Fixing the IIS Express error “HTTP Error 502.5 - Process Failure” after you update your ASP.NET Core 1.0 application’s NuGet packages to the latest versions

Assume you've got an ASP.NET Core 1.0 application that you've written with Visual Studio 2015 or 2017. Now, after ASP.NET Core 1.1 is now out, you decide to update all your project's NuGet packages to their latest versions.

After the NuGet packages have been updated, you build and run your application. Chances are, nothing happens! Yes, your application will build, but if you start debugging (F5), your browser flashes on the screen, and Visual Studio returns to editing mode.

If instead you try to launch the project without debugging (Ctrl+F5), you will be greeted with an IIS error message:

HTTP Error 502.5 - Process Failure

Common causes of this issue:

- The application process failed to start
- The application process started but then stopped
- The application process started but failed to listen on the configured port

Although this error sounds rather complicated, there's luckily a simple solution: make sure you have the correct .NET Core 1.1 runtime installed. That is, even though you update your project's NuGet packages to the latest versions, NuGet cannot install the runtime for you. But, it doesn't remind you about it, either.

To solve the issue, visit the .NET Core download pages. From there, download the correct/latest current version (might be different than the LTS = Long-Term Support version), and install it.

Once you've completed the installation, restart Visual Studio, and your project should be good to go!

Hope this helps!