How to find Grand Total of gridview rows and display in footer rows dynamically?

 private void GrandTotal()
    {
        int grandtotal = 0;
        int n;
        foreach (GridViewRow row in GridView1.Rows)
        {
            n = Convert.ToInt32(row.Cells[7].Text);     
            //TextBox tb = (TextBox)row.FindControl("txtTotal");
            //n = Convert.ToInt32(tb.Text);
            grandtotal = grandtotal + n; //Where Cells is the column. Just changed the index of cells
        }
        GridView1.FooterRow.Cells[6].Text = "Grand Total";
        GridView1.FooterRow.Cells[7].Text = grandtotal.ToString();
    }

call the function where you want to display the total.