[c#] How can you strip non-ASCII characters from a string? (in C#)

How can you strip non-ASCII characters from a string? (in C#)

This is not optimal performance-wise, but a pretty straight-forward Linq approach:

string strippedString = new string(
    yourString.Where(c => c <= sbyte.MaxValue).ToArray()
    );

The downside is that all the "surviving" characters are first put into an array of type char[] which is then thrown away after the string constructor no longer uses it.

Necromancing.
Also, the method by bzlm can be used to remove characters that are not in an arbitrary charset, not just ASCII:

// https://en.wikipedia.org/wiki/Code_page#EBCDIC-based_code_pages
// https://en.wikipedia.org/wiki/Windows_code_page#East_Asian_multi-byte_code_pages
// https://en.wikipedia.org/wiki/Chinese_character_encoding
System.Text.Encoding encRemoveAllBut = System.Text.Encoding.ASCII;
encRemoveAllBut = System.Text.Encoding.GetEncoding(System.Globalization.CultureInfo.InstalledUICulture.TextInfo.ANSICodePage); // System-encoding
encRemoveAllBut = System.Text.Encoding.GetEncoding(1252); // Western European (iso-8859-1)
encRemoveAllBut = System.Text.Encoding.GetEncoding(1251); // Windows-1251/KOI8-R
encRemoveAllBut = System.Text.Encoding.GetEncoding("ISO-8859-5"); // used by less than 0.1% of websites
encRemoveAllBut = System.Text.Encoding.GetEncoding(37); // IBM EBCDIC US-Canada
encRemoveAllBut = System.Text.Encoding.GetEncoding(500); // IBM EBCDIC Latin 1
encRemoveAllBut = System.Text.Encoding.GetEncoding(936); // Chinese Simplified
encRemoveAllBut = System.Text.Encoding.GetEncoding(950); // Chinese Traditional
encRemoveAllBut = System.Text.Encoding.ASCII; // putting ASCII again, as to answer the question 

// https://stackoverflow.com/questions/123336/how-can-you-strip-non-ascii-characters-from-a-string-in-c
string inputString = "Räksmör??????, ???gås";
string asAscii = encRemoveAllBut.GetString(
    System.Text.Encoding.Convert(
        System.Text.Encoding.UTF8,
        System.Text.Encoding.GetEncoding(
            encRemoveAllBut.CodePage,
            new System.Text.EncoderReplacementFallback(string.Empty),
            new System.Text.DecoderExceptionFallback()
            ),
        System.Text.Encoding.UTF8.GetBytes(inputString)
    )
);

System.Console.WriteLine(asAscii);

AND for those that just want to remote the accents:
(caution, because Normalize != Latinize != Romanize)

// string str = Latinize("(æøå âôû?aè");
public static string Latinize(string stIn)
{
    // Special treatment for German Umlauts
    stIn = stIn.Replace("ä", "ae");
    stIn = stIn.Replace("ö", "oe");
    stIn = stIn.Replace("ü", "ue");

    stIn = stIn.Replace("Ä", "Ae");
    stIn = stIn.Replace("Ö", "Oe");
    stIn = stIn.Replace("Ü", "Ue");
    // End special treatment for German Umlauts

    string stFormD = stIn.Normalize(System.Text.NormalizationForm.FormD);
    System.Text.StringBuilder sb = new System.Text.StringBuilder();

    for (int ich = 0; ich < stFormD.Length; ich++)
    {
        System.Globalization.UnicodeCategory uc = System.Globalization.CharUnicodeInfo.GetUnicodeCategory(stFormD[ich]);

        if (uc != System.Globalization.UnicodeCategory.NonSpacingMark)
        {
            sb.Append(stFormD[ich]);
        } // End if (uc != System.Globalization.UnicodeCategory.NonSpacingMark)

    } // Next ich


    //return (sb.ToString().Normalize(System.Text.NormalizationForm.FormC));
    return (sb.ToString().Normalize(System.Text.NormalizationForm.FormKC));
} // End Function Latinize

no need for regex. just use encoding...

sOutput = System.Text.Encoding.ASCII.GetString(System.Text.Encoding.ASCII.GetBytes(sInput));

I used this regex expression:

    string s = "søme string";
    Regex regex = new Regex(@"[^a-zA-Z0-9\s]", (RegexOptions)0);
    return regex.Replace(s, "");

If you want not to strip, but to actually convert latin accented to non-accented characters, take a look at this question: How do I translate 8bit characters into 7bit characters? (i.e. Ü to U)

I believe MonsCamus meant:

parsememo = Regex.Replace(parsememo, @"[^\u0020-\u007E]", string.Empty);

I found the following slightly altered range useful for parsing comment blocks out of a database, this means that you won't have to contend with tab and escape characters which would cause a CSV field to become upset.

parsememo = Regex.Replace(parsememo, @"[^\u001F-\u007F]", string.Empty);

If you want to avoid other special characters or particular punctuation check the ascii table

I came here looking for a solution for extended ascii characters, but couldnt find it. The closest I found is bzlm's solution. But that works only for ASCII Code upto 127(obviously you can replace the encoding type in his code, but i think it was a bit complex to understand. Hence, sharing this version). Here's a solution that works for extended ASCII codes i.e. upto 255 which is the ISO 8859-1

It finds and strips out non-ascii characters(greater than 255)

Dim str1 as String= "â, ??î or ôu? n?i?++$-?!??4?od;/?'®;?:?)///1!@#"

Dim extendedAscii As Encoding = Encoding.GetEncoding("ISO-8859-1", 
                                                New EncoderReplacementFallback(String.empty),
                                                New DecoderReplacementFallback())

Dim extendedAsciiBytes() As Byte = extendedAscii.GetBytes(str1)

Dim str2 As String = extendedAscii.GetString(extendedAsciiBytes)

console.WriteLine(str2)
'Output : â, ??î or ôu ni++$-!??4od;/';:)///1!@#$%^yz:

Here's a working fiddle for the code

Replace the encoding as per the requirement, rest should remain the same.

I use this regular expression to filter out bad characters in a filename.

Regex.Replace(directory, "[^a-zA-Z0-9\\:_\- ]", "")

That should be all the characters allowed for filenames.

Inspired by philcruz's Regular Expression solution, I've made a pure LINQ solution

public static string PureAscii(this string source, char nil = ' ')
{
    var min = '\u0000';
    var max = '\u007F';
    return source.Select(c => c < min ? nil : c > max ? nil : c).ToText();
}

public static string ToText(this IEnumerable<char> source)
{
    var buffer = new StringBuilder();
    foreach (var c in source)
        buffer.Append(c);
    return buffer.ToString();
}

This is untested code.

Here is a pure .NET solution that doesn't use regular expressions:

string inputString = "Räksmörgås";
string asAscii = Encoding.ASCII.GetString(
    Encoding.Convert(
        Encoding.UTF8,
        Encoding.GetEncoding(
            Encoding.ASCII.EncodingName,
            new EncoderReplacementFallback(string.Empty),
            new DecoderExceptionFallback()
            ),
        Encoding.UTF8.GetBytes(inputString)
    )
);

It may look cumbersome, but it should be intuitive. It uses the .NET ASCII encoding to convert a string. UTF8 is used during the conversion because it can represent any of the original characters. It uses an EncoderReplacementFallback to to convert any non-ASCII character to an empty string.