Passing by value and reference - C# Gotcha! Interview Questions.

Pass by value and pass by reference are important concepts to understand in C#.

The default method of passing a parameter in C# is by value, which creates of copy of the type that you pass. However, the kind of copy performed differs if your type is a value type (int / struct) or a reference type ( object / string). Value types have their entire value copied on the stack. Reference types have the reference to their memory location copied - so the reference type essentially has two references to it while in the scope of your method.

Passing by reference differs from passing by value because .NET passes a reference to the original memory location of the variable. This can have some unintended consequences if you aren't careful.

The parameter keywords IN and OUT also play a role in passing by reference. IN passes by reference as read only, while OUT passes by reference and requires that you add a value to the parameter before you return.

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