没有为X类型注册任何服务，但是服务注册看起来还可以吗？

Question

I have some very simple code in Startup.cs in a ASP.NET Core 2.0 web project:

public async void ConfigureServices(IServiceCollection services)
{
    services.AddMvc();

    await CreateContainer();

    services.AddSingleton<Infrastructure.Logging.Contracts.ILogger, Infrastructure.Logging.Standard.Logger>();
}

private async Task CreateContainer()
{
    string connectionString = Configuration["TestConnectionString"];
    var storageAccount = CloudStorageAccount.Parse(connectionString);
    CloudBlobClient blobClient = storageAccount.CreateCloudBlobClient();
    CloudBlobContainer container = blobClient.GetContainerReference("logs");
    await container.CreateIfNotExistsAsync();
}

In my home page view, I have:

@using Infrastructure.Logging.Contracts
@inject ILogger logger

The problem is that the application crashes (when running the code in the view) with:

An unhandled exception occurred while processing the request.
InvalidOperationException: No service for type 'Infrastructure.Logging.Contracts.ILogger' has been registered.
Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType)

All the code in Startup.cs runs successful with no exceptions.

But, if I change the ConfigureServices method by moving a single line of code like this:

public async void ConfigureServices(IServiceCollection services)
{
    services.AddMvc();

    services.AddSingleton<Infrastructure.Logging.Contracts.ILogger, Infrastructure.Logging.Standard.Logger>();

    await CreateContainer();
}

Everything now runs successfully with no error messages.

How can the call to the CreateContainer method cause an error when trying to inject the registered class? There should be no relationship whatsoever between these operations.

Note that the call to register the service runs successful in any case and in the debugger I can see the entry for the registered service by examining the services object. There are no exceptions, which could alter the flow of execution somehow. I have stepped through in the debugger and checked everything.

Answer 1

The problem is caused by calling await on an async method inside the ConfigureServices method. I tried to replace this line of code:

await CreateContainer();

with:

await Task.Delay(200);

and the problem still reproduced.

This is the fixed version of the ConfigureServices method:

public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc();

    CreateContainer().Wait();

    services.AddSingleton<Infrastructure.Logging.Contracts.ILogger, Infrastructure.Logging.Standard.Logger>();
}

I'm not exactly sure why this caused a problem, but it must have caused some sort of synchronization issues in the framework code.