EF Core multiple HTTP requests throws an error

Question

I cannot seem to find an answer to this question.

So in the frontend when the user loads a page we call an API for each item on that page (10 items). So that equals 10 API calls.

Most of the calls work but there are always a few that fail when trying to query the database resulting in the following error:

InvalidOperationException: A second operation started on this context before a previous operation completed. Any instance members are not guaranteed to be thread safe.

Now I understand that Entity Framework is not thread safe but I am unsure how to get around this error.

Everywhere where I am using a DBContext it is always injected in using the built in .net core Ioc container.

Here is the DI setup

services.AddScoped<IOmbiContext, OmbiContext>();
services.AddTransient<ISettingsRepository, SettingsJsonRepository>();

All of my repositories are setup in a Transient scope with the Context as Scoped according to this article: https://learn.microsoft.com/en-us/aspnet/core/data/entity-framework-6

Now I have tried changing the context to Transient and it still happens.

How can I avoid this?

More Information

The API Method:

[HttpGet("movie/info/{theMovieDbId}")]
public async Task<SearchMovieViewModel> GetExtraMovieInfo(int theMovieDbId)
{
    return await MovieEngine.LookupImdbInformation(theMovieDbId);
}

Which eventually calls the following where the exception is being thrown:

public async Task<RuleResult> Execute(SearchViewModel obj)
{
    var item = await PlexContentRepository.Get(obj.CustomId); <-- Here
    if (item != null)
    {
        obj.Available = true;
        obj.PlexUrl = item.Url;
        obj.Quality = item.Quality;
    }
    return Success();
}

PlexContentRepository

public PlexContentRepository(IOmbiContext db)
{
    Db = db;
}

private IOmbiContext Db { get; }
public async Task<PlexContent> Get(string providerId)
{
   return await Db.PlexContent.FirstOrDefaultAsync(x => x.ProviderId == providerId); <-- Here
}

Answer 1

If you use Entity Framework Core usually you do not need to add your Database Context as an additional service

I recommend to setup your DbContext in the Startup.cs as following:

services.AddEntityFrameworkSqlServer()
            .AddDbContext<OmbiContext>();

Followed by a Controller class for your API calls taking the DBContext as constructor parameter.

public class ApiController : Controller
{
    protected OmbiContext ctx;
    public ApiController(OmbiContext dbctx)
    {
        ctx = dbctx;
    }

    public async Task<IActionResult> yourAsyncAction()
    {
        // access ctx here
    }
}