The Difference Between Printing and Returning

It's important to know that having a method print output using Console.WriteLine is not the same as having a method return a value. If you confuse the two, your programs are going to behave strangely, and you won't know why. So I wanted to spend this video clarifying the difference.

• Here's a version of our program with the Subtract method removed.
• Suppose I remove the return statement from the Add method, and instead passed the result of adding the numbers to Console.Writeline: Console.WriteLine(first + second);
• I'll get an error: "'Program.Add(double, double)': not all code paths return a value"

    static double Add(double first, double second)
    {
        Console.WriteLine(first + second);
    }

• Converting the return type of Add to void gets the Add method declaration to compile...
  • But then we get the error "Cannot implicitly convert type 'void' to 'double'" when the code down in Main expects a return value.

    static void Add(double first, double second)
    {
        Console.WriteLine(first + second);
    }
    static void Main(string[] args)
    {
        double total = Add(3, 5);
        Console.WriteLine(total);
    }

• Just remember, if you want your method to give information to a human, you can call Console.WriteLine.
• But if you want your method to give information back to your program, you need to specify a return type and use the return keyword instead.

    static double Add(double first, double second)
    {
        return first + second;
    }