For StackOverflow: http://stackoverflow.com/a/16307237/10311

evilbool.cs

class Program {
 
static bool M(out int x)
{
   x = 123;
   return true;
}
 
static int N(EvilBool d)
{
   int y = 3;
   if (d || M(out y))
       y = 10;
   return y;
}
 
static void Main()
{
   var result = N(new EvilBool());
   // Prints 3!
   Console.WriteLine(result);
}
 
}
 
class EvilBool
{
    private bool value;
 
    public static bool operator true(EvilBool b)
    {
        return b.Value;
    }
 
    public bool Value 
    {
        // Return true the first time this is called
        // and false the second time
        get
        {
          value = !value;
          return value;
        }
    }
 
    public static bool operator false(EvilBool b)
    {
        throw new NotImplementedException();
    }
  
    public static implicit operator EvilBool(bool b) { return new EvilBool { value = b }; }
    
    public static EvilBool operator|(EvilBool left, EvilBool right)
    {
        return left.Value || right.Value;
    }
}