Convert Anonymous type to IEnumerable<> in EF6

Question

I am developing an MVC application using Entity Framework. I want to get 5 columns from a table and return them in an IEnumerable type. My code for this is:

Answer 1

First you don't need the ToList() because you don't need a list:

db.MSTs
  .Select(x => new { x.Id, x.Code, x.Desc, x.L1, x.L2 })
  .OrderBy(h => h.Code)

Now you do need the type to be MST. If this was a type EF knew about you could include this directly in the Select:

db.MSTs
  .Select(x => new MST{ Id = x.Id, Code =x.Code, Desc = x.Desc, L1 =x.L1, L2 =x.L2 })
  .OrderBy(h => h.Code)

But it's not, so you need to break from EF to in-memory with AsEnumerable and then do the creation of MST after that:

IEnumerable<MST> n = db.MSTs
  .Select(x => new { x.Id, x.Code, x.Desc, x.L1, x.L2 }).OrderBy(h => h.Code)
  .AsEnumerable()
  .Select(x => new MST{ Id = x.Id, Code =x.Code, Desc = x.Desc, L1 =x.L1, L2 =x.L2 });

(If there's some reason why you really do need the ToList() you can use that instead of AsEnumerable(), but you're probably better off just placing a final ToList() after all of that, to get a list of the type you actually want).

If you were using asynchronous code, then we would similarly place it after the await:

IEnumerable<MST> n = (await db.MSTs
    .Select(x => new { x.Id, x.Code, x.Desc, x.L1, x.L2 })
    .OrderBy(h => h.Code)
    .ToListAsync())
  .Select(x => new MST{ Id = x.Id, Code =x.Code, Desc = x.Desc, L1 =x.L1, L2 =x.L2 });

Answer 2

You need to simply project the Type MST instead of anonymous type:-

n = db.MSTs.Select(x => new MST 
                      { 
                          Id = x.Id, 
                          Code = x.Code,
                          Desc =  x.Desc, 
                          L1= x.L1, 
                          L2 = x.L2 
                       }).OrderBy(h => h.Code);

Provided, you have all these properties in MST. Also, it should not be a mapped entity it should be a DTO.

Also, you don't need ToList here since Select returns IEnumerable<T>.

Update:

Since it is a mapped entity in Entity Framework, one way is to first project the anonymous type and then the Model type like this:-

n = db.MSTs.Select(x => new 
                          { 
                              x.Id, 
                              x.Code,
                              x.Desc, 
                              x.L1, 
                              x.L2 
                           }).OrderBy(h => h.Code)
                           .AsEnumerable()
                           Select(x => new MST 
                                   { 
                                      Id = x.Id, 
                                      Code = x.Code,
                                      Desc =  x.Desc, 
                                      L1= x.L1, 
                                      L2 = x.L2 
                                   });