.NET Core 3.0: Razor views don't automatically recompile on change

Question

According to the documentation, Razor views should, by default, recompile on change on local environments for ASP.NET Core 3.0.

However, my project doesn't do this locally. If I change a view and refresh when I'm debugging locally, the change is not reflected. I have to stop the solution, re-run, and then see the change.

I am doing this on a default ASP.NET Core Web Application template on Visual Studio 2019 with ASP.NET Core 3.0.0 Preview 2 using Razor pages. Any idea if I need to change settings to enable this feature?

UPDATE NOV 2019 FOR 3.0 FULL RELEASE:

This question still gets a lot of views. A few answers have cited to add

services.AddControllersWithViews().AddRazorRuntimeCompilation(); 

To your ConfigureServices() function in Startup.cs after adding the Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation NuGet package. In my case, I am only using Razor Pages, so I don't call AddControllersWithViews(). Instead, this worked for me:

services.AddRazorPages().AddRazorRuntimeCompilation();

Answer 1

OK it looks like it's not supported yet :(

Runtime compilation removed As a consequence of cleaning up the ASP.NET Core shared framework to not depend on Roslyn, support for runtime compilation of pages and views has also been removed in this preview release. Instead compilation of pages and views is performed at build time. In a future preview update we will provide a NuGet packages for optionally enabling runtime compilation support in an app.

You can read more about the issue here https://github.com/aspnet/Announcements/issues/343

Applications that require runtime compilation or re-compilation of Razor files should:

• Add a reference to the Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation package. It'll be available as part of the 3.0.0-preview3 release.
• Update the application's ConfigureServices to include a call to AddMvcRazorRuntimeCompilation:

Answer 2

For ASP.NET Core 3 release version:

   services.AddControllersWithViews().AddRazorRuntimeCompilation();

https://docs.microsoft.com/en-us/aspnet/core/mvc/views/view-compilation?view=aspnetcore-3.0

It can also be enabled conditionally only for local development, quoted from the link:

Runtime compilation can be enabled such that it's only available for local development. Conditionally enabling in this manner ensures that the published output:

Uses compiled views.
Is smaller in size.
Doesn't enable file watchers in production.

   public Startup(IConfiguration configuration, IWebHostEnvironment env)
    {
        Configuration = configuration;
        Env = env;
    }

    public IWebHostEnvironment Env { get; set; }
    public IConfiguration Configuration { get; }

    public void ConfigureServices(IServiceCollection services)
    {
        IMvcBuilder builder = services.AddRazorPages();

#if DEBUG
            if (Env.IsDevelopment())
            {
                builder.AddRazorRuntimeCompilation();
            }
#endif
    }

Answer 3

To get runtime view compilation back in ASP.NET Core 3

1. Reference Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation
2. Call services.AddMvc().AddRazorRuntimeCompilation()
3. Remove Microsoft.VisualStudio.Web.CodeGeneration.Design if there's a version mismatch on the Microsoft.CodeAnalysis.Common package

Answer 4

Runtime compilation is enabled using the Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation package. To enable runtime compilation, apps must:

1. Install the Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation NuGet package.

2. Update the project's Startup.ConfigureServices method to include a call to AddRazorRuntimeCompilation:

services
    .AddControllersWithViews()
    .AddRazorRuntimeCompilation();

https://docs.microsoft.com/en-us/aspnet/core/mvc/views/view-compilation?view=aspnetcore-3.0

Answer 5

To get runtime Razor Views Compilation back in ASP.NET Core 3.1:

1. Install the Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation NuGet package.
2. Update the project's Startup.ConfigureServices method to include a call to AddRazorRuntimeCompilation.

3. services.AddRazorPages().AddRazorRuntimeCompilation();

   Razor file compilation in ASP.NET Core 3.1

Answer 6

Step 1: Install the below package from NuGet Package Manager for Solution.

Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation

Step 2: Add the below code in ConfigureServices of Startup.cs file

services.AddControllersWithViews().AddRazorRuntimeCompilation();

Save the page and then refresh the client browser.

If you are using Razor then add the code for services.AddRazorPages().AddRazorRuntimeCompilation();

Answer 7

In .NET Core 3.1, you need disable generation of the views.dll file.

1. Add the below code to your .csproj file (in the root of your project):

   <PropertyGroup>
       <TargetFramework>netcoreapp3.1</TargetFramework>
       <UserSecretsId>...</UserSecretsId>
   
       <!-- add from this line: -->
       <CopyRazorGenerateFilesToPublishDirectory>true</CopyRazorGenerateFilesToPublishDirectory>
       <CopyRefAssembliesToPublishDirectory>false</CopyRefAssembliesToPublishDirectory>
       <MvcRazorCompileOnPublish>false</MvcRazorCompileOnPublish>
       <RazorCompileOnBuild>false</RazorCompileOnBuild>
       <!-- to this line. -->
   
   </PropertyGroup>
   

2. Install the below package from the NuGet Package Manager for the Solution.

   Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation
   

3. Add the below code to the ConfigureServices method of your Startup.cs file:

   services.AddMvc().AddRazorRuntimeCompilation();
   

   Or

   services.AddControllersWithViews().AddRazorRuntimeCompilation();
   

   Or

   services.AddRazorPages().AddRazorRuntimeCompilation();
   

After this, publish again and run it. It will work.

Answer 8

Just an added note -- you may want to only conditionally enable this runtime compilation, so that the published output:

• Uses compiled views.
• Is smaller in size.
• Doesn't enable file watchers in production.

Conditionally enable runtime compilation

Answer 9

Simpliest way to configure Runtime Compilation for Local Development only is to update launch profiles in launchSettings.json. This method requires no code changes to configure a project which is running locally (it will not affect your production).

See the official documentation:

1. Install the Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation NuGet package.
2. Modify the launch profile environmentVariables section in launchSettings.json:
   • Verify ASPNETCORE_ENVIRONMENT is set to "Development".
   • Set ASPNETCORE_HOSTINGSTARTUPASSEMBLIES to "Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation".

Example:

{
  "iisSettings": {
    "windowsAuthentication": false,
    "anonymousAuthentication": true,
    "iisExpress": {
      "applicationUrl": "http://localhost:57676",
      "sslPort": 44364
    }
  },
  "profiles": {
    "IIS Express": {
      "commandName": "IISExpress",
      "launchBrowser": true,
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development",
        "ASPNETCORE_HOSTINGSTARTUPASSEMBLIES": "Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation"
      }
    },
    "RazorPagesApp": {
      "commandName": "Project",
      "launchBrowser": true,
      "applicationUrl": "https://localhost:5001;http://localhost:5000",
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development",
        "ASPNETCORE_HOSTINGSTARTUPASSEMBLIES": "Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation"
      }
    }
  }
}