Develop Reference

How to replace group of words in file [duplicate]

In C#, I want to use a regular expression to match any of these words:
string keywords = "(shoes|shirt|pants)";
I want to find the whole words in the content string. I thought this regex would do that:
if (Regex.Match(content, keywords + "\\s+",
RegexOptions.Singleline | RegexOptions.IgnoreCase).Success)
{
//matched
}
but it returns true for words like participants, even though I only want the whole word pants.
How do I match only those literal words?

You should add the word delimiter to your regex:
\b(shoes|shirt|pants)\b
In code:
Regex.Match(content, #"\b(shoes|shirt|pants)\b");

Try
Regex.Match(content, #"\b" + keywords + #"\b", RegexOptions.Singleline | RegexOptions.IgnoreCase)
\b matches on word boundaries. See here for more details.

You need a zero-width assertion on either side that the characters before or after the word are not part of the word:
(?=(\W|^))(shoes|shirt|pants)(?!(\W|$))
As others suggested, I think \b will work instead of (?=(\W|^)) and (?!(\W|$)) even when the word is at the beginning or end of the input string, but I'm not sure.

put a word boundary on it using the \b metasequence.

Subexpression inside Regex

I have the following Regex which I use for syntax highlighting:
static Regex inQuotes = new Regex("(\"|\').*(\"|\')", RegexOptions.Compiled);
However, there is an issue. Whenever, I encounter a text like:
"text_example1' or
'text_example2"
it actually changes the color of the text, because these two cases are considered a match. What I want to do is to change this Regex in a way that I can replace the second (\"|\') with something else.
I was thinking about subexpressions and I was wondering on how I could change it so that once I get the first match (" or '), then the last match must be the same as the first match instead of " or '.

(\"|\').*?(\1)
You can use backreferencing here to achieve what you want.Also make your expression non greedy .*? from greedy .*.See demo.
https://regex101.com/r/nM7nT5/3
string strRegex = #"(\""|\').*?(\1)";

Regex to match a word beginning with a period and ending with an underscore?

I'm quite the Regex novice, but I have a series of strings similar to this "[$myVar.myVar_STATE]" I need to replace the 2nd myVar that begins with a period and ends with an underscore. I need it to match it exactly, as sometimes I'll have "[$myVar.myVar_moreMyVar_STATE]" and in that case I wouldn't want to replace anything.
I've tried things like "\b.myVar_\b", "\.\bmyVar_\b" and several more, all to no luck.

How about this:
\[\$myVar\.([^_]+)_STATE\]
Matches:
[$myVar.myVar_STATE] // matches and captures 'myvar'
[$myVar.myVar_moreMyVar_STATE] // no match
Working regex example:
http://regex101.com/r/yM9jQ3
Or if _STATE was variable, you could use this: (as long as the text in the STATE part does not have underscores in it.)
\[\$myVar\.([^_]+)_[^_]+\]
Working regex example:
http://regex101.com/r/kW8oE1
Edit: Conforming to OP's comments below, This should be what he's going for:
(\[\$myVar\.)([^_]+)(_[^_]+\])
Regex replace example:
http://regex101.com/r/pU6yL8
C#
var pattern = #"(\[\$myVar\.)([^_]+)(_[^_]+\])";
var replaced = Regex.Replace(input, pattern, "$1"+ newVar + "$3")

What about something like:
.*.(myVar_).*
This looks for anything then a . and "myVar_" followed by anything.
It matches:
"[$myVar.myVar_STATE]"
And only the first myVar_ here:
"[$myVar.myVar_moremyVar_STATE]"
See it in action.

This should do it:
\[\$myVar\.(.*?)_STATE\]
You can use this little trick to pick out the groups, and build the replacement at the end, like so:
var replacement = "something";
var input = #"[$myVar.myVar_STATE]";
var pattern = #"(\[\$myVar\.)(.*?)_(.*?)]";
var replaced = Regex.Replace(input, pattern, "$1"+ replacement + "_$2]")

C# already has builtin method to do this
string text = ".asda_";
Response.Write((text.StartsWith(".") && text.EndsWith("_")));

Is Regex really required?
string input = "[$myVar.myVar_STATE]";
string oldVar = "myVar";
string newVar = "myNewVar";
string result = input.Replace("." + oldVar + "_STATE]", "." + newVar + "_STATE]");
In case "STATE" is a variable part, then we'll need to use Regex. The easiest way is to use this Regex pattern which matches a position between a prefix and a suffix. Prefix and suffix are used for searching but are not included in the resulting match:
(?<=prefix)find(?=suffix)
result =
Regex.Replace(input, #"(?<=\.)" + Regex.Escape(oldVar) + "(?=_[A-Z]+])", newVar);
Explanation:
The prefix part is \., which stand for ".".
The find part is the escaped old variable to be replaced. Regex escaping makes sure that characters with a special meaning in Regex are escaped.
The suffix part is _[A-Z]+], an underscore followed by at least one letter followed by "]". Note: the second ] needs not to be escaped. An opening bracket [ would have to be escaped like this: \[. We cannot use \w for word characters for the STATE-part as \w includes underscores. You might have to adapt the [A-Z] part to exactly match all possible states (e.g. if state has digits, use [A-Z0-9].

Regex.Match() won't match a substring

This is something simple but I cannot figure this out. I want to find a substring with this regex. It will mach "M4N 3M5", but doesn't match the below :
const string text = "asdf M4N 3M5 adsf";
Regex regex = new Regex(#"^[ABCEGHJKLMNPRSTVXY]{1}\d{1}[A-Z]{1} *\d{1}[A-Z]{1}\d{1}$", RegexOptions.None);
Match match = regex.Match(text);
string value = match.Value;

Try removing ^ and $:
Regex regex = new Regex(#"[ABCEGHJKLMNPRSTVXY]{1}\d{1}[A-Z]{1} *\d{1}[A-Z]{1}\d{1}", RegexOptions.None);
^ : The match must start at the beginning of the string or line.
$ : The match must occur at the end of the string or before \n at the
end of the line or string.
If you want to match only in word boundaries you can use \b as suggested by Mike Strobel:
Regex regex = new Regex(#"\b[ABCEGHJKLMNPRSTVXY]{1}\d{1}[A-Z]{1} *\d{1}[A-Z]{1}\d{1}\b", RegexOptions.None);

I know this question has been answered but i have noticed two thing in your pattern which i want to highlight:
No need to mention the single instance of any token.
For example: (Notice the missing {1})
\d{1} = \d
[A-Z]{1} = [A-Z]
Also I won't recommend you to enter a <space>in your pattern use '\s' instead because if mistakenly a backspace is pressed you might not
be able to figure out the mistake and running code will stop
working.
Personally, for this case i would recommend you to use \b since it is best fit here.

C# doesn't recognize my regular expression as a string even though i have tried escaping everything

Im using C# and wanting to use the following regular expression in my code:
sDatabaseServer\s*=\s*"([^"]*)"
I have placed it in my code as:
Regex databaseServer = new Regex(#"sDatabaseServer\s*=\s*"([^"]*)"", RegexOptions.Compiled | RegexOptions.IgnorePatternWhitespace);
I know you have to escape all parenthesis and quotes inside the string quotes but for some reason the following does still not work:
Working Version:
Regex databaseServer = new Regex(#"sDatabaseServer\s*=\s*""([^""]*)""", RegexOptions.Compiled | RegexOptions.IgnorePatternWhitespace);
Any ideas how to get C# to see my regex as just a string? I know i know....easy question...Sorry im still somewhat of an amateur to C#...
SOLVED: Thanks guys!

You went one step too far when you escaped the parentheses. If you want them to be regex meta-characters (i.e. a capturing group), then you must not escape them. Otherwise they will match literal parentheses.
So this is probably what you are looking for:
#"sDatabaseServer\s*=\s*""([^""]*)"""

string regex = "sDatabaseServer\\s*=\\s*\"([^\"]*)\""
in your first try, you forgot to escape your quotes. But since it's a string literal, escaping with a \ doesn't work.
In y our second try, you escaped the quotes, but you didn't escape the \ that's needed for your whitespace token \s

Use \x22 instead of quotes:
string pattern = #"sDatabaseServer\s*=\s*\x22([^\x22]*)\x22";
But
Ignorepattern whitespace allows for comments in the regex pattern (the # sign) or the pattern split over multiple lines. You don't have either; remove.
A better pattern for what you seek is
string pattern =#"(?:sDatabaseServer\s*=\s*\x22)([^\x22]+)(?:\x22)";
(?: ) is match but don't capture and acts like an anchor for the parser. Also it assumes there will be at least 1 character in the quotes, so using the + instead of the *.