Here is an example of how to get column based row values in an ObservableCollection "OrderCollection":
Double OrderSubTotal = (Double)0;
foreach (var data in this.OrderCollection)
{
Order orderData = (Order)data;
//MessageBox.Show(orderData.Product.SalesPrice.ToString());
OrderSubTotal = orderData.Product.SalesPrice;
}
this.OrderSum += OrderSubTotal;