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C# Extract part of the string that starts with specific letters

I have a string which I extract from an HTML document like this:
var elas = htmlDoc.DocumentNode.SelectSingleNode("//a[#class='a-size-small a-link-normal a-text-normal']");
if (elas != null)
{
//
_extractedString = elas.Attributes["href"].Value;
}
The HREF attribute contains this part of the string:
gp/offer-listing/B002755TC0/
And I'm trying to extract the B002755TC0 value, but the problem here is that the string will vary by its length and I cannot simply use Substring method that C# offers to extract that value...
Instead I was thinking if there's a clever way to do this, to perhaps a match beginning of the string with what I search?
For example I know for a fact that each href has this structure like I've shown, So I would simply match these keywords:
offer-listing/
So I would find this keyword and start extracting the part of the string B002755TC0 until the next " / " sign ?
Can someone help me out with this ?

This is a perfect job for a regular expression :
string text = "gp/offer-listing/B002755TC0/";
Regex pattern = new Regex(#"offer-listing/(\w+)/");
Match match = pattern.Match(text);
string whatYouAreLookingFor = match.Groups[1].Value;
Explanation : we just match the exact pattern you need.
'offer-listing/'
followed by any combination of (at least one) 'word characters' (letters, digits, hyphen, etc...),
followed by a slash.
The parenthesis () mean 'capture this group' (so we can extract it later with match.Groups[1]).
EDIT: if you want to extract also from this : /dp/B01KRHBT9Q/
Then you could use this pattern :
Regex pattern = new Regex(#"/(\w+)/$");
which will match both this string and the previous. The $ stands for the end of the string, so this literally means :
capture the characters in between the last two slashes of the string

Though there is already an accepted answer, I thought of sharing another solution, without using Regex. Just find the position of your pattern in the input + it's lenght, so the wanted text will be the next character. to find the end, search for the first "/" after the begining of the wanted text:
string input = "gp/offer-listing/B002755TC0/";
string pat = "offer-listing/";
int begining = input.IndexOf(pat)+pat.Length;
int end = input.IndexOf("/",begining);
string result = input.Substring(begining,end-begining);
If your desired output is always the last piece, you could also use split and get the last non-empty piece:
string result2 = input.Split(new string[]{"/"},StringSplitOptions.RemoveEmptyEntries)
.ToList().Last();

C# Regex for retrieving capital string in quotation mark

Given a string, I want to retrieve a string that is in between the quotation marks, and that is fully capitalized.
For example, if a string of
oqr"awr"q q"ASRQ" asd "qIKQWIR"
has been entered, the regex would only evaluate "ASRQ" as matching string.
What is the best way to approach this?
Edit: Forgot to mention the string takes a numeric input as well I.E: "IO8917AS" is a valid input

EDIT: If you actually want "one or more characters, and none of the characters is a lower-case letter" then you probably want:
Regex regex = new Regex("\"\\P{Ll}+\"");
That will then allow digits as well... and punctuation. If you want to allow digits and upper case letters but nothing else, you can use:
Regex regex = new Regex("\"[\\p{Lu}\\d]+\"");
Or in verbatim string literal form (makes the quotes more confusing, but the backslashes less so):
Regex regex = new Regex(#"""[\p{Lu}\d]+""");
Original answer (before digits were required)
Sounds like you just want (within the pattern)
"[A-Z]*"
So something like:
Regex regex = new Regex("\"[A-Z]*\"");
Or for full Unicode support, use the Lu Unicode character category:
Regex regex = new Regex("\"\\p{Lu}*\"");
EDIT: As noted, if you don't want to match an empty string in quotes (which is still "a string where everything is upper case") then use + instead of *, e.g.
Regex regex = new Regex("\"\\p{Lu}+\");
Short but complete example of finding and displaying the first match:
using System;
using System.Text.RegularExpressions;
class Program
{
public static void Main()
{
Regex regex = new Regex("\"\\p{Lu}+\"");
string text = "oqr\"awr\"q q\"ASRQ\" asd \"qIKQWIR\"";
Match match = regex.Match(text);
Console.WriteLine(match.Success); // True
Console.WriteLine(match.Value); // "ASRQ"
}
}

Like this:
"\"[A-Z]+\""
The outermost quotes are not part of the regex, they delimit a C# string.
This requires at least one uppercase character between quotes and works for the English language.

Please try the following:
[\w]*"([A-Z0-9]+)"

Replacing doubleslash to single slash

In my c# application i want to convert a string characters to special characters.
My input string is "G\u00f6teborg" and i want the output as Göteborg.
I am using below code,
string name = "G\\u00f6teborg";
StringBuilder sb = new StringBuilder(name);
sb = sb.Replace(#"\\",#"\");
string name1 = System.Web.HttpUtility.HtmlDecode(sb.ToString());
Console.WriteLine(name1);
In the above code the double slash remains the same , it is not replacing to single slash, so after decoding i am getting the output as G\u00f6teborg .
Please help to find a solution for this.
Thanks in advance.

string name = "G\\u00f6teborg";
Just remove one of the backslashes:
string name = "G\u00f6teborg";
If you got the input from a user then you need to do more: it’s not enough to replace a backslash because that’s not how the characters are stored internally, the \uXXXX is an escape sequence representing a Unicode code point.
If you want to replace a user input escape sequence by a Unicode code point you need to parse the user input properly. You can use a regular expression for that:
MatchEvaluator replacer = m => ((char) int.Parse(m.Groups[1].Value, NumberStyles.AllowHexSpecifier)).ToString();
string result = Regex.Replace(name, #"\\u([a-fA-F0-9]{4})", replacer);
This matches each escape group (\u followed by four hex digits), extracts the hex digits, parses them and translates them to a character.

problem in regular expression

I am having a regular expression
Regex r = new Regex(#"(\s*)([A|B|C|E|G|H|J|K|L|M|N|P|R|S|T|V|Y|X]\d(?!.*[DFIOQU])(?:[A-Z](\s?)\d[A-Z]\d))(\s*)",RegexOptions.IgnoreCase);
and having a string
string test="LJHLJHL HJGJKDGKJ JGJK C1C 1C1 LKJLKJ";
I have to fetch C1C 1C1.This running fine.
But if a modify test string as
string test="LJHLJHL HJGJKDGKJ JGJK C1C 1C1 ON";
then it is unable to find the pattern i.e C1C 1C1.
any idea why this expression is failing?

You have a negative look ahead:
(?!.*[DFIOQU])
That matches the "O" in "ON" and since it is a negative look ahead, the whole pattern fails. And, as an aside, I think you want to replace this:
[A|B|C|E|G|H|J|K|L|M|N|P|R|S|T|V|Y|X]
With this:
[A-CEGHJ-NPR-TVYX]
A pipe (|) is a literal character inside a character class, not an alternation, and you can use ranges to help hilight the characters that you're leaving out.
A single regex might not be the best way to parse that string. Or perhaps you just need a looser regex.

You are searching for a not a following DFIOQU with your negative look ahead (?!.*[DFIOQU])
In your second string there is a O at the end in ON, so it must be failing to match.
If you remove the .* in your negative look ahead it will only check the directly following character and not the complete string to the end (Is it this what you want?).
\s*([ABCEGHJKLMNPRSTVYX]\d(?![DFIOQU])(?:[A-Z]\s?\d[A-Z]\d))\s*
then it works, see it here on Regexr. It is now checking if there is not one of the characters in the class directly after the digit, I don't know if this is intended.
Btw. I removed the | from your first character class, its not needed and also some brackets around your whitespaces, also not needed.

As I understood you need to find the C1C 1C1 text in your string
I've used this regex for do this
string strRegex = #"^.*(?<c1c>C1C)\s*(?<c1c2>1C1).*$";
after that you can extract text from named groups
string strRegex = #"^.*(?<c1c>C1C)\s*(?<c1c2>1C1).*$";
RegexOptions myRegexOptions = RegexOptions.Multiline;
Regex myRegex = new Regex(strRegex, myRegexOptions);
string strTargetString = #"LJHLJHL HJGJKDGKJ JGJK C1C 1C1 LKJLKJ";
string secondStr = "LJHLJHL HJGJKDGKJ JGJK C1C 1C1 ON";
Match match = myRegex.Match(strTargetString);
string c1c = match.Groups["c1c"].Value;
string c1c2 = match.Groups["c1c2"].Value;
Console.WriteLine(c1c + " " +c1c2);

Simple regex question C#

I need to match the string that is shown in the window displayed below :
8% of setup_av_free.exe from software-files-l.cnet.com Completed
98% of test.zip from 65.55.72.119 Completed
[numeric]%of[filename]from[hostname | IP address]Completed
I have written the regex pattern halfway
if (Regex.IsMatch(text, #"[\d]+%[\s]of[\s](.+?)(\.[^.]*)[\s]from[\s]"))
MessageBox.Show(text);
and I now need to integrate the following regex into my code above
ValidIpAddressRegex = "^(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])$";
ValidHostnameRegex = "^(([a-zA-Z]|[a-zA-Z][a-zA-Z0-9\-]*[a-zA-Z0-9])\.)*([A-Za-z]|[A-Za-z][A-Za-z0-9\-]*[A-Za-z0-9])$";
The 2 regex were taken from this link. These 2 regex works well when i use the Regex.ismatch to match "123.123.123.123" and "software-files-l.cnet.com" . However i cannot get it to work when i intergrate both of them to my existin regex code. I tried several variant but not able to get it to work. Can someone guide me to integrate the 2 regex to my existing code. Thanks in advance.

You can certainly combine all these regular expressions into one, but I'd recommend against it. Consider this method, first it checks wether your input text has the correct form overall, then it checks if the "from" part is an IP address or a hostname.
bool CheckString(string text) {
const string ValidIpAddressRegex = #"^(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])$";
const string ValidHostnameRegex = #"^(([a-zA-Z]|[a-zA-Z][a-zA-Z0-9\-]*[a-zA-Z0-9])\.)*([A-Za-z]|[A-Za-z][A-Za-z0-9\-]*[A-Za-z0-9])$";
var match = Regex.Match(text, #"[\d]+%[\s]of[\s](.+?)(\.[^.]*)[\s]from[\s](\S+)");
if(!match.Success)
return false;
string address = match.Groups[3].Value;
return Regex.IsMatch(address, ValidIpAddressRegex) ||
Regex.IsMatch(address, ValidHostnameRegex);
}
It does what you want and is much more readable and than single monster-sized regular expression. If you aren't going to call this method millions of time in a loop there is no reason to be concerned about it being less performant that single regex.
Also, in case you aren't aware of that the brackets around \d or \s aren't necessary.

The "Problem" that those two regexes do not match your string is that they start with ^ and end with $
^ means match the start of the string (or row if the m modifier is activated)
$ means match the end of the string (or row if the m modifier is activated)
When you try it this is true but in your real text they are in the middle of the string, so it is not matched.
Try just remove the ^ at the very beginning and the $ at the very end.

Here you go.
^[\d]+%[\s+]of[\s+](.+?)(\.[^.]*)[\s+]from[\s+]((([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])|((([a-zA-Z]|[a-zA-Z][a-zA-Z0-9\-]*[a-zA-Z0-9])\.)*([A-Za-z]|[A-Za-z][A-Za-z0-9\-]*[A-Za-z0-9])))[\s+]Completed
Remove the ^ and $ characters from the ValidIpAddressRegex and ValidHostnameRegex samples above, and add them separated by the or character (|) enclosed by parentheses.

You could use this, its should work for all cases. I mightve accidentally deleted a character while formatting so let me know if it doesnt work.
string captureString = "8% of setup_av_free.exe from software-files-l.cnet.com Completed";
Regex reg = new Regex(#"(?<perc>\d+)% of (?<file>\w+\.\w+) from (?<host>" +
#"(\d+\.\d+.\d+.\d+)|(((https?|ftp|gopher|telnet|file|notes|ms-help):" +
#"((//)|(\\\\))+)?[\w\d:##%/;$()~_?\+-=\\\.&]*)) Completed");
Match m = reg.Match(captureString);
string perc = m.Groups["perc"].Value;
string file = m.Groups["file"].Value;
string host = m.Groups["host"].Value;