Question

I am working on a ASP.NET MVC2 website. For learning. I am working with the Visual Basic language.

In a view I would like to do this:

 <%: Html.EditorForEnumeracion(Function(v) v.combustible%>

So, I created an HtmlHelper extension method:

Imports System.Runtime.CompilerServices
Imports System.Linq.Expressions
Imports System.Reflection

Public Module HtmlHelpers
    <Extension()> _
    Public Function EditorForEnumeracion(Of TModel, TValue)(ByVal html As HtmlHelper(Of TModel), ByVal expression As Expression(Of Func(Of TModel, TValue))) As MvcHtmlString
        'My stuff goes here
     End Function
End Module

The problem is that I do not know how to get the instance of the v.combustible object that I pass to the helper. I do not care about the v object. I need to work with the combustible attribute of the v object.

Here and here seems to be how to do this, but I do not understand. Also, I work with Visual Basic, not C#.

I think that I can get the instance of the Enumeracion object through the expression parameter, but I do not understand how.

More info now.

This is my “Vehiculo” class:

Namespace Models.Automovil
    Public Class Vehiculo
        Public Property tipo As New Models.Enumeracion("TipoDeVehiculo")
        Public Property marca As String
        Public Property modelo As String
        Public Property numeroDePuertas As Integer
        Public Property combustible As New Models.Enumeracion("TipoDeCombustible")
        Public Property potencia As Integer
        Public Property fechaPrimeraMatriculacion As DateTime
        Public Property version As String
        Public Property precio As Decimal
        Public Property descripcion As String
    End Class
End Namespace

And this is my “Enumeracion” class:

Namespace Models
    Public Class Enumeracion
        Private bd As New tarificadorasegasaEntities
        Private diccionario As New Dictionary(Of String, Integer)
        Private _nombre As String
        Private _clave As String
        Private _valor As Integer
        Public ReadOnly Property nombre As String
            Get
                Return _nombre
            End Get
        End Property
        Public ReadOnly Property clave As String
            Get
                Return _clave
            End Get
        End Property
        Public ReadOnly Property valor As Integer
            Get
                Return _valor
            End Get
        End Property

        'More stuff here. Methods.

    End Class
End Namespace

The model is the Vehiculo class.

Still not resolving this.

Thanks in advance.

Answer 1

Try like this:

<Extension()> _
Public Function EditorForMyCustomClassB(Of Vehiculo, Enumeracion)(ByVal html As HtmlHelper(Of TModel), ByVal expression As Expression(Of Func(Of Vehiculo, Enumeracion))) As MvcHtmlString
    Dim res = ModelMetadata.FromLambdaExpression(expression, html.ViewData)
    Dim e As Enumeracion = DirectCast(res.Model, Enumeracion)
    ' use e here
 End Function