LINQ Operations on Lambda Grouping

Question

I'm stuck with a LINQ group by situation trying to solve it without using foreach statement, here is the escenary:

I have two generic collections List<OrderHeader> and List<OrderDetail>, both have a same field TOTRGVS that contains total amount from a order, and the number of order is the key named NDORGV.

Then I want to find "Orders that not have the same TOTRGVS in OrderHeader and OrderDetail", so I tried the following query:

 List<RGVCAFAC_ERRORES> diff = (from d in lstOrderDetail 
                               join c in lstOrderHeader on d.NDORGV equals c.NDORGV                                                     
                               group d by d.NDORGV into g
                               let difTOTOrderDetail = g.Select(p => p.TOTRGVS).Sum()
                               let difTOTOrderHeader = g.Key.????
                               let diffTOT = difTOTOrderHeader - difTOTOrderDetail
                               where diffTOT != 0
                               select new _ERRORS
                               {
                                   NDORGV = g.Key,
                                   IMPORT = diffTOT
                               }
  ).ToList();

in difTOTOrderHeader I don't know how to retrieve the TOTRGVS field from OrderHeader. I have tried using Key but can't get any field, just extensions for formatting methods.

Answer 1

This might do the trick:

var dictDetails = lstOrderDetail
  .GroupBy(d => d.NDORGV)
  .ToDictionary(g => g.Key, g => g.Sum(d => d.TOTRGVS));

var result = lstOrderHeader
  .Where(h => dictDetails[h.NDORGV] != h.TOTRGVS)
  .ToList();

Answer 2

The Except function is normally used to determine differences in lists.