How to compare strings with case insensitive and accent insensitive

Question

How to compare strings with case insensitive and accent insensitive

Alright this is done easily at SQL server

However I would like to do the same at C# .NET 4.5.1.

How can I do that with most proper way?

I mean these 3 strings should return equal when compared

http://www.buroteknik.com/metylan-c387c4b0ft-tarafli-bant-12cm-x25mt_154202.html
http://www.buroteknik.com/METYLAN-C387C4B0FT-TARAFLI-BANT-12cm-x25mt_154202.html
http://www.buroteknik.com/METYLAN-C387C4B0FT-TARAFLı-BANT-12cm-x25mt_154202.html

I need a method that would say these 2 below are same SQL server says they are equal.

 tarafli 
 TARAFLİ 

Illona

Take a look at this answer #360327 – Am‚lie

Answer 1

To ignore both case AND accents, you can use string.Compare() with both the IgnoreNonSpace AND the IgnoreCase options, like so:

string s1 = "http://www.buroteknik.com/metylan-c387c4b0ft-tarafli-bant-12cm-x25mt_154202.html";
string s2 = "http://www.buroteknik.com/METYLAN-C387C4B0FT-TARAFLI-BANT-12cm-x25mt_154202.html";
string s3 = "http://www.buroteknik.com/METYLAN-C387C4B0FT-TARAFLı-BANT-12cm-x25mt_154202.html";

Console.WriteLine(string.Compare(s1, s2, CultureInfo.CurrentCulture, CompareOptions.IgnoreNonSpace | CompareOptions.IgnoreCase));
Console.WriteLine(string.Compare(s2, s3, CultureInfo.CurrentCulture, CompareOptions.IgnoreNonSpace | CompareOptions.IgnoreCase));

In response to your comments below, this works for tarafli and TARAFLİ too.

The following code prints 0, meaning the strings are equal:

string s1 = "tarafli";
string s2 = "TARAFLİ";
Console.WriteLine(string.Compare(s1, s2, CultureInfo.CurrentCulture, CompareOptions.IgnoreNonSpace | CompareOptions.IgnoreCase));

And here it is using the Turkish culture (I'm guessing at what the correct culture is). This also prints 0:

string s1 = "tarafli";
string s2 = "TARAFLİ";

var trlocale = CultureInfo.GetCultureInfo("tr-TR");
Console.WriteLine(string.Compare(s1, s2, trlocale, CompareOptions.IgnoreNonSpace | CompareOptions.IgnoreCase));

Jabalpur

ok this method failed for these 2 strings : tarafli - TARAFLİ however SQL server says equal as supposed to be – Celia

@MonsterMMORPG What locale are those strings from? – Jabalpur

@MonsterMMORPG It works fine when I try it with those strings. I'll put it in my answer. – Jabalpur

I've tried it too and it works for me (I used the invariant culture). – Aponeurosis

Answer 2

You can use string.Compare with the overload which takes the proper CultureInfo and CompareOptions:

string.Compare(s1, s2, CultureInfo.CurrentCulture, CompareOptions.IgnoreNonSpace |
                                                   CompareOptions.IgnoreCase);

Edit:

As for your question on CultureInfo, from MSDN:

The comparison uses the culture parameter to obtain culture-specific information, such as casing rules and the alphabetical order of individual characters. For example, a particular culture could specify that certain combinations of characters be treated as a single character, that uppercase and lowercase characters be compared in a particular way, or that the sort order of a character depends on the characters that precede or follow it.

Vaginectomy

Because you want to be compatible with the culture the user runs on his machine. See my edit. – Vaginectomy

thanks for answer again can we say that MS SQL server also uses that information when i set invariant culture and invariant case ? – Celia

What does MSSQL have to do with anything? – Vaginectomy

whichever machine it works invariant culture and invariant case so i wondered :D ah i set latin though :D i see now ty – Celia

ok this method failed for these 2 strings : tarafli - TARAFLİ however SQL server says equal as supposed to be – Celia

Example: string.Compare("citroen","Citroën", CultureInfo.InvariantCulture, CompareOptions.IgnoreNonSpace | CompareOptions.IgnoreCase) 0 – Torruella