16

I have got a list of Entity, which has got an enum. 

public class Car
{
    public int CarId { get; set; }

    public string CarName { get; set; }

    public CarCategory CarCategory { get; set; }
}

public enum CarCategory
{
    None = 0,
    kLowRange = 1,
    kMidRange = 2,
    kHighRange = 3
}

Now I have got a list of Cars, I would like to use Comparer and run it on the enum such that all the entity having CarCategory as kMidRange and kHighRange will be sorted to first in the list.

I have tried with the answer but havent found any luck.

Thanks.

UPDATE: I kinda have got the mistake I am doing. I was looking at 

var sortedList = carList
  .OrderBy(x => x.CarCategory, 
                new EnumComparer<CarCategory> {
                  CarCategory.kMidRange, 
                  CarCategory.kHighRange});

But was getting only same values. I have to add .ToList() in order to get the result.

var sortedList = carList
  .OrderBy(x => x.CarCategory, 
                new EnumComparer<CarCategory> { 
                  CarCategory.kMidRange, 
                  CarCategory.kHighRange})
  .ToList();

Will give me the expected results. My mistake!

Dmitry Bychenko
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Xander
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  • Do you want to sort the original `List` or do you want an ordered sequence like `cars.OrderByDescending(car => (int)car.CarCategory)`? – René Vogt Mar 02 '17 at 09:10
  • It seems like `var sorted = cars.OrderBy(c => c.CarCategory).ToList();` should be sufficient. – Enigmativity Mar 02 '17 at 09:12
  • @Xander, Please share the *use* & *Implementation* of your Comparer, and it'd be vastly easier to assist. – Ori Nachum Mar 02 '17 at 09:28
  • 2
    `var sortedCars = cars.OrderBy(c=>(int)c.Carcategory);` or you can find another answer [here](http://stackoverflow.com/questions/12199668/in-c-what-is-the-best-way-to-sort-a-list-of-objects-by-a-string-property-and-g) – Andreea Dumitru Mar 02 '17 at 09:32
  • OrderByDescending, or possibly with a bit more complexity in there if he really wants mid to come before high, as his question kind of implies. – David Mar 02 '17 at 09:34

1 Answers1

44

enum is effectively integer (int in your case)

The approved types for an enum are byte, sbyte, short, ushort, int, uint, long, or ulong.

see https://msdn.microsoft.com/en-us/library/sbbt4032.aspx for details.

Since CarCategory implementation has the items in the desired order you can put just

 var sortedList = carList
   .OrderByDescending(x => (int) (x.CarCategory))
   .ToList();

please, note Descending: you want kHighRange to be on the top. If you want an arbitrary order, e.g.

kMidRange, kHighRange, None, kLowRange

I suggest using mapping:

 // desired order: None should be 3d, LowRange 4th, MidRange 1st, HighRange 2nd 
 int[] map = new[] {3, 4, 1, 2};

 var sortedList = carList
   .OrderBy(x => map[(int) (x.CarCategory)])
   .ToList();
Dmitry Bychenko
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