In C#, what is the difference between public, private, protected, and having no access modifier?

Question

All my college years I have been using public, and would like to know the difference between public, private, and protected

Answer 1

Hmm.

See here: Access Modifiers.

In a nutshell:

Public gives the method or type complete visibility from other types/classes.

Private allows only the type containing the private method/variable access to the private method/variable (note that nested classes also have access to the containing classes private methods/variables).

Protected is similar to private except derived classes can also access protected methods.

"Nothing" is VB.NET's equivalent to null. Although if you're referring to "nothing" meaning "no access modifier", then it depends, although a very rough rule of thumb (certainly in C#) is that if you don't explicitly specify an access modifier, the method/variable declaration is usually as restricted as it can be. i.e.

public class MyClass
{
    string s = "";
}

is effectively the same as:

public class MyClass
{
    private string s = "";
}

The linked MSDN article will offer a fully description when there's no access modifier explicitly specified.