Inconsistent accessibility In base class and derived class

[EvilProject]

While working on a scripting engine I Encountered the following problem.
First I Created an abstract base class EPType that represent a variable type in the script.

    internal abstract class EPType
    {
        private String m_Name;
        public String Name
        {
            get { return m_Name; }
        }
        public EPType(String Name)
        {
            m_Name = Name;
        }
        public abstract Object ParseValue(String str);
    }

second I Add the two following classes

   public abstract class EPValueType : EPType
    {
        private EPReferenceType m_RefType;
        public EPValueType(String strName)
            : base(strName)
        {
            m_RefType = new EPRefernceType(strName + "Ref", this);
        }
        internal EPReferenceType ReferenceType
        {
            get { return m_RefType; }
        }   
    }
    internal class EPReferenceType : EPType
    {
        private EPValueType m_Type;
        public EPReferenceType(String strName, EPValueType vType)
            : base(strName)
        {
            m_Type = vType;
        }
        public EPValueType Type
        {
            get { return m_Type; }
        }
        public override object ParseValue(string str)
        {
            return str;
        }    
    }

the problem is that i want EPValueType to be "seen" outside the current assembly so that anyone using this engine will be able to inherit from it and add new types, but I dont want it's base class EPType to be seen since there are only two categories of types, reference type and value type.But if I set EPType as an internal class and EPValueType as a public class i get an Inconsistent accessibility error. is there a way to do what i want without changing the entire design of the scripting engine?

hope I was clear...i got the the feeling that i wasn't :X

thanks in advance

[skipbr]

[System.ComponentModel.Browsable(false)]
[System.ComponentModel.EditorBrowsable(System.ComponentModel.EditorBrowsableState.Never)]
public abstract class EPType
{
        private String m_Name;
        public String Name
        {
            get { return m_Name; }
        }
        public EPType(String Name)
        {
            m_Name = Name;
        }
        public abstract Object ParseValue(String str);
}

This will hide the class, even it being public.

[EvilProject]

[System.ComponentModel.Browsable(false)]
[System.ComponentModel.EditorBrowsable(System.ComponentModel.EditorBrowsableState.Never)]
public abstract class EPType
{
        private String m_Name;
        public String Name
        {
            get { return m_Name; }
        }
        public EPType(String Name)
        {
            m_Name = Name;
        }
        public abstract Object ParseValue(String str);
}

This will hide the class, even it being public.

it hides the class partialy(only from the intellisense menu). I can still inherit from it in a diffrent assembly if I know it's name. what i'm looking for is a way to make EPType completly inaccessible.

[jjvainav]

internal abstract class EPType
    {
        private String m_Name;
        public String Name
        {
            get { return m_Name; }
        }
        public EPType(String Name)
        {
            m_Name = Name;
        }
        public abstract Object ParseValue(String str);
    }

You will have to make EPType public. However, you can prevent assemblies outside of that one from inheriting your base type, by making an internal constructor.

public abstract class EPType
    {
        private String m_Name;
        public String Name
        {
            get { return m_Name; }
        }
        internal EPType(String Name)
        {
            m_Name = Name;
        }
        public abstract Object ParseValue(String str);
    }

This way, any classes outside of EPType's assembly that tries to inherit it, will recieve an error of: The type EPType has no constructor defined.