Methods

In this post we will discuss on

Structure of  a method

Difference between static and instance methods

why methods

Methods are also called as functions.these terms are used interchangeably.

Methods are extremely useful because they allow you to define your logic once,  and use it, at many  places.

Methods make the maintenance of your application easier.

Structure of a method

[attributes]

access-modifiers return-type methodname (parameters)

{

method-body

}

NOTE : Return type can be any valid datatype or void.

Method name can be any meaningful name.

Parameters are  optional.

Access modifiers are an integral part of object-oriented programming. They support the concept of encapsulation, which promotes the idea of hiding functionality. Access modifiers allow you to define who does or doesn't have access to certain features.

In C# there are 5 different types of Access Modifiers

Modifier	Description
public	There are no restrictions on accessing public members.
private	Access is limited to within the class definition. This is the default access modifier type if none is formally specified
protected	Access is limited to within the class definition and any class that inherits from the class
internal	Access is limited exclusively to classes defined within the current project assembly
protected internal	Access is limited to the current assembly and types derived from the containing class. All members in current project and all members in derived class can access the variables.

public

The public keyword is an access modifier for types and type members. Public access is the most permissive access level.

There are no restrictions on accessing public members.

Accessibility:

• Can be accessed by objects of the class
• Can be accessed by derived classes

private

Private access is the least permissive access level.

Private members are accessible only within the body of the class or the struct in which they are declared.

Accessibility:

• Cannot be accessed by object
• Cannot be accessed by derived classes

protected

A protected member is accessible from within the class in which it is declared, and from within any class derived from the class that declared this member.

A protected member of a base class is accessible in a derived class only if the access takes place through the derived class type.

Accessibility:

• Cannot be accessed by object
• By derived classes

internal

The internal keyword is an access modifier for types and type members. We can declare a class as internal or its member as internal. Internal members are accessible only within files in the same assembly (.dll).

In other words, access is limited exclusively to classes defined within the current project assembly.

Accessibility:

In same assembly (public)

• Can be accessed by objects of the class
• Can be accessed by derived classes

In other assembly (internal)

• Cannot be accessed by object
• Cannot be accessed by derived classes

protected internal

The protected internal accessibility means protected OR internal, not protected AND internal.

In other words, a protected internal member is accessible from any class in the same assembly, including derived classes.

The protected internal access modifier seems to be a confusing but is a union of protected and internal in terms of providing access but not restricting. It allows:  

• Inherited types, even though they belong to a different assembly, have access to the protected internal members.
• Types that reside in the same assembly, even if they are not derived from the type, also have access to the protected internal members.

Default access

A default access level is used if no access modifier is specified in a member declaration. The following list defines the default access modifier for certain C# types:

enum: The default and only access modifier supported is public.

class: The default access for a class is private. It may be explicitly defined using any of the access modifiers.

interface: The default and only access modifier supported is public.

struct: The default access is private with public and internal supported as well.

The default access may suffice for a given situation, but you should specify the access modifier you want to use to ensure proper application behavior.

Note: Interface and enumeration members are always public and no access modifiers are allowed.

static vs instance methods:

when a method declaration includes static modifier that method is said to be static method.

when no static modifier is present ,the  method is said to be an instance method.

static method is involved using the class name ,where as an  instance method is involved using an instance of the class.

The difference between instance methods and static methods is that multiple instances of a class can be created and each instance has its own separate method.however, when a method is static ,there are no instances of that method and you can involve only that one definition of the static method.

Eg : with static keyword

using System;

namespace arrays {
 class Program {
  static void Main(string[] args) {

   int result = Program.Add(10, 20); //we use class name to call the method 
   Console.WriteLine(result);
   Console.ReadLine();
  }
  public static int Add(int a, int b) { //return type is int
   return a + b;

  }
 }
}

Eg : without static keyword

using System;

namespace arrays {
 class Program {
  static void Main(string[] args) {
   Program p = new Program(); //we create instance 
   int result = p.Add(10, 20);
   Console.WriteLine(result);
   Console.ReadLine();
  }
  public int Add(int a, int b) { //we can alse use void if we dont want to 
   return a + b; //re turn the value


  }
 }
}