Retrieving tread depth when stairs not of Stairs class

[Anonymous]

I'm looking at the publicly available model "210 King - Autodesk Toronto.rvt" which I upgraded from 2016 to 2018 (original 2016 version here).  When I select a stairs object in the model, it has an "Actual Tread Depth" in the Properties Panel.

I want to access this tread depth in the API.  In the sample project that ships with Revit, the stairs are of class Autodesk.Revit.DB.Architecture.Stairs (derived from Element) which has an ActualTreadDepth property.  But in this model, the stairs are all just objects of class Element.  Casting them to Stairs throws an exception.  

Two questions:
 - How can I access the tread depth?
 - Why aren't these of class Stairs? (I'm new to the Revit API)

[Anonymous]

Note: I also asked this question on Stack Overflow here (after this post had gotten stuck in the spam filter) which Jeremy Tammik gave a very helpful answer to. 

Although I did have a follow up question you can see in that link that I'm still confused about.

[RPTHOMAS108 · Accepted solution]

If try cast fails then you need to get parameter for tread depth via its built in parameter value, or you can just get it this way without trying to cast to a derived class:

Element.Parameter(STAIRS_ACTUAL_TREAD_DEPTH)

Finding the required parameter is easy via the lookup tool

[Anonymous]

Thanks!  I get how that works now.