drop down llist filters

<div>

        <asp:TextBox ID="TextBox1" runat="server" AutoPostBack="True"
            ontextchanged="TextBox1_TextChanged"></asp:TextBox>
        <br />
        <br />
        <asp:DropDownList ID="DropDownList1" runat="server">
        </asp:DropDownList>

    </div>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;

public partial class Default4 : System.Web.UI.Page
{

    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void TextBox1_TextChanged(object sender, EventArgs e)
    {
        using (SqlConnection con = new SqlConnection("----"))
        {
            con.Open();
            SqlCommand cmd = new SqlCommand("Select id,name FROM TEST WHERE name like '" + TextBox1.Text + "%'", con);
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            DataTable DT = new DataTable();
            da.Fill(DT);
            DropDownList1.DataSource = DT;
            DropDownList1.DataTextField = "name";
            DropDownList1.DataValueField = "id";
            DropDownList1.DataBind();
            con.Close();
        }
    }
}