how bind data to a dropdown in gridview

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            obj.da = new SqlDataAdapter("select Group_ID, Group_Name from dbo.Group_Details where MobileNo='" + Session["MobNo"].ToString() + "'", obj.cn);
            ds.Reset();
            obj.da.Fill(ds);
            DropDownList groupdwn = (DropDownList)e.Row.FindControl("DropDownList2");
            if (ds != null && ds.Tables[0].Rows.Count > 0)
            {
                groupdwn.DataSource = ds;
                groupdwn.DataValueField = "Group_ID";
                groupdwn.DataTextField = "Group_Name";
                groupdwn.DataBind();
                groupdwn.Items.Insert(0, new ListItem("Select", "0"));
            }
            else
            {
                groupdwn.DataSource = null;
                groupdwn.DataBind();
                groupdwn.Items.Insert(0, new ListItem("Select", "0"));

            }
        }
    }