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Regular Expression to replace Unicode between opening & closing tag

I need fastest method to replace unicode symbols from a string which is next to the '<' or '> tags
For example, input string:
<एक्सएम्ेल type = "ए"> क्सएम् </एक्सएम्ेल>
Expected output :
<REPLACED type = "ए"> क्सएम् </REPLACED>`
Values inside the tag or value of type element should not be replaced, only the tag name should be replaced
This is the code i tried & is not working
private static Regex _compiledUnicodeRegex = new Regex(#"<[^\u0000-\u007F]", RegexOptions.Compiled);
public static String StripUnicodeCharactersFromString(string inputValue)
{
return _compiledUnicodeRegex.Replace(inputValue, "REPLACED");
}
Note -
The unicode values are may not be same always
String may not be in XML format always, so i should match opening tag or closing tag only
I need a regular expression syntax to check whether string right after < is a unicode or string which left to the > is unicode

You want to replace a streak of text that consists of non-ASCII chars, only after < or </, and this is a problem that can be solved with regular expressions.
You may use
var result = Regex.Replace(text, #"(?<=</?)[^\x00-\x7F]+", "REPLACED");
See the .NET regex demo (note it allows infinite width lookbehind patterns).
The regex matches
(?<=</?) - (a positive lookbehind) a location in the string that is preceded by < or </ (in other words, that is preceded with < that may or may not be followed with /)
[^\x00-\x7F]+ - 1 or more chars other than those in the ASCII set.

How to remove multiple, repeating & unnecessary punctuation from string in C#?

Considering strings like this:
"This is a string....!"
"This is another...!!"
"What is this..!?!?"
...
// There are LOTS of examples of weird/angry sentence-endings like the ones above.
I want to replace the unnecessary punctuation at the end to make it look like this:
"This is a string!"
"This is another!"
"What is this?"
What I basically do is:
- split by space
- check if last char in string contains a punctuation
- start replacing with the patterns below
I have tried a very big ".Replace(string, string)" function, but it does not work - there has to be a simpler regex I guess.
Documentation:
Returns a new string in which all occurrences of a specified string in the current instance are replaced with another specified string.
As well as:
Because this method returns the modified string, you can chain together successive calls to the Replace method to perform multiple replacements on the original string.
Anything is wrong here.
EDIT: ALL the proposed solutions work fine! Thank you very much!
This one was the best suited solution for my project:
Regex re = new Regex("[.?!]*(?=[.?!]$)");
string output = re.Replace(input, "");

Your solution works almost fine (demo), the only issue is when the same sequence could be matched starting at different spots. For example, ..!?!? from your last line is not part of the substitution list, so ..!? and !? get replaced by two separate matches, producing ?? in the output.
It looks like your strategy is pretty straightforward: in a chain of multiple punctuation characters the last character wins. You can use regular expressions to do the replacement:
[!?.]*([!?.])
and replace it with $1, i.e. the capturing group that has the last character:
string s;
while ((s = Console.ReadLine()) != null) {
s = Regex.Replace(s, "[!?.]*([!?.])", "$1");
Console.WriteLine(s);
}
Demo

Simply
[.?!]*(?=[.?!]$)
should do it for you. Like
Regex re = new Regex("[.?!]*(?=[.?!]$)");
Console.WriteLine(re.Replace("This is a string....!", ""));
This replaces all punctuations but the last with nothing.
[.?!]* matches any number of consecutive punctuation characters, and the (?=[.?!]$) is a positive lookahead making sure it leaves one at the end of the string.
See it here at ideone.

Or you can do it without regExps:
string TrimPuncMarks(string str)
{
HashSet<char> punctMarks = new HashSet<char>() {'.', '!', '?'};
int i = str.Length - 1;
for (; i >= 0; i--)
{
if (!punctMarks.Contains(str[i]))
break;
}
// the very last punct mark or null if there were no any punct marks in the end
char? suffix = i < str.Length - 1 ? str[str.Length - 1] : (char?)null;
return str.Substring(0, i+1) + suffix;
}
Debug.Assert("What is this?" == TrimPuncMarks("What is this..!?!?"));
Debug.Assert("What is this" == TrimPuncMarks("What is this"));
Debug.Assert("What is this." == TrimPuncMarks("What is this."));

c# How do trim all non numeric character in a string

what is the faster way to trim all alphabet in a string that have alphabet prefix.
For example, input sting "ABC12345" , and i wish to havee 12345 as output only.
Thanks.

Please use "char.IsDigit", try this:
static void Main(string[] args)
{
var input = "ABC12345";
var numeric = new String(input.Where(char.IsDigit).ToArray());
Console.Read();
}

You can use Regular Expressions to trim an alphabetic prefix
var input = "ABC123";
var trimmed = Regex.Replace(input, #"^[A-Za-z]+", "");
// trimmed = "123"
The regular expression (second parameter) ^[A-Za-z]+ of the replace method does most of the work, it defines what you want to be replaced using the following rules:
The ^ character ensures a match only exists at the start of a string
The [A-Za-z] will match any uppercase or lowercase letters
The + means the upper or lowercase letters will be matched as many times in a row as possible
As this is the Replace method, the third parameter then replaces any matches with an empty string.

The other answers seem to answer what is the slowest way .. so if you really need the fastest way, then you can find the index of the first digit and get the substring:
string input = "ABC12345";
int i = 0;
while ( input[i] < '0' || input[i] > '9' ) i++;
string output = input.Substring(i);
The shortest way to get the value would probably be the VB Val method:
double value = Microsoft.VisualBasic.Conversion.Val("ABC12345"); // 12345.0

You would have to regular expression. It seems you are looking for only digits and not letters.
Sample:
string result =
System.Text.RegularExpressions.Regex.Replace("Your input string", #"\D+", string.Empty);

Regular expression to remove whitespace around a comma, except when quoted

I have a CSV file that has rows resembling this:
1, 4, 2, "PUBLIC, JOHN Q" ,ACTIVE , 1332
I am looking for a regular expression replacement that will match against these rows and spit out something resembling this:
1,4,2,"PUBLIC, JOHN Q",ACTIVE,1332
I thought this would be rather easy: I made the expression ([ \t]+,) and replaced it with ,. I made a complement expression (,[ \t]+) with a replacement of , and I thought I had achieved a good means of right-trimming and left-trimming strings.
...but then I noticed that my "PUBLIC, JOHN Q" was now "PUBLIC,JOHN Q" which isn't what I wanted. (Note the space following the comma is now gone).
What would be the appropriate expression to trim the white space before and after a comma, but leave quoted text untouched?
UPDATE
To clarify, I am using an application to handle the file. This application allows me to define multiple regular expression replacements; it does not provide a parsing capability. While this may not be the ideal mechanism for this, it would sure beat making another application for this one file.

If the engine used by your tool is the C# regular expression engine, then you can try the following expression:
(?<!,\s*"(?:[^\\"]|\\")*)\s+(?!(?:[^\\"]|\\")*"\s*,)
replace with empty string.
The guys answers assumed the quotes are balanced and used counting to determine if the space is part of a quoted value or not.
My expression looks for all spaces that are not part of a quoted value.
RegexHero Demo

Something like this might do the job:
(?<!(^[^"]*"[^"]*(("[^"]*){2})*))[\t ]*,[ \t]*
Which matches [\t ]*,[ \t]*, only when not preceded by an odd number of quotes.

Going with some CSV library or parsing the file yourself would be much more easier, and IMO should be preferable option here.
But if you really insist on a regex, you can use this one:
"\s+(?=([^\"]*\"[^\"]*\")*[^\"]*$)"
And replace it with empty string - ""
This regex matches one or more whitespaces, followed by an even number of quotes. This will of course work only if you have balanced quote.
(?x) # Ignore Whitespace
\s+ # One or more whitespace characters
(?= # Followed by
( # A group - This group captures even number of quotes
[^\"]* # Zero or more non-quote characters
\" # A quote
[^\"]* # Zero or more non-quote characters
\" # A quote
)* # Zero or more repetition of previous group
[^\"]* # Zero or more non-quote characters
$ # Till the end
) # Look-ahead end

string format(string val)
{
if (val.StartsWith("\"")) val = " " + val;
string[] vals = val.Split('\"');
for (int i = 0; i < vals.Length; i += 2) vals[i] = vals[i].Replace(" ", "").Replace("\t", "");
return string.Join("\t", vals);
}
This will work if you have properly closed quoted strings in between

Forget the regex (See Bart's comment on the question, regular expressions aren't suitable for CSV).
public static string ReduceSpaces( string input )
{
char[] a = input.ToCharArray();
int placeComma = 0, placeOther = 0;
bool inQuotes = false;
bool followedComma = true;
foreach( char c in a ) {
inQuotes ^= (c == '\"');
if (c == ' ') {
if (!followedComma)
a[placeOther++] = c;
}
else if (c == ',') {
a[placeComma++] = c;
placeOther = placeComma;
followedComma = true;
}
else {
a[placeOther++] = c;
placeComma = placeOther;
followedComma = false;
}
}
return new String(a, 0, placeComma);
}
Demo: http://ideone.com/NEKm09

Regex to match alphanumeric and spaces

What am I doing wrong here?
string q = "john s!";
string clean = Regex.Replace(q, #"([^a-zA-Z0-9]|^\s)", string.Empty);
// clean == "johns". I want "john s";

just a FYI
string clean = Regex.Replace(q, #"[^a-zA-Z0-9\s]", string.Empty);
would actually be better like
string clean = Regex.Replace(q, #"[^\w\s]", string.Empty);

This:
string clean = Regex.Replace(dirty, "[^a-zA-Z0-9\x20]", String.Empty);
\x20 is ascii hex for 'space' character
you can add more individual characters that you want to be allowed.
If you want for example "?" to be ok in the return string add \x3f.

I got it:
string clean = Regex.Replace(q, #"[^a-zA-Z0-9\s]", string.Empty);
Didn't know you could put \s in the brackets

The following regex is for space inclusion in textbox.
Regex r = new Regex("^[a-zA-Z\\s]+");
r.IsMatch(textbox1.text);
This works fine for me.

I suspect ^ doesn't work the way you think it does outside of a character class.
What you're telling it to do is replace everything that isn't an alphanumeric with an empty string, OR any leading space. I think what you mean to say is that spaces are ok to not replace - try moving the \s into the [] class.

There appear to be two problems.
You're using the ^ outside a [] which matches the start of the line
You're not using a * or + which means you will only match a single character.
I think you want the following regex #"([^a-zA-Z0-9\s])+"

bottom regex with space, supports all keyboard letters from different culture
string input = "78-selim güzel667.,?";
Regex regex = new Regex(#"[^\w\x20]|[\d]");
var result= regex.Replace(input,"");
//selim güzel

The circumflex inside the square brackets means all characters except the subsequent range. You want a circumflex outside of square brackets.

This regex will help you to filter if there is at least one alphanumeric character and zero or more special characters i.e. _ (underscore), \s whitespace, -(hyphen)
string comparer = "string you want to compare";
Regex r = new Regex(#"^([a-zA-Z0-9]+[_\s-]*)+$");
if (!r.IsMatch(comparer))
{
return false;
}
return true;
Create a set using [a-zA-Z0-9]+ for alphanumeric characters, "+" sign (a quantifier) at the end of the set will make sure that there will be at least one alphanumeric character within the comparer.
Create another set [_\s-]* for special characters, "*" quantifier is to validate that there can be special characters within comparer string.
Pack these sets into a capture group ([a-zA-Z0-9]+[_\s-]*)+ to say that the comparer string should occupy these features.

[RegularExpression(#"^[A-Z]+[a-zA-Z""'\s-]*$")]
Above syntax also accepts space