title, msg, w, h){
var objSelect = document.getElementsByTagName("select"); //捕捉所有select标签
for(var j=0;j<objSelect.length;j++){
//设为不显示，再进行下面操作
objSelect[j].style.display="none";
}

var iWidth = document.documentElement.clientWidth;
var iHeight = document.documentElement.clientHeight;

var bgObj = document.createElement("div");
bgObj.id = "BgDiv";
bgObj.style.width = iWidth+"px";
bgObj.style.height = Math.max(document.body.clientHeight, iHeight)+"px";
document.body.appendChild(bgObj);

var msgObj=document.createElement("div");
msgObj.id = "MsgDiv";
msgObj.style.top = (iHeight-h)/2+"px";
msgObj.style.left = (iWidth-w)/2+"px";
msgObj.style.width = w+"px";
msgObj.style.height = h+"px";
document.body.appendChild(msgObj);

var table = document.createElement("table");
msgObj.appendChild(table);
table.id = "MsgDivTable";
var tr = table.insertRow(-1);
var titleBar = tr.insertCell(-1);
tr.id = "MsgTitle";
titleBar.id = "MsgDivTitle";
titleBar.innerHTML = title;


var moveX = 0;
var moveY = 0;
var moveTop = 0;
var moveLeft = 0;
var moveable = false;
var docMouseMoveEvent = document.onmousemove;
var docMouseUpEvent = document.onmouseup;
titleBar.onmousedown = function() {
var evt = getEvent();
moveable = true;
moveX = evt.clientX;
moveY = evt.clientY;
moveTop = parseInt(msgObj.style.top);
moveLeft = parseInt(msgObj.style.left);

document.onmousemove = function() {
if (moveable) {
var evt = getEvent();
var x = moveLeft + evt.clientX - moveX;
var y = moveTop + evt.clientY - moveY;
if ( x > 0 &&( x + w < iWidth) && y > 0 && (y + h < iHeight) ) {
msgObj.style.left = x + "px";
msgObj.style.top = y + "px";
}
}
};

document.onmouseup = function () {
if (moveable) {
document.onmousemove = docMouseMoveEvent;
document.onmouseup = docMouseUpEvent;
moveable = false;
moveX = 0;
moveY = 0;
moveTop = 0;
moveLeft = 0;
}
};
}

var closeBtn = tr.insertCell(-1);
closeBtn.id = "MsgDivClose";
closeBtn.innerHTML = "<span title='关闭'>×</span>";
closeBtn.onclick = function(){
for(var j=0;j<objSelect.length;j++){
//再给select显出来
objSelect[j].style.display="";
}
document.body.removeChild(bgObj);
document.body.removeChild(msgObj);
}

var msgBox = table.insertRow(-1).insertCell(-1);
msgBox.id = "MsgBox";
msgBox.colSpan = "2";
msgBox.innerHTML = msg;


// 获得事件Event对象，用于兼容IE和FireFox
function getEvent() {
return window.event || arguments.callee.caller.arguments[0];
}
}

function MsgDivClose(){
$("#MsgDivClose").trigger("click");
}

[解决办法]
应该是你的弹出层导致出现了2个ddlCategory，清除一个即可。

解决方法有2个
1，
在form里面加
<form id="form1" runat="server">
<asp:HiddenField ID="xx" runat="server" />

然后绑定ddlCategory后加
ddlCategory.Attributes.Add("onchange", "document.getElementById('" + xx.ClientID + "').value=this.value");

得到的方法采用 xx.Value


方法2：
msgBox.innerHTML = msg;
$("#test").html("")

加上这个，