hi sir....i have added rowbound event and it worked for me.
 
 protected void gvDetails_RowDataBound(object sender, GridViewRowEventArgs e)
    {
        DataRowView drv = e.Row.DataItem as DataRowView;
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            if ((e.Row.RowState & DataControlRowState.Edit) > 0)
            {
                ((TextBox)gvDetails.FooterRow.FindControl("txtfpercentage")).Attributes.Add("readonly", "readonly");
                ((TextBox)gvDetails.FooterRow.FindControl("txtftrdifference")).Attributes.Add("readonly", "readonly");
                //((TextBox)gvDetails.Row.FindControl("txtdifference")).Attributes.Add("readonly", "readonly");
                RadioButtonList rbtnl = (RadioButtonList)e.Row.FindControl("rdottstatus");
                rbtnl.SelectedValue = drv[4].ToString();
             
                RadioButtonList rbtnl1 = (RadioButtonList)e.Row.FindControl("rdoConfirmation");
                rbtnl1.SelectedValue = drv[5].ToString();
                
            }
        }
    }