Validationsummary - Asp.Net MVC problems

Question

I’m having problems with Validationsummary in my application that manages Courses, I have a screen where the student enrolls in a course and in case he tries to enroll in it course again should appear the message Student is already enrolled in the course. Only this message is not showing up on View for the student.

Action

    // GET
    public ActionResult Inscricao()
    {
        Aluno aluno = db.Alunos.FirstOrDefault(a => a.Usuario == User.Identity.Name);
        if (aluno == null)
            return View("MeusCursos");

        return View(db.Cursos.ToList());
    }

    [HttpPost]
    public ActionResult Inscricao(int inscricaoId)
    {
        using (var scope = new TransactionScope())
        {
            //Aqui pega o usuario logado
            Aluno aluno = db.Alunos.FirstOrDefault(a => a.Usuario == User.Identity.Name);
            if (aluno == null)
                return View("MeusCursos");

            var curso = db.Cursos.FirstOrDefault(c => c.Id == inscricaoId);
            if (curso == null)
                return View("MeusCursos");

            if (curso.Qtd_Vagas <= 0)
            {
                ModelState.AddModelError("Qtd_Vagas", "Não existem mais vagas para este curso.");
                return RedirectToAction("Inscricao");
            }

            var alunoCurso = db.AlunoCursos.FirstOrDefault(ac => ac.Curso.Id == inscricaoId && ac.Aluno.Usuario == User.Identity.Name);
            if (alunoCurso != null)
            {
                ModelState.AddModelError("alunoCurso", "Aluno já está inscrito no curso.");
                return RedirectToAction("Inscricao", "Curso");
            }

            alunoCurso = new AlunoCurso
            {
                Aluno = aluno,
                Curso = curso
            };

            db.AlunoCursos.Add(alunoCurso);
            db.SaveChanges();

            curso.Qtd_Vagas--;
            db.Entry(curso).State = EntityState.Modified;
            db.SaveChanges();

            scope.Complete();
        }

        return View(db.Cursos.ToList());
    }

View

@model IEnumerable<MeuProjeto.Models.Curso>

<h2>Catálago de Cursos</h2>

@Html.ValidationSummary(true)
<table class="table table-hover">
    <tr>
        <th>
            Curso
        </th>
        <th>
            Sigla
        </th>
        <th>
            Ementa
        </th>
        <th>
            Inicio
        </th>
        <th>
            Fim
        </th>
        <th>
            Turno
        </th>
        <th>
            Status
        </th>
        <th>
            Quantidade de Vagas
        </th>
        <th></th>
    </tr>

    @foreach (var item in Model)
    {
        <tr>
           <td>
                @Html.DisplayFor(modelItem => item.Nome_Curso)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.Sigla)
            </td>
            <td>
                <a href="@Url.Action("Ementa", "Curso")" data_toggle="modal" data_target="#modalaviso">Ementa</a>
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.Dt_Inicio)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.Dt_Fim)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.Turno)
            </td>
            <td>
                <input type="text" name="Status" id="Status" value="@Html.DisplayFor(modelItem => item.Status)" readonly class="Status" />
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.Qtd_Vagas)
            </td>
            <td>
                <div class="btn-group">
                    <div class="col-md-offset-2 col-md-10">
                        @if (item.Qtd_Vagas > 0)
                        {
                        <input type="submit" value="Inscrição" name="detalhes" class="inscricao btn btn-success" data_toggle="modal" data_target="#modalAviso" data-inscricaoid="@item.Id"/>
                        }
                        else
                        {
                            <input type="submit" value="Não há vagas" name="detalhes" class="inscricao btn btn-default" disabled="disabled" />
                        }
                    </div>
                </div>
            </td>
        </tr>

    }

</table>
<div class="form-group">

    <a href="@Url.Action("Index", "Home")"><input type="button" value="Voltar" class="btn btn-danger" /></a>

</div>
<br />


@section Scripts {
    @Scripts.Render("~/bundles/jqueryval")
    <script>
        $(document).ready(function() {
            $(".inscricao").click(function() {
                $.ajax({
                    type: "POST",
                    url: "Inscricao/",
                    data: {inscricaoId: $(this).data("inscricaoid")},
                    success: function() {
                            $(this).attr("disabled", "disabled");
                        }
                });
            });
        });
    </script>

}

Answer 1

You can work with TempData[""] to take that information. In this case, you would do it in your controller:

     if (curso.Qtd_Vagas <= 0)
                {
                    TempData["MensagemErro"] = "Não existem mais vagas para este curso.";
                    return RedirectToAction("Inscricao");
                }

And in his View you call the message if the error occurs. Follow an example:

Editing

//A mensagem de error será apresentada aqui
@TempData["MensagemErro"]

Answer 2

Notice that:

@Html.ValidationSummary(true)

I don’t know if you ever pressed Ctrl + Shift + Space to see what that is true there:

excludePropertyErrors excludes any and all errors related to properties, including those that are defined with the empty property (your case). Switch to:

@Html.ValidationSummary(false)

This solution works if you want to print the error messages at the top of the page. In your case, you are setting by property:

ModelState.AddModelError("Qtd_Vagas", "Não existem mais vagas para este curso.");

In this case, the correct is to use:

@Html.ValidationMessageFor(model => model.Qtd_Vagas)