Question

I am creating a web application with MVC3 and MEF. I am attempting to export my HostModel to the plugin with an IDNumber and then have the plugin redirect to a link using that IDNumber. My model is not being exported correctly and then my view is also not reading the model from the plugin controller (I tested this by making a test model object and passing that to the view). I’m pretty sure I have some mix up with how I am exporting to the view in my plugin. I am using a .aspx file and not a .vbhtml because VS2010 didn’t give me the option. When I tried to drag a .vbhtml file into the project it didn’t work correctly.

Here is my HostController:

<Export(GetType(HostModel))>
<PartCreationPolicy(CreationPolicy.NonShared)>
Public Class HostController
    Inherits System.Web.Mvc.Controller


    Private m_objHost As HostModel

    Private m_IDNUmber As String
    Property IDNumber() As String
        Get
            Return m_IDNUmber
        End Get
        Set(value As String)
            m_IDNUmber = value
        End Set
    End Property


    Function Index() As ActionResult
        ViewData("Message") = "Welcome to ASP.NET MVC!"
        If m_objHost Is Nothing Then
            m_objHost = New HostModel
        End If
        Return View(m_objHost)
    End Function

    '<HttpPost()>
    Function ChangeCUNumber(model As HostModel, strIDNumber As String) As ActionResult
        ' m_IDNUmber = strIDNumber
        model.IDNumber = strIDNumber
        Return View("Index", model)
    End Function

    <HttpPost()>
    Function GoToMini(model As HostModel) As ActionResult
        m_CUNUmber = model.CUNumber
        Dim hostContollerObj As New HomeController
        hostContollerObj.CUNumber = model.IDNumber

        m_objHost = model
        Return Redirect("http://localhost:3727/miniView")
    End Function
End Class

This is my HostModel:

Public Class HostModel
Implements IHost

Private Shared m_instance As HostModel
Private m_IDNumber As String

Public Sub New()
End Sub



Shared ReadOnly Property instance() As HostModel
    Get
        If m_instance Is Nothing Then
            m_instance = New HostModel
        End If
        Return m_instance
    End Get
End Property


Public Property IDNumber As String Implements CUCMCV_Interfaces.IHost.IDNumber
    Get
        Return m_IDNumber
    End Get
    Set(value As String)
        m_IDNumber = value
    End Set
End Property

This is my plugin controller:

<Export(GetType(IPlugin))> _
<ExportMetadata("PluginName", "miniView")> _
<PartCreationPolicy(CreationPolicy.NonShared)> _
Public Class miniViewController
    Inherits System.Web.Mvc.Controller
    Implements IPlugin


    <Import(GetType(HostModel))>
    Private m_objHost As HostModel


    Public Function Index() As ActionResult
        Dim renderedView As ViewResult = View("~/Plugin/miniView.dll/miniView.Index.aspx", m_objHost)

        Return renderedView
    End Function

This is my plugin view (Index.aspx)

Public Class Index
    Inherits Mvc.ViewPage




    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load


        Dim p As ImportData = New ImportData()
        Dim strMINILink As String = "http://inside/mini?ContractNumber="
        Dim strCUNumber As String = p.instance.IDNumber
        Dim strMINIURL As String = strMINILink & strIDNumber
        Response.Redirect(strMINIURL)

    End Sub

End Class

Public Class ImportData

    <Import(GetType(HostModel))>
    Property instance As HostModel

    Public Sub New()
        Dim catalog As AggregateCatalog = New AggregateCatalog()

        catalog.Catalogs.Add(New DirectoryCatalog("C:\Documents and Settings\gbv0860\My Documents\cucmConsolidatedView\CUCMCV\cucmConsolidatedView\cucmConsolidatedView\bin"))
        Dim _container As CompositionContainer = New CompositionContainer(catalog)

        Try
            _container.ComposeParts(Me)

        Catch ex As Exception
            Console.WriteLine(ex.ToString)
        End Try

    End Sub
End Class

Any help would be much appreciated! If you need me to clarify anything please let me know! Thanks!

Answer 1

You have put <Export(GetType(HostModel))> on the HostController class which isn’t actually a HostModel. That’s not a valid export.

ASP.NET MVC will request controllers by their exact type, so you should export HostController with just <Export>.

The <Export(GetType(HostModel))> probably belongs on the HostModel class. And instead of implementing your own singleton, you should just mark it with <PartCreationPolicy(CreationPolicy.Shared)>.

Then there is the fact that you have an import on ImportData, but that class also isn’t exported and you just create it yourself with a new statement. Therefore MEF will never see these instances and won’t do anything with the imports.

Finally, note that ASP.NET MVC will not automatically use MEF to create objects. You need to register a dependency resolver which wraps a MEF container to set that up. There appears to be a composition provider for APS.NET MVC in MEF2.