Problems with View Model Implementation

Question

I’m trying to use the concept of View Model Pattern, but when I’m implementing the compiler is showing a conversion error.

Below follows the approach I used:

Structure of the viewmodel

public class EvolucaoViewModel
{
    public Chamado ChamadoAtual { get; set; }
    public virtual ICollection<Evolucao> Evolucoes { get; set; }
}

Implementation in the controller

public ActionResult DetalharChamado(int? id)
{
    EvolucaoViewModel model = new EvolucaoViewModel();

    model.ChamadoAtual = _contexto.Chamados.Find(id);
    model.Evolucoes = _contexto.Evolucoes.Where(e => e.id_chamado == id);

    ViewBag.id_usuario = new SelectList(_contexto.Usuarios, "id_usuario", "nome_usuario", model.ChamadoAtual.id_usuario).OrderBy(p => p.Text);
    ViewBag.id_chamado = id;
    ViewBag.id_setor = new SelectList(_contexto.Setores, "id_setor", "nome_setor", model.ChamadoAtual.id_setor);
    if (id == null)
    {
        return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
    }

    if (model == null)
    {
        return HttpNotFound();
    }
    return View(model);
}

When I try to do this assignment the VS presents me the message below:

model.Evolucoes = _contexto.Evolucoes.Where(e => e.id_chamado == id);

Error 3 Cannot implicitly Convert type 'System.Linq.Iqueryable' to 'System.Collections.Generic.Icollection'. An Explicit Conversion exists (are you Missing a cast?) E: Devspace Projetos Albasi.Atende Albasi.Atende.Web Controllers Chamadocontroller.Cs 77 31 Albasi.Atende.Web

What I need to modify?

Answer 1

The estate Evolucoes of Viewmodel declares a ICollection and the return of the method Where (at least when applied to a IQueryable) is always a IQueryable, I mean, you’re trying to make a ICollection receive a IQueryable, that is wrong.

It is necessary to convert the return of Where for some kind that implements ICollection, as List or others.

What you need to change is

This line

model.Evolucoes = _contexto.Evolucoes.Where(e => e.id_chamado == id);

To

model.Evolucoes = _contexto.Evolucoes.Where(e => e.id_chamado == id).ToList();

Answer 2

Use the conversion to list ". Tolist()" in the excerpt below:

model.Evolucoes = _contexto.Evolucoes.Where(e => e.id_chamado == id).ToList();

Answer 3

Try it this way:

model.ChamadoAtual = _contexto.Chamados.Include(i => i.Evolucoes).Find(id);

and removes the

model.Evolucoes = _contexto.Evolucoes.Where(e => e.id_chamado == id);