Develop Reference

Matching and replacing function expressions

I need to do some very light parsing of C# (actually transpiled Razor code) to replace a list of function calls with textual replacements.
If given a set containing {"Foo.myFunc" : "\"def\"" } it should replace this code:
var res = "abc" + Foo.myFunc(foo, Bar.otherFunc( Baz.funk()));
with this:
var res = "abc" + "def"
I don't care about the nested expressions.
This seems fairly trivial and I think I should be able to avoid building an entire C# parser using something like this for every member of the mapping set:
find expression start (e.g. Foo.myFunc)
Push()/Pop() parentheses on a Stack until Count == 0.
Mark this as expression stop
replace everything from expression start until expression stop
But maybe I don't need to ... Is there a (possibly built-in) .NET library that can do this for me? Counting is not possible in the family of languages that RE is in, but maybe the extended regex syntax in C# can handle this somehow using back references?
edit:
As the comments to this answer demonstrates simply counting brackets will not be sufficient generally, as something like trollMe("(") will throw off those algorithms. Only true parsing would then suffice, I guess (?).

The trick for a normal string will be:
(?>"(\\"|[^"])*")
A verbatim string:
(?>#"(""|[^"])*")
Maybe this can help, but I'm not sure that this will work in all cases:
<func>(?=\()((?>/\*.*?\*/)|(?>#"(""|[^"])*")|(?>"(\\"|[^"])*")|\r?\n|[^()"]|(?<open>\()|(?<-open>\)))+?(?(open)(?!))
Replace <func> with your function name.
Useless to say that trollMe("\"(", "((", #"abc""de((f") works as expected.
DEMO

Regex Help (again)

I don't really know what to entitle this, but I need some help with regular expressions. Firstly, I want to clarify that I'm not trying to match HTML or XML, although it may look like it, it's not. The things below are part of a file format I use for a program I made to specify which details should be exported in that program. There is no hierarchy involved, just that each new line contains a 'tag':
<n>
This is matched with my program to find an enumeration, which tells my program to export the name value, anyway, I also have tags like this:
<adr:home>
This specifies the home address. I use the following regex:
<((?'TAG'.*):(?'SUBTAG'.*)?)?(\s+((\w+)=('|"")?(?'VALUE'.*[^'])('|"")?)?)?>
The problem is that the regex will split the adr:home tag fine, but fail to find the n tag because it lacks a colon, but when I add a ? or a *, it then doesn't split the adr:home and similar tags. Can anyone help? I'm sure it's only simple, it's just this is my first time at creating a regular expression. I'm working in C#, by the way.

Will this help
<((?'TAG'.*?)(?::(?'SUBTAG'.*))?)?(\s+((\w+)=('|"")?(?'VALUE'.*[^'])('|"")?)?)?>
I've wrapped the : capture into a non capturing group round subtag and made the tag capture non greedy

Not entirely sure what your aim is but try this:
(?><)(?'TAG'[^:\s>]*)(:(?'SUBTAG'[^\s>:]*))?(\s\w+=['"](?'VALUE'[^'"]*)['"])?(?>>)
I find this site extremely useful for testing C# regex expressions.

What if you put the colon as part of the second tag?
<((?'TAG'.*)(?':SUBTAG'.*)?)?(\s+((\w+)=('|"")?(?'VALUE'.*[^'])('|"")?)?)?>

Regex to remove xml declaration from a string

First of all, I know this is a bad solution and I shouldn't be doing this.
Background: Feel free to skip
However, I need a quick fix for a live system. We currently have a data structure which serialises itself to a string by creating "xml" fragments via a series of string builders. Whether this is valid XML I rather doubt. After creating this xml, and before sending it over a message queue, some clean-up code searches the string for occurrences of the xml declaration and removes them.
The way this is done (iterate every character doing indexOf for the <?xml) is so slow its causing thread timeouts and killing our systems. Ultimately I'll be trying to fix this properly (build xml using xml documents or something similar) but for today I need a quick fix to replace what's there.
Please bear in mind, I know this is a far from ideal solution, but I need a quick fix to get us back up and running.
Question
My thought to use a regex to find the declarations. I was planning on: <\?xml.*?>, then using Regex.Replace(input, string.empty) to remove.
Could you let me know if there are any glaring problems with this regex, or whether just writing it in code using string.IndexOf("<?xml") and string.IndexOf("?>") pairs in a (much saner) loop is better.
EDIT
I need to take care of newlines.
Would: <\?xml[^>]*?> do the trick?
EDIT2
Thanks for the help. Regex wise <\?xml.*?\?> worked fine. I ended up writing some timing code and testing both using ar egex, and IndexOf(). I found, that for our simplest use case, JUST the declaration stripping took:
Nearly a second as it was
.01 of a second with the regex
untimable using a loop and IndexOf()
So I went for IndexOf() as it's easy a very simple loop.

You probably want either this: <\?xml.*\?> or this: <\?xml.*?\?>, because the way you have it now, the regex is not looking for '?>' but just for '>'. I don't think you want the first option, because it's greedy and it will remove everything between the first occurrence of ''. The second option will work as long as you don't have nested XML-tags. If you do, it will remove everything between the first ''. If you have another '' tag.
Also, I don't know how regexes are implemented in .NET, but I seriously doubt if they're faster than using indexOf.

strXML = strXML.Remove(0, sXMLContent.IndexOf(#"?>", 0) + 2);

What's the best way to parse a string for "bad" words in C#?

I'm thinking of something like:
foreach (var word in paragraph.split(' ')) {
if (badWordArray.Contains(word) {
// do something about it
}
}
but I'm sure there's a better way.
Thanks in advance!
UPDATE
I'm not looking to remove obscenities automatically... for my web app, I want to be notified if a word I deem "bad" is used. Then I'll review it myself to make sure it's legit. An auto flagging system of sorts.

While your way works, it may be a bit time consuming. There is a wonderful response here for a previous SO question. Though the question talks about PHP instead of C#, I think it can be easily ported.
Edit to add sample code:
public string FilterWords(string inputWords) {
Regex wordFilter = new Regex("(puppies|kittens|dolphins|crabs)");
return wordFilter.Replace(inputWords, "<3");
}
That should work for you, more or less.
Edit to answer OP clarification:
I'm not looking to remove obscenities automatically... for my web app, I want to be notified if a word I deem "bad" is used.
Much as the replacement portion above, you can see if something matches like so:
public bool HasBadWords(string inputWords) {
Regex wordFilter = new Regex("(puppies|kittens|dolphins|crabs)");
return wordFilter.IsMatch(inputWords);
}
It will return true if the string you passed to it contains any words in the list.

At my job we put some automatic bad word filtering into our software (it's kind of shocking to be browsing the source and suddenly run across the array containing several pages of obscenity).
One tip is to pre-process the user input before testing against your list, in that case that someone is trying to sneak something by you. So by way of preprocessing, we
uppercase everything in the input
remove most non-alphanumerics (that is, just splice out any spaces, or punctuation, etc.)
and then assuming someone is trying to pass off digits for letters, do the something like this: replace zero with O, 9 with G, 5 with S, etc. (get creative)
And then get some friends to try to break it. It's fun.

You could consider using the HashKey objects or Dictionary<T1, T2> instead of the array as using a Dictionary for example can make code more efficient, because the .Contains() method becomes .Keys.Contains() which is way more efficient. This is especially true if you have a large list of profanities (not sure how many there are! :)

Quick & Dirty way to update "IDs" in a string formatted as XML (C#)

For a one-shot operation, i need to parse the contents of an XML string and change the numbers of the "ID" field. However, i can not risk changing anything else of the string, eg. whitespace, line feeds, etc. MUST remain as they are!
Since i have made the experience that XmlReader tends to mess whitespace up and may even reformat your XML i don't want to use it (but feel free to convince me otherwise). This also screams for RegEx but ... i'm not good at RegEx, particularly not with the .NET implementation.
Here's a short part of the string, the number of the ID field needs to be updated in some cases. There can be many such VAR entries in the string. So i need to convert each ID to Int32, compare & modify it, then put it back into the string.
<VAR NAME="sf_name" ID="1001210">
I am looking for the simplest (in terms of coding time) and safest way to do this.

The regex pattern you are looking for is:
ID="(\d+)"
Match group 1 would contain the number. Use a MatchEvaluator Delegate to replace matches with dynamically calculated replacements.
Regex r = new Regex("ID=\"(\\d+)\"");
string outputXml = r.Replace(inputXml, new MatchEvaluator(ReplaceFunction));
where ReplaceFunction is something like this:
public string ReplaceFunction(Match m)
{
// do stuff with m.Groups(1);
return result.ToString();
}
If you need I can expand the Regex to match more specifically. Currently all ID values (that contain numbers only) are replaced. You can also build that bit of "extra intelligence" into the match evaluator function and make it return the match unchanged if you don't want to change it.

Take a look at this property PreserveWhitespace in XmlDocument class