This is a class I created to help me with MEF. It might be useful to somebody.
It is a singleton with IDisposable to create a shared object for your application’s lifetime.
It also features lambda queries for finding metadata as well.
#Region "Compiler Options"
Option Strict Off
Option Explicit On
Option Compare Binary
#End Region
#Region "Library Imports"
Imports System.ComponentModel.Composition
Imports System.ComponentModel.Composition.Hosting
#End Region
' Template version 1.2.0.2. Code developed for framework v2.0.50727.3074
' This code is copyright (c) 2009 ActiveAsp Software. All rights reserved.
''' <summary>
''' Managed Extensibility Framework Helper Class
''' </summary>
''' <remarks>
''' Singleton object
''' -- Change Log --------------------------------------------------------
''' 4/5/2009 11:55:06 PM by Rick - Initial Creation
'''
''' </remarks>
Public NotInheritable Class MefHelper
Implements IDisposable
#Region "Constructor / Deconstructor"
''' <summary>
''' The starting point for this class
''' </summary>
''' <remarks></remarks>
Private Sub New()
' Enter Shared Class Creation Code Here
Dim sPathInitial As String = System.IO.Path.GetDirectoryName(GetType(MefHelper).Assembly.Location)
_ExtensionsPath = System.IO.Path.Combine(sPathInitial, "Extensions")
End Sub
#Region " IDisposable Support "
Private disposedValue As Boolean = False ' To detect redundant calls
' IDisposable
Protected Sub Dispose(ByVal disposing As Boolean)
If Not Me.disposedValue Then
If disposing Then
_Container.Dispose()
_Container = Nothing
End If
End If
Me.disposedValue = True
End Sub
' This code added by Visual Basic to correctly implement the disposable pattern.
Public Sub Dispose() Implements IDisposable.Dispose
' Do not change this code. Put cleanup code in Dispose(ByVal disposing As Boolean) above.
Dispose(True)
GC.SuppressFinalize(Me)
End Sub
#End Region
#End Region
#Region "Public"
#Region "Public Property Declarations"
Private _Container As CompositionContainer = Nothing
Public ReadOnly Property Container() As CompositionContainer
Get
Return _Container
End Get
End Property
Private _ExtensionsPath As String = ""
Public Property ExtensionsPath() As String
Get
Return _ExtensionsPath
End Get
Set(ByVal value As String)
If Not _ExtensionsPath = value Then
_ExtensionsPath = value
End If
End Set
End Property
#End Region
#Region "Public Shared Property Declarations"
' Properties
Public Shared ReadOnly Property Instance() As MefHelper
Get
If (MefHelper._instance Is Nothing) Then
SyncLock MefHelper.syncRoot
If (MefHelper._instance Is Nothing) Then
MefHelper._instance = New MefHelper
End If
End SyncLock
End If
Return MefHelper._instance
End Get
End Property
' Fields
Private Shared _instance As MefHelper 'ModReq(IsVolatile)
Private Shared syncRoot As Object = New Object
#End Region
#Region "Public Methods"
Public Sub Compose()
Dim Catalog As New AggregateCatalog()
' Add This assembly's catalog parts
Catalog.Catalogs.Add(New AssemblyCatalog(GetType(MefHelper).Assembly))
' Directory of catalog parts
If System.IO.Directory.Exists(_ExtensionsPath) Then
Catalog.Catalogs.Add(New DirectoryCatalog(_ExtensionsPath))
End If
_Container = New CompositionContainer(Catalog)
End Sub
Public Function GetExportByContractType(Of T)() As Export(Of T)
Dim RetVal As Export(Of T) = Nothing
Try
RetVal = _Container.GetExport(Of T)()
Catch ex As Exception
End Try
Return RetVal
End Function
Public Function GetExportByContractType(Of T, U)() As Export(Of T, U)
Dim RetVal As Export(Of T, U) = Nothing
Try
RetVal = _Container.GetExport(Of T, U)()
Catch ex As Exception
End Try
Return RetVal
End Function
Public Function GetExportsByContractType(Of T)() As Generic.List(Of Export(Of T))
Dim RetVal As Generic.List(Of Export(Of T)) = Nothing
Try
RetVal = _Container.GetExports(Of T).ToList()
Catch ex As Exception
End Try
Return RetVal
End Function
Public Function GetExportsByContractType(Of T, U)() As Generic.List(Of Export(Of T, U))
Dim RetVal As Generic.List(Of Export(Of T, U)) = Nothing
Try
RetVal = _Container.GetExports(Of T, U).ToList()
Catch ex As Exception
End Try
Return RetVal
End Function
Public Function GetExportByContractName(Of T)(ByVal name As String) As Export(Of T)
Dim RetVal As Export(Of T) = Nothing
Try
RetVal = _Container.GetExports(Of T).Where(Function(p) String.Compare(p.Definition.ContractName, name, True) = 0).Single()
Catch ex As Exception
End Try
Return RetVal
End Function
Public Function GetExportByContractName(Of T, U)(ByVal name As String) As Export(Of T, U)
Dim RetVal As Export(Of T, U) = Nothing
Try
RetVal = _Container.GetExports(Of T, U).Where(Function(p) String.Compare(p.Definition.ContractName, name, True) = 0).Single()
Catch ex As Exception
End Try
Return RetVal
End Function
Public Function GetExportsByContractName(Of T)(ByVal name As String, ByVal value As String) As Generic.List(Of Export(Of T))
Dim RetVal As Generic.List(Of Export(Of T)) = Nothing
Try
RetVal = _Container.GetExports(Of T).Where(Function(p) String.Compare(p.Definition.ContractName, name, True) = 0).ToList()
Catch ex As Exception
End Try
Return RetVal
End Function
Public Function GetExportsByContractName(Of T, U)(ByVal name As String, ByVal value As String) As Generic.List(Of Export(Of T, U))
Dim RetVal As Generic.List(Of Export(Of T, U)) = Nothing
Try
RetVal = _Container.GetExports(Of T, U).Where(Function(p) String.Compare(p.Definition.ContractName, name, True) = 0).ToList()
Catch ex As Exception
End Try
Return RetVal
End Function
Public Function GetExportByMetadata(Of T)(ByVal name As String) As Export(Of T)
Dim RetVal As Export(Of T) = Nothing
Try
RetVal = _Container.GetExports(Of T).Where(Function(p) p.Metadata.ContainsKey(name) = True).Single()
Catch ex As Exception
End Try
Return RetVal
End Function
Public Function GetExportByMetadata(Of T)(ByVal name As String, ByVal value As String) As Export(Of T)
Dim RetVal As Export(Of T) = Nothing
Try
RetVal = _Container.GetExports(Of T).Where(Function(p) String.Compare(p.Metadata(name).ToString(), value, True) = 0).Single()
Catch ex As Exception
End Try
Return RetVal
End Function
Public Function GetExportByMetadata(Of T, U)(ByVal name As String, ByVal value As String) As Export(Of T, U)
Dim RetVal As Export(Of T, U) = Nothing
Try
RetVal = _Container.GetExports(Of T, U).Where(Function(p) String.Compare(p.Metadata(name).ToString(), value, True) = 0).Single()
Catch ex As Exception
End Try
Return RetVal
End Function
Public Function GetExportByMetadata(Of T, U)(ByVal name As String) As Export(Of T, U)
Dim RetVal As Export(Of T, U) = Nothing
Try
RetVal = _Container.GetExports(Of T, U).Where(Function(p) p.Metadata.ContainsKey(name) = True).Single()
Catch ex As Exception
End Try
Return RetVal
End Function
Public Function GetExportsByMetadata(Of T)(ByVal name As String, ByVal value As String) As Generic.List(Of Export(Of T))
Dim RetVal As Generic.List(Of Export(Of T)) = Nothing
Try
RetVal = _Container.GetExports(Of T).Where(Function(p) String.Compare(p.Metadata(name).ToString(), value, True) = 0).ToList()
Catch ex As Exception
End Try
Return RetVal
End Function
Public Function GetExportsByMetadata(Of T)(ByVal name As String) As Generic.List(Of Export(Of T))
Dim RetVal As Generic.List(Of Export(Of T)) = Nothing
Try
RetVal = _Container.GetExports(Of T).Where(Function(p) p.Metadata.ContainsKey(name) = True).ToList()
Catch ex As Exception
End Try
Return RetVal
End Function
Public Function GetExportsByMetadata(Of T, U)(ByVal name As String, ByVal value As String) As Generic.List(Of Export(Of T, U))
Dim RetVal As Generic.List(Of Export(Of T, U)) = Nothing
Try
RetVal = _Container.GetExports(Of T, U).Where(Function(p) String.Compare(p.Metadata(name).ToString(), value, True) = 0).ToList()
Catch ex As Exception
End Try
Return RetVal
End Function
Public Function GetExportsByMetadata(Of T, U)(ByVal name As String) As Generic.List(Of Export(Of T, U))
Dim RetVal As Generic.List(Of Export(Of T, U)) = Nothing
Try
RetVal = _Container.GetExports(Of T, U).Where(Function(p) p.Metadata.ContainsKey(name) = True).ToList()
Catch ex As Exception
End Try
Return RetVal
End Function
#End Region
#End Region
End Class
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