Question

Using LINQ to SQL, I have an Order class with a collection of OrderDetails. The Order Details has a property called LineTotal which gets Qnty x ItemPrice.

I know how to do a new LINQ query of the database to find the order total, but as I already have the collection of OrderDetails from the DB, is there a simple method to return the sum of the LineTotal directly from the collection?

I’d like to add the order total as a property of my Order class. I imagine I could loop through the collection and calculate the sum with a for each Order.OrderDetail, but I’m guessing there is a better way.

Answer 1

You can do LINQ to Objects and the use LINQ to calculate the totals:

decimal sumLineTotal = (from od in orderdetailscollection select od.LineTotal).Sum(); 

You can also use lambda-expressions to do this, which is a bit ‘cleaner’.

decimal sumLineTotal = orderdetailscollection.Sum(od => od.LineTotal); 

You can then hook this up to your Order-class like this if you want:

Public Partial Class Order {   ...   Public Decimal LineTotal {     get {       return orderdetailscollection.Sum(od => od.LineTotal);     }   } }