As for testing, I added role level for roles' management as following:

1) add a new table in my DNN database named DNN_RoleLevels with RoleLevelID(int), RoleLevelName(string), PortalID(int), Description(string) fields

2) modify table DNN_Roles by adding new field RoleLevelID

3) add stored procedure DNN_GetRoleLevels(portalID)

4) new class RoleLevelInfo with proper properties

5) change class RoleInfo for the new feature

6) implement new feature in EditRoles as a combo list selection

after re-compile the DotNetNuke.DLL file, compile the website without problem, but when I browse the website, it give me error in the address bar:

http://dnn.test.com/default.aspx?tabid=36&error=The+type+initializer+for%27DotNetNuke.Security.Roles.RoleController%27+threw+an+exception.&content=0

same time the website can not be displayed.

Anyone has any idea about this situation? Thanks ahead!