Access modifiers in c# programming

Questions :

Why we need access modifiers in programming ?

Real world example of access modifiers ?

Why should we use access modifiers?

How to use access modifiers ?

When should we use access modifiers ?

Is access modifiers related to real world example ?

How to use access modifiers ?

Which type of problem we can solved by access modifiers ?

Use

Bind the limit for access/ Define the limit 

Example in real world

Imagine You are the employee of software company.

Below are some point , you can ask one Question to you (Who can have access ….?)

1. Canteen/ reception / facility (gym/ dormitory / entertainment zone )
2. Your personal cubical / chair / laptop
3. Team Project board/ team labs room
4. Other Team members
5. Can you work with other team members
6. Project Discussion with your colleague in your private cubical

Area In Company	For you	For Other Employee
Canteen/ reception / facility (gym/ dormitory / entertainment zone )	YES	YES, It is Public
Your personal cubical / chair / laptop	YES	NO, Other employee can't access your Private cubical/ chair/ laptop
Team Project board / team labs / meeting room	YES	NO, Only you and your team members (Protected) are allowed
Share team labs or other stuff within team	YES	NO (Internal)
Can you work with other team members	NO/ YES- *if project demands	NO/ YES- if project demands (Protected Internal)
Project Discussion with your colleague in your private cubical	NO / YES -*In case your permission/call	NO/ YES -In case your permission/call (Private Protected)

In Programming, How to use Access modifiers in Programming ?
Public 

Key Point to remember

1. If you define class as public All variable/ function not public

2. Explicitly define public to class Function / variables 

3. By default, Interface is public

//Public Access Modifiers

public class facility
{

        public string Canteen = "Canteen is Public";

        public string Gym = "Gym is Public";

        public string Entertainment_Zone = "Entertainment is Public";

}

   

class Program:Team

{

        static void Main(string[] args)

        {

            facility facilityforMe = new facility();

            Console.WriteLine(facilityforMe.Canteen);

            Console.WriteLine(facilityforMe.Gym);

            Console.WriteLine(facilityforMe.Entertainment_Zone);

        }

}

Private

Key Point to remember

1. Can't define Private class top-level (Just below the namespace)

2. If access modifiers not defined, by default it is private

//Private Access

class PrivateStuff

{

        private string Chair = "Chair is Private ";

        private string Laptop = "Laptop is Private ";

        //By default private variable

        string Cubical = "Cubical is Private ";

        //use of private variable within class

        public string GetMyPrivateStuff()

        {

            return (Chair + Laptop + Cubical);

        }

}

class Program

{

        static void Main(string[] args)

        {

            PrivateStuff MyprivateStuff = new PrivateStuff();

            //We can't access private variables outside the PrivateStuff Class

            //MyprivateStuff.Chair / Laptop / Cubical

            Console.WriteLine(MyprivateStuff.GetMyPrivateStuff());

        }
}

Protected
Key Point to remember 
   1. It acts as private within class 
   2. Inherit from base class (ProtectedClassTeam) 
   3. It act as public in derived class(GetProtectedTeamDetails) only

class ProtectedClassTeam
{

        protected string ProtectedTeamMember = "Team member is protected ";

        protected string ProtectedMeetingRoom = "Meeting Room is Protected ";

}

class GetProtectedTeamDetails:ProtectedClassTeam

{

        public string ShowTeamDetails()

        {

            return ProtectedMeetingRoom +ProtectedTeamMember;

        } 

}

class Program:Team

{

        static void Main(string[] args)

        {

            GetProtectedTeamDetails getProtectedTeamDetails =
                                                                        new GetProtectedTeamDetails();

            getProtectedTeamDetails.ShowTeamDetails();          

            ProtectedClassTeam protectedClassTeam = new ProtectedClassTeam();

            //we can't access protected variable here

            //protectedClassTeam.ProtectedTeamMember / ProtectedMeetingRoom

         }
}

Internal 

Key Point to remember

In case you change the namespace. It will not work as expected

If namespace is different then, you need to give reference in used class

*Here is two assembly Company_AccessModifiers and TeamA

Now we are creating internal class and variable which is accessible for

Company_AccessModifiers Only 
If we add new TeamInternalStuff class in Company_AccessModifiers Declare internal variable as below

namespace Company_AccessModifiers 
{

    internal class TeamInternalStuff

    {

        internal string TeamInternalVariable = 
                           "Labs internally used within team only";

    }

}

//Accessible in Program.cs

class Program:Team

{

        static void Main(string[] args)

        {

TeamInternalStuff myInternalClass = new TeamInternalStuff();

        Console.WriteLine(myInternalClass.InternalVariable);

         }

}

//Not Accessible in TeamA Assembly

namespace TeamA

{

    public class TeamAMembers

    {       

        public void GetDetails()

        {  

            //TeamInternalStuff not available 

        }

    }

}

Protected Internal

Key Point to remember

It work on across namespaces

*Here is two assembly Company_AccessModifiers and TeamA

Now we are creating Protected internal variable

which is accessible for TeamA

*If we add new ProtectedInternalTeam class in TeamA

Declare internal variable as below

namespace TeamA

{

    public class ProtectedInternalTeam

    {

        protected internal string ProtectedInternalTeamAMember =

 " Protected Internl TeamA Member ";

    }

    //Internally access within the assembly

    public class TeamAInternalStuff

    {

        public void GetTeamStuff()

        {

            ProtectedInternalTeam protectedInternalTeam = 
                     new  ProtectedInternalTeam();

            Console.WriteLine(
                     protectedInternalTeam.ProtectedInternalTeamAMember);

        }

    }

}

//Accessible in Company_AccessModifiers  Assembly

class Program:ProtectedInternalTeam

 {

        static void Main(string[] args)

        {

              Console.WriteLine(ProtectedInternalTeamAMember);       

        }

 }

Private Protected 

Key Point to remember

1.      We can use it c#7.2 version

2.      It is same feature as private and protected

class PrivateStuff
{

    private protected string CubicalForMeet =

    "Project Discussion in your private cubical 
     with your coulegue ";

}

class Program:PrivateStuff

{

        static void Main(string[] args)

        {

              Console.WriteLine(CubicalForMeet);

        }
}