Well, due to overwhelming feedback for the previous post, here’s the answer: 0.
Now the most interesting part: why?
When you use inline initialization, compiler generates a static constructor for you, and does all the initialization there. It looks like, it’s not smart enough to pick this kind of dependencies, and simply initializes fields in the order they’ve been declared in the class’ body. That’s why, by the time Field is initialized, _height has value 3, but _width is still 0. If you wanted to overcome this, you’d have to use const instead of readonly (that’s an option only for primitives and strings), or move dependant properties to some other class (for example private class). Or if slight performance decrease during creation of your class’ instances is not going to be a problem, use explicit static constructor.