Static and Instance members, Public keywords and Nested types in C#

Goud.Kv
Posted by in C# category on for Beginner level | Points: 250 | Views : 3167 red flag

C# is an Object-oriented programming language. C# comes with simplicity, expressiveness and great performance to meet the programmer productivity.

Introduction

So far we have seen Identifiers and Keywords and Literals, Operators and Punctuators in C# Programming. Let's see static and instance members (also called as variables) in this chapter.

Objective

The main objective of this article is to learn about static members, instance members, public keywords and nested types in C#.

Class Members

There are two types of Class Members (Variables) in C#. They are,
  • Instance Members
  • Static Members
Instance Members:
The members (data members and function members) which operate on the instance of the type are called as Instance Members

(or)

When a method, property, event, constructor etc. declarations does not include any static modifier, then it declares an Instance Member.

Ex: ToString method of int.

These are instance by default.

Static Members:
The members (data members and function members) which doesn't operate on the instance of the type are called as Static Members.

(or)

When a methodpropertyeventconstructor etc. declarations include any static modifier, then it declares an Static Member.

Ex: Console.WriteLine. Basically Console is a static class which has all static members in it. One Console is enough to be shared across the entire application.

Let's have a simple code as example,
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Man
{
    class Program
    {
        public string Name;       // Instance field
        public static int Number; // Static field
        public Program(string n)  // Constructor of the class Program
        {
            Name = n;             // Assigning instance(Name) field
            Number = Number + 1;  // Incrementing static(Number) field
        }

        class Man 
        {
            static void Main()
            {
                Program p1 = new Program("Abhinav");
                Program p2 = new Program("Venkat");
                Program p3 = new Program("Vishruth");

                Console.WriteLine(p1.Name);        // Abhinav 
                Console.WriteLine(p2.Name);        // Venkat
                Console.WriteLine(p3.Name);        // Vishruth

                Console.WriteLine(Program.Number); // 3
            }
        }
    }
}
Now, observe the above code in which we have an instance field Name that is an instance of the class Program and a static field Number.

We have a Constructor in the above code which creates instances of the class Program, prints their Names and then the total Number.

The output of the above code prints something like below,


Public Keyword:
A Keyword which exposes members to any other classes is known as a Public Keyword.
In the above example code, if the Name field was not public, the Man class could not access it. Hence, public says that, "I am public and I want other types (classes) to see me".

In object-oriented terms, we know that public members encapsulate the private members of the class.

Nested Types

A type or a class that is declared in another class or struct is called as Nested Type or Nested Class. And a class or type which is declared in namespace or compilation unit (which is outside any class) is known as Non-Nested Type.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Nested
{
    class One
    {
        class Two
        {
            public static void Main()
            {
                Console.WriteLine("This is a Nested Type");
            }
        }
    }
}
In the above code, we have two classes One and Two. Class Two is declared within class One. Hence, class Two is called as Nested Type (class) of One.

Press Ctrl + F5 in to see the following result in your Console,


Conclusion

In this article, we have looked into static and instance members (variables), public keyword and Nested types in C#.
Hope you understand.

Thank you for reading.

Regards,
Krishna.

Recommendation
Read Conversions, CTS, Value and Reference types in C# after this article.
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About the Author

Goud.Kv
Full Name: Krishna Vamshi Goud
Member Level: Gold
Member Status: Member,MVP
Member Since: 2/12/2014 2:34:09 AM
Country: India
Thanks & Regards, Krishna


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