在启动时调用 AddTransient 中的异步方法 - Asp.Net Core

Question

I have a service which is used to get some information and the method has a bunch of async calls in the chain.

public interface IFooService
{
    Task<IFoo> GetFooAsync();
}

The concrete class,

public class FooService : IFooService
{
    public async Task<IFoo> GetFooAsync()
    {
        // whole bunch of awaits on async calls and return IFoo at last
    }
}

I register this service on StartUp,

services.AddTransient<IFooService, FooService>();

Several other services are injected with this service. One among them,

public class BarService : IBarService
{
    private readonly IFooService _fooService;

    public BarService(IFooService fooService)
    {
        _fooService = fooService;
    }

    public async Task<IBar> GetBarAsync()
    {
        var foo = await _fooService.GetFooAsync();

        // additional calls & processing
        var bar = SomeOtherMethod(foo);

        return bar;
    }
}

IFoo is integral to the application and used across several services. Most of my code is async just due to this one IFooService and the one method it has which returns IFoo .

Considering this use case, I would like to be able to just inject IFoo to all other services as opposed to injecting them with IFooService .

I gave this a shot,

services.AddTransient<IFoo>(provider => 
{
    var fooService = provider.GetService<IFooService>();
    var foo = fooService.GetFooAsync().GetAwaiter().GetResult();
    return foo;
});

but it raises a red flag to me as I'm doing sync over async and I'm unsure if this will cause any issues like race conditions. Would startup be blocked by doing this. Im looking for a clean way to handle this, any recommendation for when we need something like this? Thank you for your help.

Answer 1

2 Other options

1. Inject Func<Task> as the transient, the caller can await !

2. Task.Run( async () await abc).Wait(); // this deadlocks much less
   due to creating a task and having less issues .

Answer 2

but it raises a red flag to me as I'm doing sync over async

For this red flag, it is caused by that you call method GetFoo which is not defined in IFooService , it is not related with async or sync method.

Try the method which is defined

services.AddTransient<IFoo>(provider =>
{
    var fooService = provider.GetService<IFooService>();
    var foo = fooService.GetFooAsync().Result;
    return foo;
});

Answer 3

services.AddTransient<IFoo>(provider =>
{
    var fooService = provider.GetService<IFooService>();
    var foo = fooService.GetFooAsync().GetAwaiter().GetResult();
    return foo;
});

This option is slightly better than .Result since .Result will wrap all your exceptions into AggregateException and you won't have this side effect with code I suggested. Also don't forget both options won't run asynchronously, it will run synchronously blocking the thread