Classes

When a design-time package registers a property editor class, the registration list has to keep track of what package that property editor class is associated with. Tracking this association ensures that if the package needs to be unloaded at design time (to recompile the package), the registration list knows which property classes to delete from its list. CurrentGroup is used to obtain an indicator that represents this association. It gets incremented every time a package is loaded at design time. 

CurrentGroup is used to write design-time tools that keep track of things stored in other packages. 

RegisterPropertyEditor