[Dev] Projects use `LangVersion=latest` but are not C# 14.0 compliant

[gman-comicdb]

Describe the bug

Compiler throws errors and fails to build assemblies when trying to build ComicRackCE.
Related to C# 14.0 Enumerable.Reverse breaking change.

Exact Steps to Reproduce

VS 2022

1. Have the latest VS 2022 installed (17.14.20)
   • MSBuild version: 17.14.23.0
2. Clone and try to build any branch

VS 2026

1. Have the latest VS 2026 installed (11206.111)
   • MSBuild version: 18.1.0.0
2. Clone and try to build any branch

Screenshots

cYo.Common.Windows and ComicRack project errors get raised once these are fixed. See end for relevant lines of code.

As text

Severity	Code	Description	Project	File	Line	Suppression State
Error (active)	CS1579	foreach statement cannot operate on variables of type 'void' because 'void' does not contain a public instance or extension definition for 'GetEnumerator'	cYo.Common	cYo.Common\Mathematics\Numeric.cs	261	
Error (active)	CS1936	Could not find an implementation of the query pattern for source type 'void'.  'Select' not found.	cYo.Common.Presentation	cYo.Common.Presentation\Panels\OverlayManager.cs	227	
Error (active)	CS1579	foreach statement cannot operate on variables of type 'void' because 'void' does not contain a public instance or extension definition for 'GetEnumerator'	cYo.Common.Presentation	cYo.Common.Presentation\Panels\OverlayPanel.cs	690	

Version

VS 2022 17.14.20 + MSBuild 17.14.23.0
VS 2026 11206.111 + MSBuild 18.1.0.0

Additional context

Enumerable.Reverse

When using C# 14 or newer and targeting a .NET older than net10.0 or .NET Framework with System.Memory reference, there is a breaking change with Enumerable.Reverse and arrays.

• C# 14.0 has been out for a while; this only became a problem on upgrading to the latest VS 2022.

• Bug might only impact those using VS 2022/2026 and with the .NET 10 SDK installed

Relevant lines of code

ComicRackCE/ComicRack/Dialogs/Splash.cs

Line 256 in 9cca27e

string[] array = message.Split('\n').Reverse().Take(messageLines)

ComicRackCE/ComicRack/Views/ComicBrowserControl.cs

Line 1669 in 9cca27e

foreach (ComicBook item in source.Reverse())

ComicRackCE/ComicRack/Views/ComicBrowserControl.cs

Line 1686 in 9cca27e

foreach (ComicBook item in source.Reverse())

ComicRackCE/cYo.Common/Mathematics/Numeric.cs

Line 261 in 9cca27e

foreach (bool item in flags.Reverse())

ComicRackCE/cYo.Common.Windows/Forms/TextBoxContextMenu.cs

Line 197 in 9cca27e

foreach (ToolStripMenuItem item in array2.Reverse())

ComicRackCE/cYo.Common.Presentation/Panels/OverlayManager.cs

Line 226 in 9cca27e

return (from op in panels.ToArray().Reverse()

ComicRackCE/cYo.Common.Presentation/Panels/OverlayPanel.cs

Line 690 in 9cca27e

foreach (OverlayPanel item in panels.ToArray().Reverse())

[gman-comicdb]

This can be fixed by updating the problematic code to be C# 14.0 compliant, or specifying C# 13.0 in the project files instead of latest.

Raising as I'm not sure if the problem is specific to my setup, and what the preferred fix is.

[maforget]

This was something I though might be happening at some point. I was awaiting for it to break to update it.

From the MS site about LangVersion:

Warning

Setting the LangVersion element to latest is discouraged. The latest setting means the installed compiler uses its latest version. The value of latest can change from machine to machine, making builds unreliable. In addition, it enables language features that might require runtime or library features not included in the current SDK.

C# 14.0 has been out for a while; this only became a problem on upgrading to the latest VS 2022.

I had an update queued and just updated to that version and I do not have the problem. Not sure how things that might be cached, but I did not yet installed 2026, which is probably the main reason. You probably have some new SDK installed.

On net10.0, there is Enumerable.Reverse(this T[]) which takes precedence and hence the break is avoided. Otherwise, MemoryExtensions.Reverse(this Span<T>) is resolved which has different semantics than Enumerable.Reverse(this IEnumerable<T>) (which used to be resolved in C# 13 and lower). Specifically, the Span extension does the reversal in place and returns void. As a workaround, one can define their own Enumerable.Reverse(this T[]) or use Enumerable.Reverse explicitly:

We'd need to create our own Reverse extension that specifically calls Enumerable.Reverse so it resolve the correct namespace without changing existing code.

I will change it to 13.0 for now, since it is not recommended using latest. Moved all related to a directory.build.props so it is easier to update and this is solution wide anyway.

There are some nice things in C#14 like extensions members, Null-conditional assignment & The field keyword. Not sure what is VS, compiler or SDK related and if a probable update to PolySharp could help support these new features. So will leave this open for a future C# 14 update.

[gman-comicdb]

Great, thanks for the quick fix.

I had an update queued and just updated to that version and I do not have the problem. Not sure how things that might be cached, but I did not yet installed 2026, which is probably the main reason. You probably have some new SDK installed.

Yep, this lines up with VS 2026 or .NET 10 SDK being the root cause¹.
I've had them installed for a while though and VS 2022 only started caring after updating today.
Now realize that's probably because C# 14 + .NET 10 were released today (officially no longer preview)

Footnotes

1. First ran into this many weeks when trying to build in VS 2026 and multi-target .NET 9 + .NET 10. ↩