Question

I have a List<ShipmentInformation>

public class ShipmentInformation
{
    public string Type { get; set; }
    public long StartID { get; set; }
    public long EndID { get; set; }
    public DateTime BoxDate { get; set; }
}

I currently have this code to determine where the most stock is:

var TypeTotals = shipmentInfo.GroupBy(x => x.Type).Select(x => new { Type = x.Key, Total = x.Sum(y => (y.EndID - y.StartID) + 1) });

//Select the one with the largest amount of stock
var LargestType = TypeTotals.Aggregate((l, r) => l.Total > r.Total ? l : r).Chip;

However if the totals are exactly the same it will select the last item in TypeTotals so I now want to add a check in to make sure that the earliest BoxDate is used.

So lets say I have 10 items of Type A and 10 items of Type B, at the moment Type B will be chosen.

I want to now make sure that when I return the LargestType that it returns the earliest item with that type. So if any of my items in A have a BoxDate earlier than any of the items in B then A should be chosen.

Answer 1

Just save the minimum date for each type total and then take it into account in your aggregation (which by the way would be cleaner with a simple foreach loop in my opinion)

var TypeTotals = shipmentInfo.GroupBy(x => x.Type)
                             .Select(x => new 
                             { 
                               Type = x.Key, 
                               Total = x.Sum(y => (y.EndID - y.StartID) + 1), 
                               Date = x.Min(z=> z.BoxDate) 
                             });

var LargestType = TypeTotals.Aggregate((l, r) =>
{
 if(l.Total > r.Total)
   return l;
 else if(l.Total == r.Total)
   return l.Date < r.Date ?  l : r;
 else return r;
}).Chip;