Normally, a view is only compiled when it is first used—that is, a controller action returns ViewResult. What this means is that any eventual syntax errors will only be caught at runtime when the framework is rendering the page; plus, even if there are no errors, ASP.NET Core takes some time (in the order of milliseconds, mind you) to compile the view. This does not need to be the case, however.
Unlike previous versions, ASP.NET Core 3 does not recompile a view when the Razor file changes, by default. For that, you have to restart your server. If you want to have this behavior back, you need to add a reference to the Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation NuGet package and add the following line to the services configuration:
services
.AddMvc()
.AddRazorRuntimeCompilation();
Or, you may prefer to enable this only for the debug version of your app, which excludes it from production builds. In that case, you can do...
