String.Contains() with ignoring case and culture

Question

I had found only StringComparison, but that's not working for Contains. Another necessary thing is ignoring case, and "ä" should equials to "a".

score 11 · Accepted Answer · answered Mar 28 '16 at 01:52

11

public static bool CustomContains(this string source, string toCheck)
{
        CompareInfo ci = new CultureInfo("en-US").CompareInfo;
        CompareOptions co = CompareOptions.IgnoreCase | CompareOptions.IgnoreNonSpace;
        return ci.IndexOf(source, toCheck, co) != -1;
}

answered Mar 28 '16 at 01:52

Joao Leme

9,598
3
33
47

Can't believe I had never heard of the CompareInfo class before ! – Rémy Esmery Apr 27 '16 at 09:39
1

I was skeptical about this solution but it did handle the i, İ, ı and I characters properly (treated them as same). +1 – yasirkula Nov 23 '19 at 17:55

score 6 · Answer 2 · answered Apr 26 '13 at 22:41

Internally string.Contains use string.IndexOf passing a StringComparison.Ordinal.
So I think that you could easily write a method that use the same implementation of Contains

public bool CaseContains(string baseString, string textToSearch, StringComparison comparisonMode)
{
    return (baseString.IndexOf(textToSearch, comparisonMode) != -1);
}

and call with

if(CaseContains(myString, mySearch, StringComparison.CurrentCultureIgnoreCase))
  ....

an elegant evolution of this approach is to create an extension method

public static class StringExtensions
{
    public static bool CaseContains(this string baseString, string textToSearch, StringComparison comparisonMode)
    {
        return (baseString.IndexOf(textToSearch, comparisonMode) != -1);
    }
}

and call with

if(myString.CaseContains(mySearch, StringComparison.CurrentCultureIgnoreCase))
   .....

I believe, this is the most elegant solution. But StringComparison.CurrentCultureIgnoreCaseare is not recognizing "ä" as "a". — Vitalii Vasylenko, Apr 27 '13 at 11:58

Phil Murray · Answer 3 · 2013-04-26T22:44:48.923

1

Thats an umlaut over the a. "ä" is not the same as "a". If you want to change it you need to do it explicitly.

edited Apr 26 '13 at 22:44

answered Apr 26 '13 at 22:36

Phil Murray

6,396
9
45
95

1

Also, it's more common to replace `ä` with `ae` and `ö` with `oe` and so on. http://stackoverflow.com/questions/1271567/how-do-i-replace-accents-german-in-net If he wants to remove diacritics anyway: http://stackoverflow.com/a/7471047/284240 – Tim Schmelter Apr 26 '13 at 22:40
3

// "ä" is not the same as "a". Usually they are not the same, but i need this for product search, so its better to show more results, i think. – Vitalii Vasylenko Apr 26 '13 at 22:51

String.Contains() with ignoring case and culture

3 Answers3

Linked