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C# Regex filter problems

At this moment in time, i posted something earlier asking about the same type of question regarding Regex. It has given me headaches, i have looked up loads of documentation of how to use regex but i still could not put my finger on it. I wouldn't want to waste another 6 hours looking to filter simple (i think) expressions.
So basically what i want to do is filter all filetypes with the endings of HTML extensions (the '*' stars are from a Winforms Tabcontrol signifying that the file has been modified. I also need them in IgnoreCase:
.html, .htm, .shtml, .shtm, .xhtml
.html*, .htm*, .shtml*, .shtm*, .xhtml*
Also filtering some CSS files:
.css
.css*
And some SQL Files:
.sql, .ddl, .dml
.sql*, .ddl*, .dml*
My previous question got an answer to filtering Python files:
.py, .py, .pyi, .pyx, .pyw
Expression would be: \.py[3ixw]?\*?$
But when i tried to learn from the expression above i would always end up with opening a .xhtml only, the rest are not valid.
For the HTML expression, i currently have this: \.html|.html|.shtml|.shtm|.xhtml\*?$ with RegexOptions.IgnoreCase. But the output will only allow .xhtml case sensitive or insensitive. .html files, .htm and the rest did not match. I would really appreciate an explanation to each of the expressions you provide (so i don't have to ask the same question ever again).
Thank you.

For such cases you may start with a simple regex that can be simplified step by step down to a good regex expression:
In C# this would basically, with IgnoreCase, be
Regex myRegex = new Regex("PATTERN", RegexOptions.IgnoreCase);
Now the pattern: The most easy one is simply concatenating all valid results with OR + escaping (if possible):
\.html|\.htm|\.shtml|\.shtm|\.xhtml|\.html*|\.htm*|\.shtml*|\.shtm*|\.xhtml*
With .html* you mean .html + anything, which is written as .*(Any character, 0-infinite times) in regex.
\.html|\.htm|\.shtml|\.shtm|\.xhtml|\.html.*|\.htm.*|\.shtml.*|\.shtm.*|\.xhtml.*
Then, you may take all repeating patterns and group them together. All file endings start with a dot and may have an optional end and ending.* always contains ending:
\.(html|htm|shtml|shtm|xhtml).*
Then, I see htm pretty often, so I try to extract that. Taking all possible characters before and after htm together (? means 0 or 1 appearance):
\.(s|x)?(htm)l?.*
And, I always check if it's still working in regexstorm for .Net
That way, you may also get regular expressions for the other 2 ones and concat them all together in the end.

Regex hangs trying to find match

I am trying to match an assignment string in VB code (as in I'm passing in text that is VB code into my program that's written in C#). The assignment string that I'm trying to match is something for example like
CustomClassInitializer(someParameter, anotherParameter, someOtherClassAsParameterWithInitialization()).SomeProperty = 7
and I realize that's rather complex, but it actually isn't far off from some of the real text I'm trying to match.
In order to do so I wrote a Regex. This Regex:
#"[\w,.]+\(([\w,.]*\(*,* *\)*)+ = "
which correctly matches. The problem is it becomes VERY slow (with timeouts), which I've researched and found is probably because of "backtracking". One of the suggested solutions to help with backtracking in general was to add "?>" to the regex, which I think would go in this position:
[\w,.]+\(?>([\w,.]*\(*,* *\)*)+ =
but this no longer matches properly.
I'm fairly new to Regex, so I imagine that there is a much better pattern. What is it please? Or how can I improve my times in general?
Helpful notes:
I'm only interested in position 0 of the string I'm searching for a
match in. My code is "if (isMatch && match.index == 0) { ... }. Can
I tell it to only check position 0 and if it's not a match move on?
The reason I use all the 0 or more things is the match could be as simple as CustomClass() = new CustomClass(), and as complicated as the above or perhaps a bit worse. I'm trying to get as many cases as possible.
This Regex is interested in "[\w,.]+(" and then "whatever may be inside the parentheses" (I tried to think of what all could be inside them based on the fact that it's valid VB code) until you get to the close parenthesis and then " = ". Perhaps I can use a wildcard for literally anything until it get's to ") = " in the string? - Like I said, fairly new to Regex.
Thanks in advance!

This seems to do what you want. Normally, I like to be more specific than .*, but it is working correctly. Note that I am using the Multi-line option.
^.*=\s*.+$
Here is a working example in RegExStorm.net example

Matching a term that contains nested HTML

I have been having trouble finding a solution to this problem.
I am parsing the content of a number of ebooks, finding specific terms and characters, marking the locations and lengths of each term.
A normal case would be something like this (excerpts from A Game of Thrones):
"When he paused to look down, his head swam dizzily and he felt his fingers slipping. Bran cried out and clung for dear life."
If we are searching for the character "Bran", its location is 85 and length is 4. Easy enough.
My issue arises when there is a paragraph like this:
<span height="-0em"><font size="7">D</font></span>aenerys Targaryen wed Khal Drogo
We need to match "Daenerys Targaryn". It is easy enough to strip the HTML and match the string, but in this example the result needs to include the HTML. Thus the expected result would here be would be location = 0, length = 67.
Another situation, caused by random anchor tags scattered throughout:
Did anyone outside the Vale even suspect where Catelyn <a></a>Stark had taken him?
Again, searching for "Catelyn Stark" needs to include the HTML, so location = 47, length = 20.
I have been able to get around it temporarily by adding those specific cases (searching for "Catelyn <a></a>Stark specifically), but clearly I should have a more robust solution, which I cannot seem to get my head around. My attempts have been using RegEx but with limited success.
I have found various questions regarding HTML matching/stripping (and whether or not to use RegEx =)), but this case seems to be somewhat unique.
Stripping the tags isn't an option as the content must be preserved.
This is within a stand-alone C# application.
Any ideas, steps in the right direction, or similar examples should your search go better than mine would be greatly appreciated!

One possible approach would be to insert the following between each letter in your search string:
(?:<[^>]*>)*
So when searching for the character "Bran" your regex would become the following:
(?:<[^>]*>)*B(?:<[^>]*>)*r(?:<[^>]*>)*a(?:<[^>]*>)*n
This will allow your regex to match any number of HTML tags anywhere within the search string. Note that this will only work if your search strings are always something simple like a character's name, and not regular expressions (this method will fail if there is repetition like a* in your search string).

I would create a function that would take "Daenerys Targaryn" as a parameter and then strip the first letter. Then, it would only search for "aenerys Targaryn," and if found, it would search for ">D<" or the first variable letter. Does than make sense?
Example:
public static string searchFor(string str)
{
// strip first letter of search string (in this case "D")
// search for the rest of the string ("aenerys Targaryn")
// if found, search for ">D<"
// if found, search for HTML tags with "D" inside (using regex)
// if found, search for HTML tags with the previous HTML tag in them (using regex)
return result;
}

Well using Javascript or Php you can get the text of elements and the text of documents and search there and then do a regex to return the closest match (containing the html):
Another option:
would be to index the books first using something like Lucene Search Engine (which happens to let you index in different formats (html format being one of them).
You can then use the Lucene api to search your documents a little easier.
In php we have Zend_Search_Lucene which works perfectly for this kind of thing.
Lucene Search can be found at:
http://lucene.apache.org/core/
Have fun!

Deal with '#' through regex

Quick question , I have been trying to match any word containing a '#' from a string list and remove it, but I don't know how to handle it . been playing around on http://regexhero.net/tester/ trying but to no avail.
Essentially if it comes across #ff or wha#s up i will just regex.replace them.
any ideas on the Regular expression to use?.
Thanks.

Don't use regex - just use string.replace - it's a lot faster.

I have a previous answer that covers some hashtag matching approaches.
In summary, if you are pulling statuses containing hashtags from Twitter, you no longer need to find them yourself. You can now specify the include_entities parameter to have Twitter automatically call out mentions, links, and hashtags (if the method you are calling, like statuses/show supports this parameter.
If you just need the regular expression to locate the hashtags and capture it's elements, Twitter provides it in an open source library that contains the following pattern.
(^|[^0-9A-Z&/]+)(#|\uFF03)([0-9A-Z_]*[A-Z_]+[a-z0-9_\\u00c0-\\u00d6\\u00d8-\\u00f6\\u00f8-\\u00ff]*)
More detail and additional links are provided in the original answer.

So you're trying to remove any words containing a #?
If so, give this a try...
\w*#\w*
And replace with nothing, like so...
http://regexhero.net/tester/?id=cda1e713-bdab-4aa2-b63d-a87e9b2c9bce
apple# orange ban#ana becomes orange
But if you're simply trying to remove all instances of #, then String.Replace is the better choice. myString = myString.Replace("#", "");

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