Ex: I have 2 classes like this:

class Parent
{
   private string msg;
   public string Message
   {
       get
       {
           return this.msg;
       }
       set
       {
           this.msg = value;
       }
       .......
   }
};

class Child : Parent
{
   Child ()
   {
          // do something with property "Message"
   }
   ...
}

As the class I describe above, I have some questions. Please help me:
Q1: I just want the property "Message" is used directly when create instance
of class Parent

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
Parent obj = new Parent();
obj.Message = "Parent"; // it's ok
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

but, I don't want it (the property "Message") be used if create instance of
class Child, although it could be used inside class Child
Child obj = new Child();
obj.Message = "Parent"; // it's not allowed

could we do something like those.

Q2: could we override properties in inheritance class. I want override
System.Data.DataTable.Rows in System.Data.DataTable class
ex:

class MyDataRowCollection : System.Data.DataRowCollection
{
....
}

class MyDataTable : System.Data.DataTable
{
/// I want covert the property: base.Rows from System.Data.DataRowCollection
to MyDataRowCollection. Could we do this?
};

Please give me your ideas.
Thanks so much.