InjectAttribute outside of components

I am missing a mechanism in Blazor’s dependency injection. If it already exists and I just missed it in Blazor’s code, please let me know. If not, here is my suggestion as a user story:

As a Blazor programmer, I would like to use the InjectAttribute in classes other than BlazorComponent, too.

Example in pseudo-code:

class DataAccess : IDataAccess
{
  [Inject] <<-- This is what I am missing, member not filled by Blazor's DI
  HttpClient Http { get; set; }
  ...
  void DoSomething()
  {
    // Here I would like to use this.Http
  }
}

@page "/"
@inject IDataAccess DataAccess
...

Use case: I could implement a class DataAccess that encapsulates all web API calls for a Blazor application. Blazor components receive an instance of this class using the InjectAttribute. However, DataAccess needs HttpClient and should get it using dependency injection. As far as I have seen from Blazor’s code and based on some tests I did, the class DataAccess would not receive any value from Blazor’s DI system.

[SteveSandersonMS]

Also to be clear, the primary reason why InjectAttribute exists is just to support the Razor @inject syntax.

We’re not trying to stop developers from using [Inject] directly, but for Razor-based components, it should never be necessary. It’s much nicer to use @inject TypeName PropertyName instead. People should rarely see [Inject] explicitly in their own code.

I’m guessing you’re using it currently in a base class because of the lack of partial support, but that’s an issue we aim to address soon.

[aguacongas]

Instead of using Inject attribute, you need to inject HttpClient in the DataAccess constructor and add IDataAccess to the services collection:

publis class DataAccess : IDataAccess
{
  private readonly HttpClient _http;
  
  public DataAccess(HttpClient http)
  {
      _http = http;
  }
  ...
  void DoSomething()
  {
    // Here I would like to use _http
  }
}

class Program
{
    static void Main(string[] args)
    {
         var serviceProvider = new BrowserServiceProvider(services =>
         {
             // Add any custom services here
            services.AddSingleton<IDataAccess, DataAccess>();
         });

        new BrowserRenderer(serviceProvider).AddComponent<App>("app");
    }
}