I answered a public invitation by Eric Battalio of the VC team – and just now published an article on the VC blog, introducing the native Expression Evaluator:
Every time you use the Watch window, a lot is going on behind the scenes. Whenever you type a variable name, something needs to map that name to the memory address and type of the named variable, then display that variable, properly formatted based on its type. Conversely, when you modify the contents of a variable – something needs to take your text input, convert it to the right type and correctly update the memory at the right address.
That something is the Expression Evaluator. It is an impressive and often overlooked piece of technology and once familiar with it, you can put it to good use, sometimes in surprising ways!