Is multiple calls of AddRazorPages allowed?

Question

In Program.cs I'm calling to AddRazorPages to setup Fluent Validation and some localization stuff. Unfortunately this has a lot of repetive code and I'm wondering if it is perfectly legal to reduce it by calling AddRazorPages twice?

I have tried to run the code and it seems to work, but can any one confirm the new version is effectively the same as the old version?

Current Program.cs

if (isDevelopment)
    // Run-time compilation added during development
    builder.Services.AddRazorPages(options => options.Conventions.Add(new CultureTemplatePageRouteModelConvention()))
        .AddFluentValidation(fv =>
        {
            fv.RegisterValidatorsFromAssemblyContaining<PersonValidator>();
            fv.LocalizationEnabled = true;
            fv.DisableDataAnnotationsValidation = false;
        })
        .AddViewLocalization(LanguageViewLocationExpanderFormat.Suffix)
        .AddDataAnnotationsLocalization()
        .AddRazorRuntimeCompilation();
else
    // No Run-time compilation needed when deployed
    builder.Services.AddRazorPages(options => options.Conventions.Add(new CultureTemplatePageRouteModelConvention()))
        .AddFluentValidation(fv =>
        {
            fv.RegisterValidatorsFromAssemblyContaining<PersonValidator>();
            fv.LocalizationEnabled = true;
            fv.DisableDataAnnotationsValidation = false;
        })
        .AddViewLocalization(LanguageViewLocationExpanderFormat.Suffix)
        .AddDataAnnotationsLocalization();

New Program.cs

builder.Services.AddRazorPages(options => options.Conventions.Add(new CultureTemplatePageRouteModelConvention()))
    .AddFluentValidation(fv =>
    {
        fv.RegisterValidatorsFromAssemblyContaining<PersonValidator>();
        fv.LocalizationEnabled = true;
        fv.DisableDataAnnotationsValidation = false;
    })
    .AddViewLocalization(LanguageViewLocationExpanderFormat.Suffix)
    .AddDataAnnotationsLocalization();

// Run-time compilation added during development
if (isDevelopment)
    builder.Services.AddRazorPages().AddRazorRuntimeCompilation();

Answer 1

You can call AddRazorPages as many times as you like. Internally, it uses a series of TryAdd* calls to add the various services that the method is responsible for registering. If the service is already registered with the service container, nothing happens.

https://github.com/dotnet/aspnetcore/blob/207f2c39ee1eccbc339450570fe6297026ea549c/src/Mvc/Mvc.RazorPages/src/DependencyInjection/MvcRazorPagesMvcCoreBuilderExtensions.cs#L95