Revit Synchronization event - api

Question

Starting with this...
https://github.com/jeremytammik/RevitLookup/blob/master/CS/EventTrack/Events/ApplicationEvents.cs
I'm trying to add an event listener for a synchronization event. the code below throws an error stating that the m_app is null. Can i not subscribe to this event while Revit is starting up?
I was able to do this before with application.ViewActivated += ..... Im wondering if this has something to do with DB vs UI driven events and when they are allowed to be subscribed to? I just don't know.
namespace RevitModelHealth
{
public class checkHealth : IExternalApplication
{
// Document doc;
static public Autodesk.Revit.ApplicationServices.Application m_app = null;
public Result OnShutdown(UIControlledApplication application)
{
return Result.Succeeded;
}
public Result OnStartup(UIControlledApplication application)
{
m_app.DocumentSynchronizingWithCentral += new EventHandler<DocumentSynchronizingWithCentralEventArgs>(m_app_DocumentSavingToCentral);
return Result.Succeeded;
}
void m_app_DocumentSavingToCentral(object sender, Autodesk.Revit.DB.Events.DocumentSynchronizingWithCentralEventArgs e)
{
MessageBox.Show("asd","asd");
}
}
}
Here is updated code reflecting my response to the first answer. The message box opens when the document is loaded. No errors are thrown when I try to initialize the synchronization event handlers, however, neither of the message boxes open before or after a synchronization event.
public class checkHealth : IExternalApplication
{
// Document doc;
static public Autodesk.Revit.ApplicationServices.Application m_app;
public Result OnShutdown(UIControlledApplication application)
{
return Result.Succeeded;
}
public Result OnStartup(UIControlledApplication application)
{
application.ControlledApplication.DocumentOpened += new EventHandler<DocumentOpenedEventArgs>(app_DocOpened);
return Result.Succeeded;
}
public void app_DocOpened(object sender, DocumentOpenedEventArgs args)
{
MessageBox.Show("asd","asd");
m_app.DocumentSynchronizingWithCentral += new EventHandler<DocumentSynchronizingWithCentralEventArgs>(m_app_DocumentSavingToCentral);
m_app.DocumentSynchronizedWithCentral += new EventHandler<Autodesk.Revit.DB.Events.DocumentSynchronizedWithCentralEventArgs>(m_app_DocumentSavedToCentral);
}
void m_app_DocumentSavingToCentral(object sender, Autodesk.Revit.DB.Events.DocumentSynchronizingWithCentralEventArgs e)
{
MessageBox.Show("sync", "sync");
}
void m_app_DocumentSavedToCentral(object sender, Autodesk.Revit.DB.Events.DocumentSynchronizedWithCentralEventArgs e)
{
MessageBox.Show("Doone", "Done");
}
}
this worked.... Thanks largely in part to the SDK sample project EventsMonitor
namespace RevitModelHealth
{
public class checkHealth : IExternalApplication
{
public Result OnShutdown(UIControlledApplication application)
{
return Result.Succeeded;
}
public Result OnStartup(UIControlledApplication application)
{
application.ControlledApplication.DocumentSynchronizingWithCentral += new EventHandler<DocumentSynchronizingWithCentralEventArgs>(app_syncStart);
application.ControlledApplication.DocumentSynchronizedWithCentral += new EventHandler<DocumentSynchronizedWithCentralEventArgs>(app_syncOver);
return Result.Succeeded;
}
public void app_syncStart(object o ,DocumentSynchronizingWithCentralEventArgs args)
{
MessageBox.Show("","Stasrting");
}
public void app_syncOver(object o,DocumentSynchronizedWithCentralEventArgs args)
{
MessageBox.Show("", "Over");
}
}
}

Answer 1

Try
application.ControlledApplication.DocumentSynchronizingWithCentral += new EventHandler<DocumentSynchronizingWithCentralEventArgs>(m_app_DocumentSavingToCentral)
in your OnStartup() method.
The call is failing because instance member m_app is initialized to null.
The UIApplication.ControlledApplication object that raises the DocumentSynchronizingWithCentralEventArgs is being accessible from the parameter to OnStartup.

Answer 2

You can try this:
public void app_DocOpened(object sender, DocumentOpenedEventArgs args)
{
MessageBox.Show("asd","asd");
Autodesk.Revit.ApplicationServices.Application m_app = args.Document.Application;
m_app.DocumentSynchronizingWithCentral += new EventHandler<DocumentSynchronizingWithCentralEventArgs>(m_app_DocumentSavingToCentral);
m_app.DocumentSynchronizedWithCentral += new EventHandler<Autodesk.Revit.DB.Events.DocumentSynchronizedWithCentralEventArgs>(m_app_DocumentSavedToCentral);
}