private void CreateRailing(Document document, Stairs stairs)
{
    using (Transaction trans = new Transaction(document, "Create Railings"))
    {
        trans.Start();

        // Delete existing railings
        ICollection<ElementId> railingIds = stairs.GetAssociatedRailings();
        foreach (ElementId railingId in railingIds)
        {
            document.Delete(railingId);
        }
        // Find RailingType
        FilteredElementCollector collector = new FilteredElementCollector(document);
        ICollection<ElementId> RailingTypeIds = collector.OfClass(typeof(RailingType)).ToElementIds();
        Railing.Create(document, stairs.Id, RailingTypeIds.First(), RailingPlacementPosition.Treads);
        trans.Commit();
    }
}

Private Sub CreateRailing(document As Document, stairs As Stairs)
    Using trans As New Transaction(document, "Create Railings")
        trans.Start()

        ' Delete existing railings
        Dim railingIds As ICollection(Of ElementId) = stairs.GetAssociatedRailings()
        For Each railingId As ElementId In railingIds
            document.Delete(railingId)
        Next
        ' Find RailingType
        Dim collector As New FilteredElementCollector(document)
        Dim RailingTypeIds As ICollection(Of ElementId) = collector.OfClass(GetType(RailingType)).ToElementIds()
        Railing.Create(document, stairs.Id, RailingTypeIds.First(), RailingPlacementPosition.Treads)
        trans.Commit()
    End Using
End Sub