Why Is My Dependency Injection Failing to Resolve a Service?

Dependency Injection: Service Resolution Errors

This article addresses common errors encountered when a dependency injection container fails to resolve a required service during class activation. The container cannot create an object matching the requested type.

Troubleshooting Dependency Injection Failures

Several factors can lead to service resolution failures:

• Constructor Typos: If the error points to a specific class, double-check the controller's constructor for typos. The constructor should accept the interface of the service, not the concrete class implementation.

  Incorrect:

  <code class="language-csharp"> public BlogController(BloggerRepository repository)</code>

  Correct:

  <code class="language-csharp"> public BlogController(IBloggerRepository repository)</code>

• Missing Service Registration: If the error doesn't specify a concrete class, the service might be unregistered in Startup.cs. Use AddScoped to register the service interface and its implementation.

  Example:

  <code class="language-csharp"> services.AddScoped<IBloggerRepository, BloggerRepository>();</code>

• Custom Service Registration: Some services require custom registration methods. Refer to the library's documentation for the correct registration process.

  Example:

  <code class="language-csharp"> services.AddHttpContextAccessor(); // From Microsoft.AspNetCore.Http</code>

By carefully reviewing these points, you can effectively debug and resolve dependency injection errors, ensuring your application correctly instantiates necessary objects.

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