What are methods?

• A method  is a kind of building block that solves a small problem
   

• The Main() you are using to execute your app is a method
   

• Also known as functions, procedures, etc.

 Declare method

static void PrintLogo() // PrintLogo is the method's name
{
    Console.WriteLine("Telerik Academy");
    Console.WriteLine("https://telerikacademy.com");
}

• PrintLogo is the method name

• void is the return type of the method

• static will be explained in later lectures

• between { and } is the method body

 Declare method 

• When you see something called with () in C# it is a method

• Methods in C# (Java) could not exist without a class

// class definition
class Program
{
    // method definition
    static void Main()
    {
        Console.WriteLine("Hello World!");
    }
}

 Declare method 

// class definition
class Program
{
    // method definition
    static void Main()
    {
        Console.WriteLine("Hello World!");
    }
}

• There must be only one Main() method in a program

• It is the entry point of your program

 You have already used them

• All the blue boxes are methods (functions) of the class String

  • The wrench icon means it is a property 

  • Properties are just like methods (later in the lectures)

 Methods parameters

• Methods could have parameters or not

  • Parameters are passed and the method could use them 

// Method without parameter
static void PrintMessage()
{
    Console.WriteLine("Telerik Academy");
}

// Method WITH parameter
static void PrintMessage(string message)
{
    Console.WriteLine(message);
}

 Methods parameters

• There could be many parameters

  • Every parameter should have type and a name 

// Method with one parameter
static void PrintMessage(string message)
{
    Console.WriteLine(message);
}

// Method with two parameters
static void PrintMessage(string message, int number)
{
    for (int i = 0; i < number; i++)
    {
        Console.WriteLine(message);
    }
}

 Calling methods

• Call the method and pass parameters (if any)

class Program
{
    static void Main()
    {
        PrintMessage();
        PrintMessage("Telerik Academy passed as parameter");
    }
    static void PrintMessage()
    {
        Console.WriteLine("Telerik Academy");
    }

    static void PrintMessage(string message)
    {
        Console.WriteLine(message);
    }
}

 Methods overloading

• NOTE: These two methods could exist simultaneously

  • This is called method overloading

// Method with one parameter
static void PrintMessage(string message)
{
    Console.WriteLine(message);
}

// Method with two parameters
static void PrintMessage(string message, int number)
{
    for (int i = 0; i < number; i++)
    {
        Console.WriteLine(message);
    }
}

 Methods overloading

• There could be multiple methods with the same name

  • but they have to receive different number and/or types of parameters

// Method with one parameter
static void PrintMessage(string message)
{
    Console.WriteLine(message);
}

// Method with one parameter but the same type
static void PrintMessage(string msg)
{
    Console.WriteLine(msg);
}

 Methods overloading

• There could be multiple methods with the same name

  • but they have to receive different number and/or types of parameters

// Method with one parameter
static void PrintSomething(string message)
{
    Console.WriteLine(message);
}

// Method with one parameter but from different type
static void PrintSomething(int number)
{
    Console.WriteLine(number);
}

 Methods parameters (optional)

• Some parameters can be declared optional

  • that happens when you set them a default value

  • only the last parameters can be optional

class Program
{
    static void Main()
    {
        PrintMessage(); // This will print Telerik Academy
        PrintMessage("Hello"); // This will print Hello
    }
    // Method with optional parameter
    static void PrintMessage(string message = "Telerik Academy")
    {
        Console.WriteLine(message);
    }
}

 Methods return type

• Every method could return a value or not

  • void - the method does not return anything. It just makes something

class Program
{
    static void Main()
    {
        PrintMessage(); // This will print Telerik Academy
    }

    static void PrintMessage()
    {
        Console.WriteLine("Telerik Academy");
    }
}

 Methods return type

• Every method could return a value or not

  • any type - the method must return object of that type

class Program
{
    static void Main()
    {
        string upperCaseMessage = UpperCaseLetters("Telerik Academy");
        Console.WriteLine(upperCaseMessage); // prints TELERIK ACADEMY
    }
    // return type string
    static string UpperCaseLetters(string message)
    {
        // ToUpper() is a method of the String class
        return message.ToUpper();
    }
}

 Methods return type

• return keyword exits the method and returns a value

  • if the method is void the return keyword just exits the method

  • anything after return will not be executed

class Program
{
    static void Main()
    {
        PrintMessage("TelerikAcademy");
    }
    static void PrintMessage(string message)
    {
        return; // anything below this line will not be executed
        Console.WriteLine(message); // Unreachable code detected warning
    }
}

  params keyword

• params - you can specify a method parameter  that takes a variable number of arguments

class Program
{
    static void Main()
    {
        PrintMessage("TelerikAcademy", "test");
    }

    static void PrintMessage(params string[] arr)
    {
        foreach (var line in arr)
        {
            Console.WriteLine(line);
        }
    }
}

  params keyword

• It could be comma-separated list of arguments of the type specified in the parameter declaration
   

• It could be an array of arguments of the specified type
   

• You also can send no arguments
   

• params must be the last parameter passed to the method

 Best practices

• Each method should perform a single, well-defined task
   
• Method’s name should describe that task  in a clear and non-ambiguous way
   
  • ​CalculatePrice(), ReadName()
     
  • Process(), PrintInfoAndRegisterUser()
     
• ​​In C# the methods are named using PascalCase