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I have some websites on a production environment that need to be run from within a subdirectory and in order to carry out proper testing during development to ensure all references to CSS, JS and images files work. By default, when a .NET Core site is run from Visual Studio it will always start from the root, resulting in a broken looking page.

From .NET Core 2.0, within your Startup.cs file, you can set a sub-directory using the UsePathBase extension within the Configure method:

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    if (env.IsDevelopment())
        app.UsePathBase("/mydirectory");
}

Now when the site runs, it’ll be accessible from /mydirectory. In my code example, I only want to set the path base if it development mode. When released to production, the path will be configured at IIS level.

The only annoyance is when you run the site in Visual Studio, it will still start at the root and not at your newly declared subdirectory. I was surprised to see that the site is still accessible at the root, when you would expect the root path to be disabled or even greeted with a 404 response.

On first glance, I thought there was a bug in my path base declaration and perhaps I missed something. After viewing a closed Github issue raised back in 2017, it was stated that this is in fact the intended functionality. This is a minor bug bear I can live with.