What can be done to allow certain callers to invoke a private method in a class?

Using a delegate-returning method for authorized callers is a valid approach to allow certain callers to invoke a private method. This technique involves creating a public or internal method that acts as a gateway to the private method, where it can perform checks to determine if the caller has the necessary permissions to invoke the private functionality.

By using delegates, you can encapsulate the logic and ensure that only authorized callers can access the private method indirectly. This promotes better encapsulation and security within your class, maintaining the integrity of your internal logic while still providing necessary functionality to trusted external callers.

In contrast to this approach, altering the access modifier of the private method (such as making it public) would expose the method to all callers, which might not be desirable if you intend to limit access for security or design reasons. Invoking the method directly from within the class is simply a reaffirmation of the existing access level and does not extend access. Making the method internal to the assembly broadens the access to all classes within the same assembly, which may not provide the desired restrictions on who can call the method. Thus, using a delegate-returning method effectively strikes a balance between access control and functionality.