public class WallUpdaterApplication : Autodesk.Revit.UI.IExternalApplication
{
    public Result OnStartup(UIControlledApplication application)
    {
        // Register wall updater with Revit
        WallUpdater updater = new WallUpdater(application.ActiveAddInId);
        UpdaterRegistry.RegisterUpdater(updater);

        // Change Scope = any Wall element
        ElementClassFilter wallFilter = new ElementClassFilter(typeof(Wall));

        // Change type = element addition
        UpdaterRegistry.AddTrigger(updater.GetUpdaterId(), wallFilter,
                                    Element.GetChangeTypeElementAddition());
        return Result.Succeeded;
    }

    public Result OnShutdown(UIControlledApplication application)
    {
        WallUpdater updater = new WallUpdater(application.ActiveAddInId);
        UpdaterRegistry.UnregisterUpdater(updater.GetUpdaterId());
        return Result.Succeeded;
    }
}

public class WallUpdater : IUpdater
{
    static AddInId m_appId;
    static UpdaterId m_updaterId;
    WallType m_wallType = null;

    // constructor takes the AddInId for the add-in associated with this updater
    public WallUpdater(AddInId id)
    {
        m_appId = id;
        m_updaterId = new UpdaterId(m_appId, new Guid("FBFBF6B2-4C06-42d4-97C1-D1B4EB593EFF"));
    }

    public void Execute(UpdaterData data)
    {
        Document doc = data.GetDocument();

        // Cache the wall type
        if (m_wallType == null)
        {
            FilteredElementCollector collector = new FilteredElementCollector(doc);
            collector.OfClass(typeof(WallType));
            var wallTypes = from element in collector
                            where
                                element.Name == "Exterior - Brick on CMU"
                            select element;
            if (wallTypes.Count<Element>() > 0)
            {
                m_wallType = wallTypes.Cast<WallType>().ElementAt<WallType>(0);
            }
        }

        if (m_wallType != null)
        {
            // Change the wall to the cached wall type.
            foreach (ElementId addedElemId in data.GetAddedElementIds())
            {
                Wall wall = doc.GetElement(addedElemId) as Wall;
                if (wall != null)
                {
                    wall.WallType = m_wallType;
                }
            }
        }
    }

    public string GetAdditionalInformation()
    {
        return "Wall type updater example: updates all newly created walls to a special wall";
    }

    public ChangePriority GetChangePriority()
    {
        return ChangePriority.FloorsRoofsStructuralWalls;
    }

    public UpdaterId GetUpdaterId()
    {
        return m_updaterId;
    }

    public string GetUpdaterName()
    {
        return "Wall Type Updater";
    }
}

Public Class WallUpdaterApplication
    Implements Autodesk.Revit.UI.IExternalApplication
    Public Function OnStartup(application As UIControlledApplication) As Autodesk.Revit.UI.Result Implements IExternalApplication.OnStartup
        ' Register wall updater with Revit
        Dim updater As New WallUpdater(application.ActiveAddInId)
        UpdaterRegistry.RegisterUpdater(updater)

        ' Change Scope = any Wall element
        Dim wallFilter As New ElementClassFilter(GetType(Wall))

        ' Change type = element addition
        UpdaterRegistry.AddTrigger(updater.GetUpdaterId(), wallFilter, Element.GetChangeTypeElementAddition())
        Return Result.Succeeded
    End Function

    Public Function OnShutdown(application As UIControlledApplication) As Autodesk.Revit.UI.Result Implements IExternalApplication.OnShutdown
        Dim updater As New WallUpdater(application.ActiveAddInId)
        UpdaterRegistry.UnregisterUpdater(updater.GetUpdaterId())
        Return Result.Succeeded
    End Function
End Class

Public Class WallUpdater
    Implements IUpdater
    Shared m_appId As AddInId
    Shared m_updaterId As UpdaterId
    Private m_wallType As WallType = Nothing

    ' constructor takes the AddInId for the add-in associated with this updater
    Public Sub New(id As AddInId)
        m_appId = id
        m_updaterId = New UpdaterId(m_appId, New Guid("FBFBF6B2-4C06-42d4-97C1-D1B4EB593EFF"))
    End Sub

    Public Sub Execute(data As UpdaterData) Implements IUpdater.Execute
        Dim doc As Document = data.GetDocument()

        ' Cache the wall type
        If m_wallType Is Nothing Then
            Dim collector As New FilteredElementCollector(doc)
            collector.OfClass(GetType(WallType))
            Dim wallTypes As System.Collections.Generic.IEnumerable(Of Autodesk.Revit.DB.Element)
            wallTypes = From element In collector _
             Where element.Name = "Exterior - Brick on CMU" _
             Select element
            If wallTypes.Count() > 0 Then
                m_wallType = wallTypes.Cast(Of WallType)().ElementAt(0)
            End If
        End If

        If m_wallType IsNot Nothing Then
            ' Change the wall to the cached wall type.
            For Each addedElemId As ElementId In data.GetAddedElementIds()
                Dim wall As Wall = TryCast(doc.GetElement(addedElemId), Wall)
                If wall IsNot Nothing Then
                    wall.WallType = m_wallType
                End If
            Next
        End If
    End Sub

    Public Function GetAdditionalInformation() As String Implements IUpdater.GetAdditionalInformation
        Return "Wall type updater example: updates all newly created walls to a special wall"
    End Function

    Public Function GetChangePriority() As ChangePriority Implements IUpdater.GetChangePriority
        Return ChangePriority.FloorsRoofsStructuralWalls
    End Function

    Public Function GetUpdaterId() As UpdaterId Implements IUpdater.GetUpdaterId
        Return m_updaterId
    End Function

    Public Function GetUpdaterName() As String Implements IUpdater.GetUpdaterName
        Return "Wall Type Updater"
    End Function
End Class