Using Latest C# Features in Any Old .NET Version

Check out my courses: dometrain.com
Become a Patreon and get source code access: / nickchapsas
Join the NDC Conferences Giveaway: mailchi.mp/nickchapsas/ndc
Hello everybody I'm Nick and in this video I will show you how you can use the latest C# 11 in your old codebases such as .NET Framework or UWP.
Give PolySharp a star on GitHub: github.com/Sergio0694/PolySharp
Workshops: bit.ly/nickworkshops
Don't forget to comment, like and subscribe :)
Social Media:
Follow me on GitHub: bit.ly/ChapsasGitHub
Follow me on Twitter: bit.ly/ChapsasTwitter
Connect on LinkedIn: bit.ly/ChapsasLinkedIn
Keep coding merch: keepcoding.shop
#csharp #dotnet

[@carldaniel6510]

I love this package. Most of the apps I maintain are stuck at framework 4.8 and will likely never move to anything derived from Core, so this is very handy. I'm OK with not having new language features that require CLR changes, but language features that are purely compiler and library changes should be available on all platforms and I will definitely use them. Makes moving back & forth between framework and core so much less painful.

[@wojciechwilimowski985]

You almost made 1st place on my "top 3 mind blown moments this week", but a few days ago I learned that if you add a Select method to any class, you can use it in LINQ Query Syntax and my head exploded

[@novalogic1265]

Can you send an example for Select?

[@maxsteffey6521]

WAIT WHAT example??

[@ProtossOP]

We need more info my dude, share the wisdom.

[@protox4]

Nice find. C# has a lot of hidden duck-typed features like that. For example, you can use a foreach loop over an object that doesn't implement IEnumerable, as long as it has a GetEnumerator method that returns a type that has a MoveNext method and Current property. That also works with extensions, so you can add an extension to add foreach support on any type. Same thing with await extensions.

[@bWFyY29u]

.

[@MAO-sz3wr]

That's exactly what I needed, without knowing that I needed it. Thanks a lot, Nick!

[@zwatotem]

How did you get that timing so well? I was just using C#11 in .NETStandard2.0 and got stuck on list patterns. I took a break and here is the exact video I needed. Thank you! (Also shout out to PolySharp)

[@Delphi80SVK]

Same here, i got task to try to convert our project from NET5 for NETStandard2.0 (for compatibility reasons with older projects) and it fails to compile for using C#11 language features. Just hour ago i started to remove all new stuff i am using from c#11 and back to C#7.3 😀Now i can stay at c#11 in NETStandard 2.0. I will try PolySharp for my situation if it works for me or not.

[@Delphi80SVK]

Problem here seems to be that when u start using new stuff like ReadOnlySpan (not language stuff) you are out of luck in older projects, as i am now ;-)

[@Luke-me9qe]

Well, do you know the movie The Truman Show?

[@zachemny]

@@Delphi80SVK For ReadOnlySpan you can use official Microsoft's System.Memory nuget package. It can be used from .NET FW 4.5.

[@Brondahl]

Ditto. Literally 3 hours ago was talking with a team mate about bumping our C# version up past what is nominally supported!

[@cn-ml]

This is perfect, exactly what i just needed now. Thank you

[@1Gargo]

Thank you for this knowledge! I was just wishing the other day to be able to do exactly that. You saved my sanity!

[@drm1983]

Amazing! just what I was looking for. After working a a project with .Net6 it feels a bit bitter to work in .Net Framework 4.7. This will really help.

[@astralpowers]

I didn't know about this package. I used another package Nullable package to support nullable annotations, but this goes beyond that. Will be updating my project to use this.

[@antonmartyniuk]

This library is awesome, I was really handy for me today. Never knew before it

[@luc9volts]

That depends on the compiler installed on your machine. If you make these changes and a colleague of yours doesn't have the correct compiler, it could be a problem.

[@Petoj87]

Thanks for another great video, haven't tried it yet but seems like a life saver for source generators as they are stuck on standard 2.0 if I remember correctly.

[@mariocamspam72]

Sergio would be proud

[@Sergio0694]

I am 😄

[@F1nalspace]

Wow thats new for me, i knew you could change the language version - but i always got that those errors you are talking about. Great that there is a way to solve that ;-) Really thanks for getting that out!

[@jongeduard]

Thanks a lot for this very practical tip!! Indeed I didn't know about this single and so complete dedicated package. (Still need to support a lot of hybrid old and modern projects at work) I have been using individual packages instead like IndexRange and searched samples of those manual code fixes including that IsExternalInit one. Though it's strange but kind of an exception to the rule seems the System.Memory package from microsoft itself that gives kind of official backwards compatibility support for older versions to be able to use Span and Memory, even though it's not really mentioned in their documentation.

[@computer9764]

Very cool It's still something I wish was just supported out of the box, though

[@furious385]

As usually interesting and useful content.

[@sumittandon6246]

Good Recco, Thanks Nick

[@davidb.1905]

Awesome ! Thanks you very much 👍.

[@mickaelveril7766]

I use IsExternalInit in order to have a record in MobileDeviceSharp one of my C# library (because I want to be backward compatible to NET Standard 2) but maybe I can switch to this solution ! Thanks you Nick !

[@gavinlangley8411]

oo very nice Nick thanks

[@quelqunderandom6143]

5:06 instructions unclear typed source...net, website not found

[@nickchapsas]

HAHAHAHAHA

[@renetittel17]

Danke!

[@metalhead6604]

Damn that is really cool!

[@billy65bob]

It's worth bumping the C# version anyway. While there are some that depend on these stubs, and others that require runtime changes, there are also many features that require neither.

[@razveck]

This is insane!

[@user-pp9sx4ky9w]

The best!

[@darioabbece3948]

Finally .Net sandbox version is now

[@modernkennnern]

I heard about this about a month ago and replaced `IsExternalInit` and `Nullable` on the project I'm working on at work. Finally being able to use required 👏

[@ParkImaging]

Very nice!

[@kostasgkoutis8534]

Nice video. I knew about the first approach you have shown (adding on your own types + namespace) but last time I checked it with Razor views on an old MVC project, records just didn't work. There is some other trick there that you could pull off by introducing some other Nuget package but I cannot remember the name.. Oh well.

[@davidwilliss5555]

I gotta try this! I work on a project that's stuck in .NET 4.8 and because we have so much 4.8 code and I would love to use new language features. It seems like Microsoft could just provide a nuget package with all these things.

[@soverain]

I did the trick for init only setters but in Unity, which is stuck on a incomplete C# 9 implementation and dotnet 4.x I think.

[@EdKolis]

This is magic. What next, a Python package that lets you say "from csharp import eleven"? 😛

[@tmhchacham]

Nice!

[@vm123]

Can Polysharp enable extended pattern matching for fw472? Range pattern and nested properties?

[@inzyster]

Yes.

[@Dimich1993]

This is cool! Anyway hopefully I won't have to program any .NET Framework code ever again!

[@user-ys6nh6fe5o]

holly cow!

[@dekryptid]

If you're not using Rider, instead using Visual Studio 2022, how can one adjust the language version with the dropdown disabled?

[@nickchapsas]

You can use the LangVersion csproj parameter

[@nanvlad]

Does it work with Mono? Cool feature!

[@adrian_franczak]

Remember to update msbuild in pipelines xD!

[@nickchapsas]

Big true!

[@bluecup25]

Mind = blown

[@marvinbrouwer459]

I actually did some of this to use C# 10 in a multi-framework sln. And when I was finished I heard of this package 😅 Do you think it makes sense to migrate to this package maybe?

[@rhoward99]

This is great information! I noticed that you are using Rider, and it made switching language versions really simple. Can you suggest how to make this same change to the project using VS 2019? EDIT: Never mind. Should have Googled it myself first!

[@nickchapsas]

I haven't used VS in more than 4 years but you can always simply set the LangVersion parameter in the csproj

[@tcl78]

@@nickchapsas out of curiosity, why did you switch to Rider, which you need to pay for via a monthly or yearly subscription, when Visual Studio Community is free and is supported directly by Microsoft?

[@nickchapsas]

@@tcl78 Because I make up the money of the Rider subscription by how much better Rider is than VS and how much more productive it makes me

[@tcl78]

@@nickchapsas interesting, perhaps one day you can make a video about the differences between Visual Studio, VS Code and Rider? Thanks

[@vm123]

It does not work for me at all. Keep throwing Error CS1617 Invalid option '11.0' for /langversion. I’m using latest vs 2022 preview and after adding lang version 11 to csproj file, visual studio keeps throwing Invalid option error. Does it even suppose to work in visual studio? I needed expressionCallerAttribute but due to error above I manually copied the content of generated attribute and added to project. It looks to be working.

[@arithex]

It is mystifying to me that MS broke the line of compatibility of C# back to .Net Framework.. I kinda suspected 90% of the recent language innovations were all implemented at compiler-level, not runtime.. but this confirms it actually looks more like 99%.

[@ROBdk97]

How does the performance look here then? Is it worse or the same compared to the .Net version that has official support for this?

[@trevorprice2490]

Very useful and interesting. Are there any drawbacks or gotchas to doing this?

[@strayj2767]

leaving a comment here in case this gets answered. Hopefully there isn't any performance drawbacks or whatnot

[@nickchapsas]

The main drawback is that it’s not officially supported by Microsoft

[@protox4]

Possible type clashes if some libraries do the same trick. No performance penalties, it's just metadata.

[@palecskoda]

I believe there are major drawbacks to using this approach in libraries as it causes the consumers to be unable to use the original types easily even if the consumer uses a .NET version where they are already available.

[@lexer_]

Is it possible to use Span in async methods in .net 4.8 somehow?

[@Sergio0694]

No, you cannot use Span in any async method anywhere, that's by design. You will have to use Memory in those scenarios, or equivalent types.

[@godfreyofbouillon966]

I am getting lost between all these .net framework, .net core and .net standard versions. If I start a new desktop gui app project now, that's likely to last and need to be supported / improved for years to come, what's the best .NET to use? Is .Net Framework 4.8 with Win Forms good enough for this purpose or is it gonna be abandoned soon? End user is supposed to run Windows but if I can make it cross platform with little to no additional work, all the better.

[@murrty]

I'm pretty sure all C# features are able to be used on Framework since the compiler is shared between Framework and NET, as long as you want to go down the rabbit hole of implementing them into Framework. The only thing keeping me from upgrading to NET 6 is the fact that MainMenu and ContextMenu were removed on WinForms. There was no reason for them to remove both of those controls and I haven't found a way to bring them back. I'm sure it's possible to forward-port them, but I haven't tried since WinForms controls are more intricate than mostly empty classes.

[@modernkennnern]

As long as it doesn't require a change to the runtime, yes. Which effectively means every change to C# other than the 2 interface-related ones; Static members and default members

[@Sergio0694]

@@modernkennnern There's actually a few more as well. For instance, covariant return types for interfaces, ref fields, generic attributes and numeric IntPtr/UIntPtr are also not supported. But yeah that's relatively a small part out of all the new features, which will indeed work downlevel too 🙂

[@murrty]

​@@Sergio0694 Alongside the static and default interface members (so close, yet so far away), ref fields is added to that list. Generic attributes (I haven't fully tested it, but it compiles with an empty class so, ayo) and numeric pointers do work on framework if you change the langversion in csproj. I would be lost without numeric pointer.

[@limbique]

Wasn't able to use this in Visual studio 2019.

[@tuberklz]

wow

[@anilpillay2193]

Out of curiosity, on production environment which FW version should we install to run. Should we install .Net FW 3.5 and .Net 7 or just .Net 3.5? My hunch is just .Net FW 3.5

[@qj0n]

your hunch is correct

[@gctypo2838]

Entirely depends on what you're running and how far into development you are. If your code is built on Fw3.5, use Fw3.5. If your code is built on .NET 7, install .NET 7 (though I'd advise instead targeting LTS .NET 6). If you haven't started writing your software yet, target an LTS version on the mainline - you'll save the devs that follow you a lot of headaches and frustration; working with legacy framework versions is pain.

[@abhishekbagchi6052]

Does anyone know how can change the language version from Visual Studio?

[@Masterrunescapeer]

Just edit in the csproj file, 11 # Inside the project tags

[@derangedftw]

Has anyone released a backported library for this? Should have watched the whole video. Poly#

[@oddikaro8236]

One question Nick maybe slighlty away from topic: there is an interesting paradox between .NET vs .NET Framework. While .NET is newer, LTS versions have support "only for" 3 years, while .NET Framework, "old and forgotten" has "infinite support" from Microsoft since a big % of important apps were developed in .NET Framework so Microsoft is "forced" to provide eternal support. Can you give your opinion on this?

[@goodstas]

Thank you for your video. I followed it and tried to do the same but it doesn't work for me.. i mean to use PolySharp. The first trick (to add implementation by myself) i already used in the past. I created Console App for .NET Framework 4.7.2 and added to the project file 11.0. I installed the PolySharp package .I don't see that it produces some source generators files and i got the exceptions from the compiler.. will be appreciate for advise what's i could do wrong. I didn't see the Polysharp in my Reference list but there is packages.config file and there is a reference there.

[@adrgri]

You have to migrate your project to PackageReference because for some reason source generators don't want to work with packages.config. Right click on your packages.config and select the migrate option. Keep in mind that only VS 2017 and up and understand PackageReference, so if you're using VS 2015, you're out of luck

[@Tsunami14]

Certainly interesting from an academic perspective, but it still seems like you're playing with fire (even with PolySharp) since you're Frankensteining different compiler/language versions together in a way that's not been battle-tested by Microsoft. If it's a pure syntactic sugar change, and I fully understood what the underlying lowered code would be, then ...maybe?

[@theMagos]

There hasn't been a single patch/update of VS2022 that hasn't introduced a new annoying bug, so "battle-tested by Microsoft" doesn't hold much in my book

[@zariumsheridan3488]

Yeah, I would not want to be the one who added this in a real big project if there is a risk this might be identified as a reason for some high impact heisenbug after a long and expensive investigation...

[@Rovsau]

Would this work for projects in Unity?

[@Max-bx2dc]

I bet not :(

[@protox4]

Yes, this is actually required to get some C# 9 features working. (And even some C# 7 features before they updated the CLR)

[@soverain]

Did the trick for init only setters. Don’t know if it would work for other things. Damn I want those file namespaces so bad.

[@Rovsau]

@@protox4 Are there any drawbacks to doing this? How far have you tested it?

[@protox4]

@@Rovsau The only drawbacks are if you import multiple libraries that also hacked in the language support and you get type clashes. This doesn't work with language features that require actual runtime support and not just metadata (like default interface methods).

[@DmitriiP]

.Net Framework v3.5 compact? :)

[@adrgri]

I'd give you a 100 likes for this instead of just one if I could. Thanks so much for sharing this because I am actually stuck on C# 6 right now This almost sounds too good to be true, are there any drawbacks of doing this other than the compilation errors "target runtime doesn't support [...]"?

[@asedtf]

Microsoft: Please stop using .NET Framework! Us: lol no

[@egor5622]

What's about $"{name}" ?

[@nickchapsas]

What about it?

[@FernandoTakeshiSato]

Super interesting...but I'm kind of afraid of pushing stuff like this to prod :/

[@focl2003]

Hi bro, are you using it?, any problems?

[@FernandoTakeshiSato]

@@focl2003 not using it, sorry

[@sumittandon6246]

Can anyone point me to the package src ?

[@nickchapsas]

It’s in the video description

[@sumittandon6246]

@@nickchapsas Thank you buddy 😉

[@hichaeretaqua]

In the end, all code is just text that the compiler makes meaning of.

[@focl2003]

Most of it.

[@TechySpeaking]

First

[@BeanCoffeeBean]

Even though this gives us the advantage to use new C# features, it will sadly not give us the performance boost of newer versions of .NET :(

[@ibrahimhussain3248]

I think I used somrthing like LangVer=preview on a project before for this

[@FabioMaulo]

Ok but... if you have a 4.7.2 prj the best thing to do is convert it to NET6. We did it in 2022 moving fast converting all libraries to netstandard2.0, then surface prj (web a no web) from 4.7.2 to netcore3.5, and then to NET6. If you have an old prj you have to convert it to the new NET as soon as possible.

[@crifox16]

how painful was it really? i'm stuck with net framework 4.8 at work so i'd be curious to hear some experiences

[@FabioMaulo]

@@crifox16 it was a process. You have to start moving all base DLL (no EXE/WEB) to netstandard2.0

[@oddikaro8236]

Why would you want to convert it to .NET 6? I mean... .NET Framework has infinite support while .NET 6 only 1-year more...I don't see any reason if you have a big project in .NET Framework already working. Can you provide your opinion?

[@crifox16]

@@oddikaro8236 multi platform support is the first thing that comes to mind

[@oddikaro8236]

@@crifox16 ya..but...why would you need that? Your 10-years app is already working somewhere...

[@XxJackDjTomxX]

Hi Nick, I've seen your amzaing video about foreach loops with Ranges (Adding a BETTER way to loop in C# -> kzbin.info/www/bejne/oJ7Qq2SZftOBpdk) and I tried to loop like this: foreach (var i in -10..-5) but that didn't work since Range doesn't support negative numbers. So I was wondering if you know any way to make this foreach loop work with negative ranges?

[@klocugh12]

> Sharpen your skills I see what you did there.

[@nickchapsas]

AYE

[@brianm1864]

I had to watch this on 1.5 speed because I died a little bit inside thinking about still having to work in .NET Framework

[@realharami]

Nick, you know black magic is forbidden, do not you?

[@sacharkin]

Why you should do this? Get rid of legacy projects and upgrade to the latest .NET version ;)

[@nickchapsas]

Sometimes it is impossible to move. No every company can afford the change and it doesn't make sense for every company either

[@adrgri]

@@argamon2025 Why wouldn't it work with third party libraries? Those dependencies are typically separate assemblies, compiled elsewhere 🤔

[@jarnohonkanen4321]

Get rid of .net framework is the goal but we are stuck because our hosting doesn't support .net core and probably never will... I have been working hard get rid all old legacy to be ready to switch more modern hosting environment but that is not easy job... Too much technical debt and a lot of assumptions about hosting environment details. I'm lucky that I have able to to use lang version 10. I'm haven't heard PollySharp before but I have used IsExternalInit and BackwardsCompatibleFeatures nugets to achieve similar results. I definitely give a try for this.

[@OleksiiKorniienko]

The only drawback of doing this is that I have to install the package in EVERY project in the solution.

[@PetrVejchoda]

WOW