Introduction

This is a very small article to illustrate C# access modifiers.

Definition

So in case you don't know what an access modifier is:

Access modifiers - They are keywords you should add to your declaration of a class or class member to allow or restrict their accessibility.

The diagram above illustrates how each access modifier affects the accessibility of the class or member.

Using the code

I kind of doubt you will need any more than the diagram as a reminder, but since I want to make this article more complete for beginners, here is some more content.

And now a few examples:

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    internal class Class1
{
private int Member1;
protected int Member2;
internal int Member3;
}
public class Class2
{
private void Method1()
{
}
private int _Member1;
protected int Member1
{
get
{
return _Member1;
}
set
{
Method1();
_Member1 = value;
}
}
internal int Member2;
public int Member3;
}

The above access modifiers prevent direct access as seen by the following access attempts. These attempts produce compilation errors:

From the same assembly as the above classes:

    class Test
{
void Test1()
{
Class1 c1 = new Class1(); //OK
c1.Member1 = 0; //Compilation error here
c1.Member2 = 0; //Compilation error here
c1.Member3 = 0; //OK
}
}
internal class DerivedClass : Class1
{
private void Test2()
{
Member1 = 0; //Compilation error here
Member2 = 0; //OK
Member3 = 0; //OK
}
}

    public class Test
{
void Test1()
{
Class1 c1 = new Class1(); //Compilation error here
Class2 c2 = new Class2(); //OK
c2.Method1(); //Compilation error here
c2._Member1 = 0; //Compilation error here
c2.Member1 = 0; //Compilation error here
c2.Member2 = 0; //Compilation error here
c2.Member3 = 0; //OK
}
}
internal class DerivedClass : Class2
{
private void Test2()
{
Member1 = 0; //OK
Member2 = 0; //Compilation error here
Member3 = 0; //OK
}
}

Points of Interest

In the examples above you restrict direct access to Class2._Member1 but provide a wrapped property called Member1. The requirement is to ensure Method1 is called when _Member1 changes. The access modifiers ensure that we can only change _Member1 via the property.

And that concludes the article.