asp.net MVC Inheritance between Models

I'm trying to implement a person's registry where I have inheritances for both individuals and businesses, but my save method is not getting the person's type properly.

Following sample code

[HttpPost]
[ValidateAntiForgeryToken]
public async Task<ActionResult> Salvar(PessoaViewModel model)
{
    if (ModelState.IsValid)
    {
        if (model is PessoaFisicaViewModel)
            await SalvarPessoaFisica(context, model as PessoaFisicaViewModel);
        else if (model is PessoaJuridicaViewModel)
            await SalvarPessoaJuridica(context, model as PessoaJuridicaViewModel);
        else await SalvarPessoa(context, model);

        await context.SaveChangesAsync();

        return RedirectToAction("Index");
    }

    return View(model);
}

Clicking on save from individual or legal my method is receiving as always was the Person type, never the inheritance.

Persona.cshtml

@model PessoaViewModel

<div class="row">
    <div class="col-lg-12">
        <div class="panel panel-default">
            <div class="panel-heading">
                @if (Model.PessoaId > 0)
                {
                    <label>Edição da pessoa - @Model.Nome</label>
                }
                else
                {
                    <label>Cadastro de pessoa</label>
                }
            </div>
            <div class="panel-body">
                @using (Html.BeginForm("Salvar", "Pessoa"))
                {
                    @Html.AntiForgeryToken()

                    @Html.ValidationSummary(true, "", new { @class = "text-danger" })

                    if (Model is PessoaFisicaViewModel)
                    {
                        @Html.Partial("_PessoaFisica", Model)
                    }
                    else if (Model is PessoaJuridicaViewModel)
                    {
                        @Html.Partial("_PessoaJuridica", Model)
                    }
                    else
                    {
                        @Html.Partial("_Pessoa", Model)
                    }

                    <div class="row">
                        <div class="col-lg-12">
                            <a href="@Url.Action("Index")" class="btn btn-default"><i class="fa fa-arrow-left fa-fw"></i> Voltar</a>
                            <button type="submit" class="btn btn-primary"><i class="fa fa-save fa-fw"></i> Salvar</button>
                        </div>
                    </div>
                }
            </div>
        </div>
    </div>
</div>

@section scripts {
    @Scripts.Render("~/bundles/jqueryval")
    @Scripts.Render("~/bundles/ajax")
}

_PessoaFisica.cshtml

@model PessoaFisicaViewModel

@Html.HiddenFor(a => a.PessoaId)
@Html.HiddenFor(a => a.Ativo)

<div class="row form-group">
    <div class="col-lg-4">
        @Html.LabelFor(model => model.CpfCnpj, htmlAttributes: new { @class = "control-label" })
        @Html.EditorFor(model => model.CpfCnpj, new { htmlAttributes = new { @class = "form-control", @autofocus = "" } })
        @Html.ValidationMessageFor(model => model.CpfCnpj, "", new { @class = "text-danger" })
    </div>
</div>
<div class="row form-group">
    <div class="col-lg-4">
        @Html.LabelFor(model => model.Nome, htmlAttributes: new { @class = "control-label" })
        @Html.EditorFor(model => model.Nome, new { htmlAttributes = new { @class = "form-control", @autofocus = "" } })
        @Html.ValidationMessageFor(model => model.Nome, "", new { @class = "text-danger" })
    </div>
</div>

<div class="row form-group">
    <div class="col-lg-4">
        @Html.LabelFor(model => model.RgNumero, htmlAttributes: new { @class = "control-label" })
        @Html.EditorFor(model => model.RgNumero, new { htmlAttributes = new { @class = "form-control", @autofocus = "" } })
        @Html.ValidationMessageFor(model => model.RgNumero, "", new { @class = "text-danger" })
    </div>
</div>

_PessoaJuridica.cshtml

@model PessoaViewModel

@Html.HiddenFor(a => a.PessoaId)
@Html.HiddenFor(a => a.Ativo)

<div class="row form-group">
    <div class="col-lg-4">
        @Html.LabelFor(model => model.CpfCnpj, htmlAttributes: new { @class = "control-label" })
        @Html.EditorFor(model => model.CpfCnpj, new { htmlAttributes = new { @class = "form-control", @autofocus = "" } })
        @Html.ValidationMessageFor(model => model.CpfCnpj, "", new { @class = "text-danger" })
    </div>
</div>
<div class="row form-group">
    <div class="col-lg-4">
        @Html.LabelFor(model => model.Nome, htmlAttributes: new { @class = "control-label" })
        @Html.EditorFor(model => model.Nome, new { htmlAttributes = new { @class = "form-control", @autofocus = "" } })
        @Html.ValidationMessageFor(model => model.Nome, "", new { @class = "text-danger" })
    </div>
    <div class="row form-group">
        <div class="col-lg-4">
            @Html.LabelFor(model => (model as PessoaJuridicaViewModel).NomeFantasia, htmlAttributes: new { @class = "control-label" })
            @Html.EditorFor(model => (model as PessoaJuridicaViewModel).NomeFantasia, new { htmlAttributes = new { @class = "form-control", @autofocus = "" } })
            @Html.ValidationMessageFor(model => (model as PessoaJuridicaViewModel).NomeFantasia, "", new { @class = "text-danger" })
        </div>
    </div>
</div>
<div class="row form-group">
    <div class="col-lg-4">
        @Html.LabelFor(model => (model as PessoaJuridicaViewModel).InscricaoMunicipal, htmlAttributes: new { @class = "control-label" })
        @Html.EditorFor(model => (model as PessoaJuridicaViewModel).InscricaoMunicipal, new { htmlAttributes = new { @class = "form-control", @autofocus = "" } })
        @Html.ValidationMessageFor(model => (model as PessoaJuridicaViewModel).InscricaoMunicipal, "", new { @class = "text-danger" })
    </div>
</div>

Models

public interface IPessoa
    {
        bool Ativo { get; set; }
        string CpfCnpj { get; set; }
        string Nome { get; set; }
        int PessoaId { get; set; }
    }
    public class PessoaViewModel : IPessoa
    {
        public bool Ativo { get; set; }
        public string CpfCnpj { get; set; }
        public string Nome { get; set; }

        public int PessoaId { get; set; }

    }

    public interface IPessoaFisica : IPessoa
    {
        int? RgNumero { get; set; }
    }

    public class PessoaFisicaViewModel : PessoaViewModel, IPessoaFisica
    {
        public int? RgNumero { get; set; }
    }

    public interface IPessoaJuridica : IPessoa
    {
        string InscricaoMunicipal { get; set; }

        string NomeFantasia { get; set; }
    }

    public class PessoaJuridicaViewModel : PessoaViewModel, IPessoaJuridica
    {
        public string InscricaoMunicipal { get; set; }

        public string NomeFantasia { get; set; }
    }