gridview geting populated on dropdownlist selection

<asp:DropDownList ID="DropDownList2" runat="server" AutoPostBack="True"
            onselectedindexchanged="DropDownList2_SelectedIndexChanged">
        </asp:DropDownList>

  <asp:gridview id="GridView1" runat="server" autogeneratecolumns="False" xmlns:asp="#unknown">       </asp:gridview>

protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            using (
             SqlConnection con =
                 new SqlConnection(ConfigurationManager.ConnectionStrings["testConnectionString"].ConnectionString))
            {
                SqlCommand cmd = new SqlCommand("usp_Get_All", con);

                cmd.CommandType = CommandType.StoredProcedure;
                SqlDataAdapter adpt = new SqlDataAdapter(cmd);
                DataTable dt = new DataTable();
                adpt.Fill(dt);
                DropDownList2.DataSource = dt;
                DropDownList2.DataTextField = "name";
                DropDownList2.DataValueField = "id";
                cmd.Dispose();
            }
        }
    }
protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)
    {
        using (
              SqlConnection con =
                  new SqlConnection(ConfigurationManager.ConnectionStrings["testConnectionString"].ConnectionString))
        {
            SqlCommand cmd = new SqlCommand("usp_Search_All", con);

            cmd.CommandType = CommandType.StoredProcedure;
            cmd.Parameters.AddWithValue("id", DropDownList2.SelectedValue);
            SqlDataAdapter adpt = new SqlDataAdapter(cmd);
            DataTable dt = new DataTable();
            adpt.Fill(dt);
            GridView1.DataSource = dt;
            GridView1.DataBind();
            cmd.Dispose();
        }
    }