Beginning ASP.NET 3.5 in C# 2008: From Novice to Professional, Second Edition

8.3. Handling Exceptions

The first line of defense in an application is to check for potential error conditions before performing an operation. For example, a program can explicitly check whether the divisor is 0 before performing a calculation, or if a file exists before attempting to open it:

if (divisor != 0)
{
    // It's safe to divide some number by divisor.
}

if (System.IO.File.Exists("myfile.txt"))
{
    // You can now open the myfile.txt file.
    // However, you should still use exception handling because a variety of
    // problems can intervene (insufficient rights, hardware failure, etc.).
}

Even if you perform this basic level of "quality assurance," your application is still vulnerable. For example, you have no way to protect against all the ...