Question

Possible Duplicate:
What is the difference between 'protected' and 'protected internal'?
What is the difference between Public, Private, Protected, and Nothing?

Code is as mentioned below:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace testanotherlib
{
    public class A
    {
        internal void InternalDisplay()
        {
            Console.WriteLine("Internal Display Method.");
        }

        protected void ProtectedDisplay()
        {
            Console.WriteLine("Protected Display Method.");
        }

        protected internal void ProtectedInternalDisplay()
        {
            Console.WriteLine("ProtectedInternal Display Method.");
        }

        public void PublicDisplay()
        {
            Console.WriteLine("Public Display Method.");
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace testanotherlib
{
    public class B : A
    {
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using testanotherlib;
namespace testlib
{
    public class C:A
    {
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using testlib;
using testanotherlib;

namespace testapp
{
    class Program
    {
        static void Main(string[] args)
        {
            B objB = new B();
            C objC = new C();
        }
    }
}

I am trying to understand the difference between Internal, Protected and Protected Internal. For that I have created an example using the code above.

In a class library project testanotherlib I have class A & class B. In a class library project testlib I have class C. The program class is in a separate console application. Inside the main method of Program class I have created object for class B (objB) and class C (objC). For objB and and objC only the public method of class A are accessible. I was expected for class B all the methods of class A will be accessible. Kindly help me to understand this. If you need any other information about the project, feel free to ask me.

Regards,
Priyank

Answer 1

The following five accessibility levels can be specified using the access modifiers:

public: Access is not restricted.

protected: Access is limited to the containing class or types derived from the containing class.

Internal: Access is limited to the current assembly.

protected internal: Access is limited to the current assembly or types derived from the containing class.

private: Access is limited to the containing type.

Taken directly from Microsoft’s MSDN library.