Behavioral Design Pattern in C#

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Behavioral Design Pattern in C#

In this article, I am going to give a brief introduction to Behavioral Design Patterns in C#. Please read our previous article discussing the Structural Design Patterns in C# with examples. As part of this article, we will discuss the following three things.

1. What is the Behavioral Design Pattern?
2. When to use the Behavioral Design Pattern?
3. Examples of Behavioral Design Patterns

What is the Behavioral Design Pattern in C#?

According to Wikipedia, in Software Engineering, behavioral design patterns are design patterns that identify common communication patterns among objects and realize these patterns. By doing so, these patterns increase flexibility in carrying out this communication.

Behavioral Design Patterns deal with the communication or interaction between Classes and Objects. The interaction between the objects should be so that they talk to each other and are still loosely coupled. Loose coupling is the key to implementing the n-tier architecture.

So, the behavioral design pattern explains how objects interact with each other. It describes how different objects and classes send messages to each other to make things happen and how the steps of a task are divided among different objects.

Behavioral design patterns focus on communication between objects: how they interact and fulfill their roles in a system. These patterns ensure that objects cooperate effectively, responsibilities are clearly defined, and interactions are well-organized.

When to use Behavioral Design Patterns in C#?

In real-time applications, sometimes we want to change the behavior of a class, and again, we don’t want it to affect other classes of the project. For example, we have an Invoice class that currently applies taxes as 18%. Tomorrow, if we want to add another extra tax. That means we are changing the behavior of a class. The Behavioral Design Pattern comes into the picture to solve such behavioral issues.

Examples of Behavioral Design Patterns in C#:

The following design patterns belong to the Behavioral Design Pattern category.

1. Iterator Design Pattern: It provides a way to access the elements of an aggregate object without exposing its underlying representation.
2. Observer Design Pattern: Defines a dependency between objects so that all its dependents are notified when one object changes its state.
3. Chain of Responsibility Design Pattern: Decouples request senders from receivers by allowing multiple objects to handle the request. It passes the request through a chain of potential handlers until an object handles it or the end of the chain is reached.
4. Interpreter Design Pattern: It provides a way to evaluate language grammar or expression. This pattern is used in SQL Parsing, Symbol Processing Engines, etc.
5. Command Design Pattern: Encapsulates a request as an object, allowing for parameterization of clients with different requests.
6. Memento Design Pattern: Allows to restore an object to its previous state. Useful for ‘undo’ functionalities.
7. Mediator Design Pattern: Reduces direct communication between classes by centralizing external communications. It is useful to prevent a system with many communicating components from becoming chaotic.
8. State Design Pattern: An object can alter its behavior when its internal state changes.
9. Template Method Design Pattern: Defines the program skeleton of an algorithm in an algorithm class but delays some steps to subclasses. It lets subclasses redefine certain steps of an algorithm without changing the algorithm’s structure.
10. Strategy Design Pattern: Define a family of algorithms, encapsulate each one, and make them interchangeable
11. Visitor Design Pattern: This lets you add further operations to objects without modifying them. A visitor object is passed to each element in a structure, and elements can accept or refuse the “visit.”

These patterns address different challenges, but they all revolve around organizing the behavior and interaction of objects. The choice of which pattern to use depends on the specific behavioral complexity you’re trying to address.

Use Cases of Behavioral Design Patterns in C#

Behavioral design patterns are essential for defining how objects interact and collaborate. They help ensure that objects work together seamlessly and that the system is easy to maintain and extend. Let’s discuss use cases for some of the primary behavioral patterns in C#:

1. Strategy Pattern: A payment gateway system that supports multiple payment methods, like credit cards, PayPal, or cryptocurrency. The strategy pattern can encapsulate each payment method behind a common interface, making adding or removing payment methods easy.
2. Observer Pattern: An event-driven system like a stock market feed, where stocks update subscribed investors whenever their prices change. Another common use case is GUI systems, where buttons notify other components when clicked.
3. Command Pattern: GUI buttons and menu items. Each button might have a command associated with it. When the button is pressed, its command is executed. This way, the button is decoupled from the action it triggers. Another use case is the “undo” and “redo” application functionality.
4. State Pattern: A context-aware chatbot that changes its behavior based on the user’s status (e.g., new user, returning user, premium user). Each state would encapsulate the behavior and responses relevant to that particular user state.
5. Template Method Pattern: Database connectors for different databases. There might be a standard way (template) to connect, disconnect, query, etc., but how these actions are carried out could differ for SQL Server, MySQL, or Oracle databases.
6. Iterator Pattern: Any collection class that needs to provide a way for clients to traverse its elements without exposing its underlying representation. For example, a custom collection for a tree or graph structure.
7. Mediator Pattern: Chat rooms where users send messages to the mediator (chat room) rather than sending them directly to other users. The mediator then forwards the message to all other users.
8. Memento Pattern: Implementing “save game” functionality in a computer game. The game state (memento) can be saved at any point and later restored, allowing the player to return to a previous state.
9. Chain of Responsibility Pattern: Logging frameworks where a chain of handlers processes log messages. Each handler decides to process the message or pass it along the chain. For instance, a handler might handle only error-level messages, while another handles warnings.
10. Visitor Pattern: A document editor that allows extensions/plugins to process or transform the document. Instead of altering existing objects to support new operations (which might break them), new functionality can be added via visitors.
11. Interpreter Design Pattern: Searching within a text, data validation, syntax highlighting, etc. Whenever you want to query a database, the SQL string is interpreted and executed to return the desired data. Running scripts or code snippets in real-time in environments where compiling is not practical.

Note: While these patterns offer solutions to common problems, they’re not one-size-fits-all. Always consider the specific needs of your application and the problem you’re trying to solve before choosing a design pattern.

In the next article, I will discuss the Iterator Design Pattern in C# with Examples. Here, in this article, I try to give a brief introduction to Behavioral Design Patterns. I hope you understand the need and use of the Behavioral Design Pattern in C#.