C# Language Specification 5.0

http://www.microsoft.com/en-US/download/details.aspx?id=7029

by kristianp • 13 years ago

96 93 13 years ago

microsoft.com

mpyne5• 13 years ago

MS Word or Word Viewer to see the specification? Really?

Good to see nothing ever really changes in Redmond.

dangrossman2• 13 years ago

Is there something in this document that prevents you from reading it in your preferred viewer? The extension suggests it's just an Office Open XML doc. I can read it in QuickOffice on my Android phone.

mpyne5• 13 years ago

Given that my preferred viewer for this kind of thing is Okular, with a fallback to Firefox+pdf.js if necessary, it's already struck out twice.

My Android doesn't have Quick Office, it does have ThinkOffice but I can think of no reason I would a) read a computer language spec on my cell phone, or b) ever use ThinkOffice on purpose.

kivikakk2• 13 years ago

what on earth would you expect?

38253• 13 years ago

PDF or Postscript. Word is not a format that you should share finalized document. Why does anyone need to edit a spec?

If there is a good reason to edit, perhaps they should have made it an HTML document. Use LaTeX. Are they afraid the Office division will get them fired if they use anything other than Microsoft products?

biot• 13 years ago

I recall years ago reading that the reason Microsoft releases their documentation in Office format (other than the whole eat-your-own-dog-food thing) is so that they have the ability to cryptographically sign the documents.

mpyne5• 13 years ago

Fair enough, but PDF can do that as well.

yjh0502• 13 years ago

Here's PDF version: https://www.dropbox.com/s/dt6xzum432zine0/CSharp%20Language%...

38253• 13 years ago

Here's another version: https://www.dropbox.com/s/4n6sg31v0v3nfok/CSharp%20Language%...

5.48 MB / Has bookmarks from document headers / For download and offline reading if you want to navigate to specific chapter quickly / Not for online viewing (the parent version is only 3.70 MB and is better if you're bandwidth-capped).

voltagex_• 13 years ago

I'm curious - what's the difference between yours and the parent's in terms of the conversion?

samrift2• 13 years ago

A note to those that may be confused: C# 5.0 is the language version used by visual studio 2012, which was released in August of last year, alongside the .net framework 4.5. This is an updated revision, although a cursory look didn't reveal any differences to me.

I'm sure a few people were wondering if this was to go alongside Visual Studio 2013, expected to be released in beta later this week.

danbruc9• 13 years ago

C# 5.0 adds asynchronous methods [1] and caller info attributes [2] to the language. They also changed respectively fixed the way foreach loop variables are captured in closures [3] and changed the overload resolution algorithm [3] and argument evaluation order [3].

[1] http://msdn.microsoft.com/library/hh191443.aspx

[2] http://msdn.microsoft.com/library/hh534540.aspx

[3] http://msdn.microsoft.com/library/hh678682.aspx

samrift2• 13 years ago

I'm sorry, I meant that I didn't see any differences from the C# 5.0 specification released in August 2012 and the revision posted here, which was updated in June 2013. I am aware of the differences from c#4 to c#5.

My point being that c# 5.0 is around 1 year old, and this spec is not new.

sshconnection• 13 years ago

I wish we had an accurate spec for Ruby. RubySpec project is great, but we still let the language be defined in terms of MRI implementation.

seanmcdirmid4• 13 years ago

Sun started the trend when Guy Steele and Gilad Bracha (among others) wrote the initial Java Language Specification. Microsoft has a strong team of PL researchers, including Mads Torgersen and many people at MSRC (who published a paper on formalizing Async in ECOOP 2012), to do this work, which I think is very useful.

kailuowang2• 13 years ago

Asynchronous method... interesting. It seems to me that each version they just incorporate a little bit of some hot paradigms into this language that started as a sweeter(or less painful) java. I remember that during the ruby boom they added the "dynamic" feature into it. Together with linq, and lambda, is it me or all these attempts sometimes appear awkward and out of place?

pixie_2• 13 years ago

I program in a lot languages and C# is heads and shoulders above everything. It doesn't feel hacked together at all. It's like someone with a real vision put a lot of work into making a great language. Too bad project requirements usually dictate the language I have to use.

kalininalex• 13 years ago

One of them is Eric Lippert. If you use C# you'll enjoy his blog, http://ericlippert.com/.

hosay123• 13 years ago

As a (hardened, old) unix dev, it seems to me you've spent little time with the language. C# is one of the most successfully evolved languages of recent times, no feature was added that didn't have a clear & concise story in the context of all other features.

No Anders & co didn't just add whatever they felt fashionable, they've designed a language over the course of a decade with (to my knowledge) zero warts, bringing to the table more than 20 years of prior design experience (Turbo Pascal, Delphi).

If it weren't for the stigma of being a Microsoft design, C# would be a hugely more popular language.

frozenport• 13 years ago

I felt it compromised C++'s low level compatibility in exchange for increasingly verbose expressions. Perhaps C# has nothing to offer except for Microsoft's ecosystem. Valid in 2005 but not today.

Permit2• 13 years ago

No Anders & co didn't just add whatever they felt fashionable, they've designed a language over the course of a decade with (to my knowledge) zero warts...

There was definitely one that got me (they made a breaking change to fix it in C# 5.0, though).

http://blogs.msdn.com/b/ericlippert/archive/2009/11/12/closi...

I agree completely, though, that it is remarkable how well-designed the language is.

millstone2• 13 years ago

zero warts

C# is a nice language, but oh man, is that asking for it!

My pet example of a wart is the set of requirements on the iterated collection in foreach loops. Most C# developers probably think that the collection has to implement IEnumerable, but it is not so! I pasted the requirements from the spec at http://pastebin.com/EfsAmz6f

This is also a case where the dynamic type does something different than the static type. If you iterate over a statically typed non-IEnumerable collection, it will work fine (assuming it implements the required methods). But if you then change the type to dynamic, I think you get a runtime error.

So there's a wart for ya!

gnaritas3• 13 years ago

No language has zero warts. I use it everyday, and love the language, and it's still sometimes painful to do good OO compared to Smalltalk. No meta classes sucks, static methods are a poor substitute, can't override them, can't call them on passed type references without reflection which is ugly. Multiple equivalent syntaxes for anonymous delegates is a wart, they should have just started with the shorter one. Foreach over a container lets you declare the wrong type and throws a runtime cast exception when it could often know at compile time that it's not valid.

Still, great language, love it.

danbruc9• 13 years ago

I personally think they are doing a great job evolving the language. For every version they focus on one or at most a few features and those are really well designed. And I don't think they are following the latest trend - they are adding the things they know how to do [1] and which provide the most value.

As far as I know dynamic was added to ease interop with native code - I have never seen it heavily used in regular code. LINQ and lambda expression have been introduced together with the Entity Framework and I am unable to imagine using an O/R mapper without something similar again - it just fits together so nicely.

Async was an obvious next choice - we are getting more and more cores and traditional thread-based parallel programming just does not scale because it is so error prone. And after they extended LINQ to PLINQ they had a good part of the necessary infrastructure already in place.

[1] For example they would like to add something like Java's checked exceptions but when they considered it they came to the conclusion that there are to many unsolved problems and that it might require a few more years of research to come up with a really good way to do it and so they postponed it for later reconsideration. In general there is a lot of well researched theory behind the things they do. Another example is the Entity Framework. They didn't just implement another O/R mapper but came up with a mathematical theory comparable to the relational algebra and then implemented it based on that results.

Permit2• 13 years ago

C# is an absolute joy to use. The three features you've touched upon in your post are three of my absolute favorites (another being type inference). C# pulls concepts from a variety of other languages and it feels really well structured.

I'm sure I'm not the only one who misses these features when they're working in Java.

modarts• 13 years ago

I'd be hard pressed to find another language that I'd want to use for my server side development work. It's hands down the most expressive c style language in existence. Coupled with Visual Studio, the amount of quality software that can be written in a short amount of time is nothing short of amazing. (This is coming from someone who was a Rails dev in their previous life)

kailuowang2• 13 years ago

I am sorry but the amount of time taken to install visual studio is also not short of amazement.

jfabre• 13 years ago

Can you explain what you find more expressive in c# compared to ruby?

I've been a c# developer for over 5 years and I have to disagree with almost everything you said. Ruby blew my mind when I learned it.

spamizbad• 13 years ago

As a former C# dev, here's my subjective view:

The stuff actually fits in the language pretty well. What has resulted, however, is that there are multiple ways to skin a cat in C#, and there's very limited guidance on what's considered idiomatic.

This is complicated by the fact that many .NET/C# shops have coding standards in place that don't go much beyond C# 2.0. The last C# interview I did, at an allegedly "progressive" .NET shop, the interviewer barred me from using null coalesce in a whiteboard example because "That's hobby project code. It's not how we write production code"

Great language, terrible culture.

seanmcdirmid4• 13 years ago

What has resulted, however, is that there are multiple ways to skin a cat in C#, and there's very limited guidance on what's considered idiomatic.

I find C# to be much more idiomatic than C++ or Scala. If you think C# is bad...stay away from those languages.

MichaelGG7• 13 years ago

Yes, the whole fights of people confused about "var" and avoiding it shows that a fair amount of MS's target group is simply not interested in proper language research or design. I'll admit that I love the ideas behind the CLR (the VM design is pretty slick, although it's stagnated the past years). I think some parts are really excellent (the generics), but when I approach a vendor and I hear they're using .NET, it is a slightly negative flag.

I too had a boss (new owner after acquisition) say "no you're not allowed to use lambdas".

pjmlp7• 13 years ago

That is just a symptom of the typical enterprise culture.

The consulting company I work for still gets requests for project in Java 1.4, for example.

My last .NET project we had some issues because there was a mix of .NET 3.5 and 4.0 across teams.

adamconroy• 13 years ago

Way to go extrapolating crass generalisations from one dud interview. Every single dev team I have come across thinks they are the duck's nuts, and the team leads even more so, resulting in embarrassing overconfidence in their own opinions as per your anecdote. I noticed this over the course of a few decades spanning many languages/platforms. I recall my very first graduate programmer job interview in 1989, where I was asked by the interviewer if I defragged my hard disk weekly, and I said no I do it once in a while, and he couldn't let it go and wanted to argue about how important it is to have a regular defragging schedule, wtf, anyway I didn't get the job.

skwirl3• 13 years ago

I'm just echoing what everyone else here said, but they do a great job at adding these features to the language. I believe that if you learned C# as a first language nothing would feel out of place.

MichaelGG7• 13 years ago

Yeah, C#'s async is a weak version of F#'s workflows, but with a single hard-coded implementation. Research (Haskell) and other languages filter into F# (and team), which filters into C#. F# has had async workflows since 2007.

LINQ's another example of a place where the C# team sighted one end advantage (queries) and implemented the minimum to make it work. That's why all the features around the main LINQ part are half-assed (limited expression trees, ambiguous lambda syntax, very limited type inference.)

Overall, C#'s a nice enough language for a lot of projects. The tooling really helps sells it, too. It's just rather verbose and limiting, unnecessarily. I just can't think of any place where C# the language is significantly better than F#.

But, if you're ranking it against the likes of Java, then yes, C# is close to perfect.

Edit: C# implements a lot of stuff right into the compiler, things that'd be useful more generically. For instance, foreach and collection initializers use duck typing that's baked into the C# compiler. That's a generally useful feature, but again, hard coded for a specific scenario. F# has some of that too, but not to the same extent (F# warts arise mainly when you push the edge of F#-C#ish interop).

pjmlp7• 13 years ago

Yes, but C# is a better fit for the enterprise world than F#.

Currently my F# code is mainly for scripting when doing .NET projects, but only if I am the only user of such scripts, otherwise Powershell.

Anyway I really appreciate the work Microsoft puts on F#, Haskell and OCaml via their research arm.

runT1ME• 13 years ago

Why would you need workflows when you have LINQ. It's full fledged monadic comprehension and you can use it with Async beautifully.

skwirl3• 13 years ago

An interesting change in C# 5.0 involves the handling of foreach iteration variables when used in closure scope. This is technically a breaking change, although it is really hard to think of a case where the old behavior was legitimately desired.

Consider (stolen from the spec doc):

  int[] values = { 7, 9, 13 };
  Action f = null;
  foreach (var value in values)
  {
      if (f == null) f = () => Console.WriteLine("First value: " + value);
  }
  f();

In previous versions of C#, there is a single value variable is in the scope of the entire loop, so the above code would actually print out the last value in the list because that was the value of value (sorry) when the loop finished. In C# 5.0, a value variable is actually in the scope of each individual iteration (so within the braces). So now if you use your iteration variable in a closure scope it won't change on you when the loop iterates and the above code actually prints out the first value.

The same cannot be said for a for loop. It still functions as it always has.

danbruc9• 13 years ago

Here is Eric Lippert discussing the pros and cons of making the change.

http://blogs.msdn.com/b/ericlippert/archive/2009/11/12/closi...

gnaritas3• 13 years ago

Should have been that way from the beginning; having the loop variable have function scope was absurd to begin with and forced developers to copy the loop var to a local before using it in a lambda.

skwirl3• 13 years ago

Yeah, they could have made the change in C# 3.0. I just don't think anyone really felt the pain until the Task Parallel Library came along in .NET 4. Since the TPL API is lambda heavy people really started using lambdas for asynchronous tasks, which leads (or used to lead, anyway) to pain and misery when using a loop iteration variable.

It could always be worse, though. Look at JavaScript. Simply copying the loop variable in the body of the loop doesn't work because all variables are scoped at the function level. So your "local" loop variable is actually a single instance for the entire function and you have the same exact problem. Instead, you have to actually create another function and immediately execute it with the loop iteration variable as an argument, and then use the parameter within the function to do whatever you wanted to do. Not cool.

keyle• 13 years ago

Good nitpicking. But as you indicated, the change of behaviour should only affect people with a very dubious/interesting approach.

seanmcdirmid4• 13 years ago

No, this bug was encountered often by myself and many of my colleagues. Because I was so familiar with the problem, I could guess that this was a problem in their code after looking at it for a few seconds.

It really was a horrible wart that needed to be fixed.

Now if they would only fix the misleading lying dishonest "downcast on type bound" compiler error messages, then C# would lack warts all together.

bsaul• 13 years ago

Anyone knows if C# is used inside microsoft to buiild desktop app ( office ? Visual studio ? ) I remember it wasn't the case for a long time but stopped watching since.

TheMakeA• 13 years ago

The Visual Studio IDE and Expression Blend are (or at least were) WPF... I guess there's a pretty good chance it was C# rather than VB.NET.

Not sure if there is anything else though.

rbirkby• 13 years ago

Visual Studio since 2002 (.Net 1.0) has been partly written in C#/WinForms and then C#/WPF. Visual Interdev (from which the current Visual Studio lineage descends) was partly written in VJ++. It was these bits that were ported to C#/COOL for the 2002 release.

rottyguy• 13 years ago

Isn't part (majority) of their Singularity OS written in C#? I've been waiting to see if they were ever going to release the realtime GC as part of that project to the C# community at large.

BillyMaize• 13 years ago

Why, if this is version 5.0, does the document it downloads say version 4.0? Am I the only one seeing this? The details also mention previous version 3.0 on the webpage.

C# Language Specification 5.0

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