[D�butant] Probl�me de vue avec DropDownList

Bonjour je cr�� une vue qui me permet de cr�er un objet avec MVC mais lorsque je souhaite affich� ma vue de cr�ation, j'ai une dropdownlist qui me sort une erreur .

voici l'erreur :

Pi�ce jointe 399696

Mon controlleur n'a rien de sp�cial Get:

' GET: Fiches/Create
Function Create() As ActionResult
Return View()
End Function

Voici le code de ma classe Fiche :

Code:

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Imports System
Imports System.Collections.Generic
Imports System.ComponentModel.DataAnnotations
Imports System.ComponentModel.DataAnnotations.Schema
Imports System.Data.Entity.Spatial
 
Partial Public Class Fiches
    Public Sub New()
        Contraintes = New HashSet(Of Contraintes)()
        NatureAcquisitions = New HashSet(Of NatureAcquisitions)()
        NatureGenerales = New HashSet(Of NatureGenerales)()
        NatureMaintenances = New HashSet(Of NatureMaintenances)()
        NatureTravaux = New HashSet(Of NatureTravaux)()
        Services1 = New HashSet(Of Services)()
    End Sub
 
    <Key>
    Public Property FicheId As Long
 
    <Required>
    <StringLength(150)>
    <Display(name:="Libellé")>
    Public Property Libelle As String
 
    Public Property Description As String
 
    Public Property Montant As Double
 
    Public Property EstSubsidie As Boolean
 
    Public Property DateCollege As Date
 
    Public Property IsAutreServiceImplique As Boolean
 
    <Required>
    Public Property Responsable As String
 
    Public Property NomenclatureId As Long
 
    Public Property DemandeurId As Long
 
    Public Property PourcentageId As Long
 
    Public Property DureeId As Long
 
    Public Property ProjetId As Long
 
    Public Property PrioriteId As Long
 
    Public Property ServiceId As Long
 
    Public Overridable Property Demandeurs As Demandeurs
 
    Public Overridable Property Durees As Durees
 
    Public Overridable Property Nomenclatures As Nomenclatures
 
    Public Overridable Property Pourcentages As Pourcentages
 
    Public Overridable Property Priorites As Priorites
 
    Public Overridable Property Projets As Projets
 
    Public Overridable Property Services As Services
 
    Public Overridable Property Contraintes As ICollection(Of Contraintes)
 
    Public Overridable Property NatureAcquisitions As ICollection(Of NatureAcquisitions)
 
    Public Overridable Property NatureGenerales As ICollection(Of NatureGenerales)
 
    Public Overridable Property NatureMaintenances As ICollection(Of NatureMaintenances)
 
    Public Overridable Property NatureTravaux As ICollection(Of NatureTravaux)
 
    Public Overridable Property Services1 As ICollection(Of Services)
End Class

et le code de Nomenclature :

Code:

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Imports System
Imports System.Collections.Generic
Imports System.ComponentModel.DataAnnotations
Imports System.ComponentModel.DataAnnotations.Schema
Imports System.Data.Entity.Spatial
 
Partial Public Class Nomenclatures
    Public Sub New()
        Fiches = New HashSet(Of Fiches)()
    End Sub
 
    <Key>
    Public Property NomenclatureId As Long
 
    <Required>
    <StringLength(100)>
    Public Property Libelle As String
 
    Public Overridable Property Fiches As ICollection(Of Fiches)
End Class

Je ne comprend pas pourquoi il me jette une erreur. L'utilisateur devant faire une s�lection dans une combobox.
J'aurai certainement le m�me genre de probl�me avec des checkbox pour plusieur choix possible.

Dans l'attente de vous lire, merci.