ASP.NET 3.5 For Dummies®

21.1. Understanding Exceptions and Their Messages

An exception is the result of an unexpected or unusual situation within a program. Many exceptions are the result of mistakes in programming logic. Others stem from a failure to account for all possibilities, such as when you try to divide a number by zero. Exceptions also occur beyond the programmer's control, long after he deploys the code to a production site. For example, a server administrator inadvertently removes a file or changes a setting in Internet Information Services (IIS), and an otherwise stable Web site starts misbehaving.

You read geekspeak throughout this book and this chapter about exceptions is no, um, exception. Although technodudes generally have an aversion to sports, exception terminology tends to be sports related:

• Throw: Cause an exception. This aggressive term implies a degree of vigor because it insults and criticizes the quality of another geek's code, as in, "It not only sucks, it throws." This term's keyword is Throw.

• Raise: A more polite way of expressing the same thing as throw. When a Canadian geek doesn't want to be confrontational about a colleague's error, she says, "I'm sure you know this already, but your subroutine raises an exception that causes the unfortunate and untimely termination of my program, eh."

• Catch: The act of retrieving details about an error to cope with an undesirable situation. For example, a geek might say, "The whole site went down because of an uncaught error. I hope they ...