Requirement
ObjectARX and .NET applications
You cannot use the UNDEFINE and REDEFINE AutoCAD commands. Using these commands can confuse users and can conflict with other applications. Particularly troublesome is the situation when QUIT, END, SAVE, OPEN, and NEW are redefined by more than one application. ObjectARX provides a variety of mechanisms for applications to receive control at these key events. (Refer to the Notification chapter in the ObjectARX Developer's Guide for a discussion of reactors.)