Running and debugging ASP.NET Core apps in IIS Express with Rider

Let’s cut to the chase: the latest Rider 2019.1 EAP build supports running ASP.NET Core apps in IIS Express! There’s launchSettings.json support for IIS Express. We’ve added a settings page to help verify IIS Express is installed, including prerequisites. Oh, and we also check whether a trusted developer SSL certificate has been set up, and allow generating a self-signed certificate in case it isn’t.

After creating a new ASP.NET Core project or loading an existing one that has a launchSettings.json file with an IIS Express profile, Rider auto-imports it as a Run configuration.

Auto-import IIS Express Run Configuration in JetBrains Rider

That’s… it. Do read on if you would like to learn more – we’ll cover some details and additional configuration options that are available.

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Run/Debug configuration options

From the toolbar (or the Run | Edit Configurations… menu), we can look at the configuration that Rider generated based on the launch profiles defined in launchSettings.json. As with other launchSettings.json-based run configurations, we can specify the target framework and additional runtime arguments.  To change any other options, you’ll need to edit the launchSettings.json file.

Tip: check Using .NET Core launchSettings.json to run/debug apps in Rider for more tips and background on using launch profiles.

For IIS Express run configurations, Rider gives us a few additional configuration options:

C:\Users\maart\Desktop\JetBrains posts\rd191iisexpress

Usually, there will be no need to edit any of these – but just in case, let’s explain these three new options.

To launch IIS Express with our ASP.NET Core application, a configuration file is needed under .idea/config/applicationhost.config. Rider will create this file using a template that ships with IIS Express. When possible, customizations you make to this file are also preserved. The Generate applicationHost.config option can be disabled for heavy customizations.

The Show IIS Express output option is a toggle that can be enabled to show output from the IIS Express process itself. By default, it’s disabled (as it’s quite verbose), but when enabled we can see additional details when running the application:

Show IIS Express process output

Lastly, Send debug request will send an initial request (with a DEBUG HTTP request method) to our ASP.NET Core application. This ensures our application is started and the debugger is attached, even when we’re not launching the browser.

Running (and debugging) our ASP.NET Core application

With that out of the way, we can run (Ctrl+F5 in the Visual Studio keymap) or debug (F5) our application. We can set breakpoints in our controllers, and even in application startup, e.g. in Program or in the Startup class’ Configure/ConfigureServices methods.

Debug session in IIS Express with Rider

Of course, we’ll need IIS Express on our (Windows) machine for this to work, as well as the .NET Core Hosting Bundle. We’ve added a new settings page (under Build, Execution, Deployment | IIS Express) that can help with that!

IIS Express settings

From here, we can verify the path to IIS Express and the required ASP.NET Core module, and if one (or both) of them are missing, Rider will provide us with guidance.

Note: In case IIS Express still does not start or returns an empty error, there’s a chance the .NET Core Hosting Bundle did not install correctly. This article (under Fixing the applicationhost.config template) may help troubleshoot and fix the default IIS Express configuration template on your machine.

Generating a self-signed SSL certificate

For launchSettings.json-based run configurations, Rider will check whether an ASP.NET Core developer certificate or IIS Express self-signed certificate has been set up on our machine. If not, we can let Rider generate one for us.

Set up ASP.NET developer certificate / IIS self-signed certificate

Setting up a certificate can be done from that warning, or using the Set up certificate action, for example from Search Everywhere (Ctrl+T or Double-shift):

Set up certificate from Search Everywhere

For ASP.NET Core, Rider will use the dotnet dev-certs https command to check whether the certificate has been installed. For IIS Express, Rider will check the http.sys certificate settings (similar to the netsh http show sslcert command line).

The IDE also verifies the certificate is trusted by our system. This should make it easier to develop ASP.NET and ASP.NET Core web applications that make use of SSL on our developer machine.

Give Rider 2019.1 EAP a try! We’d love to hear your feedback on updates in this coming release.

About Maarten Balliauw

Maarten Balliauw is a Developer Advocate at JetBrains, working on .NET tools. He focuses on .NET, Azure, web technologies and application performance. Maarten is a frequent speaker at various national and international events. In his free time, he brews his own beer. Follow him on Twitter or check his personal blog.
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19 Responses to Running and debugging ASP.NET Core apps in IIS Express with Rider

  1. Pingback: The Morning Brew - Chris Alcock » The Morning Brew #2708

  2. cocowalla says:

    Anyone else found that configured environment variables (such as ASPNETCORE_ENVIRONMENT) are being ignored when running with IIS Express?

  3. cocowalla says:

    I’m running with Windows authentication, so have this In my launchsettings.json file:


    "iisSettings": {
    "windowsAuthentication": true,
    "anonymousAuthentication": false,
    ...
    }

    But when Rider generates an applicationhost.config, it didn’t allow Windows Authentication, so I had to manually change to:

    Would be useful if Rider could so this automatically, based on the launchsettings.json file

  4. James says:

    Still can’t run asp net core apps on IIS express, checked Maarten’s blog about it but no luck.
    I don’t see the option to run the apps as “MyApp : IIS Express”
    I have IIs express installed, the hosting bundle, Rider EAP 3…, everything needed in launchsettings.json…
    And I definitly don’t have the .idea/config folder in my solution so no idea/config/applicationhost.config either…. tried to copy paste it from vs but nothing…

    • Hi James,

      Would you mind opening an issue on https://youtrack.jetbrains.com/issues/RIDER#newIssue ?

      If possible to share your project or a repro, that would be great.
      Additionally, a screenshot of Build, Execution, Deployment | IIS Express would be helpful there.

    • Ivan Migalev says:

      It looks like the run configuration is missing from your project for some reason (maybe because you’ve opened it in earlier version of Rider that wasn’t capable of processing IIS Express config).

      You may create it manually (new “.NET Launch Settings Profile” run configuration → select your project and “IIS Express” command there) or generate it by right-clicking the “launchSettings.json” file in the project tree.

      .idea/config/applicationhost.config will be auto generated just before you start IIS Express for the first time.

  5. James says:

    Cloned the solution in a new folder, opened it & now I have the .idea/config/applicationhost.config, thanks

  6. Marcel Bradea says:

    Sorry if I’m asking the obvious – but what are the benefits of running in IIS Express?

    The blog cuts right to all the great support/helpers of doing so, without touching on any of the motivation why you might want to do this.

    I believe SSL support for local development is one benefit, are there other aspects such as performance, startup time, other aspects?

    Kind thanks!

    • cocowalla says:

      It’s useful if you’ll be running in IIS in production, and want to keep your dev environment as similar as possible.

      It’s also useful if you need to support Windows authentication, as Kestrel doesn’t support it (you can use Windows’ built-in HTTP.sys as an alternative, but there are some caveats and it can be a total PITA to figure out when things go wrong).

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