Develop Reference

.Net Core Dependency Injection in Console App

I am trying to use dependency injection in a .NET Core Console App.
There are a lot of articles about it, but did not find one that fixes my problem.
I am trying to use services original from an aspnet core web app, thats why i have the WebHost.
My main problem is to create an instance of my own class, all the dependency seems to work, and my console app starts up.
I have this code in my Program class:
static void Main(string[] args)
{
var host = WebHost.CreateDefaultBuilder(args)
.UseKestrel(options => options.AddServerHeader = false)
.UseStartup<Startup>()
.Build();
var services = new ServiceCollection().AddLogging();
var container = new Container();
var serviceProvider = container.GetInstance<IServiceProvider>();
This code will not compile due to this error:
'Container' does not contain a definition for 'GetInstance'
How can i create an instance of my custom class App which has this implementation:
public class App
{
private readonly IProductService _productService;
public App(IProductService productService)
{
_productService = productService;
}
}

You don't even need to create your own ServiceCollection or ServiceProvider in this scenario - You can just use the IWebHost's Services property that you already have:
var app = host.Services.GetService<App>();
WebHost.CreateDefaultBuilder already adds the logging services, so there's no need to do that either.
Note: I'm assuming that you've registered your App and IProductService types in Startup.ConfigureServices.

I have no idea what a "Container" is in your setting, but you normally create a service provider by calling BuildServiceProvider on the ServiceCollection.
var provider = services.BuildServiceProvider();
var instance = provider.GetService<App>();
You will need to register both App and whatever IProductService you want with the services collection first though.

How to pass dependencies to a custom .NET Core ILoggerProvider

I am creating a custom .NET Core ILoggerProvider that requires some dependencies to be passed into its constructor.
I believe I am using a fairly common pattern to initialize my logging implementation; it looks something like this:
var services = new ServiceCollection();
// Register some services here
services.AddLogging(builder =>
{
builder.AddProvider(new DebugLoggerProvider());
});
var provider = services.BuildServiceProvider();
I want to add my new provider within the AddLogging block, in the same way that the DebugLoggerProvider is currently added.
My custom provider requires some other services to be passed into its constructor and since these are already registered with the ServiceCollection, I assume that I should be able to reference them. However, unlike methods such as AddSingleton, which have an overload that exposes the IServiceProvider, AddLogging doesn't seem to offer an equivalent.
Is there a simple way to achieve this, or am I attempting to do something that contradicts the way .NET Core logging was designed to be deployed?
UPDATE:
After experimenting with the suggestions proposed by #Nkosi, I can confirm that it is possible to get this to work by bypassing AddLogging and directly implementing what it does internally, as follows:
var services = new ServiceCollection();
// Register some services
services.AddSingleton<IMyService, MyService>();
// Initialize logging
services.AddOptions();
services.AddSingleton<ILoggerFactory, LoggerFactory>();
services.AddSingleton(typeof(ILogger<>), typeof(Logger<>));
services.AddSingleton<ILoggerProvider>(p => new DebugLoggerProvider());
services.AddSingleton<ILoggerProvider>(p => new MyLoggerProvider("Constant value", p.GetService<IMyService>()));
var provider = services.BuildServiceProvider();

Now I am not sure if an extension already exists to do this but I see potential here.
First this is how AddProvider is defined in the source code repo.
public static ILoggingBuilder AddProvider(this ILoggingBuilder builder, ILoggerProvider provider) {
builder.Services.AddSingleton(provider);
return builder;
}
You could build up on that by making your own generic version
public static class MyLoggingBuilderExtensions {
public static ILoggingBuilder AddProvider<T>(this ILoggingBuilder builder)
where T: class, ILoggerProvider{
builder.Services.AddSingleton<ILoggerProvider, T>();
return builder;
}
}
which should allow the DI container to build up the object graph when resolved
services.AddLogging(builder =>
{
builder.AddProvider<CustomLoggerProvider>();
});
And there is room to extend this functionality, like adding your own overload that exposes the IServiceProvider and passing that on to the AddSingleton within the extension.
public static ILoggingBuilder AddProvider<T>(this ILoggingBuilder builder, Func<IServiceProvider, T> factory)
where T: class, ILoggerProvider {
builder.Services.AddSingleton<ILoggerProvider, T>(factory);
return builder;
}
And used
services.AddLogging(builder => {
builder.AddProvider<CustomLoggerProvider>(p => new CustomLoggerProvider("Constant value", p.GetService<IMyService>()));
});

Apologies for being a bit late to the party on this one, but I ran into exactly the same problem after having searched high and low. Inspired by the excellent entries in this page, I ended up with the solution below.
services.AddTransient<IMyLogRepository, LogRepository>();
var loggerFactory = LoggerFactory.Create(builder =>
{
builder.AddConsole()
.AddDbLoggerProvider(services.BuildServiceProvider().GetService<IMyLogRepository>());
});
services.AddSingleton(loggerFactory.CreateLogger("MyLogging"));
The key to this being:
services.BuildServiceProvider().GetService<IMyLogRepository>())
Which allowed me to link my database repository to the dbLogger object I created in a single extra line. In essence, it gives me the ability to pluck my DI database object an send it to the Logging service via standard ILoggerProvider and ILogger interfaces

I got a simple solution to work which is kinda lighter.
serviceCollection.AddLogging(logBuilder =>
{
logBuilder.AddConfiguration(theConfigRoot.GetSection("Logging"));
});
serviceCollection.AddSingleton<ILoggerProvider, MyLogProvider>();
However.... Instanciating the Provider keeps you from running in circular dependency problems--> The service you may want to inject soon want´s a logger himself^^

Dependency Injection for Azure chat bot middleware?

I am working on a new chat bot using Azure Bot Service and QnAMaker. We are using BotBuilder middleware, including custom middleware, to tailor the bot behavior.
One of the middlewares will be calling an Azure function and I would like to use the new HttpClientFactory feature with the custom middleware - but this requires dependency injection.
How can I use dependency injection in BotBuilder middleware like you do with regular .NET Core middleware?
When you look at the bot configuration in the Startup.cs, you can see how it requires you to new up all of the bot dependencies:
services.AddHttpClient<MyFunctionClient>(client =>
{
client.BaseAddress = new Uri(mySettings.GetValue<string>("myFunctionUrl"));
client.DefaultRequestHeaders.Add("x-functions-key", mySettings.GetValue<string>("myFunctionKey"));
});
services.AddBot<QnAMakerBot>(options =>
{
options.CredentialProvider = new ConfigurationCredentialProvider(Configuration);
options.ConnectorClientRetryPolicy = new RetryPolicy(
new BotFrameworkHttpStatusCodeErrorDetectionStrategy(),
3,
TimeSpan.FromSeconds(2),
TimeSpan.FromSeconds(20),
TimeSpan.FromSeconds(1));
var middleware = options.Middleware;
middleware.Add(new ConversationState<ChatLog>(new MemoryStorage()));
middleware.Add(new MyCustomMiddleware()); // <- I want to inject a typed HttpClient here
//... etc. ....
Is there a different way to configure the bot that allows for dependency injection?
If MyCustomMiddleware requires a typed HttpClient in its constructor, I have to create a new instance right here, so I don't get the benefit of the DI and the configuration I just set up.

While I am not a fan of service locator pattern, the current design of the bot configuration is not very dependency injection friendly.
Using the nature of how the bot middleware are setup but having to provide a new instance during startup, I came up with the following work around.
public class BotMiddlewareAdapter<TMiddleware> : IMiddleware
where TMiddleware : IMiddleware {
private readonly Lazy<TMiddleware> middleware;
public BotMiddlewareAdapter(IServiceCollection services) {
middleware = new Lazy<TMiddleware>(() =>
services.BuildServiceProvider().GetRequiredService<TMiddleware>());
}
public Task OnTurn(ITurnContext context, MiddlewareSet.NextDelegate next) {
return middleware.Value.OnTurn(context, next);
}
}
It takes the IServiceCollection as an explicit dependency and defers the creation of the service provider and eventual resolution of the actual middleware in a factory delegate.
It can then be implemented using
middleware.Add(new BotMiddlewareAdapter<MyCustomMiddleware>(services));
When the adapter is invoked it will lazy resolve the intended middleware on initial call and then invoke it.
In fact you can take this another step further and convert it to an extension method
public static class BotBuilderMiddlewareExtension {
public static void Add<TMiddleware>(this IList<IMiddleware> middleware, IServiceCollection services)
where TMiddleware : IMiddleware {
middleware.Add(new BotMiddlewareAdapter<TMiddleware>(services));
}
}
Which simplifies the setup to
middleware.Add<MyCustomMiddleware>(services);

How to get the ServiceContext of a Reliable Service in Service Fabric?

The ServiceContext of a reliable service in Service Fabric is registered with the runtime (DI container) in the program.cs of the service:
ServiceRuntime.RegisterServiceAsync("RelDictQuerySvcType",
context => new RelDictQuerySvc(context)).GetAwaiter().GetResult();
How can I get that ServiceContext back from the DI container? There is no property on the ServiceRuntime to get it back. Also, I did not find it via the FabricClient. Do I need to put the context on an own static class in the service constructor to be able to get a reference to it somewhere else in my code?

Service Fabric does not really has a build-in DI mechanism, at least it is a very simple one.
If you want to inject dependencies into you services itself you can use a factory. for example:
ServiceRuntime.RegisterServiceAsync("MyStatelessType",
context =>
{
var loggerFactory = new LoggerFactoryBuilder(context).CreateLoggerFactory(applicationInsightsKey);
ILogger logger = loggerFactory.CreateLogger<MyStateless>();
return new MyStateless(context, logger);
}).GetAwaiter().GetResult();
this is a way to inject concrete implementations in your service. This mechanism is used to inject the context as well. Unfortunately, since it is not a full fledged DI container you cannot get this context outside the service instance itself.
So, you have to bring your own DI container to really use it, for example in a stateless web api you can do something like:
protected override IEnumerable<ServiceInstanceListener> CreateServiceInstanceListeners()
{
return new[]
{
new ServiceInstanceListener(serviceContext =>
new WebListenerCommunicationListener(serviceContext, "ServiceEndpoint", (url, listener) =>
{
logger.LogStatelessServiceStartedListening<WebApi>(url);
return new WebHostBuilder().UseWebListener()
.ConfigureServices(
services => services
.AddSingleton(serviceContext)
.AddSingleton(logger)
.AddTransient<IServiceRemoting, ServiceRemoting>())
.UseContentRoot(Directory.GetCurrentDirectory())
.UseServiceFabricIntegration(listener, ServiceFabricIntegrationOptions.None)
.UseStartup<Startup>()
.UseUrls(url)
.Build();
}))
};
}
Otherwise you have to do it yourself. There are some initiatives already, see this one for an AutoFac extensions and there is also a Unity extensions.

.NET Core with Autofac DI

I want to integrate Autofac to my API. Solution is split on several projects so that everything stays decoupled. I have set up my configure services like this:
public IServiceProvider ConfigureServices(IServiceCollection services)
{
// Add framework services.
...
...
// Autofac
var builder = new ContainerBuilder();
builder.RegisterType<RouteRepository>().As<IRouteRepository>();
builder.Populate(services);
ApplicationContainer = builder.Build();
return new AutofacServiceProvider(ApplicationContainer);
}
However now with this code integrated, my API won't start anymore. If I start it in debug mode, I get no errors, but I don't get response either.
API landing route is pretty straightforward:
public IActionResult GetIndex()
{
return Ok("You are seeing this because controller is working!");
}
Also, what might be connected to the problem is that RouteRepository takes one variable as an argument in the constructor and I don't know where can I define what will be passed through? There is no config file by default.

If you're saying that you have one dependency for your RouteRepository, then you have to notify Autofac container how to resolve that:
// singletone
builder.RegisterInstance(new TaskRepository())
.As<ITaskRepository>();
// or instance based creation
builder.Register(c => new LogManager(DateTime.Now))
.As<ILogger>();
Or Autofac couldn't resolve your type.