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Whats the difference between the 'ref' and 'out' keywords?

What is the difference between ref and out? I am confused about when to use ref and out. So please explain how to use ref and out, and in which situations.

Answer 1

• You use Ref when you pass an initialized parameter and you expect the method/function to modify it.

• You use Out when you pass an un-initialized parameter and the method will have to initialize and fill that parameter (you get a warning or even error otherwise).

  bool IsUserValid(string username);

  void IsUserValid(string username, out bool valid);

The declarations above are roughly the same. It’s easier to return the value, so in this case you will use the return type. But if your method also needs to return the birth date of the user you can’t return both parameters in the return, you have to use out parameters to return one of them (or void the method and return both as out).