SumOfNumbers.cs

// SumOfNumbers.cs
// Sum Of (5) integers, entered from standard input
//
// Build with "csc SumOfNumbers.cs" or "mono-csc SumOfNumbers.cs"
// execute with "SumOfNumbers.exe"

using System;
class SumOfNumbers
{
    public static void Main( )
    {
        const int numbersRequested = 5; // total requested numbers
        int numbersRead = 0; // current count of correctly read numbers.
                             // Should be the same type as numbersRequested
                             // For 5 elements, "byte" type is also good.
        string userInput;    // string to hold Console.ReadLine() result.
        long result = 0;     // Result. Must be big enough to store
                             // numbersRequested * (max 32bit integers)

        Console.Title = "Sum of numbers";
        Console.WriteLine("Sum of {0} integers.", numbersRequested);
        do
        {
            Console.WriteLine("Please enter number: ");
            // Handling exceptions on WriteLine() is pointless,
            // Since we can't inform the user anyways
            // On the ReadLine(), however, the story is different
            // E.g. the input filestream might get closed
            try
            {
                userInput = Console.ReadLine();
            }
            catch (Exception e)
            {
                Console.WriteLine("Could not read user input, caught {0}. ", e.ToString());
                //since this is Main(), we just return.
                return;
            }

            // We might as well read "EOF" (End of File) condition.
            // Generated with Ctrl+D from Console
            if ( null == userInput )
            {
                Console.WriteLine("Reached end of input. ");
                //since this is Main(), we just return.
                return;
            }

            // OK, we've got input. Try to parse it as an integer
            int currentNumber = 0;
            bool tryParse = int.TryParse(userInput, out currentNumber);
            if (!tryParse)
            {
                Console.WriteLine("Invalid number. ");
                continue;
            }
            result += currentNumber;
            numbersRead++;
        } while (numbersRead < numbersRequested);

        Console.WriteLine("Sum of the numbers is {0}. ", result);
        return;
    }
}
// Tests:

// Test case 1: correct input
// Input:
//1
//2
//3
//4
//5
// Output:
//Sum of 5 numbers.
//Please enter number:
//Please enter number:
//Please enter number:
//Please enter number:
//Please enter number:
//Sum of the numbers is 15.

// Test case 2: invalid number
// Input:
//1
//2
//3
//foo
//4
//5
// Output:
//Sum of 5 numbers.
//Please enter number:
//Please enter number:
//Please enter number:
//Please enter number:
//Invalid number.
//Please enter number:
//Please enter number:
//Sum of the numbers is 15.

// Test case 3: premature EOF
// Input:
//1
//2
//3
//5 (_EOF)
// Output:
//Sum of 5 numbers.
//Please enter number:
//Please enter number:
//Please enter number:
//Please enter number:
//Please enter number:
//Reached end of input.