3.1. Introduction

Methods/functions are reusable, callable, and customizable piece of code in a computer program. When a function is a part of a class, it’s called a method. In OOP languages, functions are called methods because they are always declared inside and operated through designated classes. It is, therefore, by definition, more accurate to call these subroutines methods rather than functions in C# since C# is an OOP language. However, when discussing the construct of subroutine in general, the general term function seems appropriate and you will see people use the terms interchangeably from time to time.

Note

In C# or other object oriented programming (OOP) languages, methods are associated with a class. In other languages, you may hear the term function. A function is similar to a method, but it is not tied to a class. Due to the similarity in overall usage, it is common to use the terms methods and functions as synonyms.

You have seen the Main() method in the C# console app programs that you generated using the .NET template. In C#, the Main() method is the application’s entry point. When the application is run, execution begins at the start of the Main() method.

Up until this unit, you wrote all code in the main method, but now you will be creating new methods that can be called by the main method. Methods are named code blocks that can be reused (called) whenever we needed. Methods are an abstraction of your code because the methods abstracting away the details (you use the methods by their names only) and that serves to organize your code by function and reduce the repetition of code. In addition, it helps with debugging and maintenance since changes to that block of code only need to happen in one place. Here are some of the main reasons to use multiple methods in your programs:

Reducing Complexity: Divide a problem into sub-problems to solve it a piece at a time.
Reusing Code: Avoid repetition of code.
Maintainability and Debugging: Smaller methods are easier to debug and understand.

When you see duplicate lines of code, that is a signal for you to make a new method. A method is a named set of statements. When we want to execute the statements, we call the method using its name. In a subsequent lesson you will create methods that are called using an object, referred to as instance methods or object methods. The methods in this unit are called without an object, so they are static methods. Static methods are also referred to as class methods.

Some important characteristics of methods/functions are:

We design methods to be reusable subroutines perform certain actions so that we do not have to write the same/similar code repetitively.
In general, a method should do a single thing. You then combine a sequence to perform desired actions.
Methods will not run until it is called. We say we are making a “function call” or “method call” when we invoke/use the subroutine.
When calling a method, we often pass data into the method and we usually design the method to return values when called.
The data that are passed to the method are called arguments and the variables defined for the argument intake are called parameters (although they are often not differentiated from each others). [1]

Observing a C# method: The Main method in a console application is a method and it looks like the follows when you generate it with dotnet new console --use-program-main:

namespace HelloWorld;

class Program
{
   static void Main(string[] args)
   {
      Console.WriteLine("Hello, World!");
   }
}

The Main method, however, is unique by design because it is designated to be the enter point of an application. Although you can write code in the Main method, you will learn how to write methods in addition to, and outside of, the Main method to extend the functionality of your code.

Footnotes