Solutions for those exercises.

Questions

1. In computing, what is an exception?

   • A compilation error.
   • When a program user requires a special accommodation.
   • When a behaviour not supposed to happen occurs during execution.
   • A keyword.

2. When a program meets an unexpected behaviour, we say that it…

   • … raises an exception.
   • … throws an exception.
   • All of the above.

3. An exception can occur when…

   • … a user enters for example the string “Test” when asked for a numerical value.
   • … a division by 0 occurs.
   • … the program tries to access an array outside of its index range.
   • All of the above.

4. A try-catch block…

   • … executes all the code inside its try block, then all its code inside its catch block.
   • … executes all the code inside its try block, then all its code inside its catch block if an exception was raised at any point.
   • … executes only if an exception was raised in the program before.
   • … executes the code inside its try block, and switches to its catch block if an exception was thrown.
   • … executes its catch block first, and then its try block if an exception was raised.

5. A try-catch-finally block…

   • … can have multiple catch block.
   • … can omit the finally block.
   • … can omit the catch block.
   • All of the above.

Warm-up Exercise

1. Consider the following code:

   using System;
    
   class Program
   {
       static void Main()
       {
           try
           {
               Console.WriteLine("Enter a number");
               int uInput = int.Parse(Console.ReadLine());
               int[] t = { 10 };
               int div = 0 / (uInput -1);
               int tAcces = t[uInput];
           }
           catch (IndexOutOfRangeException)
           {
               Console.WriteLine("IndexOutOfRangeException");
           }
           catch (DivideByZeroException)
           {
               Console.WriteLine("DivideByZeroException");
           }
           catch (FormatException)
           {
               Console.WriteLine("FormatException");
           }
           catch (ArgumentNullException)
           {
               Console.WriteLine("ArgumentNullException");
           }
       }
   }

   (Download this code)

   • Determine which input would the user needs to enter to get “IndexOutOfRangeException”, “DivideByZeroException”, “FormatException” and “ArgumentNullException” displayed.
   • Is there something the user could enter that would not raise any exception?