Question

Having a little trouble constructing a linq statement (C#, query syntax but I could handle method sytax). It needs to support grouping as well as a exposing a calculated property. I have a handle on each individually but can’t get them to seem to work together. Any help would be appreciated.

Data

GrpField          Qty      Price
-------------     ---      -----
RED                1        10
RED                2        10
RED                1        50
BLUE               2        30
BLUE               2        50

Output needs to be sum of Total Price (Qty * Price) for each group

Desired Result

RED    80
BLUE  160

This gets me the Total Price line

from x in origdata
let linetotal = x.qty * x.price
select new { x.grpfield, x.qty, x.price, linetotal } 

But I am unable to group by the new anonymous type since you can’t run aggregates like sum on anonymous types. If I run the group first, I can’t figure out how to work the linetotal into the mix BEFORE the aggregate sum.

Answer 1

As evidence against your since you can’t run aggregates like sum on anonymous types statement…

var data = new[]
    {
        new {GrpField = "RED", Qty = 1, Price = 10},
        new {GrpField = "RED", Qty = 2, Price = 10},
        new {GrpField = "RED", Qty = 1, Price = 50},
        new {GrpField = "BLUE", Qty = 2, Price = 30},
        new {GrpField = "BLUE", Qty = 2, Price = 50},
    };

var grouped =
    from d in data
    group d by d.GrpField
    into g
    select new {Group = g.Key, Sum = g.Sum(x => x.Qty * x.Price)};

foreach(var g in grouped)
    Console.WriteLine("{0} - {1}", g.Group, g.Sum);