Sorry, but if someone were to ask me how to swap two variables w/o a temp variable I’d ask them to give me a good reason why.
Not being able to answer that particular question certainly doesn’t preclude someone from being a good programmer. That’d be like asking a C# programmer how to do modulo 16 using only a logical and. Why the hell would they need to know that, and how does that help you determine that they understand the ASP.Net framework, etc.?