Question

I am getting this error:

‘CTest.A.A()’ is inaccessible due to its protection level.

when compiling this code:

public class A
{
    private A()
    {
    }
}

public class B : A
{
    public void SayHello()
    {
        Console.WriteLine("Hello");
    }
}

Can anyone explain why?

Answer 1

Because the default constructor for A is private, try protected A() {} as the constructor.

Class B automatically calls the default constructor of A, if that is inaccessible to B or there is no default constructor (if you have constructor protected A(string s) {}) B can not be instantiated correctly.

The compiler automatically generates the following default constructor in B

public B() : base()
{
}

Where base() is the actual call to the default constructor of A.