值选择afer dropdownlist选择已更改的事件调用

Question

我有下拉列表我想在单击选定的更改索引后选择值SELECT文件 调用

<asp:DropDownList ID="pdfdropdown" runat="server" AutoPostBack="true" OnSelectedIndexChanged="pdfdropdown_SelectedIndexChanged">
    <asp:ListItem Value="-1">Select file</asp:ListItem>
    <asp:ListItem Value="open">download excel</asp:ListItem>
    <asp:ListItem Value="download">dowload pdf</asp:ListItem>
</asp:DropDownList>


protected void pdfdropdown_SelectedIndexChanged(object sender, EventArgs e)
{              
    pdfdropdown.SelectedValue = "-1";
    Response.AppendHeader("Content-Disposition", "attachment; filename=" + name + ".pdf");
    //......funtions script
}

但是当我下载文件时我很奇怪。未选择所选值。（下载后）如何更改下拉列表值

Answer 1

试试这个

pdfdropdown.Items.FindByValue("-1").Selected = true;