public Presentation GetPresentation()

//Reference a presentation associated with an active presentation view
PresentationView activePresentationView = PresentationView.Active;
if (activePresentationView != null)
{
  Presentation presentation = activePresentationView.Presentation;
}

PresentationProjectItem presentationProjItem = Project.Current.GetItems<PresentationProjectItem>().FirstOrDefault(item => item.Name.Equals(presentationName));
Presentation presentationFromItem = presentationProjItem?.GetPresentation();

//Open a presentation project item in a new view.
//A presentation project item may exist but it may not be open in a view. 

//Reference a presentation project item by name
PresentationProjectItem presentationPrjItem = Project.Current.GetItems<PresentationProjectItem>().FirstOrDefault(item => item.Name.Equals(presentationName));

//Get the presentation associated with the presentation project item
Presentation presentationToOpen = await QueuedTask.Run(() => presentationPrjItem.GetPresentation());

//Create the new pane
IPresentationPane iNewPresentationPane = await ProApp.Panes.CreatePresentationPaneAsync(presentationToOpen); //GUI thread

//Assume we want to open a view for a particular presentation or activate a view if one is already open

//A presentation project item is an item that appears in the Presentation folder in the Catalog pane.
PresentationProjectItem presentationItem = Project.Current.GetItems<PresentationProjectItem>()
                                             .FirstOrDefault(item => item.Name.Equals(presentationName));

//Reference a presentation associated with a presentation project item
if (presentationItem != null)
{
  //Get the presentation associated with the presentationItem
  Presentation presentationToOpen = await QueuedTask.Run(() => presentationItem.GetPresentation());

  //Next check to see if a presentation view is already open that references the presentation
  foreach (var pane in ProApp.Panes)
  {
    var prePane = pane as IPresentationPane;
    if (prePane == null)  // Not a presentation view, continue to the next pane
      continue;

    //if there is a match, activate the view
    if (prePane.PresentationView.Presentation == presentationToOpen)
    {
      (prePane as Pane).Activate();
      return;
    }
  }

  //No pane found, activate a new one - must be called on UI
  IPresentationPane iNewPresentationPane = await ProApp.Panes.CreatePresentationPaneAsync(presentationToOpen); //GUI thread
}