Illustrated C# 2008

Chapter 11. Exceptions

What Are Exceptions?

An exception is aruntime error in a program that violates a system or application constraint, or a condition that is not expected to occur during normal operation. Examples are when a program tries to divide a number by 0 or tries to write to a read-only file. When these occur, the system catches the error and raises an exception.

If the program has not provided code to handle the exception, the system will halt the program.

For example, the following code raises an exception when it attempts to divide by 0:

static void Main()
   {
      int x = 10, y = 0;
      x /= y;              // Attempt to divide by zero--raises an exception
   }

When this code is run, the system displays the following error message:

Unhandled Exception: System.DivideByZeroException: ...