Sum of items in a collection

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.

From stackoverflow Adrian

• 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);
      }
    }
  }
  

  aku : Arghh! You outran me this time. Anyway +1 vote.

  Omer van Kloeten : note that the order class should be partial, since it's already been generated by the LINQ to SQL generator.

  Espo : aku: Finally, thanks for the vote :) Omer: Thank you, i will update the code
  From Espo