private void CreateStairsPath(Document document, Stairs stairs)
{
    Transaction transNewPath = new Transaction(document, "New Stairs Path");
    transNewPath.Start();

    // Find StairsPathType
    FilteredElementCollector collector = new FilteredElementCollector(document);
    ICollection<ElementId> stairsPathIds = collector.OfClass(typeof(StairsPathType)).ToElementIds();

    // Find a FloorPlan
    ElementId planViewId = ElementId.InvalidElementId;
    FilteredElementCollector viewCollector = new FilteredElementCollector(document);
    ICollection<ElementId> viewIds = viewCollector.OfClass(typeof(View)).ToElementIds();
    foreach (ElementId viewId in viewIds)
    {
        View view = document.GetElement(viewId) as View;
        if (view.ViewType == ViewType.FloorPlan)
        {
            planViewId = view.Id;
            break;
        }
    }

    LinkElementId stairsLinkId = new LinkElementId(stairs.Id);
    StairsPath.Create(stairs.Document, stairsLinkId, stairsPathIds.First(), planViewId);
    transNewPath.Commit();
}

Private Sub CreateStairsPath(document As Document, stairs As Stairs)
    Dim transNewPath As New Transaction(document, "New Stairs Path")
    transNewPath.Start()

    ' Find StairsPathType
    Dim collector As New FilteredElementCollector(document)
    Dim stairsPathIds As ICollection(Of ElementId) = collector.OfClass(GetType(StairsPathType)).ToElementIds()

    ' Find a FloorPlan
    Dim planViewId As ElementId = ElementId.InvalidElementId
    Dim viewCollector As New FilteredElementCollector(document)
    Dim viewIds As ICollection(Of ElementId) = viewCollector.OfClass(GetType(View)).ToElementIds()
    For Each viewId As ElementId In viewIds
        Dim view As View = TryCast(document.GetElement(viewId), View)
        If view.ViewType = ViewType.FloorPlan Then
            planViewId = view.Id
            Exit For
        End If
    Next

    Dim stairsLinkId As New LinkElementId(stairs.Id)
    StairsPath.Create(stairs.Document, stairsLinkId, stairsPathIds.First(), planViewId)
    transNewPath.Commit()
End Sub