How to Create Dropdownlist in ASP.NET MVC 4

Question

You could help me create a DropDownList on MVC4?

I have the class ProjetoFuncionario which is an associative class of Projeto and Funcionario.

I must create a class for Dropdown?

I’m having a hard time creating a DropDownList. Got any good tutorial or tip you can give me?

Thank you.

namespace Exercicio1.Models
{
    public class ProjetoFuncionario
    {
        public Projeto IdProjeto { get; set; }
        public Funcionario IdFuncionario { get; set; }

        public List<ProjetoFuncionario> listaProjetoFuncionario()
        {
            return new List<ProjetoFuncionario>();
        }
    }
}

Answer 1

The DropDownList requires a well-defined Id. Your association does not have this Id. Also, your class is well out of the standard. Let’s make some adjustments:

public class ProjetoFuncionario
{
    [Key]
    public int ProjetoFuncionarioId { get; set; }
    public int ProjetoId { get; set; }
    public int FuncionarioId { get; set; }

    public virtual Projeto Projeto { get; set; }
    public virtual Funcionario Funcionario { get; set; }
}

In the Entity Framework convention, the standard MVC4 data access framework, the naming convention asks Id to be a suffix, not a prefix, so I switched to FuncionarioId, ProjetoId, etc..

Another thing is that I put a primary key to the association. This ensures the correct functioning of the DropDown.

Still, note that there are integer properties (which are the keys that will be saved in the database) and navigation properties (the classes with the virtual in front). Each one has its function, which is not the same. The classes virtual serve Entity Framework to automatically bring the database records to you.

Done this, the rest is simple. Possibly you will need to have a Action in the Controller to bring this to you.

public ActionResult Index() {
    var projetosFuncionario = contexto.ProjetoFuncionarios.Where(pf => pf.FuncionarioId == 1);

    ViewBag.ProjetosFuncionario = projetosFuncionario.ToList();
    return View();
}

I put the return inside a ViewBag. Viewbags are dynamic objects used to send additional information to a View.

Finally, we arrived at View. To mount a Dropdown, use Razor’s Helper @Html:

@Html.DropDownListFor(model => model.ProjetoFuncionarioId, 
    ((IEnumerable<ProjetoFuncionario>)ViewBag.ProjetosFuncionario).Select(option => new SelectListItem {
        Text = option.Projeto.Nome + ", " + option.Funcionario.Nome, 
        Value = option.ProjetoFuncionarioId,
        Selected = (Model != null) && (option.ProjetoFuncionarioId == Model.ProjetoFuncionarioId)
}), "Escolha uma opção...", new { @class = "form-control" })