Case invariant search for a string in an array/list of strings

Question

The following code could be used to search in an array / List of strings using LINQ.

String[] someArray
    = { "Test1", "test2", "test3", "TEST4" };

string toCheck = "Test1";

if (someArray.Any(toCheck.Contains))
{
    // found -> Do sth.
}
// or with list 

List<string> someList
    = new List<string>(new string[] { "TEST1", "test2", "test3", "TEST4"  });

if (someList.Any(toCheck.Contains))
{
    // "Test1" != "TEST1"
}

But how could you do this case invariant?

My approach was to convert the complete list to upper, and then test using contains:

if ((someList.ConvertAll(item => item.ToUpper()).Any(toCheck.ToUpper().Contains)))
{
    // found -> Do sth.
}

In this case the original list is not altered.

if ((someList.Select(item => item.ToUpper()).Any(toCheck.ToUpper().Contains)))
{
    // works with both
}

Well it works... (also with some language specific things like the turkish 'i' letter... (also we still don't have turkish customers as far as i know.. but who knows if they're are in future?)), but it seems not very elegant.

Is there a way to do an case invariant comparision if an item is in a list?

Best regards, Offler

Case insensitive contains: stackoverflow.com/questions/444798/… — Ric
– Ric, Commented Jun 11, 2013 at 7:56
Your examples don't need to use Contains. Should "TeSt1" match "tEsT12"? — Jodrell
– Jodrell, Commented Jun 11, 2013 at 8:04
@ric this is a another topic. it is not if a string contains a substirng like your link. — Offler
– Offler, Commented Jun 11, 2013 at 8:09

Tim Schmelter · Accepted Answer · 2013-06-11 08:01:16Z

3

Instead of Contains use IndexOf with StringComparison.OrdinalIgnoreCase:

String[] strings = { "Test1", "test2", "test3", "TEST4" };
String text = "TEST123";
if (strings.Any(str => text.IndexOf(str, StringComparison.OrdinalIgnoreCase) > -1))
{
    // we will enter this if clause
}

Demo

edited Jun 11, 2013 at 8:01

answered Jun 11, 2013 at 7:56

Tim Schmelter

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4 Comments

Bob Vale Over a year ago

But won't that also match for substrings?

Tim Schmelter Over a year ago

@BobVale: Yes, that's what OP wants, the same what Contains does. Actually String.Contains uses IndexOf internally. I've edited my answer to clarify what it does and to add a demo.

Bob Vale Over a year ago

Doh, completely missed that, misread that as collection contains search string.

Offler Over a year ago

@BobVale yes, missed to put it in the question, was to focussed on a specific solution. If an exact match would be needed Tims solution could be changed to Equals instead of IndexOf, but IndexOf is the right one for my purpose

brianestey · Accepted Answer · 2013-06-11 07:58:14Z

1

Could you not just do a simple check with the IndexOf that uses the appropriate StringComparison value? For example:

if(someArray.Any(s => s.IndexOf(toCheck, StringComparison.CurrentCultureIgnoreCase) != -1)
{
    // do something
}

answered Jun 11, 2013 at 7:58

brianestey

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3 Comments

Bob Vale Over a year ago

But that would match if the match was a substring of the other

brianestey Over a year ago

@BobVale Since the OP used Contains in his original code, I'm assuming that's his intent.

Bob Vale Over a year ago

Doh, completely missed that, misread that as collection contains search string.

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