Ensures the types are not marked with the beforefieldinit flag (causing lazy initialization). This ensures the registration (mapping) of the control GUIDs to the Uia_ControlIds is guaranteed to exist during first access of the '_identifierDirectory' via ControlType.LookupById() Note on the static constructor performance: The performance points measured typically depend on the initialization that goes with the type initialization. So if that's within permissible limits, in this case the Register() calls for the controltypes which aren't expensive, having static constructor isn't that bad. Follow link for more details. http://coderjournal.com/2009/08/static-constructors-in-net-3-5-still-a-bad-thing/