Convert an array of one datatype to array of another in NET core in an efficient way?

Question

I have an array of database entities that I need to convert to some different class in order to serve as a REST request result:

DatabaseDTO[] arrayFromDb = _repo.GetAllData();
OutgoinDTO[] = convertFromDatabaseDTO (arrayFromDb);

what is the most efficient way to do so (I assume that OutgoingDTO has a constructor that takes DatabaseDTO)

Given that you are converting between arrays, maybe Array.ConvertAll() will do the trick? This is likely to be optimally efficient. — Matthew Watson
– Matthew Watson, Commented Feb 26, 2020 at 11:27
define "efficient"; coding effort? memory usage? runtime? dependency tree? lines of code? allocations? These are all competing factors: you can't say "all of them" — Marc Gravell
– Marc Gravell, Commented Feb 26, 2020 at 11:33
Why not create a new array with the desired size and just loop? That's what Array.ConvertAll does. Do you have a specific performance issue? The conversion constructor itself is extra complexity that binds the two types together for example. Why not use a separate conversion method? Or AutoMapper? What are you looking for? — Panagiotis Kanavos
– Panagiotis Kanavos, Commented Feb 26, 2020 at 11:37
One approach is to not build the array of the "wrong" types to begin with. If you could convert them on the fly, you'd save a whole bunch of memory. See if your repository might not be amenable to a rewrite where it returns IEnumerable instead of an array. — Jeroen Mostert
– Jeroen Mostert, Commented Feb 26, 2020 at 11:44
Explicitly, DatabaseDTO[] arrayFromDb = _repo.GetAllData(); OutgoinDTO[] = Array.ConvertAll(arrayFromDb, x => new OutgoinDTO(x)); — Jeppe Stig Nielsen
– Jeppe Stig Nielsen, Commented Feb 26, 2020 at 11:46

AlleXyS · Accepted Answer · 2020-02-26 12:06:45Z

2

you can use LINQ to map an object from another, as:

var outgoinDTO = arrayFromDb.Select(x => new OutgoinDTO() {
  outgoing_param1 = arrayFromDb.param1,
  outgoing_param2 = arrayFromDb.param2,
  outgoing_param3 = calcSum(arrayFromDb.param2, arrayFromDb.param3),
  ..
  outgoing_paramn = arrayFromDb.paramn
});

calcSum(int a, int b) {
  return a + b;
}

So, you can calculate some results for Dto parameters from your DbClass. If both classes have same parameters (DbClass and DtoClass), you can use AutoMapper, how @Adem Aygun said below

edited Feb 26, 2020 at 12:06

answered Feb 26, 2020 at 11:29

AlleXyS

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Adem Aygun · Accepted Answer · 2020-02-27 07:16:41Z

1

you can use AutoMapper.Collection

Mapper.Map<List<OrderDTO>,List<Order>>(orderDtos, orders);

and here this

for different members:

    Mapper.CreateMap<Employee, EmployeeDto>()
   .ForMember(dest => dest.FullName, opt => opt.MapFrom(src => src.Name));

edited Feb 27, 2020 at 7:16

answered Feb 26, 2020 at 11:31

Adem Aygun

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1 Comment

AlleXyS Over a year ago

use automapper only if almost parameters exist in both classes. if need to execute some functions to calculate params result, will be better to use linq

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