How do I remove all non alphanumeric word from a List

Question

How do I remove all non alphanumeric words from a list of strings (List<string>) ?

I found this regex !word.match(/^[[:alpha:]]+$/) but in C# how can I obtain a new list that contains only the strings that are purely alphanumeric ?

if c# then with linq `list.Where(x => Regex.IsMatch(x, @"^[a-zA-Z0-9]$")).ToList();` — M.kazem Akhgary, Oct 15 '15 at 13:56
You want to remove all the non-alphanumeric *characters* from all the strings? Or you want a new list that contains *only the strings that are purely alphanumeric*? — Konamiman, Oct 15 '15 at 13:57
I want a new list that contains only the strings that are purely alphanumeric — LeMoussel, Oct 15 '15 at 13:57
A new list is not quite the same, as removing all the unwanted elements from an existing list. — Mithrandir, Oct 15 '15 at 13:59
@M.kazemAkhgary shouldn't it be `list.Where(x => Regex.IsMatch(x, @"[a-zA-Z0-9]*")).ToList();` ? — Thomas Ayoub, Oct 15 '15 at 13:59
@Thomas oh true. i forgot. pattern should be `^[a-zA-Z0-9]*$` — M.kazem Akhgary, Oct 15 '15 at 14:04

score 10 · Accepted Answer · answered Oct 15 '15 at 13:59

10

You can use LINQ for this. Assuming you have a theList (or array or whatever) with your strings:

var theNewList = theList.Where(item => item.All(ch => char.IsLetterOrDigit(ch)));

Add a .ToList() or .ToArray() at the end if desired. This works because the String class implements IEnumerable<char>.

answered Oct 15 '15 at 13:59

Konamiman

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Actually, `[[:alpha:]]` class only matches letters, thus `Char.IsLetter()` must be used. However, it might be OP regex issue :) – Wiktor Stribiżew Oct 15 '15 at 14:02
1

OP says Alphanumeric. So `Char.IsLetterOrDigit` is correct – wingerse Oct 15 '15 at 14:02
The OP needs *alphanumeric* strings, I assume that this includes numbers. The regex in the question is only an example that (s)he found elsewhere. – Konamiman Oct 15 '15 at 14:03

score 3 · Answer 2 · answered Oct 15 '15 at 14:10

  Regex rgx = new Regex("^[a-zA-Z0-9]*$");
  List<string> list = new List<string>() { "aa", "a", "kzozd__" ,"4edz45","5546","4545asas"};
  List<string> list1 = new List<string>();
  foreach (var item in list)
  {
     if (rgx.Match(item).Success)
     list1.Add(item);
  }

score 1 · Answer 3 · edited Oct 15 '15 at 14:25

1

With LINQ + regex, you can use this:

list = list.Where(s => Regex.IsMatch(s, "^[\\p{L}0-9]*$")).ToList();

^[\\p{L}0-9]*$ can recognise Unicode alphanumeric characters. If you want to use ASCII only, ^[a-zA-Z0-9]*$ will work just as well.

edited Oct 15 '15 at 14:25

M.kazem Akhgary

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answered Oct 15 '15 at 14:05

wingerse

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GeorgDangl · Answer 4 · 2015-10-15T14:09:38.810

0

There's a static helper function that removes all non-alphanumeric strings from a List:

    public static List<string> RemoveAllNonAlphanumeric(List<string> Input)
    {
        var TempList = new List<string>();
        foreach (var CurrentString in Input)
        {
            if (Regex.IsMatch(CurrentString, "^[a-zA-Z0-9]+$"))
            {
                TempList.Add(CurrentString);
            }
        }
        return TempList;
    }

edited Oct 15 '15 at 14:09

answered Oct 15 '15 at 13:59

GeorgDangl

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Your code will return all the string that contains at least one alphanumeric char – Thomas Ayoub Oct 15 '15 at 14:06

How do I remove all non alphanumeric word from a List

4 Answers4