Question

In C# given a function with the below signature

public static void Foo(ref int x, ref int y)

If the function was called using

int A = 10;
Foo(ref A, ref A)

Inside the function Foo is it possible to test that the x and y arguments reference the same variable? A simple equivalent test of x and y isn’t sufficient as this is also true in the case two different variable have the same value.

Answer 1

If you’re willing to use unsafe code, you can compare the underlying variable addresses:

public static bool Foo(ref int a, ref int b)
{
    unsafe
    {
        fixed (int* pa = &a, pb = &b)
        {
            // return true iff a and b are references to the same variable
            return pa == pb; 
        }
    }
}

(Edited to remove unsafe from method signature, based on @Michael Graczyk’s comment.)