Open source ASP.NET Core 2.1 is out, and Architect David Fowler took to twitter to share some hidden gems that not everyone knows about. Sure, it’s faster, builds faster, runs faster, but there’s a number of details and fun advanced techniques that are worth a closer look at.
ASP.NET Core introduced a new hosting model. .NET apps configure and launch a host.
The host is responsible for app startup and lifetime management. The goal of the Generic Host is to decouple the HTTP pipeline from the Web Host API to enable a wider array of host scenarios. Messaging, background tasks, and other non-HTTP workloads based on the Generic Host benefit from cross-cutting capabilities, such as configuration, dependency injection (DI), and logging.
This means that there’s not just a WebHost anymore, there’s a Generic Host for non-web-hosting scenarios. You get the same feeling as with ASP.NET Core and all the cool features like DI, logging, and config. The sample code for a Generic Host is up on GitHub.
A way to run long running background operations in both the generic host and in your web hosted applications. ASP.NET Core 2.1 added support for a BackgroundService base class that makes it trivial to write a long running async loop. The sample code for a Hosted Service is also up on GitHub.
Check out a simple Timed Background Task:
public Task StartAsync(CancellationToken cancellationToken)
_logger.LogInformation("Timed Background Service is starting.");
_timer = new Timer(DoWork, null, TimeSpan.Zero,
You can now host ASP.NET Core inside a Windows Service! Lots of people have been asking for this. Again, no need for IIS, and you can host whatever makes you happy. Check out Microsoft.AspNetCore.Hosting.WindowsServices on NuGet and extensive docs on how to host your own ASP.NET Core app without IIS on Windows as a Windows Service.
public static void Main(string args)
var pathToExe = Process.GetCurrentProcess().MainModule.FileName;
var pathToContentRoot = Path.GetDirectoryName(pathToExe);
var host = WebHost.CreateDefaultBuilder(args)
IHostingStartup – Configure IWebHostBuilder with an Assembly Attribute
Simple and clean with source on GitHub as always.
This is an interesting one you should definitely take a moment and pay attention to. It’s possible to build packages that are used as helpers to share source code. We internally call these “shared source packages.” These are used all over ASP.NET Core for things that should be shared BUT shouldn’t be public APIs. These get used but won’t end up as actual dependencies of your resulting package.
<PackageReference Include="Microsoft.Extensions.ClosedGenericMatcher.Sources" PrivateAssets="All" Version="" />
<PackageReference Include="Microsoft.Extensions.ObjectMethodExecutor.Sources" PrivateAssets="All" Version="" />
If you ever need to invoke a method on a type via reflection and that method could be async, we have a helper that we use everywhere in the ASP.NET Core code base that is highly optimized and flexible called the ObjectMethodExecutor.
The team uses this code in MVC to invoke your controller methods. They use this code in SignalR to invoke your hub methods. It handles async and sync methods. It also handles custom awaitables and F# async workflows
A small and commonly requested one. If you hate the output that dotnet run gives when you host a web application (printing out the binding information) you can use the new SuppressStatusMessages extension method.
They made it easier in 2.1 to configure options that require services. Previously, you would have had to create a type that derived from IConfigureOptions<TOptions>, now you can do it all in ConfigureServices via AddOptions<TOptions>
public void ConfigureServicdes(IServiceCollection services)
o.Path = env.WebRootPath;
You likely shouldn’t be digging around for IHttpContext, but lots of folks ask how to get to it and some feel it should be automatic. It’s not registered by default since having it has a performance cost. However, in ASP.NET Core 2.1 a PR was put in for an extension method that makes it easy IF you want it.
New features in this release include:
Go give it a try. Follow this QuickStart and you can have a basic Web App up in 10 minutes.
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