Class VS ref Struct

Question

I am programming a game using C #, so my performance is very worried.

I would like to know what are the main differences and, if possible, performance considerations when using either a class to pass data or a structure passed by reference.

I want to not copy the data for performance reasons (suppose the ref transfer is much faster than the value here).

I know that a class is always passed by reference and that struct is passed by value, but I'm talking about passing a structure by reference here.

Example data that I want to transfer:

public delegate void PathCompleteDelegate(List<PathFinderNode> path); public struct PathFinderJob{ public PathCompleteDelegate callback; public Vector3 start, end; public PathSize unitSize; public BoxCollider boxCollider; } 

In the previous example, the use of the class will change? If so, what's the difference? Will the class be faster than the structure in this example? Why?

Thanks. Joao Carlos

Answer 1

Your delegate gets the reference type - a List , so you still pass the entire list by reference.

The transfer of a large structure by value is certainly the most expensive than the transfer of only links. When you have a large structure, it usually doesn't make sense to use it as a structure, just turn it into a class.

In any case, are you sure you will have a performance problem? Seems like a very premature optimization.

Answer 2

I know that a class is always passed by reference and that a structure is passed by value, but I'm talking about passing a structure by reference here.

You probably have the right idea, but this is not true. Everything in C # is passed by value unless you use the ref keyword.

Instance instances are reference types; struct instances are value types.

When you pass a reference type by value, you pass a copy of the help (small). When you pass a value of a type by value, you pass a copy of all the data (potentially large).

Jon Skeet has a good explanation of all of this here .