C#- ToLower() is sometimes removing dot from the letter "I"

Question

We have noticed a weird error when calling ToLower() on certain strings.

The input string is:

string s = "DocumentInfo";
string t = s.ToLower();
// sometimes, t == documentinfo
// other times, t == documentınfo  (note dot is missing from i - INCORRECT)

We are passing the string to a web service query downstream, so it is causing problems for us.

My initial guess is that it has something to do with Culture or UICulture, as some of our pages customize these settings per user.

Could this be the issue? Is there are way I can force this to work properly?

UPDATE 2011.07.06

I found that I could duplicate the issue by setting Culture to tr-TR. Not sure if other cultures are impacted.

Turkey, by any chance? Note: all "system" strings (i.e. strings that have meaning to code rather than to humans) should almost always be compared, sorted, capitalised, etc using the *invariant* culture (as already answered), or *at the minimum* some known fixed culture. — Marc Gravell, Jul 06 '11 at 18:10
Here's the obligatory [Turkey Test](http://www.moserware.com/2008/02/does-your-code-pass-turkey-test.html) link. — R. Martinho Fernandes, Jul 06 '11 at 18:26
Re your edit, indeed Turkey is the notorious one for this - hence the "Turkey test" (search for it), very common in IT — Marc Gravell, Jul 06 '11 at 18:26
yep, I tested with tr-TR and that isolated the problem. thanks — frankadelic, Jul 06 '11 at 18:27
Related: http://thedailywtf.com/Articles/TransAtlantic-Time-Trap.aspx — R. Martinho Fernandes, Jul 06 '11 at 18:33

score 33 · Accepted Answer · edited Jul 06 '11 at 20:41

33

Try using String.ToLowerInvariant().

edited Jul 06 '11 at 20:41

Matthew

28,056
26
104
170

answered Jul 06 '11 at 18:08

Daniel A. White

187,200
47
362
445

score 3 · Answer 2 · answered Jul 06 '11 at 18:14

3

Try :

s.ToLower(new CultureInfo("en-US", false));

If you get a different result, your CultureInfo.CurrentCulture may be set to something else.

answered Jul 06 '11 at 18:14

Eric H

1,759
1
11
14

8

While this will probably work fine, the invariant culture is more convenient (you don't need to look it up by key), and more indicative of our intent, IMO – Marc Gravell Jul 06 '11 at 18:18
The user should just know that the Invariant in ToLowerInvariant assumes they want lower case general English. Per MSDN: It is associated with the English language but not with a country or region. – Eric H Jul 06 '11 at 18:27
2

But using the invariant culture is not the same thing as using the en-US culture. If you see ToLowerInvariant, you can assume it's going to be a non-visible string used for internal computation. If you see "en-US", you have no idea what's going on. Also, the first is so much easier to write. – R. Martinho Fernandes Jul 06 '11 at 18:30
1

CultureInfo seems undefined? – Bengi Besçeli Nov 16 '15 at 13:27

C#- ToLower() is sometimes removing dot from the letter "I"

2 Answers2

Linked