Dynamically loading a dll using MEF vb.net .net framework 4.5

Question

I am using the following to Dynamically load a dll in vb.net I am using the LoadPlugins method to use an AggregateCatalog To find the plugins in the directory called Extensions all that is working perfect and i run the dll with the second listing below as you can see im using lazy loading of the classes below

Imports System.ComponentModel.Composition Imports System.ComponentModel.Composition.Hosting

My Problem is how do i exit the dll application properly is it just simple enough to use Applicaiton.Exit in the dll or will this still reside in memory until the main application ends?.

First Code Listing

 Private Sub LoadPlugins()
    ' Add any initialization after the InitializeComponent() call.

    'An aggregate catalog that combines multiple catalogs
    Dim catalog = New AggregateCatalog()

    'Adds all the parts found in the same assembly as the Program class
    catalog.Catalogs.Add(New AssemblyCatalog(GetType(frmMainImports).Assembly()))

    'IMPORTANT!
    'You will need to adjust this line to match your local path!
    catalog.Catalogs.Add(New DirectoryCatalog("Extensions"))

    'Create the CompositionContainer with the parts in the catalog
    _container = New CompositionContainer(catalog)

    'Fill the imports of this object
    Try
        _container.ComposeParts(Me)
    Catch ex As Exception
        MsgBox(ex.ToString)
    End Try
End Sub

Second Code Listing

Private Sub btnRunImport_Click(sender As Object, e As EventArgs) Handles btnRunImport.Click
    Try

        For Each i As Lazy(Of IImport, IMetaName) In extensions

            'Search for matching extension name then invoke MyMethod in that extension then
            'set textbox1.text to the return value
            If i.Metadata.MyName = lbPlugins.SelectedItem Then txtDescription.Text = i.Value.Import("Hello From")


        Next

    Catch ex As Exception
        MsgBox(ex.ToString)
    End Try