C# Cookbook

5.3. Choosing when to Throw a Particular Exception

Problem

There are many exceptions to choose from in the FCL. You need an easily accessible list of these exceptions that indicates when and where to use them. By throwing exceptions in a consistent manner (e.g., throwing an IndexOutOfRangeException when an array index is greater than the length of the array), you and others on your team will be able to debug problems more easily.

Solution

Use the list of exceptions and their definitions in Table 5-1 to determine which exception to employ when throwing or catching exceptions.

Discussion

Table 5-1. The built-in exception types

Exception name	Derives from	Description
System.ApplicationException	Exception	Use this class as the base class to user-defined exceptions; a more derived exception should be thrown.
System.ArgumentNullException	ArgumentException	Thrown when a parameter value for a method is null and null is not allowed.
System.ArgumentOutOfRangeException	ArgumentException	Thrown when a parameter value for a method is out of the range of expected values.
System.ArrayTypeMismatchException	SystemException	Thrown when an incompatible data type is assigned to an element in an array.
System.Runtime.InteropServices.COMException	ExternalException	Thrown when an unknown HRESULT is returned from a COM object.
System.Configuration.ConfigurationException	SystemException	Thrown when an invalid configuration setting is encountered.