Chapter 10. Methods

In the current chapter we get familiar with methods and learn what they are, and which are the base concepts when working with them. We will also learn why it is a good practice to use them, how to declare and call them. We will look at parameters and return value of a method, and also understand how to use the returned value. At the end of the chapter we will look at the established practices when using methods.

Introduction by Examples

Methods allow invoking a parameterized named piece of code several times from many places in the code. Example:

static void PrintLetter(char letter, int count)
{
    for (int i = 0; i < count; i++)
        Console.Write(letter + " ");
    Console.WriteLine();
}

static void Main()
{
    int count = 0;
    for (char letter = 'a'; letter <= 'd'; letter++)
        PrintLetter(letter, ++count);
    for (char letter = 'c'; letter >= 'a'; letter--)
        PrintLetter(letter, --count);
}

Run the above code example: https://repl.it/@nakov/triangle-of-letters-csharp.

The above code produces the following output:

a
b b
c c c
d d d d
c c c
b b
a

The above method (named piece of code) PrintLetter(letter, count) prints given character (letter) several times (count). It is invoked several times in two loops from the program Main() method.

Let's get into details how methods are defined, how methods are invoked, how methods accept parameters (input values) and how methods return results (output values).

Methods can take parameters and can return values, e.g.

static double CalcCircleArea(double radius)
{
    return Math.PI * radius * radius;
}

static void Main()
{
    Console.WriteLine("r = {0}, area = {1}", 5, CalcCircleArea(5));
    Console.WriteLine("r = {0}, area = {1}", 2.8, CalcCircleArea(2.8));
}

Run the above code example: https://repl.it/@nakov/circle-area-methods-csharp.

The output from the above code is like this:

r = 5, area = 78.5398163397448
r = 2.8, area = 24.630086404144

Let's get into details on how to define, invoke and use methods in C#, how to take and pass parameters and to return values.