Program.cs

[MethodImpl(MethodImplOptions.AggressiveOptimization)]
static void Test()
{
    var obj = new object();

    // Run a garbage collection in 1 second
    Task.Delay(1000).ContinueWith(_ => { GC.Collect(); });

    // As soon as MyNativeMethod is called, there are no more references to obj
    MyNativeMethod(new WeakReference(obj));
}

static void MyNativeMethod(WeakReference obj)
{
    // The native method does not keep the object alive

    // Doing stuff
    Thread.Sleep(2000);

    // Trying to use the object
    Console.WriteLine("Is alive: " + obj.IsAlive); // Is alive: False
}