Here’s some interview questions I’ve been asked / seen:

  • Name three features introduced with C# 3.0

  • How does ASP.NET MVC’s Anti Forgery Token work?

  • How can you update web.config programatically?

The last one is from CSharpStar, where it is presented with a series of other interview questions for ‘Experienced Professionals’.

What do these questions have in common? If you don’t know the answer off the top of your head, you can find it with about two minutes of Googling. These are trivia questions - do you know this piece of information about your framework of choice? If someone answers all these questions correctly - are they a good programmer? How much confidence do you have that they know how to structure an application? That they’ll write maintainable code?

I don’t rate these types of questions. Good programming consists of applying skills pragmatically, analysing trade-offs between simplicity and complexity, and delivering a product which can be maintained, understood, extended, and used. How does knowing what features were introduced in C# 3.0 help with that?

Here’s an interview question I think is worth its salt:

Class Switch takes an instance of Light in its constructor, and wraps its LightUp() and TurnOff() methods:

public class Switch
    private readonly Light _light;

    public Switch(Light light)
        _light = light;

    public void On() { _light.LightUp(); }

    public void Off() { _light.TurnOff(); }

What changes would you make to be able to use Switch with an instance of Light or Rotor? Rotor has the methods Start() and Stop().

Easy question? You may be surprised how often I’ve asked interview candidates this and they’ve been unable to answer. One person - with years of experience - suggested making Rotor derive from Light.

To answer that question you need to have an at-least basic understanding of dependency inversion, coupling, encapsulation, composition and abstraction. These are not things you can get your head around with two minutes on Google. For my money (of which - as usual - I’m offering none) this is vastly more useful than finding out if someone knows off the top of their head how to use an XML writer.

If you’re in the position of putting technical interview questions together, try to pick ones which tell you about someone’s ability to design software. That’s the most difficult thing about the job - not parrot-fashion familiarity with a framework’s intricacies.