Calculator Conundrum

Exceptions

Exceptions in C# provide a structured, uniform, and type-safe way of handling error conditions that occur during runtime. Proper handling of exceptions and error is important when trying to prevent application crashes.

In C#, all exceptions have System.Exception class as their base type. It contains important properties such as Message, which contains a human-readable description of the reason for the exception being thrown.

To signal that there should be an error in a certain part of the code, a new exception object needs to be created and then thrown, using the throw keyword:

using System;
static int Square(int number)
{
    if (number >= 46341)
    {
        throw new ArgumentException($"Argument {number} cannot be higher than 46340 as its' square doesn't fit into int type.");
    }
    return number * number;
}

When an exception gets thrown, the runtime has the task of finding a piece of code that is responsible for handling of that exception. If no appropriate handler is found, the runtime displays the unhandled exception message in addition to stopping the execution of the program.

To create a handler for an exception, C# uses the try-catch statement, which consists of a try block and one or more catch clauses. The try block should contain and guard code that may result in the exception getting thrown. The catch clauses should contain code that handles the behavior of the program after the error has occurred. It is important to note that the order of exceptions matters after the try block, as when multiple exceptions are listed, the first matching catch clause is executed.

try
{
   if (number == 42)
   {
       throw new ArgumentException("The number cannot be equal to 42.", "number");
   }

   if (number < 0)
   {
      throw new ArgumentOutOfRangeException("number", "The number cannot be negative.");
   }

    // Process number ...
}
catch (ArgumentOutOfRangeException e)
{
    Console.WriteLine($"Number is out of range: {e.Message}.");
}
catch (ArgumentException)
{
    Console.WriteLine("Invalid number.");
}