LINQ and multiple aggregates

Question

I have code similar to this:

decimal total1 = 0;
decimal poTotal = 0;
foreach( var record in listOfRecords)
{
   total1 += record.Price;
   if ( record.HasPo){
     poTotal += record.PoTotal;
   }
 }

This works fine but I'd like to know how to perform multiple aggregates using linq without excessive coding for groups etc... is there a simple way that doesn't require scanning the list of objects each time?

I know I could do this:

var poTotal = listOfRecords.Where(r=> r.HasPo).Sum(r.PoTotal);

But that requires scanning the entire list and I if I'm to aggregate multiple values I only want to loop/scan one time.

Answer 1

You can use Aggregate method, but I don't think it will be more clear than a simple foreach loop you already have:

var totals = listOfRecords.Aggregate(
    new { Total = 0m, PoTotal = 0m },
    (a, r) => new {
        Total = a.Total + r.Price,
        PoTotal = a.PoTotal + (r.HasPo ? r.PoTotal : 0m)
    });

Console.WriteLine(totals.Total);
Console.WriteLine(totals.PoTotal);

Answer 2

You could also do something like this:

decimal poTotal = 0;
decimal total = listOfRecords.Sum(record => {
    if (record.HasPo) {poTotal +=  record.PoTotal;}
    return record.Price;
});

But I'm not saying you should . As MarcinJurasek says, the simple foreach is clearest in this case.