Compare two managed references

Question

Is it possible to compare two managed references (of type ref T) if they are equal? I don't mean references to objects, but references to variables. Example:

public static bool Compare(ref int a, ref int b)
{
    return ref a == ref b; //something like that, not possible this way in C#
}

int x, y;
Compare(ref x, ref x); //true
Compare(ref x, ref y); //false

Answer 1

You can use the official Microsoft NuGet package System.Runtime.CompilerServices.Unsafe to accomplish this without having to mark your method as unsafe.

using System.Runtime.CompilerServices;

static void Main()
{
    int value = 0;
    ref int ref1 = ref value;
    ref int ref2 = ref value;
    Debug.Assert(Unsafe.AreSame(ref ref1, ref ref2));
}

Do note that I'd argue this method is not really Unsafe and perhaps should be moved to another class/package along with Unsafe.SizeOf.

Answer 2

The definitive reference (no pun intended) is here - Equality Comparisons (C# Programming Guide).

You can compare two objects of type T for reference equality by using Object.ReferenceEquals if (and so far as I know only if) T is a reference type.

As Haedrian points out, this is not possible for value types even when they are passed by reference due to boxing in the call to ReferenceEquals.

int x = 0, y = 0;
IsSameReference(ref x, ref x).Dump(); // Passing the same value type variable twice, by reference. We want a result of 'true'
IsSameReference(ref x, ref y).Dump(); // We expect 'false'

public static bool IsSameReference(ref int a, ref int b)
{
    return Object.ReferenceEquals(a, b);
}

Both calls dump false. (Note I renamed the function Compare as that is usually used for sort-ordering comparisons).

Essentially then, where T can be of any type, the answer is no.

(Fun and games with int only removed from answer as superceded by another answer).