DESIGN PATTERNS SERIES

Decoupling with Chain of Responsibility Pattern in C#

The Chain of Responsibility Pattern allows us to easily separate dependent parts to make code more extensible and testable.

created by Freepik

The article cooperates with the sample project. Walkthrough with the downloaded project is not required, but I recommend it for better understanding.

The sample project consists of two different approaches to validating the user’s data within a registration. Two processors simulate the user’s registration process.

BasicUserRegistrationProcessor.cs follows the simple path of if statements.

public class BasicUserRegistrationProcessor
{
  public void Register(User user)
  {
    if (string.IsNullOrWhiteSpace(user.Username))
    {
        throw new Exception("Username is required.");
    }
    if (string.IsNullOrWhiteSpace(user.Password))
    {
        throw new Exception("Password is required.");
    }
    if (user.BirthDate.Year > DateTime.Now.Year - 18)
    {
        throw new Exception("Age under 18 is not allowed.");
    }
  }
}

ChainPatternRegistrationProcessor.cs is taking advantage of the Chain of Responsibility Pattern. This…