Using the dynamic Keyword in C# to Improve Object-Orientation

With polymorphism, object-oriented languages allow “…different data types to be handled using a uniform interface”.  Ad-hoc polymorphism is when you declare multiple methods of the same name but differ by the type of an argument.  For example: private static void Draw(Circle circle) { //… } private static void Draw(Square square) { //… } These are usually referred to as method overloads or method overloading.  Which Draw method that gets invoked would be decided upon at compile-time based on the type of the parameter passed to it. This is great, there are many situations where this is useful; but what about … Continue reading Using the dynamic Keyword in C# to Improve Object-Orientation

A Upcoming Pandemic of Domain Anaemia

There’s a well-known anti-pattern called the anaemic domain model[1][2].  This anti-pattern basically says domain entities, chronically, have little or no behaviour (remember, object-oriented design is about attributes and behaviour). It should be obvious that a domain model that isn’t truly object oriented is a domain model with a problem.  But, let’s look at other reasons why the Anaemic Domain Model is an anti-pattern.  Your Domain is the nexus, the essence, of your system. An anaemic domain model is basically a reporting system.  Each “Entity” becomes, essentially, a query.  This is fine, reporting systems are necessary and prevalent.  But, to shoe-horn … Continue reading A Upcoming Pandemic of Domain Anaemia

Pontificating Virtual Parameterized Constructors in C#

Tom Hollander recently posted about a change he required to the Enterprise Library for date/time validation.  He had to create a new class (rather than modify the Enterprise Library) that derived from another, defective class.  One of his complaints was that in order to effectively implement the base class he had to also write matching constructors that simply called the base class.  His suggestion was effectively to add the concept of virtual parameterized constructors to C#.  I detail “parameterized constructors” because C# already effectively has virtual default constructors.  In the following example the base constructor (Form()) is automatically called by … Continue reading Pontificating Virtual Parameterized Constructors in C#

Fundamentals of OOD Part 3: Method Cohesion

Single Responsibility Principle (SRP) helps us write more cohesive types and methods.  Cohesion is the relatedness of the members of a type to each other and the relatedness parts of a method’s code to other parts. Method cohesionOften times a method is not very cohesive, meaning the code that it executes relates to more than one thing.  This can often be seen with a method that contains a large switch statement.  For any invocation of the method only one case statement may be executed; meaning that blocks of code within the method don’t relate to all the other blocks.  Switch … Continue reading Fundamentals of OOD Part 3: Method Cohesion