﻿1. When choosing an option from the menu, try entering text instead of numbers.

	Method ReadNumber is expecting a string parameter representing user input option.
	It tries to convert received string value to an integer which will be the option selected by the user.
	Inside this method, for parsing mechanism method int.Parse(string) is used which will throw an System.FormatException (with message: 'Input string was not in a correct format.') if the string doesn't represent a valid integer number.
	Because the application doesn't handle this exeception (use a try-catch mechanism) and no previous validation is used, it will stop the execution of the code without letting the used know the problems.

	As an alternative, we can use int.TryParse method for converting the string input into an integer valid number (option) which will return a true/false value if the conversion was made or not.
	Also we can have a try-catch over the ReadNumber method block code and in case of a exception then an error message will be displayed.

2. When the user is asked if they wish to quit, the only input value that can be entered is “YES”. Try other variations e.g. “Yes”, “yes”, “y”, etc.

	  If the user is not entering the exact string value "YES" the application will not stop because string comparison is case-insensitive in c# which means that "YES" is not equal with "yes" or any other combination ("YeS" etc).
	  As an alternative, we can use a switch statement which will apply a transforming method like ToLower() or ToUpper() and in case statements we will compare with "YES" or "yes" (lower or upper).
	  In this way we will cover all the possible combinations for "yes" answer. Aditionally for "y" answer we add into the same switch other case for it.

3. Try displaying all the numbers entered.

	When option 4 is selected - "Display all numbers" then the user will receive the message for quiting the application, because ProcessMenu method has inside the switch a case for option 4 that is 
	calling a wrong method (IsQuitting).