Update Column value of Datatable

Hi

  I have below code & i want to Update column value of each row

foreach (DataRow row in dt.Rows)
{
    for (int i = 8; i < dt.Columns.Count - 2; i++)
    {
        if (dt.Columns[i].ToString().ToUpper().Trim() == "D")
        {
            row.SetField = "Done";
        }

    }
}

Thanks