Question

class MyClass
{
    **private** delegate void MyDelegate(); //error: MyDelegate is less accessible than property Del
    private MyDelegate del;
    public MyDelegate Del
    {
        get { return this.del; }
        set { this.del = value; }
    }
}

Changing to public fixes, but I would like to know why in more detail.

Answer 1

MyDelegate is part of the signature of the public property Del.

If something consumes the return value of Del, it certainly needs the definition of the type being returned.

In other words, if some other class has an instance of MyClass like this:

MyClass myclass = new MyClass();
MyDelegate del = myclass.Del;

would not be possible unless MyDelegate is a type known to that class.