How to: Create Rules Extensions from Multiple Sources

One limitation of rules extensions for the Forefront Identity Manager Synchronization Service (FIM Synchronization Service) database (metaverse) is that all the work is done in only one assembly. This makes it difficult for a team of developers to work on a metaverse rules extension. This topic presents one technique that you can use to assign multiple developers to a metaverse rules extension.

The strategy behind this technique is to create additional assemblies that other developers can work on. We strongly recommend that, however you partition the work, you should ensure that each provisioning extension operates on separate, disjoint objects. Failure to follow this rule can result in unpredictable provisioning.

For example, you could create two additional assemblies, MV_Extension_MA1.dll and MV_Extension_MA2.dll, through which you provision objects to management agents MA1 and MA2, respectively.

To identify your assembly as the metaverse rules extension, compile your code into an extension DLL and configure that DLL as the metaverse extension in the Configure Extensions dialog box.

The following code examples use multiple DLLs that contain classes that implement the IMVSynchronization interface and its methods. The example loads any DLL it finds in the ExtensionsDirectory property that has the prefix MV_Extension and executes each of the DLL methods in the example's corresponding method.

The following example shows how to use a rules extension to use multiple provisioning DLLs.

Imports System.IO
Imports System.Reflection
Imports Microsoft.MetadirectoryServices
Imports Microsoft.MetadirectoryServices.Logging

Public Class MVExtensionObject
    Implements IMVSynchronization

    Dim myMVDlls() As IMVSynchronization
    Dim PREFIX As String = "MV_Extension"

    Public Sub Initialize() Implements IMVSynchronization.Initialize

        ' Get list of files that start with PREFIX and have a .dll extension.
        Dim fileNames() As String = Directory.GetFiles( _
            Utils.ExtensionsDirectory, _
            PREFIX + "*.dll")

        ' Create the array the size of the number of files we found.
        Dim numFiles As Int32 = fileNames.Length -1

        ReDim myMVDlls(numFiles)

        Dim i As Integer
        Dim fileName As String
        Dim assem As [Assembly]
        Dim type, types() As Type
        Dim objLoaded As Object

        ' Load the extension files into the array.
        For i = 0 To numFiles

            ' Load the assembly.
            fileName = fileNames(i)
            assem = [Assembly].LoadFrom(fileName)

            types = assem.GetExportedTypes()

            ' Examine all the object types in the assembly for
            ' ones that starts with "MVExtension". We assume
            ' this object type is an MV extension object type.
            For Each type In types
                If (Not (type.GetInterface("Microsoft.MetadirectoryServices.IMVSynchronization") Is Nothing)) Then

                    ' Create an instance of the MV extension object type.
                    objLoaded = assem.CreateInstance(type.FullName)
                    Exit For
                End If
            Next

            ' If an object type starting with "MVExtension" could not be found,
            ' or if an instance could not be created, throw an exception.
            If objLoaded Is Nothing Then
                Throw New UnexpectedDataException("Found MV extension " + _
                    "DLL (" + fileName + ") without an " + PREFIX + "* type")
            End If

            ' Add this MV extension object to our array of objects.
            myMVDlls(i) = objLoaded

            ' Call the Initialize() method on each MV extension object.
            myMVDlls(i).Initialize()
        Next
    End Sub

    Public Sub Terminate() Implements IMVSynchronization.Terminate
        Dim myDll As IMVSynchronization

        ' Call the Terminate() method on each MV extension object.
        For Each myDll In myMVDlls
            myDll.Terminate()
        Next
    End Sub

    Public Sub Provision(ByVal mventry As MVEntry) Implements IMVSynchronization.Provision
        Dim myDll As IMVSynchronization

        ' Call the Provision() method on each MV extension object.
        For Each myDll In myMVDlls
            myDll.Provision(mventry)
        Next

    End Sub

    Public Function ShouldDeleteFromMV(ByVal csentry As CSEntry, _
        ByVal mventry As MVEntry) As Boolean _
        Implements IMVSynchronization.ShouldDeleteFromMV

        Dim myDll As IMVSynchronization

        Dim shouldDelete As Boolean = False

        ' Call the ShouldDeleteFromMV() method on each MV extension object.
        For Each myDll In myMVDlls
            If myDll.ShouldDeleteFromMV(csentry, mventry) Then
                shouldDelete = True
                Exit For
            End If
        Next

        ShouldDeleteFromMV = shouldDelete
    End Function
End Class

using System;
using System.IO;
using System.Reflection;
using Microsoft.MetadirectoryServices;
using Microsoft.MetadirectoryServices.Logging;

namespace Miis_Metaverse
{
    public class MVExtensionObject : IMVSynchronization
    {
        IMVSynchronization [] myMVDlls;
        string PREFIX = "MV_Extension";

        void IMVSynchronization.Initialize ()
        {

            // Get list of files that start with PREFIX and have a .dll extension.
            string[] fileNames =
                Directory.GetFiles(
                Utils.ExtensionsDirectory,
                PREFIX + "*.dll");

            int numFiles = fileNames.Length;

            // Create the array the size of the number of files we found.
            myMVDlls = new IMVSynchronization[numFiles];

            string   fileName;
            Assembly assem;
            Type[]   types;
            Object   objLoaded = null;

            // Load the extension files into the array.
            for(int i = 0; i < numFiles; i++)
            {

                // Load the assembly.
                fileName = fileNames[i];
                assem    = Assembly.LoadFrom(fileName);

                types = assem.GetExportedTypes();

                // Examine all the object types in the assembly for
                // ones that starts with "MVExtension". We assume
                // this object type is an MV extension object type.
                foreach(Type type in types)
                {
                    if(type.GetInterface("Microsoft.MetadirectoryServices.IMVSynchronization") != null)
                    {

                        // Create an instance of the MV extension object type.
                        objLoaded = assem.CreateInstance(type.FullName);
                        break;
                    }
                }

                // If an object type starting with "MVExtension" could not be found,
                // or if an instance could not be created, throw an exception.
                if(null == objLoaded)
                {
                    throw new UnexpectedDataException("Found MV extension " +
                        "DLL (" + fileName + ") without an " + PREFIX + "* type");
                }

                // Add this MV extension object to our array of objects.
                myMVDlls[i] = (IMVSynchronization)objLoaded;

                // Call the Initialize() method on each MV extension object.
                myMVDlls[i].Initialize();
            }
        }

        void IMVSynchronization.Terminate ()
        {

            // Call the Terminate() method on each MV extension object.
            foreach(IMVSynchronization mvextension in myMVDlls)
            {
                mvextension.Terminate();
            }
        }

        void IMVSynchronization.Provision (MVEntry mventry)
        {

            // Call the Provision() method on each MV extension object.
            foreach(IMVSynchronization mvextension in myMVDlls)
            {
                mvextension.Provision(mventry);
            } 
        }

        bool IMVSynchronization.ShouldDeleteFromMV (CSEntry csentry, MVEntry mventry)
        {
            bool shouldDelete = false;

            // Call the ShouldDeleteFromMV() method on each MV extension object.
            foreach(IMVSynchronization mvextension in myMVDlls)
            {
                if(mvextension.ShouldDeleteFromMV(csentry, mventry))
                {
                    shouldDelete = true;
                    break;
                }
            }

            return(shouldDelete);
        }
    }
}

See Also

Reference

IMVSynchronization

Concepts

Rules Extensions Examples
Using Rules Extensions
Provisioning Objects in the Connector Space