asp.net可输入下拉框

 <asp:TextBox ID="TextBox1" runat="server" style="width: 200px; position: absolute"></asp:TextBox>

    <asp:DropDownList ID="DropDownList1" runat="server" onchange="document.getElementById('TextBox1').value=this.options[this.selectedIndex].value" style="width: 217px; clip: rect(auto auto auto 198px); position: absolute">

        <asp:ListItem Value="0"></asp:ListItem>

        <asp:ListItem Value="1">1</asp:ListItem>

        <asp:ListItem Value="2">2</asp:ListItem>

        <asp:ListItem Value="3">3</asp:ListItem>

        <asp:ListItem Value="4">4</asp:ListItem>

    </asp:DropDownList>