What would I suggest? Well, first of all: “Don’t use exceptions for flow control” is a guideline, a goal you try to reach, not a low set in stone. So if there are situations where you find that using exceptions is actually the best, or the only, approach to a specific problem, you should probably just use them. In this case, I’d suggest use them, make a TODO comment in your code and replace that code with a call to TryParse when you change to .NET 2 at the earliest possible point.

Using regular expressions is an alternative, of course. Or even, for simple numeric values, to code up your own validity check - checking whether a string comprises of a number of numeric digits is not a hard task. When things are more difficult, the code-it-yourself approach is not so good, and I have never tested how the performance of regular expressions stacks up against catching an exception in a case like this. It’s certainly a nicer way to implement the functionality, but then regular expressions are a big and mighty tool to call for when all you need is a simple numeric validity check.

Int32.Parse().

In ASP.NET, when you request a querystring variable it comes back as a string. A lot of times we expect an integer, but you obviously cannot trust it.

int myIntVal = Int32.Parse( Request.QueryString[”someVar”] ); //this could throw an exception, in fact quite easily. Whidbey brings us Int32.TryParse(), but for our 1.1 apps this doesn’t help us.

What would you suggest? Regular Expressions?