How to fill a Dropdownliste with ASP MVC

Question

Good afternoon, as I can fill a dropdown with data from a database using pure Ado.net (code) and without using Entity framework?

I have two tables in my bank that relate. First I must register a department and when registering a user, there will be a dropdown that will load the registered departments.

In user model user model I set the following:

public List<SelectListItem> ListaDepartamento { get; set; }
    public int DepartamentoSelecionado { get; set; }

I created a file that calls userHandler and created a function that queries the departments

 public List<DepartamentoModel> DepList()
    {
        Conexao();

        List<DepartamentoModel> listaDepartamento = new List<DepartamentoModel>();

        string query = "select * from departamento";
        SqlCommand cmd = new SqlCommand(query, con);

        SqlDataAdapter adapter = new SqlDataAdapter(cmd);
        DataTable dt = new DataTable();

        con.Open();
        adapter.Fill(dt);
        con.Close();

        foreach (DataRow dr in dt.Rows)
        {
            listaDepartamento.Add(new DepartamentoModel
            {
                Id = Convert.ToInt32(dr["id"]),
                Nome = Convert.ToString(dr["nome"])                   
            });
        }
        return listaDepartamento;
    }

In my controller I call inside the get method Register, the listing of departments

    [HttpGet]
    public ActionResult Cadastrar()
    {
        UsuarioHandler usuariohandler = new UsuarioHandler();
        ModelState.Clear();
        return View(usuariohandler.DepList());
    }

and my view:

@model projetinho.Models.UsuarioModel

@using (Html.BeginForm()) 
{
@Html.AntiForgeryToken()

<div class="form-horizontal">
    <h4>UsuarioModel</h4>        
    @Html.DropDownListFor(model => model.ListaDepartamento, new SelectList(Model.ListaDepartamento, "Value", "Text"), "Selecione")       
</div>

<div class="form-group">
    <div class="col-md-offset-2 col-md-10">
       <input type="submit" value="Create" class="btn btn-default" />
    </div>
</div>
}

<div>
    @Html.ActionLink("Back to List", "Index")
</div>

When executing I got the following error:

O item de modelo inserido no dicionário é do tipo'System.Collections.Generic.List`1[projeto.Models.DepartamentoModel]', mas esse dicionário requer um item do tipo 'projeto.Models.UsuarioModel'. 

Answer 1

MVC Dropdown methods use lists SelectList with the data. They also support storing the user’s last selection, by the way. So you can either send this SelectList by Viewbag or add a property to your model.

public SelectList DepList(){
    Conexao();

    List<DepartamentoModel> listaDepartamento = new List<DepartamentoModel>();

    // resto do código aqui

    // Lista/coleção com os dados, valor de cada opção do dropdown,
    // texto de cada opção e opção selecionada da lista
    SelectList dropdownDepartamento = new SelectList(listaDepartamento, "id", "nome", null);

    return dropdownDepartamento;
}

Or by Viewbag.

public ActionResult Cadastrar(){
    UsuarioHandler usuarioHandler = new UsuarioHandler();
    ModelState.Clear();
    ViewBag.departamentos = new SelectList(usuarioHandler.DepList(), "id", "nome", null);
}

Aí na View

@Html.DropdownListFor(model => model.ListaDepartamento, ViewBag.departamentos as SelectList, new { @class = "form-control" })