What Is a "Method"?

Up until now we found out that when writing the code of a program, which solves a problem, what makes it easier is that we divide the task into parts. Each part fulfills a given action and this way it is not only easier to solve the task, but the readability of the code and looking for mistakes is significantly better.

Each piece of code, which executes some functionality and has been separated logically can take the functionality of the method. This is exactly what methods are – pieces of code with names given by us in a certain way and which can be invoked as many times as we need them.

A method can be invoked as many times, as we think we need to solve a problem. This saves us repeating the same code over and over, and also reduces the possibility to miss a mistake when correcting the code.

Simple Methods

The simple methods are tasked to do a certain task, which helps to solve a given problem. These actions can be printing a string on the console, doing a verification, executing a loop and others.

Let's see the following simple example of method definition:

static void PrintHeader()
{
    Console.WriteLine("-----------");
}

This method prints a header, which is a sequence of the - symbol. Because of this its name is PrintHeader. The parentheses ( and ) always follow the name, no matter what we called the method. We will later see how to name the methods we work with and for the moment we will only say that it is important for its name to describe the task the method is doing.

The body of the method contains the program code, which is between the curly brackets { and }. These brackets always follow its declaration and between them we write the code, which solves the problem described by the methods name.

To invoke this method, we just write its name, along with () like it is shown below:

PrintHeader();

A method should be called from a code inside another method, e.g. from the Main() method of the C# program:

static void Main()
{
    PrintHeader();
}

Why Use Methods?

So far we determined, that methods help with dividing larger programs into smaller tasks, which leads to easier solving of the problem in question. This makes our program not only better structured and easier to read, but more understandable as well.

By using methods we avoid repeating code. Repetition is bad practice, because it complicates maintaining the program and leads to errors. If a certain part of our code can be found more than once in the program and we need to change it, the changes must be made in all of the repetitions of the code in question. There is a great probability to miss a spot where correction is needed, which would lead to incorrect behaviour of the program. This is the reason why it is good practice if we use a certain fragment of code more than once in our program, to define it as a separate method.

Methods make it possible to use certain code multiple times. With solving more and more problems you will find that using already existing methods saves a lot of time and effort.

Declaring Methods

In C# you can declare methods inside a class, i.e. between the opening { and closing } brackets of the class. Declaring is registering the method in the program, so that it can be recognized in the rest of it. The best known example is the Main(…) method, which we use in every program that we write.

With the next example we will look at the obligatory elements in the declaration of a method.

  • Type of the return value. In this case the type is double, which means that the method will return a result, which is of type double. The return value can be int, double, string etc., and also void. If the type is void, this means that the method doesn't return a result, but only does a given task.
  • Method name. The name of the method is defined by us, but we shouldn't forget that it has to describe the function, which is executed by the code in its body. In the example the name is GetSquare, which tells us that this method is made to find the area of a square.
  • Parameter list. It is declared between the parentheses ( and ), which we write after its name. This is where we list all the parameters, which the method will use. There can be only one parameter, multiple ones or it could be an empty list. If there aren't any parameters, we will write only the parentheses (). In this example we declare the parameter double num.
  • static declaration in the method description. For the moment you can accept that we write static always when you declare a method, and later when we meet object oriented programming (OOP), you will learn about the difference between static methods (shared for the whole class) and methods of an object, which work on the data of a certain instance of the class (object).

When declaring methods you must follow the sequence of its base elements - first type of the return value, then method name and in the end list of parameters, surrounded by parentheses ().

After we have declared a method, its implementation (body) follows. In the body of the method we write down the algorithm, by which it solves a problem, i.e. the body contains the code (program block), which realizes the methods logic. In the shown example we are calculating the area of a square, which is num * num.

When declaring a variable in the body of a method, it is called local variable of the method. The area where this variable exist and can be used starts from the row where we have declared it and reaches the closing curly bracket } of the body of the method. This area is called variable scope.

Invoking Methods

Invoking (calling) a method means starting to execute the code, which is in the body of the method. This happens by writing its name, followed by parentheses () and the sign ; to end the row. If the method needs input data, it is given in the parentheses (), and the succession of the parameters should be the same as the one of the given parameters when declaring the method. Here is an Example:

A method can be invoked from several places in the program. One way is to call it in the main method.

A method can also be called from the body of another method, which is not the main method of the program.

There is also a possibility for the method to be invoked in its own body. This is called recursion and you can find more information about it in Wikipedia or you can search on your own in the Internet.

It is important to know that if a method is declared in a class, it can be invoked before the line, on which it has been declared.

Example: Blank Receipt

Write a method, which prints a blank receipt. The method should call another three methods: one to print the header, one for the middle part of the receipt and one for the lower part.

Part of the receipt Text
Upper part CASH RECEIPT
------------------------------
Middle part Charged to____________________
Received by___________________
Lower part ------------------------------
(c) SoftUni

Sample Input and Output

Input Output
(няма) CASH RECEIPT
------------------------------
Charged to____________________
Received by___________________
------------------------------
(c) SoftUni

Tips and Tricks

The first step is to create a void method to print the upper part of the receipt (header). Let's give it a meaningful name, which describes what the method does, e.g. PrintReceiptHeader. In its body write the code from the example below:

In the same way we'll create two more methods to print the middle part of the receipt (body) PrintReceiptBody and to print the lower part of the receipt (footer) PrintReceiptFooter.

After this we will create another method , which will invoke the three methods we already wrote, one after the other:

In the end we'll invoke the PrintReceipt method from the body of the Main method of our program:

Testing in the Judge System

The program with five methods, which invoke each other, is ready and we can run and test it, after which we can send it for testing in the judge system: https://judge.softuni.bg/Contests/Practice/Index/594#0.

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