Contents Single Responsibility Principle The Chain of Responsibility Pattern Double Dispatch Liskov Substitution Principle Finding Closure This is the first installment of a new MSDN® Magazine column on software design fundamentals. Discuss design patterns and principles in a manner that isn't bound to a specific tool or lifecycle methodology. Talk about the bedrock knowledge that can lead you to better designs in any technology or project. A discussion of the Open Closed Principle and other related ideas popularized by Robert C. Martin in his book, Agile Software Development, Principles, Patterns, and Practices. Don't be turned off by the word "agile" in the title, because this is all about striving for good software designs.