Pfthb

I've created 3 classes, A, B and C.

• B inherits from A


• C inherits a Collection of A

However, I can't understand why when inheriting from a collection, the derived class can access only the protected member of the base class.

public class A

 public int MyPublic get; set; 
 protected int MyProtected get; set; 
 internal int MyInternal get; set; 
 protected internal int MyProtectedInternal get; set; 

public class B : A

 B MyB get; set; 
 B()
 
 MyB.MyProtected++;
 MyB.MyInternal++;
 MyB.MyPublic++;
 MyB.MyProtectedInternal++;
 

public class C : Collection<A>

 C MyC get; set; 
 C()
 
 MyC[0].MyProtected++; // Inaccessible due to its protection level.
 MyC[0].MyInternal++;
 MyC[0].MyPublic++;
 MyC[0].MyProtectedInternal++;
 

Firstly, and probably not strictly relevant to your question, I'm not sure why C has a member MyC. Type C is a Collection<A> so you can just use the indexer this[int x] to access the collection items.

To give C access to ALL of the members of A while still limiting access for anything else, you could make C a nested type.

public class A

 protected int MyProtected get; set; 
 private int MyPrivate get; set; 

 public class C : Collection<A>
 
 public void Foo()
 
 this[0].MyProtected++; // Allowed
 this[0].MyPrivate++; // Also allowed!
 
 

Note that this gives C more access to A than you intended (all member regardless of access modifier).

Some discussion of pros/cons of nested classes here: What are reasons why one would want to use nested classes?

As mentioned in the comments, you aren't actually inheriting from A. You're inheriting from Collection<T>.

If your goal is to expose the protected properties of A, then make a class that inherits from A and make public properties of the same name that just modify the properties of the inherited class. Then make a collection of that new class.

Something like this. Notice the new class D:

public class D : A 
 new public int MyProtected 
 get return base.MyProtected;
 set base.MyProtected = value; 
 
 new public int MyProtectedInternal 
 get return base.MyProtectedInternal; 
 set base.MyProtectedInternal = value; 
 

public class C : Collection<D>

 C MyC get; set; 
 C()
 
 MyC[0].MyProtected++;
 MyC[0].MyInternal++;
 MyC[0].MyPublic++;
 MyC[0].MyProtectedInternal++;
 

The new modifier keyword indicates that you are replacing the property from the inherited type.