Datagrid row and column value

int a=0,b=0;
protected void GV_OnRowDataBound(object sender, GridViewRowEventArgs e)
{
    if(e.Row.RowType==DataControlRowType.DataRow)
   {
       int index=e.Row.RowIndex;
       if(index==0)
       {
           a=((Label)e.Row.FindControl("lblval")).Text;
       }
       else if(index==1)
       {
           b=((Label)e.Row.FindControl("lblval")).Text;
       }
       else if(index==2)
       {
           c=a+b;
           ((Label)e.Row.FindControl("lblval")).Text=c.ToString();
       }
   }
}

void Studentdatagrid_LoadingRow(object sender, DataGridRowEventArgs e)
{
                       EnrollRef.StudentDetail slist = e.Row.DataContext as EnrollRef.StudentDetail;
            FrameworkElement el;
            el = this.Studentdatagrid.Columns[1].GetCellContent(e.Row);
            DataGridCell changeCell = GetParent(el, typeof(DataGridCell)) as DataGridCell;
            SolidColorBrush brush = new SolidColorBrush(Colors.Black);
            if (changeCell != null)
            {
                if (slist.value > 0)
                {
                    brush = new SolidColorBrush(Colors.Green);
                }
                else if (slist.value < 0)
                {
                    brush = new SolidColorBrush(Colors.Red);
                }
                changeCell.Foreground = brush;
            }
           
    }