Martin Fowler wrote a book called "Refactoring: Improving the Design of Existing Code," and in the book he discusses the "Introduce Null Object" refactoring. Instead of assigning a null value to a reference-type property, a nullable object can be used to represent a null value, instead of directly assigning a null value itself. This makes it easier to reference and you do not have to worry about getting a null exception when using the property. Here is how it works.