access modifiers - C# - Improving encapsulation of property in this example?

Question

I know of the error "The accessibility modifier of the set accessor must be more restrictive than the property or indexer". I also know the solution. Just not in this very specific case.

Consider this example:

    internal virtual bool IsFocused
    {
        get
        {
            return isFocused;
        }
        protected set
        {
            isFocused = value;
        }
    }
    private bool isFocused;

It shows the error. I just don't know why. How is "protected" not less accessible than internal? What would be the solution to this problem? I tried putting "internal protected" instead, without luck.

Answer 1

As it turns out, protected is more accessible than internal. Recall that internal means "not visible outside of this assembly" (except through InternalsVisibleTo access, which makes internal look like public), whereas protected means visible to all subclasses.