c# – ASP .NET MVC 5 – DropDownList com ModelState?

Question:

I'm developing a registration system using MVC5 with DAO , but there were some doubts that I couldn't solve.

I have a table where I register Projects and another one where the types of Projects are:

Table: Projects

Fields:

  • ProjectProjectId
  • ProjName
  • ProjectTypeId

Table: ProjectType

Fields:

  • ProjectTypeId
  • ProjectTypeName

I need to show in my view a DropDownList with all projects for the user to select (on registration). And I also need to bring these Types of Projects in the Edit Project page, so that the value registered previously is selected.

After some research I managed to get it to work, but not the way I would like the code to look like this:

(Project Controller)

//Controller GET: Projeto/Edit/5
public ActionResult Editar(int id)
{
    //Pesquisar projeto selecionado
    ProjetoDAO proj_dao = new ProjetoDAO();
    Projeto proj = proj_dao.listById(id);

    //Pesquisar todos os TIPOS de projetos
    ProjetoTipoDAO proj_tipo_dao = new ProjetoTipoDAO();
    List<ProjetoTipo> lista_projetotipo = proj_tipo_dao.ListAll();

    //Lista de SelectListItem
    List<SelectListItem> lista_ddl = new List<SelectListItem>();

    //Percorrer lista de Tipos de Projetos e adicionar na lista de SelectListItem
    bool selected = false;
    foreach (var item in lista_projetotipo)
    {
        //Checar se é o ID selecionado
        selected = (proj.ProjTipoId.ToString().Equals(item.ProjTipoId.ToString()));

        //Adicionar item na lista
        lista_ddl.Add(
            new SelectListItem()
            {
                Text = item.ProjTipoNome,
                Value = item.ProjTipoId,
                Selected = selected
            });
    }

    //Enviando a lista de Tipos de Projetos para a view através de ViewBag
    ViewBag.ListaTiposProjeto = lista_ddl;
}

(Edit.cshtml)

<div class="row">
    <div class="form-group">
        <div class="col-md-2">
            @Html.LabelFor(model => model.ProjTipo, 
                 new { @class = "control-label" })
        </div>
        <div class="col-md-10">
            @Html.DropDownList("ListaTiposProjeto", null, 
              "Selecione um item", new { @class = "form-control" })
        </div>
    </div>
</div>

This way, I can display the data in DropDownList and also bring it selected on the edit page, but I can't use ModelState to validate the form.

  • How would I do the same thing using @Html.DropDownListFor<> ?
  • Is this really the way?, because I followed some tutorials and they didn't work!

Answer:

You can create a ViewBag with the ProjectType information, it would look something like this:

  public ActionResult Editar(int id)
    {
        //Pesquisar projeto selecionado
        ProjetoDAO proj_dao = new ProjetoDAO();
        Projeto proj = proj_dao.listById(id);

        //Pesquisar todos os TIPOS de projetos
        ProjetoTipoDAO proj_tipo_dao = new ProjetoTipoDAO();
        List<ProjetoTipo> lista_projetotipo = proj_tipo_dao.ListAll();

        SelectList dropDown = new SelectList(lista_projetotipo, "ProjTipoId", "ProjTipoNome");

        ViewBag.ListaTiposProjeto = dropDown;

        return View(proj);
    }

View:

 <div class="row">
                <div class="form-group">
                    <div class="col-md-2">
                        @Html.LabelFor(model => model.ProjTipo, new { @class = "control-label" })
                    </div>
                    <div class="col-md-10">
                        @Html.DropDownListFor(model => model.ProjTipo, (SelectList)ViewBag.ListaTiposProjeto, "Selecione um item", new { @class = "form-control" })
                    </div>
                </div>
            </div>

it is necessary that in your Project class it has the Project Type ID and that when retrieving the object this ID has value

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