Why is it faster to check if dictionary contains the key, rather than catch the exception in case it doesn't?

Question

Imagine the code:

public class obj
{
    // elided
}

public static Dictionary dict = new Dictionary();

Answer 1

Dictionaries are specifically designed to do super fast key lookups. They are implemented as hashtables and the more entries the faster they are relative to other methods. Using the exception engine is only supposed to be done when your method has failed to do what you designed it to do because it is a large set of object that give you a lot of functionality for handling errors. I built an entire library class once with everything surrounded by try catch blocks once and was appalled to see the debug output which contained a seperate line for every single one of over 600 exceptions!