Question

I would like to compare two classes that look like this

public class Order
{
        public string KundNummer, KundNamn, ErReferens, VarReferens, KontraktsNummer, Betvillk, Levvillk, Levsatt, Speditor,
            Resenh, Projekt, OrderDatum, LeveransDatum, ErtOrdernr, LagerbokfDatum, KundPostAdr, KundPostAdr2, KundGLN, KundPostnr, 
            KundOrt, KundLandKod, KundLand, KundVATnr, KundDistrikt, KundSaljare, KundText1, KundText2, KundText3, KundSprak,
            KundValuta, KundRabattAvtal, KundRabattAvtalBenamning, KundPrislista, KundPrislistaBenamning, KundALnamn, KundALpostAdr, KundALpostAdr2, KundALGLN, KundALpostnr, KundALort,
            KundALlandKod, KundALland;
        public double OrderNummer, Fakturarabatt, Frakt, Expavg, Brutto, Netto, ExklMoms, Totalt, Moms, Avrundn, KundValutaKurs, KundValutaEnhet;
        public int EUPeriodSamman, InklMoms, EjKlar, Levererad, Malukerad, BestallningSkapad, Ordererk,
            Plocklista, Foljesedel, ExtraOrderdokument, Restorder, Faktura, KundSparaText, KundExport, KundRantefakturering, KundKravbrev,
            KundKravavgift, KundRestnoteraEj, KundSamlingsfakturera;
    }

i want to compare two objects of this class for logging which fields in my database that changed.

public string OrderUppdateraOrder(Order order)
    {
        Order OrderToCompare = new Order();
        OrderToCompare = OrderVisaOrderInformation(order.OrderNummer);

        //then the code goes on to make the changes to the database from the class order
        //while OrdertoComapre still have the values from before this function was called
    }

So is it possible to loop through these classes and compare them or do I have to write an if for every variable in my class? 🙂

Or maybe convert it to a List? I don’t know? 😛

Thank you for answers

Answer 1

i want to log if there is a difference and log the difference something like this CustomerNumber: changed from 456 to 345

The best option is probably just to use reflection to crawl over the public properties and fields, comparing them. This will have less code to compare, but will have a performance overhead. You can greatly reduce that overhead using tools like FastMember:

static class Program {
    static void Main()
    {
        Order o1 = new Order { Resenh = "abc" },
              o2 = new Order { Resenh = "abc" };
        ShowDiffs(o1, o2); // {nothing}
        o2.Resenh = "def";
        ShowDiffs(o1, o2); // Resenh changed from abc to def
    }
    static void ShowDiffs<T>(T x, T y)
    {
        var accessor = TypeAccessor.Create(typeof(T));
        if (!accessor.GetMembersSupported) throw new NotSupportedException();
        var members = accessor.GetMembers();

        foreach (var member in members)
        {
            object xVal = accessor[x, member.Name],
                   yVal = accessor[y, member.Name];
            if (!Equals(xVal, yVal))
            {
                Console.WriteLine("{0} changed from {1} to {2}",
                    member.Name, xVal, yVal);
            }
        }
    }
}