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how to strip html code from a string in c#

Im coding an app for windows phone in c#.
the program creates a html file, in the course of the programs running i add a lot of html tags.
now i need to strip those from a string when needed.
now all my searches show me i can take a string turn it into an array then put it back together minus any words i dont want, now this is handy but wont work for my needs. i have no idea where to start or even if it is possible
here is an example of the strings i need to remove
testString = "AnotherTest<br>";
so this is a string of the parts i need to remove
List<string> partsToRemove ={"</a>","\">","<br>","<a","href=\"#"};
so how do i take "AnotherTest<br>" and remove all the parts included in partsToRemove?
To clarify:
i will only be removing html from small strings as needed not from a whole html file
to give a working concept:
my program is creating a back ground for a roleplay character, part of that process uses a "gang" generator, the gang generator provides the strings with html tags ready for placement (adding them on the fly is not possible with out radical alteration to my whole program) this is fine for the end result BUT i give users access to the generator itself so if they just want a gang they can use what i have created, this is then diplayed in a textbox (i could easierly change that to another web box) and if enabled the phone reads it out, so here i would take the string created for the gang and feed it through a method that strips the html code and returns a "clean" string
before posting i searched for a solution but all i came across was how to remove words, whole words.

You can try to use regex to do this:
Remove all html tags:
String result = Regex.Replace(htmlDocument, #"<[^>]*>", String.Empty);

for the case that you've shown, you can use this : /(<a|href=\\"#|">|</a>|<br>|\\)/gm regex
But since you might have many different types, the best is to keep a list of patterns, or try to figure out a pattern that matches all the different combinations that you have. It might be more suitable to split the document, and execute a regex multiple times, to keep the regex as simple as possible.
Hope I've answered you're question.

Regex: Find pagenumber from partial matching urls

As we all know, Regex patterns will make your stomache turn the first time you see them (or 10th time since you never went head first and truly learned it. Quilty.). I'm currently reading upon it, but since I'm on a tight deadline I'll check here if I can get a quicker and better answer/explaination meanwhile.
I have some url to a forum thread, and I want to scan through the html and find the last page for the thread.
So say I have one of the following urls identifying the thread in question:
https://www.somesite.com/forum/thread-93912* (absolute url to the
thread)
/forum/thread-93912 (relative url to the thread)
and I want to get all values (integers) that appear directly (next path) after any of the above "partial" match in the html-document.
So from any of the following hrefs located anywhere in the html-document (the doc is represented as a single string):
https://www.somesite.com/forum/thread-93912/34
https://www.somesite.com/forum/thread-93912/34/morestuffhere/whatevs
/forum/thread-93912/34
/forum/thread-93912/34/somethingheretoo
I want to extract the number 34 (only 34), so I can parse it to int.
EDIT
Okay, to make it simpler:
Say I have all the html in htmlString, and in this string I want to find all numbers x that appear after my inputString /forum/thread-93912.
These all appear in the htmlString, and I want to extract the numbers:
thread-93912/34
thread-93912/14
thread-93912/84
thread-93912/64
thread-93912/4

You don't need regex. Just use System.Uri.Segments
Uri url = new Uri("your url here");
Console.WriteLine(url.Segments[4]);

\b(\d+)\b(?=[^\d]*$)
Try this.See demo.grab the capture.
http://regex101.com/r/sU3fA2/55
using System;
using System.Text.RegularExpressions;
class Program
{
static void Main()
{
Regex regex = new Regex(#"\b\d+\b(?=[^\d]*$)");
Match match = regex.Match("/forum/thread-93912/34");
if (match.Success)
{
Console.WriteLine(match.Value);
}
}
}

Since my question was a little hard to explain thuroughly (and since I "changed" my problem a little), I thought I'd add my own answer to get the exact code I went with (which I came up with thanks to the other answers here, so I'll give you all an upvote!).
I'm sure this can be made prettier and more compact, but I went for clearity since I'm new to regex!
First, get all strings matching the url + some number (separated with a slash "/"), then extract that number to a group called "page".
Regex regex = new Regex(urlToThread + #"/(?<page>\d+)");
MatchCollection matches = regex.Matches(htmlString);
Then iterate all matches and extract the "page"-value (garanteed to be an integer), and parse it to an integer. Add all parsed integers to a list and sort when done. The last one will be the greatest (last page).
List<int> pages = new List<int>();
foreach(Match match in matches)
pages.Add(int.Parse(match.Groups["page"].Value));
pages.Sort();
// And here we get the last page
int nrOfPages = pages[pages.Count-1];

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!

Regex MatchCollection obj hangs\"Function evuluation timed out" after Regex.Matches

I'm kind of new too C#, and regular expression for that matter, but I've searched a couple of hours to find a solution too this problem so, hopefully this is easy for you guys:)
My application uses a regex to match email addresses in a given string,
then loops throu the matches.:
String EmailPattern = "\\w+([-+.]\\w+)*#\\w+([-.]\\w+)*\\.\\w+([-.]\\w+)*";
MatchCollection mcemail = Regex.Matches(rawHTML, EmailPattern);
foreach (Match memail in mcemail)
Works fine, but, when I downloaded the string from a certain page, http://www.sp.se/sv/index/services/quality/sidor/default.aspx, the MatchCollection(mcemail) object "hangs" the loop. When using a break point and accessing the object, I get "Function evuluation timed out" on everything(.Count etc).
Update
I've tried my pattern and other email patterns on the same string, everyone(regex desingers, python based web pages etc.) fails/timesout when trying too match this particular string.
How can I detect that the matchcollection obj is not "ready" to use?

If you can post the email that's causing the problem (perhaps anonymized in some way), that will give us more information, but I'm thinking the problem is this little guy right here:
([-.]\\w+)*\\.\\w+([-.]\\w+)*
To understand the problem, let's break that into groups:
([-.]\\w+)*
\\.\\w+
([-.]\\w+)*
The strings that will match \\.\\w+ are a subset of those that will match [-.]\\w+. So if part of your input looks like foo.bar.baz.blah.yadda.com, your regex engine has no way of knowing which group is supposed to match it. Does that make sense? So the first ([-.]\\w+)* could match .bar.baz.blah, then the \\.\\w+ could match .yadda, then the last ([-.]\\w+)* could match .com...
...OR the first clause could match .bar.baz, the second could match .blah, and the last could match .yadda.com. Since it doesn't know which one is right, it will keep trying different combinations. It should stop eventually, but that could still take a long time. This is called "catastrophic backtracking".
This issue is compounded by the fact that you're using capturing groups rather than non-capturing groups; i.e. ([-+.]\\w+) instead of (?:[-+.]\\w+). That causes the engine to try and separate and save whatever matches inside the parentheses for later reference. But as I explained above, it's ambiguous which group each substring belongs in.
You might consider replacing everything after the # with something like this:
\\w[-\\w]*\\.[-.\\w]+
That could use some refinement to make it more specific, but you get the general idea. Hope I explained all this well enough; grouping and backreferences are kind of tough to describe.
EDIT:
Looking back at your pattern, there's a deeper issue here, still related to the backtracking/ambiguity problem I mentioned. The clause \\w+([-.]\\w+)* is ambiguous all by itself. Splitting it into parts, we have:
\\w+
([-.]\\w+)*
Suppose you have a string like foobar. Where does the \\w+ end and the ([-.]\\w+)* begin? How many repetitions of ([-.]\\w+) are there? Any of the following could work as matches:
f(oobar)
foo(bar)
f(o)(oba)(r)
f(o)(o)(b)(a)(r)
foobar
etc...
The regex engine doesn't know which is important, so it will try them all. This is the same problem I pointed out above, but it means you have it in multiple places in your pattern.
Even worse, ([-.]\\w+)* is also ambiguous, because of the + after the \\w. How many groups are there in blah? I count 16 possible combinations: (blah), (b)(lah), (bl)(ah)...
The amount of different possible combinations is going to be huge, even for a relatively small input, so your engine is going to be in overdrive. I would definitely simplify it if I were you.

I just did a local test and it appears either the sheer document size or something in the ViewState causes the Regex match evaluation to time out. (Edit: I'm pretty sure it's the size, actually. Removing the ViewState just reduces the size significantly.)
An admittedly crude way to solve this would be something like this:
string[] rawHtmlLines = File.ReadAllLines(#"C:\default.aspx");
string filteredHtml = String.Join(Environment.NewLine,
rawHtmlLines.Where(line => !line.Contains("_VIEWSTATE")).ToArray());
string emailPattern = #"\w+([-+.]\w+)*#\w+([-.]\w+)*\.\w+([-.]\w+)*";
var emailMatches = Regex.Matches(filteredHtml, emailPattern);
foreach (Match match in emailMatches)
{
//...
}
Overall I suspect the email pattern is just not well optimised (or intended) to filter out emails in a large string but just used as validation for user input. Generally it might be a good idea to limit the string you search in to just the parts you are actually interested in and keep it as small as possible - for example by leaving out the ViewState which is guaranteed to not contain any readable email addresses.
If performance is important, it's probably also a better idea to create the filtered HTML using a StringBuilder and IndexOf (etc.) instead of splitting lines and LINQing up the result :)
Edit:
To further minimize the length of the string the Regex needs to check you could only include lines that contain the # character to begin with, like so:
string filteredHtml = String.Join(Environment.NewLine,
rawHtmlLines.Where(line => line.IndexOf('#') >= 0 && !line.Contains("_VIEWSTATE")).ToArray());

From "Function evaluation timed out", I'm assuming you're doing this in the debugger. The debugger has some fairly quick timeouts with regard to how long a method takes. Not eveything happens quickly. I would suggest going the operation in code, storing the result, then viewing that result in the debugger (i.e. let the call to Matches run and put a breakpoint after it).
Now, with regard to detecting whether the string will make Matches take a long time; that's a bit of a black art. You basically have to perform some sort of input validation. Just because you got some value from the internet, doesn't mean that value will work well with Matches. The ultimate validation logic is up to you; but, starting with the length of rawHtmlLines might be useful. (i.e. if the lenght is 1000000 bytes, Matches might take a while) But, you have to decide what to do if the length is too long; e.g give an error to the user.

How to find a repeated string and the value between them using regexes?

How would you find the value of string that is repeated and the data between it using regexes? For example, take this piece of XML:
<tagName>Data between the tag</tagName>
What would be the correct regex to find these values? (Note that tagName could be anything).
I have found a way that works that involves finding all the tagNames that are inbetween a set of < > and then searching for the first instance of the tagName from the opening tag to the end of the string and then finding the closing </tagName> and working out the data from between them. However, this is extremely inefficient and complex. There must be an easier way!
EDIT: Please don't tell me to use XMLReader; I doubt I will ever use my custom class for reading XML, I am trying to learn the best way to do it (and the wrong ways) through attempting to make my own.
Thanks in advance.

You can use: <(\w+)>(.*?)<\/\1>
Group #1 is the tag, Group #2 is the content.

Using regular expressions to parse XML is a terrible error.
This is efficient (it doesn't parse the XML into a DOM) and simple enough:
string s = "<tagName>Data between the tag</tagName>";
using (XmlReader xr = XmlReader.Create(new StringReader(s)))
{
xr.Read();
Console.WriteLine(xr.ReadElementContentAsString());
}
Edit:
Since the actual goal here is to learn something by doing, and not to just get the job done, here's why using regular expressions doesn't work:
Consider this fairly trivial test case:
<a><b><a>text1<b>CDATA<![<a>text2</a>]]></b></a></b>text3</a>
There are two elements with a tag name of "a" in that XML. The first has one text-node child with a value of "text1", and the second has one text-node child with a value of "text3". Also, there's a "b" element that contains a string of text that looks like an "a" element but isn't because it's enclosed in a CDATA section.
You can't parse that with simple pattern-matching. Finding <a> and looking ahead to find </a> doesn't begin to do what you need. You have to put start tags on a stack as you find them, and pop them off the stack as you reach the matching end tag. You have to stop putting anything on the stack when you encounter the start of a CDATA section, and not start again until you encounter the end.
And that's without introducing whitespace, empty elements, attributes, processing instructions, comments, or Unicode into the problem.

You can use a backreference like \1 to refer to an earlier match:
#"<([^>]*)>(.*)</\1>"
The \1 will match what was captured by the first parenthesized group.

with Perl:
my $tagName = 'some tag';
my $i; # some line of XML
$i =~ /\<$tagName\>(.+)\<\/$tagname\>/;
where $1 is now filled with the data you captured

Going forward, if you get stuck check out regexlib.com
It's the first place I go when i get stuck on regex