How to check special characters in input string in C#

Question

0.00/5 (No votes)

See more:

Hi

How to check the input string contain only special characters ,using regular expression.

C#

public static bool IsSpecialCharacters(this string stringToTest)
       {
           const string charSet = "[^a-z0-9]";

           //Regex RgxUrl = new Regex("[^a-z0-9]");
           //blnContainsSpecialCharacters = RgxUrl.IsMatch(stringToCheck);

           return Regex.Match(stringToTest, @"^[" + charSet + @"]+$").Success;
       }

Is this method is correct?

Posted 15-Apr-13 21:50pm

sugunakumaravel

Updated 18-May-23 3:20am

Add a Solution

Comments

Zoltán Zörgő 16-Apr-13 3:56am

do not double square brackets

Prasad Khandekar 16-Apr-13 4:00am

Hello,

The regular expression should work. However all characters other than a-z,0-9 will mbe treated as special characters even uppercase letters and whitespace. If you don;t want that to happen then change it to [^a-zA-Z0-9\s]+. You can use Expresso (http://www.ultrapico.com/) regular expresion tester to test your expressions.

Regards,

Maciej Los 16-Apr-13 4:02am

Please, post it as an answer.
My virtual 5!

paracha1 9-Nov-17 10:19am

you can use only this simple way. its working fine

public static bool HasSpecialChars(string stString)
{
if (stString.Any(ch => !Char.IsLetterOrDigit(ch)))
{
return true;
}
else {
return false;
}
}

3 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

gopal2007 · Answer 1 · 2023-05-18T03:20:00

Solution 3

public static bool hasSpecialChar(string input)
{
string specialChar = @"\|!#$%&/()=?»«@£§€{}.-;'<>_,*+";
foreach (var item in specialChar)
{
if (input.Contains(item.ToString())) return true;
}

return false;
}

Posted 18-May-23 3:20am

gopal2007

Comments

Richard Deeming 18-May-23 9:34am

Aside from the fact that you're more than ten years late on this question, that's a horrible solution!

At the very least, you should remove the .ToString() call within the loop. The Contains method has had an overload which accepts a char since .NET Core 2.1; if you're still stuck in .NET Framework, you can use IndexOf instead:

if (input.IndexOf(item) != -1) return true;

A better option would be to use a char array and call IndexOfAny:

private static readonly char[] SpecialChars = 
{
    '\\', '|', '!', '#', '$', '%', '&', '/', '(', ')', 
    '=', '?', '»', '«', '@', '£', '§', '€', '{', '}', 
    '.', '-', ';', '\'', '<', '>', '_', ',', '*', '+'
};

public static bool HasSpecialChar(string input) => input != null && input.IndexOfAny(SpecialChars) != -1;

Hemant761 · Answer 2 · 2013-04-16T02:50:00

Solution 2

you can simply check like below.

just add namespace

using system.linq

int PasswordSpecialChar = txtMonth.Text.Count(p => !char.IsLetterOrDigit(p));

Posted 16-Apr-13 2:50am

Hemant761

v2

OriginalGriff · Answer 3 · 2013-04-15T22:03:00

Solution 1

No.
Your solution will not work with upper case, for example. Try this:

C#

return Regex.Match(stringToTest, @"^\W+$").Success;

Which matches everything that is not alphanumeric.

Posted 15-Apr-13 22:03pm

OriginalGriff

Comments

Arjun Menon U.K 13-Nov-13 6:37am

Hi,
\w --> checks for [A-Za-z0-9_] and
\W--> checks for characters other than [A-Za-z0-9_]
rt?
So what if i have to check only alphanumerics a-z or -0-9 or combination of both.... Currently am using this
Regex regexUSerName = new Regex("^[a-zA-Z0-9 ]*$");

OriginalGriff 13-Nov-13 7:19am

Don't hijack threads that aren't directly related to your question - ask a new question instead. Otherwise it is rude - particularly with an old question!

Arjun Menon U.K 20-Nov-13 5:58am

My apologies...