Design Patterns in C# With Real-time Examples

In this article series, I will discuss all the Design Patterns in C# with Real-Time Examples using different types of dot net applications, including ASP.NET MVC, Web API, ASP.NET Core, and Console Applications. It is very easy to understand and implement design patterns in Real-Time Applications. Writing the code with design patterns will make your applications more Reliable, Scalable, and Maintainable.

For Whom?

These tutorials are designed for Students, Beginners, and Professional Developers who want to learn and enhance their knowledge of Design Patterns with Real-time Examples using .NET Applications. Here, I will explain all the design patterns step by step. First, we will discuss the definition and then give simple and multiple real-time examples. We will discuss how to implement the same using a .NET Application. We will compare the example with the UML diagram of the design pattern so that you will understand the concept very easily. This Design Patterns in C# with Examples tutorial series provides a hands-on approach to the subject with step-by-step programming examples that will assist you in learning and putting the acquired knowledge into practice.

History and Evolution of Design Patterns

The four authors of the book, famously known as the Gang of Four, introduced the concepts of design patterns in their book Elements of Reusable Object-Oriented Software. Gang of Four (GOF) divided the book into two parts: the first explains the Pros and Cons of Object-Oriented Programming, and the second describes the Evolution Of 23 Classic Software Design Patterns.

What are Design Patterns?

Design Patterns are nothing but, you can say, documented and tested solutions for recurring problems in a given context. So, in simple words, we can say that Design Patterns are reusable solutions to the problems that, as developers, we encounter in our day-to-day programming. Design Patterns are used to solve the problems of Object Generation and Integration. As we progress in this Design Patterns series, you will understand what Object Generation and Integration problems are and how we solve them using different design patterns.

So, Design patterns are reusable solutions to common problems that occur in software design. They represent best practices and have evolved over time through trial and error by experienced software developers. Design patterns can be thought of as templates for solving particular design problems rather than finished designs that can be transformed directly into code.

• Design Pattern is not a Silver Bullet. While developing your project, you know your project requirements better. And we have many design patterns. Take the design pattern as a reference and see whether the design pattern solves your project problem. If yes, then only use the design pattern.
• Do not Overdo Design Patterns. You need to remember that the design patterns are for projects, and projects are not for patterns. I saw many developers enforcing the design pattern in their projects even though the design pattern is not required, making the project messy. So, use Design Patterns only when required.

Note: Sometimes, we may need to use more than one design pattern to solve the problem for a given context. Every design pattern has pros and cons, so only use the design pattern when you are getting more pros than cons.

Types of Design Patterns

Gang of Four (GOF) categorized the Design Pattern into three main categories based on the three problem areas (Object Creation and Initialization, Structural Changes of Classes and Interfaces, and the Relationship Between Classes and communication Between Objects) of software architecture. They are as follows.

1. Creational Design Pattern (Object Creation and Initialization)
2. Structural Design Pattern (Structural Changes of Classes, and Interfaces, and the Relationship Between Classes)
3. Behavioral Design Pattern (Communication Between Objects)

Creational Design Patterns:

The Creational Design Pattern deals with Object Creation and Initialization. The Creational Design Pattern gives the programmer more flexibility in deciding which objects need to be created for a given case. For example, if we have a huge project, a huge project means we have a lot of classes, and a lot of classes means we are dealing with many objects. So we need to create different objects (like new Customer(), new Product(), new Invoice(), etc.) based on some conditions.

If the object creation logic based on some condition is implemented in the client code, then it leads to a lot of complicated logic in the client code. Client code means the class that is going to consume the object. That means if the object creations and initialization logic are not centralized, it leads to a complicated client code.

The Creational Design Pattern helps us to centralize the object creation and initialization logic, and depending upon the condition, it will create and initialize the appropriate object and return that object to the client. Then, the client can consume the object by calling the necessary methods and properties. The client does not know how the object is created and initialized. If this is unclear now, don’t worry; we will discuss Creational Design Patterns in detail in our upcoming articles.

Examples of Creational Design Patterns are Singleton, Factory, Builder, Prototype, Fluent Interface, Factory Method, and Abstract Factory.

So, these patterns deal with object creation mechanisms, trying to create objects in a manner suitable to the situation. The basic approach to object creation might result in design problems or increased complexity. Creational design patterns solve this problem by controlling the object-creation process.

Structural Design Patterns: 

The Structural Design Pattern is used to Manage the Structure of Classes and Interfaces and the Relationship Between the Classes and Interfaces. For example, if we have a Customer and Product class and the Product class is used inside the Customer class, making One-to-Many relationships. As the project proceeds tomorrow, we want to keep the product class from the Customer class as we want to use the Product and Customer classes independently. This is a structural change, and we don’t want this structural change to affect our project. This is where the Structural Design Pattern helps us. If this is unclear now, don’t worry; we will discuss Structural Design Patterns in detail in our upcoming articles.

Examples of Structural Design Patterns are Adapter, Facade, Decorator, Composite, Proxy, Flyweight, and Bridge Design Patterns. These patterns concern how classes and objects can be composed to form larger structures. They help ensure that the entire structure doesn’t need to change when one part of a system changes.

Behavioral Design Patterns: 

Behavioral Design Patterns deal with the Communication Between Classes and Objects. That means if you want to change the behavior of a class again, you want it to affect other classes of the project as well. For example, you have an Invoice class that currently applies taxes as 18%. Tomorrow, if you have to add another extra tax. That means you are changing the behavior of a class. To solve such Behavioral issues, Behavioral Design patterns come into the picture.

Behavioral Design Patterns include Chain of Responsibility, Command,  Observer, Iterator, State, Template Method, Visitor, Strategy, Mediator, Memento, and Interpreter Design Pattern.

So, these patterns are focused on communication between objects: how they interact and fulfill their intended purpose. They define clear patterns of communication among objects.

• Dependency Injection Design Pattern.
• Dependency Injection using Unity Container.
• Repository Design Pattern using C#.
• Repository Design Pattern using Unity of Work.
• Inversion of Control in C#.

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Author: Pranaya Rout Pranaya Rout is a Senior Technical Architect with more than 11 Years of Experience, Microsoft MVP, Author, YouTuber, and Blogger eager to learn new technologies. Pranaya Rout has published more than 3,000 articles in his 11-year career. Pranaya Rout has very good experience with Microsoft Technologies, Including C#, VB, ASP.NET MVC, ASP.NET Web API, EF, EF Core, ADO.NET, LINQ, SQL Server, MYSQL, Oracle, ASP.NET Core, Cloud Computing, Microservices, Design Patterns and still learning new technologies.