Programming C#, Second Edition

Exception Objects

So far you’ve been using the exception as a sentinel -- that is, the presence of the exception signals the errors -- but you haven’t touched or examined the Exception object itself. The System.Exception object provides a number of useful methods and properties. The Message property provides information about the exception, such as why it was thrown. The Message property is read-only; the code throwing the exception can set the Message property as an argument to the exception constructor.

The HelpLink property provides a link to the help file associated with the exception. This property is read/write.

The StackTrace property is read-only and is set by the runtime. In Example 11-6, the Exception.HelpLink property is set and retrieved to provide information to the user about the DivideByZeroException. The StackTrace property of the exception is used to provide a stack trace for the error statement. A stack trace displays the call stack : the series of method calls that lead to the method in which the exception was thrown.

Example 11-6. Working with an exception object

namespace Programming_CSharp { using System; public class Test { public static void Main( ) { Test t = new Test( ); t.TestFunc( ); } // try to divide two numbers // handle possible exceptions public void TestFunc( ) { try { Console.WriteLine("Open file here"); double a = 12; double b = 0; Console.WriteLine ("{0} / {1} = {2}", a, b, DoDivide(a,b)); Console.WriteLine ( "This line may or may not print"); ...