Simplify my class mapping common class properties between model and viewmodel classes

Question

I have an ASP.NET MVC 5 app and I map properties between model and viewmodel and vice versa.

I could use automapper to do this but since I don't need mapping rules to convince me to use it as I mostly do simple 1 to 1 mapping the performance overhead that automapper will add is not worthwhile.If I have mapping differences I'll map it manually where I reference it in my controller.

Here is my code

public class Dog
{
 public int Id { get; set; }
 public string Name { get; set; }
 public DateTime? BirthDate { get; set; }
 public int? CreatedBy{ get; set; }
 public DateTime? DateCreated { get; set; }
}
public class DogViewModel
{
 public int Id { get; set; }
 public string Name { get; set; }
 public DateTime? BirthDate { get; set; }
 public static implicit operator DogViewModel(Dog dm)
 {
 var vm= new DogViewModel{
 Id = dm.Id,
 Name = dm.Name,
 BirthDate = dm.BirthDate 
 };
 return vm;
 }
 public static implicit operator Dog(DogViewModel vm)
 {
 var dm = new Dog
 {
 Id = vm.Id,
 Name = vm.Name,
 BirthDate = vm.BirthDate 
 };
 return dm;
 }
}

This allows me to in my controller actionmethods easily map one class to another.

e.g.

 public async Task<IActionResult> Edit(int? id)
 {
 var dog= await _db.Dogs.FirstOrDefaultAsync(d => md.Id == id);
 DogViewModel dogVm = dog;
 ...
 }
 [HttpPost]
 public async Task<IActionResult> Edit(DogViewModel dogVm)
 {
 Dog dog= dogVm;
 ...
 }

In my index ActionMethod I need to map a list of items.

 public async Task<IActionResult> Index()
 {
 var dogs = await _db.Dogs.ToListAsync();
 var dogVms = new List<DogViewModel>();
 foreach (var dog in dogs)
 {
 DogViewModel dogVm = dog;
 dogVms.Add(dogVm);
 }
 return View(dogVms);
 }

Question: Is there a way in LINQ or some other way in C# to eliminate the above foreach clause to simplify this code?

• t3chb0t: You crate a List<MonthViewModel>() but you are adding DogViewModels - is this correct? Is DogViewModel derived from MonthViewModel? I cannot try it out because you didn' show the MonthViewModel but I think since you have an implicit cast operator this might work _db.Months.ToListAsync().Cast<DogViewModel>().ToList(); that repaces your loop.
• devfric: Sorry was just a typo. I corrected it. Should read dog not month
• mr5: I think your understanding of how ViewModel and Model work is not that good yet. Assigning a Model to morph into a VM is not a good practice.

Answer 1

Providing

var dogVms = new List<MonthViewModel>();

is meant to actually be

var dogVms = new List<DogViewModel>();

Then to use LINQ you could do

List<DogViewModel> dogVms = (from dog in dogs select (DogViewModel)dog).ToList();

Answer 2

You could also write;

var dogVms = dogs.Select<Dog, DogViewModel>(dog => dog);

(assuming you have implicit operators)

• TheCoffeeCup: Hi! Welcome to Code Review. Please explain more on why your way is better.
• anon: To add on to Coffee's comment: Here, we expect answers that both provide a better way and explain why those ways are better.
• Christian: hi guys. because it's shorter and seems more elegant :)