Skip to main content

ASP.NET Core - IHostingStartup

ASP.NET Core 2.0 introduces a new interface called IHostingStartup. Through this interface you can manipulate the process of building the web host outside your ASP.NET Core project. Just by including the DLL, you can hook into the configuration pipeline.

Implementing IHostingStartup

Let’s start by implementing this interface:

  • Create a new .NET Standard Class Library
  • Reference the Microsoft.AspNetCore.Hosting.Abstractions package. This package contains the IHostingStartup interface.
  • Create a new class and implement this interface. Just as an example we add a Console.Writeline to the Configure method:

Make the magic work

Unfortunately we are not there yet and we have to take some extra steps:

  • First add the HostingStartup attribute to your class library:

[assembly: HostingStartup(typeof(ClassLibrary1.MyCustomStartup))]

  • Now the ASP.NET Core runtime has the necessary information where to find our startup inside the DLL.
  • Next step is to setup an environment variable to let the runtime scan the dependency:
    • Right click on your ASP.NET Core project and go to Properties
    • Go to the Debug tab and add the following environment variable:
      • ASPNETCORE_HOSTINGSTARTUPASSEMBLIES=ClassLibrary1
    • The environment variable is a semicolon-delimited list of assemblies.
  • As a last step we have to activate the assembly. Probably the easiest way is by adding a reference, but using the Runtime store is also possible

If we now run our application, we see that the IHostingStartup Configure method is invoked:

More information: https://docs.microsoft.com/en-us/aspnet/core/fundamentals/host/platform-specific-configuration?view=aspnetcore-2.2

Labels:

Popular posts from this blog

Azure DevOps/ GitHub emoji

I’m really bad at remembering emoji’s. So here is cheat sheet with all emoji’s that can be used in tools that support the github emoji markdown markup: All credits go to rcaviers who created this list.
Read more

Podman– Command execution failed with exit code 125

After updating WSL on one of the developer machines, Podman failed to work. When we took a look through Podman Desktop, we noticed that Podman had stopped running and returned the following error message: Error: Command execution failed with exit code 125 Here are the steps we tried to fix the issue: We started by running podman info to get some extra details on what could be wrong: >podman info OS: windows/amd64 provider: wsl version: 5.3.1 Cannot connect to Podman. Please verify your connection to the Linux system using `podman system connection list`, or try `podman machine init` and `podman machine start` to manage a new Linux VM Error: unable to connect to Podman socket: failed to connect: dial tcp 127.0.0.1:2655: connectex: No connection could be made because the target machine actively refused it. That makes sense as the podman VM was not running. Let’s check the VM: >podman machine list NAME         ...
Read more

Cleaner switch expressions with pattern matching in C#

Ever find yourself mapping multiple string values to the same result? Being a C# developer for a long time, I sometimes forget that the C# has evolved so I still dare to chain case labels or reach for a dictionary. Of course with pattern matching this is no longer necessary. With pattern matching, you can express things inline, declaratively, and with zero repetition. A small example I was working on a small script that should invoke different actions depending on the environment. As our developers were using different variations for the same environment e.g.  "tst" alongside "test" , "prd" alongside "prod" .  We asked to streamline this a long time ago, but as these things happen, we still see variations in the wild. This brought me to the following code that is a perfect example for pattern matching: The or keyword here is a logical pattern combinator , not a boolean operator. It matches if either of the specified pattern...
Read more