How To

How To Implement Repository Pattern In C# And .Net Core With Entity Framework (Async) – By Michael Etim

Repository Pattern


If someone walked up to me and asked that I explain repository pattern as if I’m talking to a tech newbie, here is what I will say:  

“The Repository Pattern is an architectural design pattern in C# and .NET applications that promotes code maintainability, testability, and scalability.” 

Putting different levels of readers into consideration, I will be sharing some technical, yet clear, insights about Repository Pattern, its advantages, implementation techniques, and best practices with practical code examples. 


The Repository Pattern is a software design pattern that acts as an intermediary between the business logic and the data storage. It provides a consistent interface for performing Create, Read, Update, and Delete (CRUD) operations on data entities while encapsulating the complexities of data access. This separation enhances modularity, code reusability, and facilitates the development and maintenance of robust applications. Now that sounds interesting, but that is not all. RP has many benefits which I am about to share. 


1. Separation of Concerns

One of the major benefits of Repository Pattern is the separation of concerns capacity. RP separates the data access logic from the rest of the application, resulting in a modular and maintainable codebase. It isolates the business logic from the underlying data storage implementation, allowing changes to either component without affecting the other.

2. Testability

Aside from separation of concerns, RP simplifies unit testing by enabling easy mocking of the data access layer. With well-defined interfaces, you can replace the actual repository implementation with a mock repository during testing, thoroughly testing the business logic without relying on a physical database.

3. Code Reusability

By abstracting the data access logic into repositories, RP allows users to reuse these repositories across multiple parts of the application, reducing code duplication (Okay, that is my favourite). This approach promotes a consistent and efficient way of accessing data throughout the system.

4. Scalability

The Repository Pattern provides a structured approach to manage data access, facilitating scalability. You can introduce caching mechanisms, database sharding, or other performance optimisations within the repository layer to improve the application’s scalability as needed. Cool right? Well, let’s see how it can be implemented. 


The first step to implementing RP is by creating an interface that defines the contract for data access operations. This interface should include methods for common operations such as GetById, GetAll, Add, Update, and Delete. Consider the following example:

Repository Pattern

Next, create concrete repository classes that implement the repository interface. These classes interact with the underlying data storage and provide the necessary operations for data retrieval and manipulation. Here’s an example of a repository implementation using Entity Framework:

Repository Pattern

Repository Pattern

Repository Pattern

To use the repository within the business logic layer, you have to employ dependency injection. By injecting the repository interface into your business logic classes, you decouple them from the specific repository implementation, making it easier to switch repositories or mock them during testing. Here’s an example of using constructor injection with a hypothetical UserService class:

Repository Pattern

Last tip on RP implementation: Consider implementing the Unit of Work pattern alongside the repository pattern to manage transactional operations that involve multiple repositories. The Unit of Work pattern allows you to group related repository operations within a single transaction, ensuring atomicity and consistency. This pattern helps maintain data integrity and simplifies error handling. However, its implementation depends on the specific requirements of your application.

Well, that is all about RP implementation. But I cannot leave you without some tips on how to make the best out of it. Below are some RP best practices.


  • Consider keeping the repository interface focused and granular, representing a single entity or aggregate root.
  • You might want to use meaningful method names that accurately describe the intent of the operation (e.g., GetUserById instead of GetById).
  • Consider implementing additional query methods in the repository to encapsulate complex data retrieval operations.
  • Avoid mixing business logic within the repository classes. Keep them focused on data access concerns only.
  • Leverage generics and IQueryable (if applicable) to create a more generic and flexible repository interface.


Remember, while the repository pattern provides many benefits, it’s essential to evaluate the specific requirements of your project before adopting it. Assess whether the complexity of your application justifies the additional abstraction and potential overhead introduced by the pattern. Have fun trying RP!

About the Author: Michael Andifon Etim is a seasoned Software Engineer adept at leading cross-functional teams. Remarkable relationship building, decision making and communication skills. Known for best-in-class development and collaboration. Hardworking software development professional with solid experience, driven to increase team effectiveness. Focused on usability and performance improvements. Proven history of developing useful, efficient and cost-effective projects.

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