It's a bit of an unfair comparison, the benchmarked C# code here is also post-processed which none of the other targets are. See this comment[1] on reddit where the author announced this on the /r/dotnet subreddit, Rust can go much, much lower. The title is misleading at best and a lie at worst, this is great but saying it beats Rust is a far cry from the truth except for the very narrow benchmark made to showcase this tool.
This is an entirely different toolchain from the official .NET one, which is kind of the point of the post. It is experimental, but intended to for production, not for beating benchmarks.
Rust also builds a pretty small binary, which is cool. This isn't really meant to be a 'C# is better than Rust' post, but more pointing out that Blazor (which is the official MS implementation) builds huge binaries; often >10MB, which is a real problem. This fixes that.
TFA did [0] the most important stuff for minimizing Rust binaries: release mode, LTO, strip, and abort on panic. But there is a lot more you can do if you really care about Rust binary size [1]: remove location details, purge the debug formatters, rebuild the standard library for size, abort with no error message at all, and nuttier stuff.
I think the benchmark game was really useful. It wasn't a which is better, it was what are the tradeoffs. Some of that was provided subjectively by curating it into safe and portable vs hyperoptimized categories. But there is also memory footprint etc. It was also a gauge of which languages people who care about performance preferred, as those got rapid updates.
Yes I think it's a bit underrated. The problem I find is that no one writes C# libraries that actually do anything (e.g. even basic linear algebra is pretty crap compared to python) and that the JIT is a pointless hindrance but the experience of using the stack is pretty good.
I agree completely regarding libraries, C# has never had the "libraries for everything", especially open source ones. The better libraries have moved to ( or always have been ) licensed too which doesn't help that impression.
I'd like to hear more about your issue with the JIT and where do you find it a hindrance?
I've had a few benchmarks lately that performed better under JIT than AOT compilation, and while that isn't always the case, the JIT, especially on dotnet 10, performs very well.
> The problem I find is that no one writes C# libraries that actually do anything
Yes, because when you think about it, why should they?
MS has showed many times how unreliable and even user-hostile they can be, so the community at large is very wary of their ecosystem in spite of real advancements.
I really like TS as well, but what kills it for me is the fragmented tooling landscape and tendency to bad practices by undisciplined devs (lack of explicit types making things hard to track down). I also hate writing intermediate schemas (zod, valibot, etc.) to get runtime type safety (love Typia for this). Debugger is flaky based on setup as well. I like writing TS solo, but hate doing it in a team environment.
That's probably the very reason it's arguably not the best language ever created. It has way too large surface area, getting close to C++ levels.
Sure, it's a valid language design, but it's also a negative in "understandability of each line of code", and thus maintainability, and even stuff like tooling, verification.
C# is an odd one. It's surprisingly flexible, but then oddly lacking in other areas. Quite productive, but also quite inconsistent and uncomposable.
Once you've tried a better type system (Rust), it's difficult to go back to C#. People jump through all kinds of hoops to get good performance out of it, and they're mostly able to.
Things I dearly miss from Rust when I'm using C#:
- Associated types in interfaces. (IEnumerable should not be forced to return a type-erased = heap allocated IEnumerator instance.)
- Move-only structs. (Currently, every type with value semantics is trivially copyable, even ref structs.)
"IEnumerable should not be forced to return a type-erased = heap allocated IEnumerator instance."
Foreach loops use compile-time duck typing, so if you don't intend to use your enumerable in LINQ then both the enumerable and enumerator don't need to implement any interfaces.
This optimisation covers only one common use case, but that's the way of things in C# land.
IEnumerators can also be value types So no heap allocation, just stack.
slightly off topic but a lot of things in .NET actually use compile time duct typing. like how async works To make your own task, you don't add an interface to it. You just implement a single method.
C# is often like Java but without taking a wrong turn when it came to type-erased generics, the generics are uncomplicated enough even if slightly less powerful than what you get with the full instantiation of C++.
C++ was severely lacking before reflection came along in 26, I'm actually writing some new reflection based libraries and it's mostly a joy and quite capable.
But C++ has so many outrightly dangerous semantics when it comes to writing secure code, the coping of pointing to realtime systems,etc as another security "dimension" doesn't hold when Rust,etc exist today.
C# is good in that it's "easy" yet the performance profile of the features allows optimized code to run far closer to C++/rust/etc in performance compared to Java,etc. (that said, a wast majority is probably running like Java due to programmer patterns, but not needing to drop down to another language when it's needed feels good).
Slightly off topic it is just so bizarre how often Claude uses this turn of phase. It’s almost seems forced here. Anthropic has to be hard coding it to do this.
The comparison is unfair for other reasons (the C# runtime was optimized for WASM size and the Rust not, it's possible to be much smaller in Rust), but it's still cool.
Any cross-language benchmarks are always unfair for those kinds of reasons, because ultimately everything is eventually possible against any given hardware.
What matters more for comparing what you get out of languages is the output of idiomatic code written against typical frameworks.
Indeed, it's still cool to see, even if it's optimised to beyond recognition, as seeing the occasional C# win is nice to keep the "re-write in rust" wolves from the door, who seem to ever lurk, especially in a world where re-writes appear easier.
> ultimately everything is eventually possible against any given hardware.
Not everything, no. You can't run C# without the .NET runtime. Some parts of it are irreplaceable.
And the Rust optimizations to shrink binary size (see https://github.com/johnthagen/min-sized-rust) are commonly done in production when it matters, not just in WASM but also in embedded.
Not necessarily true (especially with the new Zig Io interface), a vanilla Rust Hello World compiles to a 40 KBytes WASI blob, while a vanilla Zig Hello World compiles to 45 KBytes. Both are in the same ballpark. The vanilla C Hello World on the other hand comes out at around 4 KBytes (with the caveat that the compiler is free to replace a non-formatting printf with a direct puts call).
I never understood the appeal of wasm outside special performance cases. We never once considered moving from Blazor server side to the wasm mode. Not one time in 5+ years did it ever come up. The whole idea turned out to be a huge distracting waste of engineering talent. Instead of chasing this idealistic wasm pipeline and struggling with weird websocket transports, we could have been writing boring old cshtml and JavaScript on top of stateless HTTP.
Unless you are building a web version of autocad or premiere, I don't see the point of engaging with this technology.
> Unless you are building a web version of autocad or premiere,
Yes, but that's the use case. I don't think you'll be able to find someone respected saying "yes we should use this for all use cases regardless of what you're doing". At the other end, htmx is completely fine.
It's for in-browser, security and portability, generally not worth it performance.
A lot of edge cases they'd rather run WASM then a JS or Python VM, it has nicer containerization characteristics. But even with those key cases - it's not necessarily a core, critical technology.
WASM is 'always on the horizon' as being important.
If we had in 2015 what we had today, there might have been a bit of a breakthrough.
It's a bit of an unfair comparison, the benchmarked C# code here is also post-processed which none of the other targets are. See this comment[1] on reddit where the author announced this on the /r/dotnet subreddit, Rust can go much, much lower. The title is misleading at best and a lie at worst, this is great but saying it beats Rust is a far cry from the truth except for the very narrow benchmark made to showcase this tool.
[1]: https://www.reddit.com/r/dotnet/comments/1x7wsgb/rust_just_l...
This is an entirely different toolchain from the official .NET one, which is kind of the point of the post. It is experimental, but intended to for production, not for beating benchmarks.
Rust also builds a pretty small binary, which is cool. This isn't really meant to be a 'C# is better than Rust' post, but more pointing out that Blazor (which is the official MS implementation) builds huge binaries; often >10MB, which is a real problem. This fixes that.
TFA did [0] the most important stuff for minimizing Rust binaries: release mode, LTO, strip, and abort on panic. But there is a lot more you can do if you really care about Rust binary size [1]: remove location details, purge the debug formatters, rebuild the standard library for size, abort with no error message at all, and nuttier stuff.
[0]: https://github.com/zion-sati/NetWasm/blob/main/docs/size-and...
[1]: https://github.com/johnthagen/min-sized-rust
personally, I disregard and ignore cross-language benchmarks. Benchmarks are hard, benchmarks in managed languages are extra hard.
And then the person writing the code has to be an expert in all languages involved to make it even half fair, instead of just a sound-bite/click-bait.
I think the benchmark game was really useful. It wasn't a which is better, it was what are the tradeoffs. Some of that was provided subjectively by curating it into safe and portable vs hyperoptimized categories. But there is also memory footprint etc. It was also a gauge of which languages people who care about performance preferred, as those got rapid updates.
There's something about C# that just feels so right for me for backends (as long as you stick to the more modern conventions).
Good tooling, modern language features (C# 15 has the long awaited unions, closed hierarchies), great debugging experience, etc.
Yes I think it's a bit underrated. The problem I find is that no one writes C# libraries that actually do anything (e.g. even basic linear algebra is pretty crap compared to python) and that the JIT is a pointless hindrance but the experience of using the stack is pretty good.
I agree completely regarding libraries, C# has never had the "libraries for everything", especially open source ones. The better libraries have moved to ( or always have been ) licensed too which doesn't help that impression.
I'd like to hear more about your issue with the JIT and where do you find it a hindrance?
I've had a few benchmarks lately that performed better under JIT than AOT compilation, and while that isn't always the case, the JIT, especially on dotnet 10, performs very well.
> The problem I find is that no one writes C# libraries that actually do anything
Yes, because when you think about it, why should they?
MS has showed many times how unreliable and even user-hostile they can be, so the community at large is very wary of their ecosystem in spite of real advancements.
If all possible metrics are considered, C# might be the best language ever created.
I really like TS as well, but what kills it for me is the fragmented tooling landscape and tendency to bad practices by undisciplined devs (lack of explicit types making things hard to track down). I also hate writing intermediate schemas (zod, valibot, etc.) to get runtime type safety (love Typia for this). Debugger is flaky based on setup as well. I like writing TS solo, but hate doing it in a team environment.
That's probably the very reason it's arguably not the best language ever created. It has way too large surface area, getting close to C++ levels.
Sure, it's a valid language design, but it's also a negative in "understandability of each line of code", and thus maintainability, and even stuff like tooling, verification.
C# is an odd one. It's surprisingly flexible, but then oddly lacking in other areas. Quite productive, but also quite inconsistent and uncomposable.
Once you've tried a better type system (Rust), it's difficult to go back to C#. People jump through all kinds of hoops to get good performance out of it, and they're mostly able to.
Things I dearly miss from Rust when I'm using C#:
- Associated types in interfaces. (IEnumerable should not be forced to return a type-erased = heap allocated IEnumerator instance.)
- Move-only structs. (Currently, every type with value semantics is trivially copyable, even ref structs.)
"IEnumerable should not be forced to return a type-erased = heap allocated IEnumerator instance."
Foreach loops use compile-time duck typing, so if you don't intend to use your enumerable in LINQ then both the enumerable and enumerator don't need to implement any interfaces.
This optimisation covers only one common use case, but that's the way of things in C# land.
IEnumerators can also be value types So no heap allocation, just stack.
slightly off topic but a lot of things in .NET actually use compile time duct typing. like how async works To make your own task, you don't add an interface to it. You just implement a single method.
Nice, but still lacking proper generics (i.e. à la C++ templates) and typedef.
Different use-cases.
C# is often like Java but without taking a wrong turn when it came to type-erased generics, the generics are uncomplicated enough even if slightly less powerful than what you get with the full instantiation of C++.
C++ was severely lacking before reflection came along in 26, I'm actually writing some new reflection based libraries and it's mostly a joy and quite capable.
But C++ has so many outrightly dangerous semantics when it comes to writing secure code, the coping of pointing to realtime systems,etc as another security "dimension" doesn't hold when Rust,etc exist today.
C# is good in that it's "easy" yet the performance profile of the features allows optimized code to run far closer to C++/rust/etc in performance compared to Java,etc. (that said, a wast majority is probably running like Java due to programmer patterns, but not needing to drop down to another language when it's needed feels good).
> The 46.7 KiB program is the baseline, not the boundary.
what does this even mean
Slightly off topic it is just so bizarre how often Claude uses this turn of phase. It’s almost seems forced here. Anthropic has to be hard coding it to do this.
I speak claude, it means 46.7 is the minimum and it could go further.
He was absolutely right to push back though.
Worth pointing out this is not open source, if that is an important consideration when you're comparing the two (it is to me).
Yeah, I'm not going to use a toolchain where if my project is successful, I'm going to end up having to pay.
This is s bit of an unfair comparison, isn't it?
Since WASM ships with a garbage collector that C# can use while Rust does all the memory management itself, of course it will be bigger.
EDIT: Reading OP more thoroughly I think I'm wrong. Apparently in the compared versions, the C# version ships a runtime with garbage collector.
C# doesn't (and can't) use WASM GC.
The comparison is unfair for other reasons (the C# runtime was optimized for WASM size and the Rust not, it's possible to be much smaller in Rust), but it's still cool.
Any cross-language benchmarks are always unfair for those kinds of reasons, because ultimately everything is eventually possible against any given hardware.
What matters more for comparing what you get out of languages is the output of idiomatic code written against typical frameworks.
Indeed, it's still cool to see, even if it's optimised to beyond recognition, as seeing the occasional C# win is nice to keep the "re-write in rust" wolves from the door, who seem to ever lurk, especially in a world where re-writes appear easier.
> ultimately everything is eventually possible against any given hardware.
Not everything, no. You can't run C# without the .NET runtime. Some parts of it are irreplaceable.
And the Rust optimizations to shrink binary size (see https://github.com/johnthagen/min-sized-rust) are commonly done in production when it matters, not just in WASM but also in embedded.
> Not everything, no. You can't run C# without the .NET runtime
You can compile C# to an AOT exe, and when you do that it will literally only be what it needs to work, less and dynamic libs.
> You can't run C# without the .NET runtime
With NativeAOT, same a golang then. NativeAOT has worked wonderfully for us, and in some specific situations faster than Rust.
Is the support gap mostly related to weak references and finalizers? Or is something else missing?
(Obviously those are already pretty significant gaps.)
Those are supported afaics. It's reflection that isn't supported according to the docs.
Wasm GC does not offer weak refs or finalizers at this point: https://github.com/WebAssembly/gc/blob/main/proposals/gc/Pos...
C# will slowly fade in relevance. Nowadays it gets picked mainly when the company already has a lot of .NET in place.
Why? What makes you say that? In favor of what?
The models aren't writing new applications in C# unless you direct it to.
X is better than Y where Y is irrelevant and the difference is marginal is a low relevance observation.
this looks phenomenal. Can't wait to try it out.
Not very hard... Rust wasm binaries are ginormous.
If you care about WASM performance, size and memory usage, Zig is a much better candidate.
Not necessarily true (especially with the new Zig Io interface), a vanilla Rust Hello World compiles to a 40 KBytes WASI blob, while a vanilla Zig Hello World compiles to 45 KBytes. Both are in the same ballpark. The vanilla C Hello World on the other hand comes out at around 4 KBytes (with the caveat that the compiler is free to replace a non-formatting printf with a direct puts call).
Of course, they lobbied to transfer the bloat onto the WASM runtime itself
Maybe I'm ignorant of some fundamental limitation here, but I cannot get excited for 47kB for a `print(42)`.
I never understood the appeal of wasm outside special performance cases. We never once considered moving from Blazor server side to the wasm mode. Not one time in 5+ years did it ever come up. The whole idea turned out to be a huge distracting waste of engineering talent. Instead of chasing this idealistic wasm pipeline and struggling with weird websocket transports, we could have been writing boring old cshtml and JavaScript on top of stateless HTTP.
Unless you are building a web version of autocad or premiere, I don't see the point of engaging with this technology.
> Unless you are building a web version of autocad or premiere,
Yes, but that's the use case. I don't think you'll be able to find someone respected saying "yes we should use this for all use cases regardless of what you're doing". At the other end, htmx is completely fine.
It's for in-browser, security and portability, generally not worth it performance.
A lot of edge cases they'd rather run WASM then a JS or Python VM, it has nicer containerization characteristics. But even with those key cases - it's not necessarily a core, critical technology.
WASM is 'always on the horizon' as being important.
If we had in 2015 what we had today, there might have been a bit of a breakthrough.
Because the abundance of javascript has made the web a bloated mess