Which is faster? ByVal or ByRef?

Question

In VB.NET, which is faster to use for method arguments, ByVal or ByRef?

Also, which consumes more resources at runtime (RAM)?

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Answer 1

If you're using a very large value type (Guid is pretty big, for example) it may be very slightly faster to pass a parameter by reference. In other cases, there may be more copying etc when you pass by reference than by value - for instance, if you've got a byte parameter, then one byte is clearly less than the four or eight bytes that the pointer would take if you passed it by reference.

In practice, you should almost never worry about this. Write the most readable code possible, which almost always means passing parameters by value instead of reference. I use ByRef very rarely.

If you want to improve performance and think that ByRef will help you, please benchmark it carefully (in your exact situation) before committing to it.

EDIT: I note in the comments to another (previously accepted, now deleted) answer that there's a great deal of misunderstanding about what ByRef vs ByVal means when it comes to value types. I have an article about parameter passing which has proved popular over the years - it's in C# terminology, but the same concepts apply to VB.NET.