Listen to ArcGIS Pro project save event

This sample subscribes to project open, saving and saved events. Make sure to unsubscribe when no longer needed.

namespace N {        
    public class X {
       private SubscriptionToken _eventToken = null;
       private SubscriptionToken _eventToken2 = null;
       private SubscriptionToken _eventToken3 = null;
       
       public X() {
           Project proj = Project.Current;
           if (proj == null)
           {
             // Wait for project to open.
             _eventToken = ProjectOpenedEvent.Subscribe(OnProjectInitialized);              
           }
           else
           {
               ProjectEventArgs projEventAgs = new ProjectEventArgs(proj);
               OnProjectInitialized(projEventAgs);
           }
               _eventToken2 = ProjectSavingEvent.Subscribe(OnProjectSaving); 
               _eventToken3 = ProjectSavedEvent.Subscribe(OnProjectSaved); 
      }
        
      private void OnProjectInitialized(ProjectEventArgs project)
      {
          NotifyUser("Project has loaded", false);
        
          if (_eventToken != null)
          {
              ProjectOpenedEvent.Unsubscribe(_eventToken);
              _eventToken = null;
          }
      }
        
      private async Task<bool> OnProjectSaving(ProjectEventArgs project)
      {
          return await QueuedTask.Run(() =>
          {
              if (MessageBox.Show("Are you sure?", "Save Project?", 
                            MessageBoxButton.OKCancel) == MessageBoxResult.OK)
              {
                  return true;
              }
              return false;
          });
      }
        
      private void OnProjectSaved(ProjectEventArgs project)
      {
          MessageBox.Show("Project was saved");
      }
   }
}

Please note that when I tested this, the project was saved regardless of whether OnProjectSaving() returned true or false. This could be a bug in the framework, but is much more likely to be a bug in my code or understanding.