[CONNECT .NET] Use IElementPropertyEnabler to obtain DGN Element properties

I want to get DGN element properties.  I think that I should be using IElementPropertyEnabler to obtain element properties, using something like GetPropertyValue (className, accessString, element).

Looking at method GetProperties(..., ..., propertyCategory), the third argument is a category mask, documented as A mask indicating the categories to return. However, neither the MstnPlatformNet documentation nor the SDK examples reveal how that mask should be created.  Is there an enum defined for its flags?