c# poco class

Understanding POCO Class, Dependency Injecon, and Repository Design Paern in C#
Posted on Csharpmaster.com
In the world of C#, designing scalable, maintainable, and ecient applicaons is paramount. One of the
most important aspects of creang well-structured soware is the ability to manage data access, control
dependencies, and model domain objects in a way that is exible and clean. In this arcle, we will delve
into key concepts such as POCO class, dependency injecon in .NET Core, and the repository design
paern in C#, explaining their relevance and how they help in creang a robust soware architecture.
What is a POCO Class in C#?
The term POCO stands for Plain Old CLR Object. It refers to a class in C# that is designed without any
dependency on a framework or external infrastructure. A POCO class is typically simple, focusing purely
on represenng data, without being ed to any complex inheritance structures or specic technology
stacks like Enty Framework or other ORM systems.
Key Characteriscs of POCO Classes:
• No Framework Dependencies: POCOs do not rely on any framework-specic features such as
data annotaons or base classes from a specic ORM (Object-Relaonal Mapping) system.
• Focused on Domain Logic: POCOs are oen used to represent domain enes, storing and
manipulang data without being coupled to the underlying storage mechanism.
• Lightweight: These classes tend to be simple and contain only properes and methods that are
directly related to the data or behavior they represent.
For example, here is a basic POCO class in C#:
In this example, the Product class is a POCO. It contains basic properes to represent a product and has
no es to any external library or framework.
Why Use POCO Classes in C#?

1. Separaon of Concerns: POCOs help in keeping your domain model independent of frameworks.
This means that your business logic is not ed to any external library, making it easier to test and
maintain.
2. Flexibility: Because POCOs are not bound to a parcular technology, they can be easily migrated
between dierent data storage soluons or frameworks.
3. Simplied Tesng: POCO classes are easier to mock in unit tests since they are not ghtly
coupled to external dependencies.
Dependency Injecon in .NET Core
Dependency Injecon (DI) is a design paern used to implement IoC (Inversion of Control), allowing for
more modular and testable code. In .NET Core, dependency injecon is built-in, making it a rst-class
cizen in the framework.
What is Dependency Injecon?
In simple terms, Dependency Injecon is a way to provide an object’s dependencies from the outside,
rather than hardcoding them inside the object. This makes your code more exible and easier to
maintain. Instead of an object creang instances of the services it depends on, these services are
provided to the object, typically through the constructor or via properes.
Why Use Dependency Injecon in .NET Core?
1. Loose Coupling: With DI, the classes don’t need to know about the concrete implementaon of
their dependencies. They only depend on abstracons (interfaces), leading to more loosely
coupled code.
2. Easier Tesng: Since dependencies are injected, it becomes much easier to substute real
dependencies with mocks or stubs during unit tesng.
3. Centralized Conguraon: In .NET Core, you can congure all your dependencies in the
Startup.cs or Program.cs le, making it easy to manage the applicaon's services.
Example of Dependency Injecon in .NET Core
Here’s an example of how dependency injecon works in a simple .NET Core applicaon:
1. Dene an Interface:

4. Implement the I
By using DI, you decouple the ProductController from the ProductService, making the applicaon more
exible and easier to maintain.
Repository Design Paern in C#
The Repository Design Paern is a structural paern used to encapsulate the logic for accessing data
from a data source. This paern abstracts the data layer, making it easier to manage and maintain.
What is the Repository Paern?
The repository paern provides a way to encapsulate the logic required to access data sources, typically
databases or external services, in a way that separates concerns. It acts as a middle layer between the
data access logic and the business logic. The repository paern is commonly used to interact with POCO
classes and provide methods for fetching, saving, updang, and deleng enes.
Why Use the Repository Paern?
1. Separaon of Concerns: The repository separates the data access code from business logic,
making the applicaon easier to manage.
2. Simplies Data Access: By using a repository, you can encapsulate all the data access logic into a
single place, reducing duplicaon.
3. Increased Testability: The repository paern makes it easier to mock the data layer in unit tests.
Example of Repository Paern in C#
Here’s how you can implement a simple repository paern with POCO classes and Dependency
Injecon in a .NET Core applicaon: