How do I strip non-alphanumeric characters (including spaces) from a string?

Question

How do I strip non alphanumeric characters from a string and loose spaces in C# with Replace?

I want to keep a-z, A-Z, 0-9 and nothing more (not even \" \" spaces).<

Answer 1

In your regex, you have excluded the spaces from being matched (and you haven't used Regex.Replace() which I had overlooked completely...):

result = Regex.Replace("Hello there(hello#)", @"[^A-Za-z0-9]+", "");

should work. The + makes the regex a bit more efficient by matching more than one consecutive non-alphanumeric character at once instead of one by one.

If you want to keep non-ASCII letters/digits, too, use the following regex:

@"[^\p{L}\p{N}]+"

which leaves

BonjourmesélèvesGutenMorgenliebeSchüler

instead of

BonjourmeslvesGutenMorgenliebeSchler

Answer 2

In .Net 4.0 you can use the IsNullOrWhitespace method of the String class to remove the so called white space characters. Please take a look here http://msdn.microsoft.com/en-us/library/system.string.isnullorwhitespace.aspx However as @CodeInChaos pointed there are plenty of characters which could be considered as letters and numbers. You can use a regular expression if you only want to find A-Za-z0-9.

Answer 3

Or you can do this too:

    public static string RemoveNonAlphanumeric(string text)
    {
        StringBuilder sb = new StringBuilder(text.Length);

        for (int i = 0; i < text.Length; i++)
        {
            char c = text[i];
            if (c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' || c >= '0' && c <= '9')
                sb.Append(text[i]);
        }

        return sb.ToString();
    }

Usage:

string text = SomeClass.RemoveNonAlphanumeric("text LaLa (lol) á ñ $ 123 ٠١٢٣٤");

//text: textLaLalol123

Answer 4

And as a replace operation as an extension method:

public static class StringExtensions
{
    public static string ReplaceNonAlphanumeric(this string text, char replaceChar)
    {
        StringBuilder result = new StringBuilder(text.Length);

        foreach(char c in text)
        {
            if(c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' || c >= '0' && c <= '9')
                result.Append(c);
            else
                result.Append(replaceChar);
        }

        return result.ToString();
    } 
}

And test:

[TestFixture]
public sealed class StringExtensionsTests
{
    [Test]
    public void Test()
    {
        Assert.AreEqual("text_LaLa__lol________123______", "text LaLa (lol) á ñ $ 123 ٠١٢٣٤".ReplaceNonAlphanumeric('_'));
    }
}

Answer 5

var text = "Hello there(hello#)";

var rgx = new Regex("[^a-zA-Z0-9]");

text = rgx.Replace(text, string.Empty);

Answer 6

Use following regex to strip those all characters from the string using Regex.Replace

([^A-Za-z0-9\s])