Currently, we are wiring up our event handlers in the code behind instead of taking advantage of the command infrastructure to pass user input from the view to the view model. There's a lot of talk in the development community as to how much code is alright in the code behind and I won't attempt to end that debate here, instead what I will do is, provide the tools and techniques that allow for taking the pure approach. This will allow you to decide what the best approach for your project is and use whatever level of purity makes the most sense.
That said, in my projects I prefer to keep it as pure as possible and I am yet to find a situation where I had to put code in the code behind. The following are a few reasons that I favor the pure approach apart from just being a bit of a purist at heart: