This example uses the following OrderItem class. Notice that the constructor calculates the TotalCost from the Quantity and UnitPrice.

class OrderItem
{
    public string Description;
    public int Quantity;
    public decimal UnitPrice, TotalCost;
    public OrderItem(string new_description, decimal new_unitprice, int new_quantity)
    {
        Description = new_description;
        UnitPrice = new_unitprice;
        Quantity = new_quantity;

        // Calculate total.
        TotalCost = UnitPrice * Quantity;
    }
}

The form's Load event handler creates an array of OrderItem objects. It then calls the following AddOrderItems method to add the items to the DataGridView.

// Add the items to the DataGridView.
private void AddOrderItems(OrderItem[] order_items)
{
    foreach (OrderItem item in order_items)
    {
        dgvValues.Rows.Add(new object[]
            {
                item.Description,
                item.UnitPrice,
                item.Quantity,
                item.TotalCost
            }
        );
    }
}

AddOrderItems loops through the items. For each item, it creates an array of objects holding the item's values and adds the array to the DataGridView control.