Web.Config File

• The web.config is not the actual configuration file.
• The only job of the web.config file is to tell the IIS to route the request to aspNetCore handler.
• We can provide the json configuration file to provide the run time settings to the application.

We already know that web.config is not used as the configuration file for ASP .NET Core web applications. Those applications now use appsettings.json, a JSON configuration file.

IIS uses the ASP.NET Core Module to handle the ASP .NET Core application’s requests. The module is an HTTP handler. The handler has some settings which are read by IIS. The handler has settings like processPath, arguments, hostingModel. These settings decide which .NET core application should be invoked and what is the hosting model for the application.

If a web.config file is not present at root, then it is created with the correct processPath and arguments during the publish operation.

If a web.config is already present at app’s root, then it is transformed to use correct values for processPath and arguments settings and it is copied to published output directory.

Reference - The Code Blogger - ASP .NET Core Module and Web.Config File For IIS Hosting