Defining boolean local variables

Question

Note: This is my first time using "Stack Overflow" and I am relatively new to C#

(please excuse my poor programming skills at the moment)

My Code:

static void Main(string[] args)
    {
        Challenge(5, 12);
    }
    static void Challenge(int num1, int num2)
    {
        //finds the sum of the two variables
        int sum = num1 + num2;
        Console.WriteLine("The sum of {0} and {1} is...\n{2}", num1, num2, sum);

        bool isDivisible = true;
        //checks if divisible by 5 and sets a value for 'isDivisible'
        if ((sum % 10 == 5) || (sum % 10 == 0))
        {
            Console.WriteLine("\nThe sum is divisible by 5!");
            isDivisible = true;
        }
        else if ((sum % 10 != 5) || (sum % 10 != 0))
        {
            Console.WriteLine("\nThe sum is not divisible by 5!");
            isDivisible = false;
        }

        //depending on value of 'isDivisible', returns certain functions
        if (isDivisible == true)
        {
            Console.WriteLine("This value is usable.");
            Console.WriteLine("\n\nThe remaining usable values are: ");

            for (int newVal = sum + 1; newVal <= 55; newVal++) // '+ 1' added to make sure 'sum' is not printed again
            {
                if ((newVal % 10 == 5) || (newVal % 10 == 0))
                {
                    Console.WriteLine(newVal);
                }
            }
        }
        else if (isDivisible == false)
        {
            Console.WriteLine("This value is not usable.");
            Console.WriteLine("\n\nThese values are considered usable: ");

            for (int newVal = 0; newVal <= 55; newVal++)
            {
                if ((newVal % 10 == 5) || (newVal % 10 == 0))
                {
                    Console.WriteLine(newVal);
                }
            }
        }
        Console.ReadLine();
    }

I viewed some articles online, as well as the "Stack Overflow" post: Why compile error "Use of unassigned local variable"? . After learning that local variables are not initialized (and must be given a value), I set my bool value for "isDivisible" equal to true by default.

Question:

Is there a better way to define a local variable that is of Boolean value (at least in the case of the program I am trying to run here)?

Thanks!

Answer 1

Your condition in the else if is wrong, it's not the complement of the first condition, so it doesn't make sense. The correct complement would be:

else if ((sum % 10 != 5) && (sum % 10 != 0))

However, you don't need to use an else if at all, you can just use an else as you want to catch every case that is not caught by the first condition. That also means that you don't have to initialise the boolean variable, as the compiler can see that it always will be set by one of the code blocks:

    bool isDivisible;
    //checks if divisible by 5 and sets a value for 'isDivisible'
    if ((sum % 10 == 5) || (sum % 10 == 0))
    {
        Console.WriteLine("\nThe sum is divisible by 5!");
        isDivisible = true;
    }
    else
    {
        Console.WriteLine("\nThe sum is not divisible by 5!");
        isDivisible = false;
    }

Side note: Instead of (sum % 10 == 5) || (sum % 10 == 0) you could just use sum % 5 == 0.

Side note 2: You don't need to compare a boolean variable to true, you can just use it as a condition. Also, you don't need the else if there either. Instead of this:

    if (isDivisible == true)
    {
        ...
    }
    else if (isDivisible == false)
    {
        ...
    }

you can use:

    if (isDivisible)
    {
        ...
    }
    else
    {
        ...
    }

Answer 2

Comparison expressions in C# will return a boolean value indicating whether or not they are true. So you could simplify your initial assignment to:

bool isDivisible = ((sum % 10 == 5) || (sum % 10 == 0));

Instead of explicitly setting it to true or false. Then your variable would always be set.

This doesn't work for all cases. Sometimes, it is difficult to reduce the comparison operation to a simple expression. But, it is often a handy way to initialize bools.