客户端用JavaScript填充DropDownList控件 服务器端读不到值

复制代码 代码如下:

<form runat="server">
<div>
<h3>看看用js填充的dropdownlist控件在服务器端能读出来吗？</h3>
三个级联下拉列表框：
<asp:DropDownList runat="server">
</asp:DropDownList>
<asp:DropDownList runat="server">
</asp:DropDownList>
<asp:DropDownList runat="server">
</asp:DropDownList>
<br />
<asp:Button runat="server" Text="读取下拉表" /><br />
你选的是：<asp:Label runat="server" Text="Label"></asp:Label>
</div>
</form>

复制代码 代码如下:

protected void OK_Click(object sender, EventArgs e)
{
ListItem[] array = new ListItem[3];
array[0] = bigTypeList.SelectedItem; //为null
array[1] = typeList.SelectedItem; //为null
array[2] = smalltypeList.SelectedItem; //为null
}

复制代码 代码如下:

string s=Request.Form[typeList.ClientID];

复制代码 代码如下:

<script language="javascript" type="text/javascript">
$(function () {
var bigId = '#<%=bigTypeList.ClientID%>';
var mediumId = '#<%=typeList.ClientID%>';
var smallId = '#<%=smalltypeList.ClientID%>';
$(bigId).cascadingDropDown(mediumId,
'../Services/AutoTypeService.asmx/getAutoType',
{ valueMember: 'id', displayMember: 'name', cascadingArgName: 'parent' });
$(mediumId).cascadingDropDown(smallId,
'../Services/AutoTypeService.asmx/getSubAutoType',
{ valueMember: 'id', displayMember: 'name', cascadingArgName: 'parent' });
});
</script>