动态填充Dropdownlist并获取ASP.net中文件后面的代码值

Question

我有一个.aspx页面

<%@ Page Title="" Language="C#" MasterPageFile="~/Site.Master" AutoEventWireup="true" CodeBehind="DropdownList.aspx.cs" Inherits="Test_WSMS_TV.DropdownList" EnableEventValidation="false" %>
<asp:Content ID="Content1" ContentPlaceHolderID="HeadContent" runat="server">
    <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js" type="text/javascript"></script>

    <script type="text/javascript">
        // alert('akash');
        $(document).ready(function () {
            //var arr = ["val1", "val2", "val3"];
            //alert('akash');
          //  $("#DropDownList1").prepend('<option value="akash">akash</option>');
            $("#DropDownList1").append(new Option('option1', 'option1'));
        });

    </script>

</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">
    <asp:DropDownList ID="DropDownList1" runat="server" ClientIDMode="Static">
        <asp:ListItem>A</asp:ListItem>
    </asp:DropDownList>
    <br />
    <asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Button" />
    <br />
    <br />
</asp:Content>

和文件后面的代码是

protected void Button1_Click(object sender, EventArgs e)
        {
            //var selectedOption = Request["DropDownList1"];
           // DropDownList1.SelectedValue
            Response.Write(DropDownList1.SelectedValue);
        }

当我单击按钮时，所选的服务器控件值（＆＃34; A＆＃34;）正在显示但是 动态添加的值未显示在DropDownList1.SelectedValue

中

属性。如何在.cs文件中获取动态添加的值。