How to use code file that inherits `Custom.Dnn.Code12` within `Custom.Dnn.Razor12` file? - dotnetnuke

Question

I want to write a custom view using new version of razor page in 2sxc module. My view "_MyView.cshtml" inherits Custom.Dnn.Razor12. So I've created a file "_MyView.code.cshtml" which starts with #inherits Custom.Dnn.Code12 (tried #inherits ToSic.Sxc.Dnn.RazorComponent as well but didn't help).
So when I'm trying to call something like this within "_MyView.cshtml":
#{
Code.MyMethod();
}
it gives me error:
Error: System.Web.HttpCompileException (0x80004005): d:\Projects\mywebsite.com.ua\Host\Portals\2\2sxc\MyApp_MyView.cshtml(5): error CS0103: The name 'Code' does not exist in the current context at System.Web.Compilation.AssemblyBuilder.Compile() at System.Web.Compilation.BuildProvidersCompiler.PerformBuild() at System.Web.Compilation.BuildManager.CompileWebFile(VirtualPath virtualPath) at System.Web.Compilation.BuildManager.GetVPathBuildResultInternal(VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile, Boolean throwIfNotFound, Boolean ensureIsUpToDate) at System.Web.Compilation.BuildManager.GetVPathBuildResultWithNoAssert(HttpContext context, VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile, Boolean throwIfNotFound, Boolean ensureIsUpToDate) at System.Web.Compilation.BuildManager.GetVirtualPathObjectFactory(VirtualPath virtualPath, HttpContext context, Boolean allowCrossApp, Boolean throwIfNotFound) at System.Web.Compilation.BuildManager.GetCompiledType(VirtualPath virtualPath) at ToSic.Sxc.Engines.RazorEngine.CreateWebPageInstance() in C:\Projects\2sxc\2sxc\Src\Dnn\ToSic.Sxc.Dnn.Razor\Engines\Razor\RazorEngine.cs:line 146 at ToSic.Sxc.Engines.RazorEngine.InitWebpage() in C:\Projects\2sxc\2sxc\Src\Dnn\ToSic.Sxc.Dnn.Razor\Engines\Razor\RazorEngine.cs:line 155 at ToSic.Sxc.Engines.RazorEngine.Init() in C:\Projects\2sxc\2sxc\Src\Dnn\ToSic.Sxc.Dnn.Razor\Engines\Razor\RazorEngine.cs:line 80 at ToSic.Sxc.Engines.EngineBase.Init(IBlock block) in C:\Projects\2sxc\2sxc\Src\Sxc\ToSic.Sxc\Engines\EngineBase.cs:line 77 at ToSic.Sxc.Blocks.BlockBuilder.GetEngine() in C:\Projects\2sxc\2sxc\Src\Sxc\ToSic.Sxc\Blocks\BlockBuilder_Render.cs:line 227 at ToSic.Sxc.Dnn.Web.DnnClientResources.NeedsPre1025Behavior() in C:\Projects\2sxc\2sxc\Src\Dnn\ToSic.Sxc.Dnn.Core\Dnn\Web\DnnClientResources.cs:line 95 at ToSic.Sxc.Dnn.View.<>c__DisplayClass13_0.<Page_Load>b__1() in C:\Projects\2sxc\2sxc\Src\Dnn\ToSic.Sxc.Dnn\View.ascx.cs:line 82 at ToSic.Sxc.Dnn.View.TryCatchAndLogToDnn(Action action, LogCall timerWrap) in C:\Projects\2sxc\2sxc\Src\Dnn\ToSic.Sxc.Dnn\View.ascx.Errors.cs:line 22 - CONTEXT: Page: 126; Module: 1724
I understand that if I keep using old classes it might work now but it might stop working later. So how do I use this one?
I tried to look through 2sxc documentation and github code, but I didn't find a single example of it.
So what am I doing wrong? How do I use it?

Answer 1

The Code.xxx convention was introduced around v11 because it looked like a good idea. It kind of felt like a separation of code and layout.
https://docs.2sxc.org/net-code/razor/code-behind.html
Basically it was a kind of simplification, but not major, since you could already just do something like var code = CreateInstance("razorfile.cshtml"); to get the same effect.
But as we went to v12 and supported Oqtane - which was .net Core 3.0 at that time, we realized that this will never work on Oqtane. To us it's really important to keep the API consistent across platforms because otherwise the docs get really confusing.
Since it was such a minor feature, we decided to not support it any more on newer base classes.
So if you do have shared code, just use a something.cs file and use CreateInstance("something.cs").
For a simulated code-behind which utilizez Razor features you can still create a _xyz.code.cshtml and also instantiate it with CreateInstance(...) but this would never work in Oqtane.