Using Dependency Injection for Runtime Object Instantiation in C#

Описание: Discover how to implement Dependency Injection (DI) for runtime instantiated classes in C# with practical examples and solutions.
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This video is based on the question https://stackoverflow.com/q/75049196/ asked by the user 'Musaffar Patel' ( https://stackoverflow.com/u/3469841/ ) and on the answer https://stackoverflow.com/a/75061958/ provided by the user 'MrC aka Shaun Curtis' ( https://stackoverflow.com/u/13065781/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Leveraging Dependency Injection for Runtime Classes in C#

In modern software development, Dependency Injection (DI) plays a crucial role in creating maintainable and testable code. However, when dealing with classes instantiated at runtime, integrating DI can become a challenge. This guide will delve into your issue of injecting dependencies into classes that are only identified during execution, particularly focusing on a practical C# example.

The Problem

You have a base class (ImportBase) and a derived class (ImportFleet) designed to handle the import of CSV files. Within your InvestmentService, you face the hurdle of instantiating the correct child class based on runtime data. The main problem arises because you want to utilize Dependency Injection to provide dependencies, like repository classes, to these dynamically created instances, but cannot do this in the traditional sense.

Here’s a brief overview of your existing code structure:

ImportBase: The parent abstract class implementing the necessary methods.

ImportFleet: A concrete inherited class extending the functionality of ImportBase.

InvestmentService: The service where the logic for determining the correct import class takes place.

Currently, your instantiation logic looks something like this:

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

This prevents you from leveraging Dependency Injection to pass dependencies into your ImportFleet instance at runtime.

The Solution

Fortunately, there is a way to achieve Dependency Injection even for classes that are instantiated based on runtime criteria in C# . This involves using the IServiceProvider and the ActivatorUtilities class provided by .NET.

Step-by-Step Implementation

Inject IServiceProvider: First, modify your InvestmentService to accept an IServiceProvider instance via dependency injection.

Use ActivatorUtilities: This utility allows you to create instances using the DI container, enabling you to resolve the dependencies required by the class.

Proper Disposal: Make sure to properly dispose of instances that implement IDisposable or IAsyncDisposable.

Here’s how your modified InvestmentService might look:

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

An Asynchronous Approach

If your import process involves asynchronous operations, you may want to implement an asynchronous version as well. Here’s how you could adjust your method for async support:

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

Conclusion

By leveraging ActivatorUtilities and IServiceProvider, you can harness the power of Dependency Injection even when dealing with classes instantiated at runtime. This approach not only makes your code cleaner but also helps maintain the principles of loose coupling and testability.

Implementing these techniques ensures you can dynamically create and manage class instances while still utilizing the benefits of Dependency Injection. Adopt this strategic coding practice to enhance your applications and streamline your development processes!

If you have questions or need further clarity on integrating Dependency Injection into your projects effectively, feel free to reach out!