Develop Reference

VB.Net/C# - Split string on custom function

I'm working on a custom mathematical expression calculator, but I'm having problems at parsing nested conditional expression like this one:
IIF("M"="M",(IIF(100 < 50,(IIF(2 > 0.45,2,1)),(IIF(2 > 0.45,4,3)))),(IIF(100 < 46,(IIF(2 > 0.45,2,1)),(IIF(2 >0.45,4,3)))))
What I'd like to do is to split the IIF function by commas in order to get its parameters:
Dim condition = "M"="M"
Dim truePart = (IIF(100 < 50,(IIF([2 > 0.45,2,1)),(IIF(2 >0.45,4,3))))
Dim falsePart = (IIF(100 < 46,(IIF(2 > 0.45,2,1)),(IIF(2 >0.45,4,3)))))
At the moment I'm using Regex to parse single IIF function by getting what is inside the parentheses and the split it by commas:
\((.*?)\)
Obviously that doesn't work with such expression since it will stop at the first closing parentheses, therefore I thought about using this to get all the other characters:
\((.*?)\).*
But now I'm not sure how to split it, since using commas is not an option anymore.

The answer from theory is that regular expressions are not capable to do what you requested because they "cannot count". However, you need to count.
The practise says that .NET regular expressions are no regular expressions but stack machines. With a group (?<Group>.*) you in fact add an entry to a stack of that group. With (?<-Group>), you can remove an entry from that stack. You can also test whether the stack is empty.
Out of curiosity, I gave it a try and I believe that
[\(,]([^\(\)]|(?<Par>\()|(?<-Par>\)))*(?(Par)---|[,\)])
should work, where --- is used as an escape sequence. If you understand that "regular expression" right away, then I think you are good to go. In all other cases, I would rather recommend you to write a parser manually. Otherwise, you are not going to understand your code 5min after you have tested it.

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 to identify C# functions

I need to find all functions in my VS solution with a certain attribute and insert a line of code at the end and at the beginning of each one. For identifying the functions, I've got as far as
\[attribute\]\r?\n(.*)void(.*)\r?\n.*\{\r?\n([^\{\}]*)\}
But that only works on functions that don't contain any other blocks of code delimited by braces. If I set the last capturing group to [\s\S] (all characters), it simply selects all text from the start of the first function to the end of the last one. Is there a way to get around this and select just one whole function?

I am afraid balancing constructs themselves are not enough since you may have unbalanced number of them in the method body. You can still try this regex that will handle most of the caveats:
\[attribute\](?<signature>[^{]*)(?<body>(?:\{[^}]*\}|//.*\r?\n|"[^"]*"|[\S\s])*?\{(?:\{[^}]*\}|//.*\r?\n|"[^"]*"|[\S\s])*?)\}
See demo on RegexStorm
The regex will ignore all { and } in the string literals and //-like comments, and will consume {...} blocks. The only thing it does not support is /*...*/ multiline comments. Please let me know if you also need to account for them.

The bad news is that you can't do that by the Search-And-Replace feature because it doesn't support balancing groups. You can write a separate program in C# that does it for you.
The construct to get the matching closing brace is:
(?=\{)(?:(?<open>\{)|(?<-open>\})|[^\{\}])+?(?(open)(?!))
This matches a block of {...}. But as #DmitryBychenko mentioned it doesn't respect comments or strings.

.Net regex not replacing correctly

Background
I am trying to do some regex matching and replacing, but for some reason the replacement isn't correct in .NET.
Regex pattern - "^.*?/rebate/?$"
Input string - "/my-tax/rebate"
Replacement string - "/new-path/rebate"
Basically, if the word 'rebate' is seen in a string, the input string needs to be replaced entirely by the replacement string.
Problem
If I create a regex with the pattern and execute
patternMatch.Pattern.Replace("/my-tax/rebate", "/new-path/rebate")
I get /my-tax/new-path/rebate, which isn't correct.
But, if I execute -
new Regex(#"^.*?/rebate/?$").Replace("/my-tax/rebate", "/new-path/rebate"),
the result is correct - /new-path/rebate
Why is that?
patternMatch is an object with two properties - one Pattern (which is the Regex Pattern) and another one is TargetPath (which is the replacement string). In this example, I am only using the pattern property.
patternMatch.Pattern on debugging is
Here are the results during run time-

You are simply wrongly using the function. I'm not sure how you are getting /my-tax/new-path/rebate since it is giving me an error on ideone.com (Maybe you have a regex named Pattern?).
Anyway, you shouldn't have any issues with using the function like this:
patternMatch.Replace("/my-tax/rebate", "/new-path/rebate");
ideone demo

A number of points in your question are incorrect. The regex is replacing correctly.
Per #XiaoguangQiao's comment, what is patternMatch.Pattern.Replace? Your example...
var patternMatch = new Regex("^.*?/rebate/?$");
patternMatch.Pattern.Replace("/my-tax/rebate", "/new-path/rebate");
...errors with the message...
'System.Text.RegularExpressions.Regex' does not contain a definition for 'Pattern' and no extension method 'Pattern' accepting a first argument of type 'System.Text.RegularExpressions.Regex' could be found
...when I throw it into a quick LINQPad 4 query (set to C# Statement(s)).
pattern is a private string field of System.Text.RegularExpressions.Regex; and patternMatch.Replace("/my-tax/rebate", "/new-path/rebate") - which I expect is what you meant - yields the correct result ("/new-path/rebate") rather than the incorrect result you said you get ("/my-tax/new-path/rebate").
Otherwise your pattern(s) (i.e. with and without the extra / that #rene pointed out) is fine for the input ("/my-tax/rebate") and replacement ("/new-path/rebate") you initially outline - insofar as they match and yield the result you want. You can check this outside your code in quick fiddles with the extra / and without the extra /.

Use String.Replace Method.
str.replace("rebate","new-path/rebate")
http://msdn.microsoft.com/en-us/library/fk49wtc1%28v=vs.110%29.aspx

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'.*[^'])('|"")?)?)?>