Reference equality of value types

Question

I have made some ref keyword tests and there is one think I can\'t understand:

static void Test(ref int a, ref int b)
{
    Console.WriteLine(In         


        

Answer 1

Why does this code display False?

Because int a and int b are being boxed when you call object.ReferenceEquals. Each integer is boxed inside an object instance. Thus, you are actually comparing references between two boxed values, which clearly aren't equal.

You can easily see this if you look at the generated CIL for the method:

Test:
IL_0000:  nop
IL_0001:  ldarg.0     Load argument a
IL_0002:  ldind.i4
IL_0003:  box         System.Int32
IL_0008:  ldarg.1     Load argument b
IL_0009:  ldind.i4
IL_000A:  box         System.Int32
IL_000F:  call        System.Object.ReferenceEquals
IL_0014:  call        System.Console.WriteLine
IL_0019:  nop
IL_001A:  ret

Checking for storage location equality can be achieved either by using verifiable CIL (such as in @leppie's answer) or by unsafe code:

unsafe static void Main(string[] args)
{
    int a = 4;
    int b = 5;
    Console.WriteLine(Test(ref a, ref a)); // True
    Console.WriteLine(Test(ref a, ref b)); // False;
}

unsafe static bool Test(ref int a, ref int b)
{
    fixed (int* refA = &a)
    fixed (int* refB = &b)
    {
        return refA == refB;
    }
}