Understanding Access Modifiers in C-Sharp

Hi friends, In this article, we will understand Access Modifiers in C# with only on common example.

The type or member can be accessed by any code in the same assembly, but not from another assembly.

Step 1: Create console application ConsoleApp1.

Step 2: Add new ClassLibrary (.net framework) in same solution TestLibrary.

Step 3: Add reference of TestLibrary in ConsoleApp1

Step 4: Add new class in TestLibrary project TestLibBaseClass and copy following code.

namespace TestLibrary
{
    public class TestLibBaseClass
    {
        //Data Member Declaration with access modifiers
        private int pvt;
        public int pub;
        protected int prot;
        internal int i;
        protected internal int pi;

        // Initialization using constructor
        public TestLibBaseClass()
        {
            pvt = pub = prot = i = pi = 0;
        }

        // Member function
        public System.Collections.Generic.ListTestLibBaseMethod()
        {
            System.Collections.Generic.List testlibvar = new System.Collections.Generic.List();
            //Private Member Accessible  With Declared Class same Assembly
            testlibvar.Add(pvt);

            //Public Member Accessible With Declared Class same Assembly
            testlibvar.Add(pub);

            //Protected Accessible With Declared Class same Assembly
            testlibvar.Add(prot);

            //internal Member Accessible With Declared Class same Assembly
            testlibvar.Add(i);

            //protected internal Member Accessible With Declared Class same Assembly
            testlibvar.Add(pi);

            return testlibvar;

        }
    }

    public class Derivedclass : TestLibBaseClass
    {
        public System.Collections.Generic.List DerivedOfTestMethod()
        {
            System.Collections.Generic.List testlibvar = new System.Collections.Generic.List();
            //Private Member Not Accessible  With Derived Class same Assembly
            //testlibvar.Add(pvt);

            //Public Member Accessible With Derived Class same Assembly
            testlibvar.Add(pub);

            //Protected Accessible With Derived Class same Assembly
            testlibvar.Add(prot);

            //internal Member Accessible With Derived Class same Assembly
            testlibvar.Add(i);

            //protected internal Member Accessible With Derived Class same Assembly
            testlibvar.Add(pi);

            return testlibvar;
        }
    }

    public class OtherClass
    {
        TestLibBaseClass t = new TestLibBaseClass();

        //private Not Accessible With Other Class same Assembly
        //public int OtherClass_Private_Not_Access() => t.prv;

        public int OtherClassPublic_Access() => t.pub;

        //protected Not Accessible With Other Class same Assembly
        //public int OtherClass_Protected_Not_Access() => t.prot;

        //internal Accessible With Other Class same Assembly
        public int OtherClass_Internal_Access() => t.i;

        //protected internal Accessible With Other Class same Assembly
        public int OtherClass_Protected_Internal_Access() => t.pi;
    }
}

EXPLANATION:

1) TestLibBaseClass Class

TestLibBaseClass class has Data members with private, public, protected, internal and protected internal access modifiers with data type int. One default constructor for initialization of data members and one public member function TestLibBaseMethod, with generic List collection of int i.e. List.

DDATA MEMBER SCOPE:

With in TestLibBaseClass class all data members are accessible with in its member function TestLibBaseMethod().

2) TestLibBaseClass Class

Derivedclass class which inherits TestLibBaseClass with in same assembly TestLibrary having one public member function DerivedOfTestMethod, with generic List collection of int i.e. List.

DDATA MEMBER SCOPE:

With in DerivedOfTestMethod member function all data member of base class TestLibBaseClass are accessible except one private member i.e. pvt.

3) OtherClass Class

OtherClass with in same assembly is simple Class. In which an local private object of TestLibBaseClass is created. and return its data members by different methods.

DDATA MEMBER SCOPE:

Here five methods are created. out of them public, internal and protected internal are accessible and private and protected are not accessible due to protection level.

Step 5: Add new class in ConsoleApp1 project DerivedFromTestBase and copy following code.

using TestLibrary;

namespace ConsoleApp1
{
    public class DerivedFromTestBase : TestLibBaseClass
    {
        public System.Collections.Generic.List DerivedMethod()
        {
            System.Collections.Generic.List testlibvar = new System.Collections.Generic.List();

            //Private Member Not Accessible With Derived Class Other Assembly
            //testlibvar.Add(pvt);

            //Public Member Accessible With Derived Class Other Assembly
            testlibvar.Add(pub);

            //Protected Member Accessible With Derived Class Other Assembly
            testlibvar.Add(prot);

            //protected internal  Not Accessible With Derived Class Other Assembly
            //testlibvar.Add(i);

            //protected internal Member Accessible With Derived Class Other Assembly
            testlibvar.Add(pi);

            return testlibvar;
        }
    }
   
    class Program
    {
        static void Main()
        {
            DerivedFromTestBase d = new DerivedFromTestBase();
            // Only public method Accessible with Other Class Other Assembly
            System.Console.WriteLine(d.pub);
        }
    }
}

EXPLANATION:

DerivedFromTestBase Class

DerivedFromTestBase Class, which is located in other assembly (ConsoleApp1), derived from TestLibBaseClass which is also created in different assembly (TestLibrary).

In DerivedFromTestBase Class, we created a public member function DerivedMethod, with generic List collection of int i.e. List. Each method have return type int. Each method will return data member of TestLibBaseClass.

DATA MEMBER SCOPE:

out of five access modifiers it will access only public, protected and protected internal data members.

protected and internal are not accessible due to protection levels.

Access Modifiers	Same Assembly			Other Assembly
Access Modifiers	Declared Class (Local)	Other Class	Derived Class	Other Class	Derived Class
PRIVATE	YES	NO	NO	NO	NO
PUBLIC	YES	YES	YES	YES	YES
PROTECTED	YES	NO	YES	NO	YES
INTERNAL	YES	YES	YES	NO	NO
PROTECTED INTERNAL	YES	YES	YES	NO	YES
PRIVATE PROTECTED (C# 7.2)	YES	NO	YES	NO	NO

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Understanding Access Modifiers in C-Sharp

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