asp.net后台取得select 选中项

后台代码取值：

//省 市 县
model.Province = Request.Form.GetValues("txtProvince")[0];
model.City = Request.Form.GetValues("txtCity")[0];
model.Area = Request.Form.GetValues("txtArea")[0];

html页面

<form id="form1" runat="server">

<dl>
<dt class="Province City Area">所属省市</dt>
<dd>
　　<select id="txtProvince" name="txtProvince" class="select" runat="server"></select>
　　<select id="txtCity" name="txtCity" class="select" runat="server"></select>
　　<select id="txtArea" name="txtArea" class="select" runat="server"></select>
</dd>
</dl>

</form>