Mark all AddRazorRuntimeCompilation extension methods and related APIs as obsolete for consistent Razor runtime compilation deprecation in .NET 10

[joperezr]

Background and Motivation

As raised in dotnet/aspnetcore#64338: Razor runtime compilation is being fully deprecated in .NET 10 with the intent to remove it in a future release. While some extension methods currently show the obsolete warning, others (e.g., AddRazorRuntimeCompilation with no arguments) do not, leading to confusion for end users.

Bug Details

• Only some overloads (those taking Action) display an obsolete warning due to the argument type being obsolete.
• Parameterless method overloads for AddRazorRuntimeCompilation do NOT display any warning.
• API users can unknowingly continue using obsolete runtime compilation APIs with no warning.

Solution Proposal

• Mark ALL overloads of AddRazorRuntimeCompilation and related extension methods with the ASPDEPR003 [Obsolete] attribute (not just on the parameter type or static class).
• Ensure every use of AddRazorRuntimeCompilation (parameterless or otherwise) triggers the intended obsolete warning in .NET 10 and future releases.
• Reference obsolete warning to Hot Reload as the recommended alternative for development workflows.

Code references

Relevant source files needing updates:

• RazorRuntimeCompilationMvcBuilderExtensions.cs
• RazorRuntimeCompilationMvcCoreBuilderExtensions.cs

Example usage

mvcBuilder.AddRazorRuntimeCompilation(); // Should generate ASPDEPR003 obsolete warning
mvcBuilder.AddRazorRuntimeCompilation(options => {}); // Should generate ASPDEPR003 obsolete warning

Risks

• Breaking change for developers using runtime compilation extension APIs for development
• Required migration pain for scenarios relying on runtime view loading (e.g. from a database, custom provider, or dynamic sources)

Related context

• dotnet/aspnetcore#64338
• Announcement: [Breaking change]: Razor runtime compilation is obsolete aspnet/Announcements#522