How to add footer row on datagrid in WPF

DataTable dt=new DataTable();
dt.Columns.Add("Subject",typeof(string));
dt.Columns.Add("Paper",typeof(string));
dt.Columns.Add("MaxMarks",typeof(string));
dt.Columns.Add("MinMarks",typeof(string));
dt.Columns.Add("ObtainMarks",typeof(string));
int totalMax = 0, totalMin = 0, totalObtain = 0;
DataGridShow.ItemsSource = ds.Tables[0].DefaultView ;
for (int i = 0; i < DataGridShow.Items.Count; i++)
{
    try
    {
        DataGridShow.SelectedIndex = i;
        DataRowView drv = (DataRowView)DataGridShow.SelectedItem;
        totalMax = totalMax + Convert.ToInt32(drv["MaxMarks"]);
        totalMin = totalMin + Convert.ToInt32(drv["MinMarks"]);

        totalObtain = totalObtain + Convert.ToInt32(drv["ObtainMarks"]);
    }
    catch(Exception x) { }
}

dt.Rows.Add("Total","",totalMax.ToString(),totalMin.ToString(),totalObtain.ToString());
DataGridShow.Items.Add(dt.Rows[0]);