Modelo nulo en POST

Estoy trabajando en un proyecto desarrollado por algunas personas que realmente no conozco. Encontré un problema en un método POST. El modelo es realmente nulo. Parece que el modelo no aparece en la vista.

public ActionResult ConfermaRistampa(int IDTitolo, Ristampa ristampa) //Ristampa is the model
{
    //some code
    if (ristampa.RichiestaRistampaWeb != null) //the field "RichiestaRistampaWeb" is null
    {
        ristampa.RichiestaRistampa = Utilities.ConverteFileInToFileUploadInfo(ristampa.RichiestaRistampaWeb, TipiDocumenti.Documento_Generico);
    }
}

//this is the code of field on the Ristampa class declaration, in the set i noticed that value is null
public System.Web.HttpPostedFileBase RichiestaRistampaWeb
{
    get
    {
        return this.RichiestaRistampaWebField;
    }
    set
    {
        if ((object.ReferenceEquals(this.RichiestaRistampaWebField, value) != true))
        {
            this.RichiestaRistampaWebField = value;
            this.RaisePropertyChanged("RichiestaRistampaWeb");
        }
    }
}

Esa es la definición completa del modelo. Es ASP.NET Core usando MVC obviamente. Noté que la mayoría de los atributos del modelo son nulos en los establecedores.

[System.Diagnostics.DebuggerStepThroughAttribute()]
[System.CodeDom.Compiler.GeneratedCodeAttribute("System.Runtime.Serialization", "4.0.0.0")]
[System.Runtime.Serialization.DataContractAttribute(Name = "Ristampa", Namespace = "http://schemas.datacontract.org/2004/07/RSM.SourceData.Models.Serialized")]
[System.SerializableAttribute()]
public partial class Ristampa : object, System.Runtime.Serialization.IExtensibleDataObject, System.ComponentModel.INotifyPropertyChanged
{

    [System.NonSerializedAttribute()]
    private System.Runtime.Serialization.ExtensionDataObject extensionDataField;

    [System.Runtime.Serialization.OptionalFieldAttribute()]
    private string ComuneLicenzaField;

    [System.Runtime.Serialization.OptionalFieldAttribute()]
    private string DenominazioneField;

    [System.Runtime.Serialization.OptionalFieldAttribute()]
    private decimal ImportoOperazioneField;

    [System.Runtime.Serialization.OptionalFieldAttribute()]
    private RSM.BusTuristiciWeb.SourceDataReference.FileUploadInfo LibrettoDiCircolazioneField;

    [System.Runtime.Serialization.OptionalFieldAttribute()]
    private System.Web.HttpPostedFileBase LibrettoDiCircolazioneWebField;

    [System.Runtime.Serialization.OptionalFieldAttribute()]
    private RSM.BusTuristiciWeb.SourceDataReference.FileUploadInfo LicenzaField;

    [System.Runtime.Serialization.OptionalFieldAttribute()]
    private System.Web.HttpPostedFileBase LicenzaWebField;

    [System.Runtime.Serialization.OptionalFieldAttribute()]
    private string MotivazioneField;

    [System.Runtime.Serialization.OptionalFieldAttribute()]
    private string NumeroLicenzaField;

    [System.Runtime.Serialization.OptionalFieldAttribute()]
    private RSM.BusTuristiciWeb.SourceDataReference.FileUploadInfo RicevutaPagamentoField;

    [System.Runtime.Serialization.OptionalFieldAttribute()]
    private System.Web.HttpPostedFileBase RicevutaPagamentoWebField;

    [System.Runtime.Serialization.OptionalFieldAttribute()]
    private RSM.BusTuristiciWeb.SourceDataReference.FileUploadInfo RichiestaRistampaField;

    [System.Runtime.Serialization.OptionalFieldAttribute()]
    private System.Web.HttpPostedFileBase RichiestaRistampaWebField;

    [System.Runtime.Serialization.OptionalFieldAttribute()]
    private System.Nullable<System.DateTime> ScadenzaLicenzaField;

    [System.Runtime.Serialization.OptionalFieldAttribute()]
    private string TargaAttualeField;

    [global::System.ComponentModel.BrowsableAttribute(false)]
    public System.Runtime.Serialization.ExtensionDataObject ExtensionData
    {
        get
        {
            return this.extensionDataField;
        }
        set
        {
            this.extensionDataField = value;
        }
    }

    [System.Runtime.Serialization.DataMemberAttribute()]
    public string ComuneLicenza
    {
        get
        {
            return this.ComuneLicenzaField;
        }
        set
        {
            if ((object.ReferenceEquals(this.ComuneLicenzaField, value) != true))
            {
                this.ComuneLicenzaField = value;
                this.RaisePropertyChanged("ComuneLicenza");
            }
        }
    }

    [System.Runtime.Serialization.DataMemberAttribute()]
    public string Denominazione
    {
        get
        {
            return this.DenominazioneField;
        }
        set
        {
            if ((object.ReferenceEquals(this.DenominazioneField, value) != true))
            {
                this.DenominazioneField = value;
                this.RaisePropertyChanged("Denominazione");
            }
        }
    }

    [System.Runtime.Serialization.DataMemberAttribute()]
    public decimal ImportoOperazione
    {
        get
        {
            return this.ImportoOperazioneField;
        }
        set
        {
            if ((this.ImportoOperazioneField.Equals(value) != true))
            {
                this.ImportoOperazioneField = value;
                this.RaisePropertyChanged("ImportoOperazione");
            }
        }
    }

    [System.Runtime.Serialization.DataMemberAttribute()]
    public RSM.BusTuristiciWeb.SourceDataReference.FileUploadInfo LibrettoDiCircolazione
    {
        get
        {
            return this.LibrettoDiCircolazioneField;
        }
        set
        {
            if ((object.ReferenceEquals(this.LibrettoDiCircolazioneField, value) != true))
            {
                this.LibrettoDiCircolazioneField = value;
                this.RaisePropertyChanged("LibrettoDiCircolazione");
            }
        }
    }

    [System.Runtime.Serialization.DataMemberAttribute()]
    public System.Web.HttpPostedFileBase LibrettoDiCircolazioneWeb
    {
        get
        {
            return this.LibrettoDiCircolazioneWebField;
        }
        set
        {
            if ((object.ReferenceEquals(this.LibrettoDiCircolazioneWebField, value) != true))
            {
                this.LibrettoDiCircolazioneWebField = value;
                this.RaisePropertyChanged("LibrettoDiCircolazioneWeb");
            }
        }
    }

    [System.Runtime.Serialization.DataMemberAttribute()]
    public RSM.BusTuristiciWeb.SourceDataReference.FileUploadInfo Licenza
    {
        get
        {
            return this.LicenzaField;
        }
        set
        {
            if ((object.ReferenceEquals(this.LicenzaField, value) != true))
            {
                this.LicenzaField = value;
                this.RaisePropertyChanged("Licenza");
            }
        }
    }

    [System.Runtime.Serialization.DataMemberAttribute()]
    public System.Web.HttpPostedFileBase LicenzaWeb
    {
        get
        {
            return this.LicenzaWebField;
        }
        set
        {
            if ((object.ReferenceEquals(this.LicenzaWebField, value) != true))
            {
                this.LicenzaWebField = value;
                this.RaisePropertyChanged("LicenzaWeb");
            }
        }
    }

    [System.Runtime.Serialization.DataMemberAttribute()]
    public string Motivazione
    {
        get
        {
            return this.MotivazioneField;
        }
        set
        {
            if ((object.ReferenceEquals(this.MotivazioneField, value) != true))
            {
                this.MotivazioneField = value;
                this.RaisePropertyChanged("Motivazione");
            }
        }
    }

    [System.Runtime.Serialization.DataMemberAttribute()]
    public string NumeroLicenza
    {
        get
        {
            return this.NumeroLicenzaField;
        }
        set
        {
            if ((object.ReferenceEquals(this.NumeroLicenzaField, value) != true))
            {
                this.NumeroLicenzaField = value;
                this.RaisePropertyChanged("NumeroLicenza");
            }
        }
    }

    [System.Runtime.Serialization.DataMemberAttribute()]
    public RSM.BusTuristiciWeb.SourceDataReference.FileUploadInfo RicevutaPagamento
    {
        get
        {
            return this.RicevutaPagamentoField;
        }
        set
        {
            if ((object.ReferenceEquals(this.RicevutaPagamentoField, value) != true))
            {
                this.RicevutaPagamentoField = value;
                this.RaisePropertyChanged("RicevutaPagamento");
            }
        }
    }

    [System.Runtime.Serialization.DataMemberAttribute()]
    public System.Web.HttpPostedFileBase RicevutaPagamentoWeb
    {
        get
        {
            return this.RicevutaPagamentoWebField;
        }
        set
        {
            if ((object.ReferenceEquals(this.RicevutaPagamentoWebField, value) != true))
            {
                this.RicevutaPagamentoWebField = value;
                this.RaisePropertyChanged("RicevutaPagamentoWeb");
            }
        }
    }

    [System.Runtime.Serialization.DataMemberAttribute()]
    public RSM.BusTuristiciWeb.SourceDataReference.FileUploadInfo RichiestaRistampa
    {
        get
        {
            return this.RichiestaRistampaField;
        }
        set
        {
            if ((object.ReferenceEquals(this.RichiestaRistampaField, value) != true))
            {
                this.RichiestaRistampaField = value;
                this.RaisePropertyChanged("RichiestaRistampa");
            }
        }
    }

    [System.Runtime.Serialization.DataMemberAttribute()]
    public System.Web.HttpPostedFileBase RichiestaRistampaWeb
    {
        get
        {
            return this.RichiestaRistampaWebField;
        }
        set
        {
            if ((object.ReferenceEquals(this.RichiestaRistampaWebField, value) != true))
            {
                this.RichiestaRistampaWebField = value;
                this.RaisePropertyChanged("RichiestaRistampaWeb");
            }
        }
    }

    [System.Runtime.Serialization.DataMemberAttribute()]
    public System.Nullable<System.DateTime> ScadenzaLicenza
    {
        get
        {
            return this.ScadenzaLicenzaField;
        }
        set
        {
            if ((this.ScadenzaLicenzaField.Equals(value) != true))
            {
                this.ScadenzaLicenzaField = value;
                this.RaisePropertyChanged("ScadenzaLicenza");
            }
        }
    }

    [System.Runtime.Serialization.DataMemberAttribute()]
    public string TargaAttuale
    {
        get
        {
            return this.TargaAttualeField;
        }
        set
        {
            if ((object.ReferenceEquals(this.TargaAttualeField, value) != true))
            {
                this.TargaAttualeField = value;
                this.RaisePropertyChanged("TargaAttuale");
            }
        }
    }

    public event System.ComponentModel.PropertyChangedEventHandler PropertyChanged;

    protected void RaisePropertyChanged(string propertyName)
    {
        System.ComponentModel.PropertyChangedEventHandler propertyChanged = this.PropertyChanged;
        if ((propertyChanged != null))
        {
            propertyChanged(this, new System.ComponentModel.PropertyChangedEventArgs(propertyName));
        }
    }
}

Esa es la forma:

@using (Html.BeginForm("ConfermaRistampa", "Abbonamenti", new { @IDTitolo = Request.QueryString["IDTitolo"] }, FormMethod.Post, null))
{
    <br />
    <table class="table table-bordered table-striped">
        <thead>
            <tr class="color">
                <th>
                    @Html.Label(Risorse.Language.TargaAttuale)
                </th>
                <th>
                    @Html.Label(Risorse.Language.Motivazione)
                </th>
                <th>
                    @Html.Label(Risorse.Language.Importo)
                </th>
            </tr>
        </thead>
        <tbody>
            <tr>
                <td>
                    @Html.DisplayFor(model => model.TargaAttuale)

                </td>
                <td>
                    @Html.DropDownListFor(model => model.Motivazione, new SelectList(motivazioni, "Key", "Value"), "[Scegli una motivazione]", new { id = "ddlMotivazione", onchange = "SetPanelMotivazione();", required = "required" })

                </td>
                <td>
                    @Html.DisplayFor(model => model.ImportoOperazione)
                </td>
            </tr>
        </tbody>
    </table>




    <div class="row">
        <div class="col-sm-2">
        </div>
        <div class="col-sm-3">
        </div>
    </div>
    <div class="row">
        <div class="col-sm-6">
            @Html.Label(Risorse.Language.DichiarazioneRichiestaRistampa + ":")
            @Html.TextBoxFor(model => model.RichiestaRistampaWeb, new { type = "file", required = "required" })
        </div>
        @*<div class="col-sm-6">
                @Html.Label(Risorse.Language.LibrettoDiCircolazione + ":")
                @Html.TextBoxFor(model => model.LibrettoDiCircolazioneWeb, new { type = "file", required = "required" })
            </div>*@
    </div>
    <br />
    <div id="pnlLicense" style="display:none">
        <div class="row">
            <div class="col-sm-3">
                @Html.Label(Risorse.Language.NumeroLicenza)
                @Html.TextBoxFor(model => model.NumeroLicenza)
                @Html.ValidationMessage("errNumLicenza", new { @class = "text-danger" })
            </div>
            <div class="col-sm-3">
                @Html.Label(Risorse.Language.Provincia)
                @Html.DropDownList("ddlProvince", new SelectList(listaProvince, "Key", "Value"), "Seleziona la provincia", new { @id = "ddlProvince", @onchange = "javascript:GetComuni(this.value, '#ddlComuni');" })
                @Html.ValidationMessage("errProvince", new { @class = "text-danger" })
            </div>
            <div class="col-sm-3">
                @Html.Label(Risorse.Language.Comune)
                @Html.DropDownListFor(model => model.ComuneLicenza, new SelectList(new List<string>()), new { id = "ddlComuni" })
                @Html.ValidationMessage("errComune", new { @class = "text-danger" })
            </div>
            <div class="col-sm-3">
                @Html.Label(Risorse.Language.ScadenzaLicenza)
                @Html.TextBoxFor(model => model.ScadenzaLicenza, new { type = "text", @language = "it", @class = "datepicker-here" })
            </div>
        </div>
        <br />
        <div class="row">
            <div class="col-sm-6">
                @Html.Label(Risorse.Language.DocumentazioneNuovaLicenza + ":")
                @Html.TextBoxFor(model => model.LicenzaWeb, new { type = "file" })
            </div>
            @*<div class="col-sm-6">
                    @Html.Label(Risorse.Language.RicevutaAvvenutaPagamento + ":")
                    @Html.TextBoxFor(model => model.RicevutaPagamentoWeb, new { type = "file" })
                </div>*@
        </div>
    </div>

    <div id="pnlRagSoc" style="display:none">
        <h4 class="colorH4">
            @Html.Label(Risorse.Language.DatiNuovoIntestatario)
        </h4>

        <div class="row">
            <div class="col-sm-4">
                @Html.Label(Risorse.Language.Denominazione)
                @Html.TextBoxFor(model => model.Denominazione)
                @Html.ValidationMessage("errDenominazione", new { @class = "text-danger" })
            </div>
        </div>
    </div>
    <br />
    <div class="row">
        <div class="col-sm-8"></div>
        <div class="col-sm-4">
            <input type="submit" value="@Risorse.Language.Invia" class="btnRegister btn btn-default" />
            <input type="button" value="@Risorse.Language.Annulla" onclick="Annulla();" class="btnRegister btn btn-default" />
        </div>
    </div>
}

En su formulario cshtml, establezca el enctype en 'multipart / form-data'. De lo contrario, los archivos no se incluirán en su modelo:

// Magic all the way to the right -->
@using (Html.BeginForm("ConfermaRistampa", "Abbonamenti", new { @IDTitolo = Request.QueryString["IDTitolo"] }, FormMethod.Post, new { enctype="multipart/form-data" }))