CODE.RNR

Render Razor view from a dotnet core 3 console app

Posted by codernr on 2020-04-17 12:45

My colleague and I were wondering how we could use our existing, predefined Razor views in a console application that is ran to do some background job. Typical use case: automated regular email sending. We were searching for the solution but all we found were examples of this case in dotnet core 2.1. So we had to do some investigation on how to upgrade to netcoreapp3.1.

The example project was one of the aspnet entropy experimental repository: https://github.com/aspnet/Entropy/tree/master/samples/Mvc.RenderViewToString

You can find the source of the updated project in my repo: https://github.com/codernr/dotnet-mvc-renderviewtostring

Differences

Long story short, you can see all the changes needed to be made in this commit. But let's see the inside:

The .csproj file

As the documentation says, A project that includes Razor views or Razor Pages must use the Microsoft.NET.Sdk.Razor SDK. In addition you have to set AddRazorSupportForMvc property to true and include the FrameworkReference for the 1shared framework. The whole .csproj file looks like this:

<Project Sdk="Microsoft.NET.Sdk.Razor">

  <PropertyGroup>
    <OutputType>exe</OutputType>
    <TargetFramework>netcoreapp3.1</TargetFramework>
    <AddRazorSupportForMvc>true</AddRazorSupportForMvc>
  </PropertyGroup>

  <ItemGroup>
    <FrameworkReference Include="Microsoft.AspNetCore.App" />
  </ItemGroup>

</Project>

The main program

The way you can configure RazorViewEngine has changed since dotnet core 2.1, now you can't set the FileProvider through RazorViewEngineOptions. This is set through IWebHostEnvironment.ContentRootFileProvider, where IWebHostEnvironment is the dependency that replaces the old IHostingEnvironment (you can check the diff here). Since the implementing classes are internal, you have to create a custom implementation and add it to the service collection.

There are two other changes in the DI configuration that are needed for the RazorViewEngine to work:

• A DiagnosticListener
• And insted of services.AddMvc() it is enough to use services.AddMvcCore().AddRazorViewEngine() so you can reduce the registered services

See the whole dependency injection container setup here:

private static void ConfigureDefaultServices(IServiceCollection services, string customApplicationBasePath)
{
    string applicationName;
    string rootPath;

    if (!string.IsNullOrEmpty(customApplicationBasePath))
    {
        applicationName = Path.GetFileName(customApplicationBasePath);
        rootPath = customApplicationBasePath;
    }
    else
    {
        applicationName = Assembly.GetEntryAssembly().GetName().Name;
        rootPath = Directory.GetCurrentDirectory();
    }

    var fileProvider = new PhysicalFileProvider(rootPath);

    var environment = new CustomHostingEnvironment
    {
        WebRootFileProvider = fileProvider,
        ApplicationName = applicationName,
        ContentRootPath = rootPath,
        WebRootPath = rootPath,
        EnvironmentName = "DEVELOPMENT",
        ContentRootFileProvider = fileProvider
    };

    services.AddSingleton<IWebHostEnvironment>(environment);

    var diagnosticSource = new DiagnosticListener("Microsoft.AspNetCore");
    services.AddSingleton<ObjectPoolProvider, DefaultObjectPoolProvider>();
    services.AddSingleton<DiagnosticSource>(diagnosticSource);
    services.AddSingleton<DiagnosticListener>(diagnosticSource);
    services.AddLogging();
    services.AddMvcCore()
        .AddRazorViewEngine();
    services.AddTransient<RazorViewToStringRenderer>();
}

Happy email sending!

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