Are arrays or lists passed by default by reference in c#?
The reference is passed by value.
Arrays in .NET are object on the heap, so you have a reference. That reference is passed by value, meaning that changes to the contents of the array will be seen by the caller, but reassigning the array won't:
void Foo(int[] data) { data[0] = 1; // caller sees this}void Bar(int[] data) { data = new int[20]; // but not this}If you add the ref modifier, the reference is passed by reference - and the caller would see either change above.
Yes, they are passed by reference by default in C#. All objects in C# are, except for value types. To be a little bit more precise, they're passed "by reference by value"; that is, the value of the variable that you see in your methods is a reference to the original object passed. This is a small semantic point, but one that can sometimes be important.