I've noticed a glitch in the syntax highlighting of C# code on Stack Overflow. The c# tag's standard highlighting doesn't include the keywords using and namespace
However, when adding the language directive <!-- language: lang-csharp -->, those are highlighted. So I request to add this directive to every post in c# tag.
Here's the rendering screenshot.
If the identifier you use in the language directive
lang-you would get the default syntax highlighting behavior.
Specifically, invalid identifiers such as lang-csharp, lang-doesnotexist, and lang-iambanana are treated as lang-default.
The default syntax highlighting (lang-default) works by highlighting any keyword from any predefined keyword list in prettify.js. This means it can "grab" keywords from multiple languages, even though the code is written in a single language.
== End of TL;DR region ==
Some examples to illustrate what I'm saying
lang-csThis markdown
<!-- language: lang-cs -->
public static bool IsAwesome { get { return true; } }
renders as
lang-i-am-a-bananaThis markdown
<!-- language: lang-i-am-a-banana -->
public static bool IsAwesome { get { return true; } }
renders as
lang-cs and lang-i-am-a-bananaIf we compare Examples 1 and 2, note that bool and get which was not highlighted with lang-cs was highlighted with lang-i-am-a-banana.
Looking at the C#'s keyword list
var FLOW_CONTROL_KEYWORDS = ["break,continue,do,else,for,if,return,while"];
var C_KEYWORDS = [FLOW_CONTROL_KEYWORDS,"auto,case,char,const,default," +
"double,enum,extern,float,goto,inline,int,long,register,short,signed," +
"sizeof,static,struct,switch,typedef,union,unsigned,void,volatile"];
var COMMON_KEYWORDS = [C_KEYWORDS,"catch,class,delete,false,import," +
"new,operator,private,protected,public,this,throw,true,try,typeof"];
var CSHARP_KEYWORDS = [COMMON_KEYWORDS,
"abstract,as,base,bool,by,byte,checked,decimal,delegate,descending," +
"dynamic,event,finally,fixed,foreach,from,group,implicit,in,interface," +
"internal,into,is,let,lock,null,object,out,override,orderby,params," +
"partial,readonly,ref,sbyte,sealed,stackalloc,string,select,uint,ulong," +
"unchecked,unsafe,ushort,var,virtual,where"];
bool was not highlighted with lang-cs, maybe SO/SE is not using the most recent revision of prettify.js? The latest revision at the time of writing, r303 added bool to C#'s keyword list.get is most definitely not in C#'s keyword list, even in the latest revisionAssuming that SO/SE is using an older revision, in lang-i-am-a-banana mode, bool is "grabbed" from C++'s keyword list
var CPP_KEYWORDS = [COMMON_KEYWORDS,"alignof,align_union,asm,axiom,bool," +
"concept,concept_map,const_cast,constexpr,decltype,delegate," +
"dynamic_cast,explicit,export,friend,generic,late_check," +
"mutable,namespace,nullptr,property,reinterpret_cast,static_assert," +
"static_cast,template,typeid,typename,using,virtual,where"];
in lang-i-am-a-banana mode, get is "grabbed" from JavaScript's keyword list
var JSCRIPT_KEYWORDS = [COMMON_KEYWORDS,
"debugger,eval,export,function,get,null,set,undefined,var,with," +
"Infinity,NaN"];
lang-The fallback to lang-default isn't triggered if your identifier doesn't start with lang-
<!-- language: i-am-a-banana -->
public static bool IsAwesome { get { return true; } }
renders as
or renders according to language tag the question is using. In this case, the language directive simply gets silently ignored.
Like animuson said, the correct identifier for the C# language is lang-cs. Alternatively, you could use the name of the tag, in which case it would be c#. This is all documented here, which gives the identifiers for each language.
What you're using (lang-csharp) is no different than lang-apples-and-bananas or lang-invalid-language. Because there is no lang-csharp identifier, you're just getting the default syntax highlighting, used when no (valid) language is specified.
So the real problem here is that namespace is not highlighted as a keyword when the C# syntax highlighting is applied. We've had this problem before with the virtual keyword, and the get and set keywords, and the new C# 5.0 keywords.
The same answer applies to this as it did to all of those previous cases: Stack Exchange outsources syntax highlighting to Google Prettify, so if there's a bug in the implementation, it's their bug.
Looking at the code, the problem is fairly obvious. In the current revision of prettify.js, where the keywords are defined for various supported languages, namespace is missing from the C# list:
var FLOW_CONTROL_KEYWORDS = ["break,continue,do,else,for,if,return,while"];
var C_KEYWORDS = [FLOW_CONTROL_KEYWORDS,"auto,case,char,const,default," +
"double,enum,extern,float,goto,int,long,register,short,signed,sizeof," +
"static,struct,switch,typedef,union,unsigned,void,volatile"];
var COMMON_KEYWORDS = [C_KEYWORDS,"catch,class,delete,false,import," +
"new,operator,private,protected,public,this,throw,true,try,typeof"];
var CPP_KEYWORDS = [COMMON_KEYWORDS,"alignof,align_union,asm,axiom,bool," +
"concept,concept_map,const_cast,constexpr,decltype," +
"dynamic_cast,explicit,export,friend,inline,late_check," +
"mutable,namespace,nullptr,reinterpret_cast,static_assert,static_cast," +
"template,typeid,typename,using,virtual,where"];
var JAVA_KEYWORDS = [COMMON_KEYWORDS,
"abstract,boolean,byte,extends,final,finally,implements,import," +
"instanceof,null,native,package,strictfp,super,synchronized,throws," +
"transient"];
var CSHARP_KEYWORDS = [JAVA_KEYWORDS,
"as,base,by,checked,decimal,delegate,descending,dynamic,event," +
"fixed,foreach,from,group,implicit,in,interface,internal,into,is,lock," +
"object,out,override,orderby,params,partial,readonly,ref,sbyte,sealed," +
"stackalloc,string,select,uint,ulong,unchecked,unsafe,ushort,var," +
"virtual,where"];
The only language that has a namespace keyword is C++, and the C++ keywords are not imported to the list of C# keywords. The fix is therefore quite simple, it just needs to be brought to the attention of someone with commit rights to the source code.
<!-- language: lang-cs --> is <!-- language: c# -->. <-- language: lang-c# -->, mentioned in your post, would trigger the default behavior much like <!-- language: lang-csharp --> would.
Commented
Jul 22, 2013 at 7:01
lang-csharpdoes not exist. You're seeing the default syntax highlighting by using that. The c# tag is set to uselang-cs.namespaceisn't highlighted.lang-csdoesn't work for some keywords. But thelang-csharpworks.lang-csorlang-c#(tag name) can be used.lang-csharpdoes not exist. By using that it's reverting to default. If those keywords happen to get highlighted, that's merely coincidence.lang-csharp?lang-csharpis not real.lang-cs. Maybe I'll file a issue on their site.