how to add discount column in gridview c# windows form

Question

how to add discount column in gridview c# windows application

 

decimal Qty = Convert.ToDecimal(txtqty.Text);

decimal Unit_Price = Convert.ToDecimal(qtytxtprice.Text);

decimal Tax = Convert.ToDecimal(txttax.SelectedValue);

decimal Amount = (Qty * Unit_Price);

decimal PercentageAmount = ((Amount * Tax) / 100);

decimal TotalAmount = Amount + PercentageAmount;

 

 

public void CalculateTotalAmount()

{

decimal taxtotal=0;

decimal totalamount=0;

for(int i=0;i<dataGridView.Rows.Count;i++)

{

decimal TotalAmount = (Convert.ToDecimal(dataGridView.Rows[i].Cells[4].Value) * Convert.ToDecimal(dataGridView.Rows[i].Cells[6].Value));

taxtotal = taxtotal + ((Convert.ToDecimal(dataGridView.Rows[i].Cells[7].Value)*TotalAmount)/100); totalamount=totalamount+ TotalAmount;

}

TotalTaxtxt.Text=taxtotal.ToString();

totalamounttxt.Text=totalamount.ToString();

_subTotal = taxtotal + totalamount;

txtNewTotal.Text = (_subTotal).ToString();

Subtxt.Text = (_subTotal).ToString();

CalcDiscountShopCost();

}