Develop Reference

RegEx for matching special chars no spaces or newlines

I have a string and want to use regex to match all the chars, but no spaces.
I tried to replace all the spaces with nothing, using:
Regex.Replace(seller, #"[A-z](.+)", m => m.Groups[1].Value);
//rating
var betyg = Regex.Replace(seller, #"[A-z](.+)", m => m.Groups[1].Value);`
I expect the output of
"Iris-presenter | 5"
but, the output is
"Iris-presenter"
seen in this also seen in this demo.
The string is:
<spaces>Iris-presenter
<spaces>|
<spaces>5

Great question! I'm not quite sure, if this would be what you might be looking for. This expression however matches your input string:
^((?!\s|\n).)*
Graph
The graph shows how it might work:
Edit
Based on revo's advice, the expression can be much simplified, because
^((?!\s|\n).)* is equal to ^((?!\s).)* and both are equal to ^\S*.

I used (\s(.*?)) for it to work. This removes all spaces and new lines seen here

Writing a proper regex to allow number and only combinations of letters and numbers mixed up

I have a string example which looks like this:
51925120851209567
The length of the string and numbers may vary, however I want to only enable the string to contain just either numbers, or for it to be a combination of letters and numbers. For example a valid one would be something like this:
B0031Y4M8S // contains combination of letters and numbers without white space
Invalid regex would be:
Does not apply // this one contains white spaces and has only letters
To summarize things up, the regex should allow only these combinations:
51925120851209567 // contains only numbers and is valid
B0031Y4M8S // contains combination of numbers and letters and is valid as well
Everything else is invalid...
The current solution that I have covers only for the string to be a set of integers and nothing else... However I'm not really sure how to filter out combination of numbers and letters without white spaces and special charachters to be valid as well for the regex?
Regex regex = new Regex("^[0-9]+$");
if (regex.IsMatch(parameter))
{
// allow if statement to pass if the regex matches
}
Can someone help me out ?

You may use
^(?![A-Za-z]+$)[0-9A-Za-z]+$
It matches 1+ alphanumeric chars but will fail a match if all string consists of just letters.
Details
^ - start of a string
(?![A-Za-z]+$) - a negative lookahead that fails the match if there are 1+ ASCII letters followed with the end of string immediately to the right of the current location
[0-9A-Za-z]+ - 1+ ASCII letters
$ - end of string.
See the regex demo.

#The fourth bird's answer will almost get you there. I'm no regex expert, but an easy way to get you what you want would be to use:
Regex regex = new Regex("^[a-zA-Z0-9]+$");
This will get you the first level of exclusion. If it passes that, then check with:
Regex regex = new Regex("^[a-zA-Z]+$");
If it matches that, then you know it's only alphabetical characters and you can skip it. I'm sure there's a better way to code golf this one out, but this should work for now if you're in a crunch.

Checking C input for regex value of "IntegerxInteger"

I am new to C and I am trying to detect if a user entered some regex of IntxInt (i.e. 2x5 or 10x15). I will not go over 15.
From what I have gathered I can just make a regex to detect this. I have been confused on making regex's for C though and no examples have been very useful yet.
I found this example here
string pattern = #"\*\d*\.txt";
Regex rgx = new Regex(pattern)
input = rgx.Replace(input, "");
And my guess of making it fit the above criteria would be something like this
string pattern = #"[0-9][0-9]*[x|X][0-9][0-9]*";
I would guess this as I need at least 1 digit, followed by possible another? Not sure how to limit it to 0 or 1 more numbers. Followed by an X. Then the same thing as the first part.
Is this right/wrong, why?
If this is correct, how do I "test" the input I get in?

Use this regex:
^(?i)(?:1[0-5]|[1-9])x(?:1[0-5]|[1-9])$
(?i) makes x case-insensitive so it can match both x and X.
(?:1[0-5]|[1-9]) matches digits from "1" to "15".
Here is a regex demo.

Regex to exclude all chars except letters

I'm a real regex n00b so I ask your help:
I need a regex witch match only letters and numbers and exclude punctations, non ascii characters and spaces.
"ilikestackoverflow2012" would be a valid string.
"f### you °§è" not valid.
"hello world" not valid
"hello-world" and "*hello_world*" not valid
and so on.
I need it to make a possibly complex business name url friendly.
Thanks in advance!

You don't need regex for this.
string s = "......"
var isValid = s.All(Char.IsLetterOrDigit);
-
I need it to make a possibly complex business name url friendly
You can also use HttpUtility.UrlEncode
var urlFriendlyString = HttpUtility.UrlEncode(yourString);

To validate a string you can use the following regular expression with Regex.IsMatch:
"^[0-9A-Za-z]+$"
Explanation:
^ is a start of string anchor.
[...] is a character class.
+ means one or more.
$ is an end of string anchor.
I need it to make a possibly complex business name url friendly
Then you want to replace the characters that don't match. Use Regex.Replace with the following regular expression:
"[^0-9A-Za-z]+"
Explanation:
[^...] is a negated character class.
Code:
string result = Regex.Replace(input, "[^0-9A-Za-z]+" , "");
See it working online: ideone
Note that different business names could give the same resulting string. For example, businesses whose names contain only Chinese characters will all give the empty string.

You can use below regex.
^[a-zA-Z0-9]+$

^[0-9a-zA-Z]+$
Matches one or more alphanumeric characters with no spaces or non-alpha characters.

Try this:
var regex = new Regex(#"^[a-zA-Z0-9]+$");
var test = new[] {"ilikestack", "hello world", "hello-world", "###"};
foreach (var s in test)
Console.WriteLine("{0}: {1}", s, regex.IsMatch(s));
EDIT: If you want something like #Andre_Miller said, you should use the same regex with Regex.Replace();
Regex.Replace(s, #"[^a-zA-Z0-9]+", "")
OR
var regex = new Regex(#"^[a-zA-Z0-9]+$");
regex.Replace("input-string-##$##");

Try
^[a-zA-Z0-9]+$
www.regexr.com is a GREAT resource.

What's wrong with [:alnum:]? It's a posix standard. So your whole regex would be: ^[:alnum:]+$.
The wikipedia article for regular expressions includes lots of examples and details.

Regular Expression Not working in .net

I'm using the following expression.
\W[A-C]{3}
The objective is to match 3 characters of anything between A and C that don't have any characters before them. So with input "ABC" it matches but "DABC" does not.
When i try this expression using various online regex tools (eg. http://gskinner.com/RegExr/), it works perfectly. When i try to use it in an asp.net RegularExpressionValidator or with the RegEx class, it never matches anything.
I've tried various different methods of not allowing a character before the match. eg.
[^\w] and [^a-zA-Z0-9]
all work in the online tools, but not in .net.
This test fails, but i'm not sure why?
[Test]
public void RegExWorks()
{
var regex = new Regex("\\W[A-C]{3}");
Match match = regex.Match("ABC");
Assert.IsTrue(match.Success);
}

How about something like this:
^[A-C]{3}
It is simple, but seems to fit what you are asking, and I tested it in rubular.com and .NET

Problem is that you require there to be a \W character. Use alteration to fix that, or a lookbehind to make sure there are no invalid characters.
Alteration:
(?:\W|^)[A-C]{3}
But I'd prefer a negative lookbehind:
(?<!\w)[A-C]{3}
\b (as in gymbralls answer) is short for (?<!\w)(?=\w)|(?<=\w)(?!\w), which in this case would just mean (?<!\w), thus being equivalent.
Also, in C# you can use the # quoting so you don't have to double escape things, eg:
var regex = new Regex(#"(?<!\w)[A-C]{3}");

You should consider trying:
[Test]
public void RegExWorks()
{
var regex = new Regex("\\b[A-C]{3}");
Match match = regex.Match("ABC");
Assert.IsTrue(match.Success);
}
The \\b matches a word boundary, which means it will match "ABC" as well as " ABC" and "$ABC". Using \\W requires there to be a non-word character, which doesn't sound like it is what you want.
Let me know if I'm missing something.

It is simple like "[A-C]{3}" this

OK so you can try following Expression
"[A-C][A-C]{2}"