protected void Change(object sender, EventArgs e)
    {
            DropDownList ddl = (DropDownList)sender;
            GridViewRow row = (GridViewRow)ddl.Parent.Parent;
            int idx = row.RowIndex;
            DropDownList dlMng = (DropDownList)sender;
            TextBox txtreason = (TextBox)GridView1.Rows[idx].FindControl("txtreason");
            if (dlMng.SelectedIndex == 0)
            {
                txtreason.ReadOnly = true;
            }
            if (dlMng.SelectedIndex == 1)
            {
                txtreason.ReadOnly = false;
            }
        }