what is the use of Private Classes in C# [closed]

Answer 1

It is widely considered to be a good practice to divide our code up into separate logical units. Each unit has a limited number of reponsibilities that are all related. That makes it easier to test the code, and once it is well-tested, those units become building blocks with which we can create more complex patterns. Private classes are useful for creating building blocks that are implementing internal functionality that you don't necessarily want visible to other projects using a library. They can also implement interfaces, and thus are useful if you want to set up a factory so that you control what instances of the class get made -- callers can then still use the class via the interface, even though they can't see the class type itself.

Answer 2

Private classes can only be created inside nested classes and are used to retrict access and to only be used inside this nested class.

Answer 3

Private classes (or private anything, really) are important because control of scope is important, due to the notion of encapsulation.

If you are building a library will private classes, your library can use those classes while anyone using your library will not be able to even see them. This can hide implementation-specific details that you wish to conceal.

If you are building a class that has private nested classes, the containing class can use those private classes without anyone else being able to see them. Again, you can use this to hide implementation-specific details that you wish to conceal.

If you do not hide implementation-specific details (e.g. by making a private class public) then it becomes more difficult to change the implementation, since you can't be sure that users of your library haven't created dependencies on those classes. But if they are private, you can change them, replace them, or remove them, all without any worry of disrupting external dependencies.