When you create a new ASP.NET Core application,by default you can access the controller action methods using the default routes defined for the application.If you want to access static resources such as HTML page or images then you need to change some configuration in your ASP.NET Core project.
For example if you create a new html page in asp.net core application and try to access it then you will get the following error page:
Call the UseStaticFiles() method in Configure method of Startup class
public void Configure(IApplicationBuilder app)
now you can add the required html page in the wwwroot directory in the solution
now if you can access the html page