When to throw an exception?

Question

I have exceptions created for every condition that my application does not expect. UserNameNotValidException, PasswordNotCorrectException etc.

Answer 1

There are two main classes of exception:

1) System exception (eg Database connection lost) or 2) User exception. (eg User input validation, 'password is incorrect')

I found it helpful to create my own User Exception Class and when I want to throw a user error I want to be handled differently (ie resourced error displayed to the user) then all I need do in my main error handler is check the object type:

            If TypeName(ex) = "UserException" Then
               Display(ex.message)
            Else
               DisplayError("An unexpected error has occured, contact your help  desk")                   
               LogError(ex)
            End If