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Object-oriented Programming in C# Abstract classes, Interfaces, and Patterns * Method Combination Method Combination Parameter Variance Covariance and Contravariance * Abstract Classes - Sealed Classes Abstract Classes Abstract classes and abstract methods in C# Abstract Properties Sealed Classes and Sealed Methods * Interfaces Interfaces Interfaces in C# Examples of Interfaces Interfaces from the C# Libraries Sample use of IComparable Sample use of IEnumerator and IEnumerable Sample use of IFormattable Explicit Interface Member Implementations * Patterns and Techniques The Composite design pattern A Composite Example: Music Elements An application of Music Elements Implementation of MusicElement classes A Composite example: IntSequence A Composite example: IntSequence application Implementation of the IntSequence classes A Composite Example: A GUI A Composite Example: A GUI A Composite Example: A GUI Cloning Cloning in C# The fragile base class problem The Visitor design pattern Natural object-oriented IntSequence traversals Towards a Visitor solution A Visitor example: IntSequence Visitors - Pros and Cons

Abstract Classes - Sealed Classes