Resolving Dependency Injection Conflicts with Multiple Interfaces and Partial Classes in .NET Core

Learn how to effectively implement `Dependency Injection` with multiple interfaces and partial classes in your .NET Core applications. This guide provides clear examples and solutions to common issues.
---

Visit these links for original content and any more details, such as alternate solutions, comments, revision history etc. For example, the original title of the Question was: Dependency Injection with multiple interface and partial class

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Dependency Injection Made Easy with Multiple Interfaces and Partial Classes

Dependency Injection (DI) is a powerful design pattern widely used in .NET Core applications to enhance modularity and facilitate better testing practices. However, when managing shared functionalities across multiple projects, developers often face challenges, especially when the need arises for employing multiple interfaces and partial classes. In this guide, we'll explore a common issue faced while attempting to implement DI in such scenarios and provide a comprehensive solution.

The Challenge

In scenarios where a class serves common functionalities for multiple applications, managing the dependencies can become cumbersome. Imagine you have several individual classes for handling tasks such as sending emails, connecting to a database, and caching data. If your applications scale to over 40 different projects, you'll want to avoid repetitive code and excessive DI registrations.

In this case:

You need a solution that consolidates different functionalities into a single class.

You wish to maintain separate interfaces for functionality while leveraging a partial class to implement the methods.

However, when you attempt to register your common interface, you encounter the following error:

[[See Video to Reveal this Text or Code Snippet]]

The Solution

To overcome this challenge and streamline your DI configuration, we can create a project dedicated to our common dependencies. The steps below will guide you through a systematic approach:

Step 1: Create a Project for Common Dependencies

First, create a project (let's call it Api.CommonDependencies). Within this project, you will define your common services and interfaces.

Step 2: Define Your Interfaces

Here's an example of how your common and separate interfaces can be structured:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Implement the Common Class

Next, you will implement the common functionalities using a partial class. This allows you to extend the functionality later as needed:

[[See Video to Reveal this Text or Code Snippet]]

Step 4: Extend the Partial Class

For the other methods defined in your interfaces, you can extend the partial class as follows:

[[See Video to Reveal this Text or Code Snippet]]

Step 5: Create an Extension Method for DI

Now, it's time to simplify your DI registration by creating a static extension method in your Api.CommonDependencies project:

[[See Video to Reveal this Text or Code Snippet]]

Step 6: Register the Common Dependencies in Any Project

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By taking advantage of partial classes and a centralized dependency registration process, you can significantly reduce redundancy in your configurations. This approach not only makes your code cleaner and more manageable but also allows you to efficiently maintain and extend your shared library functionalities across multiple applications. If you encounter any issues, please feel free to ask for assistance!