Exception handle with your own exception class

   

/*
Learning C# 
by Jesse Liberty

Publisher: O'Reilly 
ISBN: 0596003765
*/
 using System;

 namespace ExceptionHandling
 {
     // custom exception class
     class MyCustomException :
         System.ApplicationException
     {
         public MyCustomException(string message):
             base(message) // pass the message up to the base class
         {

         }
     }

    public class TesterExceptionHandling
    {
       public void Run()
       {
           try
           {
               Console.WriteLine("Open file here");
               double a = 0;
               double b = 5;
               Console.WriteLine ("{0} / {1} = {2}",
                   a, b, DoDivide(a,b));
               Console.WriteLine (
                   "This line may or may not print");
           }

               // most derived exception type first
           catch (System.DivideByZeroException e)
           {
               Console.WriteLine(
                   "
DivideByZeroException! Msg: {0}",
                   e.Message);
               Console.WriteLine(
                   "
HelpLink: {0}
", e.HelpLink);
           }

           // catch custom exception
           catch (MyCustomException e)
           {
               Console.WriteLine(
                   "
MyCustomException! Msg: {0}",
                   e.Message);
               Console.WriteLine(
                   "
HelpLink: {0}
", e.HelpLink);
           }
           catch     // catch any uncaught exceptions
           {
               Console.WriteLine(
                   "Unknown exception caught");
           }
           finally
           {
               Console.WriteLine ("Close file here.");
           }
       }

        // do the division if legal
        public double DoDivide(double a, double b)
        {
            if (b == 0)
            {
                DivideByZeroException e =
                    new DivideByZeroException();
                e.HelpLink=
                    "http://www.libertyassociates.com";
                throw e;
            }
            if (a == 0)
            {
                // create a custom exception instance
                MyCustomException e =
                    new MyCustomException(
                    "Can't have zero divisor");
                e.HelpLink =
                    "http://www.libertyassociates.com/NoZeroDivisor.htm";
                throw e;
            }
            return a/b;
        }

        static void Main()
        {
            Console.WriteLine("Enter Main...");
            TesterExceptionHandling t = new TesterExceptionHandling();
            t.Run();
            Console.WriteLine("Exit Main...");
        }
    }
 }