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C# Cookbook by Jay Hilyard, Stephen Teilhet

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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.

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