C# Primer: A Practical Approach

3.8. A Hybrid Abstract Base Class

The solution-set data member is the same for each derived-class query type: an array of integers indicating the matching lines of text. In our initial design, our Query class defines an abstract property encapsulating the solution set:

abstract public class Query
{
    abstract public int [] Solution { get; }
    // ...
}

Each derived class, in turn, defines the actual solution-set instance data member and provides the actual implementation of get for the Solution property—for example,

public class NotQuery : Query
{
   private int [] solution_set;
   virtual public int [] Solution
   {
          get{ return solution_set; }
   }
   // ...
}

Consider the following code fragment, in which parseQuery() represents a utility that transforms a ...