How to Pass Additional Parameters to DbContext with Dependency Injection in ASP.NET Core

Описание: Learn how to pass parameters to your `DbContext` in ASP.NET Core applications using Dependency Injection effectively.
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This video is based on the question https://stackoverflow.com/q/66383701/ asked by the user 'Jens Neitz' ( https://stackoverflow.com/u/10300756/ ) and on the answer https://stackoverflow.com/a/66383855/ provided by the user 'Mohsen Esmailpour' ( https://stackoverflow.com/u/1385614/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Passing Additional Parameters to DbContext with Dependency Injection in ASP.NET Core

In ASP.NET Core applications, using Entity Framework Core (EF Core) to interact with the database is a standard practice. However, one common challenge developers face is how to pass additional parameters to their DbContext classes using Dependency Injection (DI). In this guide, we'll discuss this problem and provide a clear solution to enable you to effectively manage your DbContext parameters.

The Problem: Passing Extra Parameters

Consider a scenario where you want to pass an additional string parameter, such as a configuration value or any other data, into your DbContext. Your initial instinct might lead you to try something like the following:

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However, this approach won't work as expected since EF Core doesn't support passing additional parameters like this directly to the DbContext constructor.

The Solution: Create a Dependency Class

To successfully pass extra parameters to your DbContext, you'll need to wrap your additional parameters in a class. Here’s how to do it step-by-step:

Step 1: Define a Parameter Class

First, create a class that will hold the parameters you want to pass. For this example, we're going to define a class named MyClass:

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Step 2: Modify Your DbContext Constructor

Next, modify your DbContext class constructor to accept this new parameter class instead of a raw string:

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Step 3: Register Your Parameter Class in the Service Collection

In your Startup.cs or wherever you are configuring your services, you need to register your newly created class MyClass as a singleton in the ServiceCollection. This ensures that the same instance is used throughout the lifecycle of the application:

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Summary

When dealing with DbContext in ASP.NET Core and wanting to pass additional parameters, wrapping those parameters in a dedicated class is the most effective approach. Here's a quick recap of the outlined steps:

Create a new class to hold your parameters.

Change your DbContext constructor to accept an instance of this class.

Register the parameter class with your dependency injection container.

By following these steps, you can cleanly and effectively manage additional parameters in your DbContext, leading to more organized and maintainable code.