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Copy Every thing after a regex is matched

i have to create a function GetSourceCodeOfClass("ClassName",FilePath) this function will be used more than 10000 times to get Srouce code from c# Files, and from every source file i have to extract the source code of a complete class i.e
" Class someName { every thing in the body including sinature} "
Now this is simple, if a single file contains a single class but there will be many source files that will contain more than two classes in them , further more the bigger problem is there maybe nested classes inside a single class.
i want following thing :-
i want to extract the complete source of a given Class
if file contains more than two classes then i want to extract only the source code of specified class.
if file contains more than one class and my specified class have nested classes in it then i want to capture myClasses's source as well as all nested classes.
i have an algorithm in mid that is:
1-open file
2-match regex (C# classes signature ) - parameterized
#"(public|private|internal|protected|inline)?[\t ]*(static)?[\t
]class[\t ]" + sOurClassName + #"(([\t ][:][\t ]([a-zA-z]+(([
])[,]([ ])\w+))+))?\s[\n\r\t\s]?{"
3- If Regex is matched in the source file
4 Start copying at that point until the same regex is matched again but without parameters
regex is:
#" (public|private|internal|protected)?[\t ]*(static)?[\t ]class[\t
]\w+(([\t ][:][\t ]([a-zA-z]+(([ ])[,]([
])\w+))+))?\s[\n\r\t\s]?{"
(this is where i have no clue and i am stuck. I want to copy every thing after first matched to the second matched or after first match till the end )
copying nested classes is still an issue and i am still thinking about it if some one have an idea , can help me in this too.
Note- match.groups[0] or match.groups[1] this will only copy the signature but i want the complete source of the class thats why i am doing this way . ..
BTW i am using C#

I agree with Nathan's sentiment that you would be better using an existing C#-aware parser. Trying to write a regex for the task is a lot of work, and you are unlikely to get it right on the first try. It may work on your first example code, or even the first few, but eventually you'll find some code that's slightly different than what you expected and the regex will fail to catch something important.
That said, if you are comfortable with that limitation and risk, the general technique you are asking about (if I understand correctly…the question isn't entirely clear) is common enough, and worth understanding if you expect to use regex a lot. The key points to understand are that with a Match object, you can call the NextMatch() method to obtain the next match in the next, and that when calling the Regex.Match() method, you can pass the start and length of a substring you want to check, and it will limit its processing to that substring.
You can use the latter point to switch from one regex to another mid-parse.
In your scenario, I understand it to be that you want to run a regex containing the specific class name, to find that particular class in the file, and then to search the text after the initial match for any subsequent class in the file. If the second search finds something, you want to only return the text from the start of the first match to the start of the second match. If the second search finds nothing, you want to return the text from the start of the first match to the end of the whole file.
If that's correct, then something like this should work:
string ExtractClass(string fileContents, Regex classRegex, Regex nonClassRegex)
{
Match match1 = classRegex.Match(fileContents);
if (!match1.Success)
{
return null;
}
Match match2 = nonClassRegex.Match(fileContents, match1.Index + match1.Length);
if (!match2.Success)
{
return fileContents.Substring(match1.Index);
}
return fileContents.Substring(match1.Index, match2.Index - match1.Index);
}
I should note that between two class declarations, or between the end of a lone class declaration and the actual end of the file there can easily be other non-white-space text that isn't part of the class declaration. I assume you have a plan for dealing with that.
If the above doesn't address your need, you should examine your question closely, and edit it both for length and clarity.

Too short control escape. How to get Regex for this?

So, let's say I have a result from a search that comes back as:
\\my.test.site#SSL\JohnDoe\SusanSmith\courses\PDFs\Science_Math\BIOL\S12014 Syllabi\BIOL-1322-S12014-John-Doe.pdf
Whenever the result is listed in a text box I get the entire path instead of just the file. This is functioning as designed since I can't use the .Select(Path.GetFileName) while enumerating directories lest it doesn't have the full path to do the search on.
So, I was going to use Regex to do a replace at the end when the results are displayed however when I went to Rubular it doesn't like either my expression or the test string(can't figure out which).
I basically want to cut down everything except the file name and extension.
So my Regex was supposed to be something like:
\\my.test.site#SSL\JohnDoe\SusanSmith\courses\PDFs\.+\.+\.+\
So that I get everything up to the file name and extension for deletion. However Rubular doesn't like something as I get a "too short control escape" error. I don't want to test this in C# without verifying in Rubular since I use it heavily and figure if it won't work there it won't work at runtime.
Any ideas? Thanks.

Remember to escape the \ characters, as well as the literal . characters:
\\\\my\.test\.site#SSL\\JohnDoe\\SusanSmith\\courses\\PDFs\\.+\\.+\\.+\\
Also note, you probably want to avoid over-matching on the .+ by using non-greedy quantifiers:
\\\\my\.test\.site#SSL\\JohnDoe\\SusanSmith\\courses\\PDFs\\.+?\\.+?\\.+?\\
Or using character classes:
\\\\my\.test\.site#SSL\\JohnDoe\\SusanSmith\\courses\\PDFs\\[^\\]+\\[^\\]+\\[^\\]+\\

Maybe I'm misinterpreting the question, but it sounds like your approach has been overly complicated.
Can't you simply match this: .+\\
And then replace with '' (nothing)?

Regular expression to define format of backup filenames

In the application I am currently working on, I have an option to create automatic backups of a certain file on the hard disk. What I would like to do is offer the user the possibility to configure the name of the file and its extension.
For example, the backup filename could be something like : "backup_month_year_username.bak". I had the idea to save the format in the form of a regular expression. For the example above, the regexp would look like :
"^backup_(?<Month>\d{2})_(?<Year>\d{2})_(?<Username>\w).(?<extension>bak)$"
I thought about using regex because I will also have to browse through the directory of backuped files to delete those older than a certain date. The main trouble I have now is how to create a filename using the regex. In a way I should replace the tags with the information. I could do that using regex.replace and another regex, but I feel it's a big weird doing that and it might be a better way.
Thanks
[Edit] Maybe I wasn't really clear in the first go, but the idea is of course that the user (in this case an admin that will know regex syntax) will have the possibility to modify the form of the filename, that's all the idea behind it[/Edit]

... and if the regex changes, it is next to impossible to reconstruct a string from a given regex.
Edit:
Create some predefined "place-holders": %u could be the user's name, %y could be the year, etc.:
backup_%m_%y_%u.bak
and then simple replace the %? with their actual values.

It sounds like you're trying to use the regular expression to create the file name from a pattern which the user should be able to specify.
Regular expressions can - AFAIK - not be used to create output, but only to validate input, so you'd have the user specify two things:
a file name production pattern like Bart suggested
a validation pattern in form of a regular expression that helps you split the file names into their parts
EDIT
By the way, your sample regex contains an error: The "." is use for "any character", also \w only matches one word character, so I guess you meant to write
"^backup_(?<Month>\d{2})_(?<Year>\d{2})_(?<Username>\w+)\.(?<extension>bak)$"

If the filename is always in this form, there is no reason for a regex, as it's easier to process with string.Split ...

With Bart's solution it is easy enough to split (using string.Split) the generated file name using underscore as the delimiter, to get back the information.

Ok, I think I have found a way to use only the regex. As I am using groups to get the information, I will use another regular expression to match the regular expression and replace the groups with the value:
Regex rgx = new Regex("\(\?\<Month\>.+?\)");
rgx.Replace("^backup_(?<Month>\d{2})_(?<Year>\d{2})_(?<Username>\w+)\.(?<extension>bak)$"
, DateTime.Now.Month.ToString());
Ok, it's really a hack, but at least it works and I have only one pattern defined by the user. It might not work if the regex is too complex, but I think I can deal with that problem.
What do you think?

Parser using RegEx and XML, in C#

I am making an application where I need to verify the syntax of each line which contains a command involving a keyword as the first word.
Also, if the syntax is correct I need to check the type of the variables used in the keywords.
Like if there's a print command:
print "string" < variable < "some another string" //some comments
print\s".*"((\s?<\s?".*")*\s?<\s?(?'string1'\w+))?(\s*//.*)?
So i made the following Regex:
\s*[<>]\s*((?'variant'\w+)(\[\d+\])*)
This is to access all words in variant group to extract the variables used and verify their type.
Like this my tool has many keywords and currently I am crudely writing regex for each keyword. And if there's a change tomorrow I would be replacing the respective change everytime everywhere in every keyword.
I am storing a Regex for each keyword in an XML file. However I was interested in making it extensible, where say the specification changes tomorrow so I need to change it only once and it would reflect in all the places something like I transform the print regex to:
print %string% (%<% %string%|%variable%)* %comments%
Now like this, I write a specification for each keyword and write the definition of string, variable, comments in another file which stores their regex. Then I write a parser which parses this string and create a regex string for me.
Is this possible?
Is there any better way of doing this or is there any way I can do this in XML?

Last time I asked a question like this, someone pointed me to http://www.antlr.org/. Enjoy. :-)

I got an idea and made my own replacer. I used %myname% kind of tags to define my regular expression, and i wrote the definition of %myname% tags seperately using regex. Then i scanned the string recursively and converted the occurance of %myname% tags to the specification they had. It did my work.Thanks any ways

Regex index in matching string where the match failed

I am wondering if it is possible to extract the index position in a given string where a Regex failed when trying to match it?
For example, if my regex was "abc" and I tried to match that with "abd" the match would fail at index 2.
Edit for clarification. The reason I need this is to allow me to simplify the parsing component of my application. The application is an Assmebly language teaching tool which allows students to write, compile, and execute assembly like programs.
Currently I have a tokenizer class which converts input strings into Tokens using regex's. This works very well. For example:
The tokenizer would produce the following tokens given the following input = "INP :x:":
Token.OPCODE, Token.WHITESPACE, Token.LABEL, Token.EOL
These tokens are then analysed to ensure they conform to a syntax for a given statement. Currently this is done using IF statements and is proving cumbersome. The upside of this approach is that I can provide detailed error messages. I.E
if(token[2] != Token.LABEL) { throw new SyntaxError("Expected label");}
I want to use a regular expression to define a syntax instead of the annoying IF statements. But in doing so I lose the ability to return detailed error reports. I therefore would at least like to inform the user of WHERE the error occurred.

I agree with Colin Younger, I don't think it is possible with the existing Regex class. However, I think it is doable if you are willing to sweat a little:
Get the Regex class source code
(e.g.
http://www.codeplex.com/NetMassDownloader
to download the .Net source).
Change the code to have a readonly
property with the failure index.
Make sure your code uses that Regex
rather than Microsoft's.

I guess such an index would only have meaning in some simple case, like in your example.
If you'll take a regex like "ab*c*z" (where by * I mean any character) and a string "abbbcbbcdd", what should be the index, you are talking about?
It will depend on the algorithm used for mathcing...
Could fail on "abbbc..." or on "abbbcbbc..."

I don't believe it's possible, but I am intrigued why you would want it.

In order to do that you would need either callbacks embedded in the regex (which AFAIK C# doesn't support) or preferably hooks into the regex engine. Even then, it's not clear what result you would want if backtracking was involved.

It is not possible to be able to tell where a regex fails. as a result you need to take a different approach. You need to compare strings. Use a regex to remove all the things that could vary and compare it with the string that you know it does not change.
I run into the same problem came up to your answer and had to work out my own solution. Here it is:
https://stackoverflow.com/a/11730035/637142
hope it helps