C# ref keyword usage

Question

I understand (or at least I believe I do) what it means to pass an instance of a class to a method by ref versus not passing by ref. When or under what circumstances should one pass a class instance by ref? Is there a best practice when it comes to using the ref keyword for class instances?

Answer 1

The clearest explanation I've ever run across for output and ref parameters is ... Jon Skeet's.

Parameter Passing in C#

He doesn't go into "best practices", but if you understand the examples he's given, you'll know when you need to use them.

Answer 2

When you may replace the original object, you should send him as ref. If it's just for output and can be uninitialized before calling the function, you'll use out.