Difference between InvariantCulture and Ordinal string comparison

Question

When comparing two strings in c  for equality  what is the difference between InvariantCulture and Ordinal comparison

User · Accepted Answer

InvariantCulture  Uses a  standard  set of character orderings  a b c      etc     This is in contrast to some specific locales  which may sort characters in different orders   a-with-acute  may be before or after  a   depending on the locale  and so on    Ordinal  On the other hand  looks purely at the values of the raw byte s  that represent the character       There s a great sample at http   msdn microsoft com en-us library e6883c06 aspx that shows the results of the various StringComparison values   All the way at the end  it shows  excerpted    StringComparison InvariantCulture  LATIN SMALL LETTER I  U 0069  is less than LATIN SMALL LETTER DOTLESS I  U 0131  LATIN SMALL LETTER I  U 0069  is less than LATIN CAPITAL LETTER I  U 0049  LATIN SMALL LETTER DOTLESS I  U 0131  is greater than LATIN CAPITAL LETTER I  U 0049   StringComparison Ordinal  LATIN SMALL LETTER I  U 0069  is less than LATIN SMALL LETTER DOTLESS I  U 0131  LATIN SMALL LETTER I  U 0069  is greater than LATIN CAPITAL LETTER I  U 0049  LATIN SMALL LETTER DOTLESS I  U 0131  is greater than LATIN CAPITAL LETTER I  U 0049    You can see that where InvariantCulture yields  U 0069  U 0049  U 00131   Ordinal yields  U 0049  U 0069  U 00131

User · Answer

Always try to use InvariantCulture in those string methods that accept it as overload  By using  InvariantCulture you are on a safe side  Many  NET programmers may not use this functionality but if your software will be used by different cultures  InvariantCulture is an extremely handy feature

User · Answer

Although the question is about equality  for quick visual reference  here the order of some strings sorted using a couple of cultures illustrating some of the idiosyncrasies out there   Ordinal          0 9 A Ab a aB aa ab ss      b         b           A IgnoreCase       0 9 a A aa ab Ab aB ss         b   b              A -------------------------------------------------------------------- InvariantCulture 0 9 a A A       aa ab aB Ab   b   b ss              IgnoreCase       0 9 A a A       aa Ab aB ab   b   b    ss           -------------------------------------------------------------------- da-DK            0 9 a A A ab aB Ab ss            b   b aa           IgnoreCase       0 9 A a A Ab aB ab    ss         b   b aa           -------------------------------------------------------------------- de-DE            0 9 a A A       aa ab aB Ab   b   b    ss           IgnoreCase       0 9 A a A       aa Ab aB ab   b   b ss              -------------------------------------------------------------------- en-US            0 9 a A A       aa ab aB Ab   b   b    ss           IgnoreCase       0 9 A a A       aa Ab aB ab   b   b ss              -------------------------------------------------------------------- ja-JP            0 9 a A A       aa ab aB Ab   b   b    ss           IgnoreCase       0 9 A a A       aa Ab aB ab   b   b ss                Observations     de-DE  ja-JP  and en-US sort the same way Invariant only sorts ss and    differently from the above three cultures da-DK sorts quite differently the IgnoreCase flag matters for all sampled cultures   The code used to generate above table   var l   new List lt string gt         0    9    A    Ab    a    aB    aa    ab    ss                        b            b                        A           foreach  var comparer in new         StringComparer Ordinal      StringComparer OrdinalIgnoreCase      StringComparer InvariantCulture      StringComparer InvariantCultureIgnoreCase      StringComparer Create new CultureInfo  da-DK    false       StringComparer Create new CultureInfo  da-DK    true       StringComparer Create new CultureInfo  de-DE    false       StringComparer Create new CultureInfo  de-DE    true       StringComparer Create new CultureInfo  en-US    false       StringComparer Create new CultureInfo  en-US    true       StringComparer Create new CultureInfo  ja-JP    false       StringComparer Create new CultureInfo  ja-JP    true            l Sort comparer       Console WriteLine string Join      l

User · Answer

Pointing to Best Practices for Using Strings in the  NET Framework    Use StringComparison Ordinal or StringComparison OrdinalIgnoreCase for comparisons as your safe default for culture-agnostic string matching  Use comparisons with StringComparison Ordinal or StringComparison OrdinalIgnoreCase for better performance  Use the non-linguistic StringComparison Ordinal or StringComparison OrdinalIgnoreCase values instead of string operations based on CultureInfo InvariantCulture when the comparison is linguistically irrelevant  symbolic  for example     And finally    Do not use string operations based on StringComparison InvariantCulture in most cases  One of the few exceptions is when you are persisting linguistically meaningful but culturally agnostic data

User · Answer

Invariant is a linguistically appropriate type of comparison  Ordinal is a binary type of comparison   faster  See http   www siao2 com 2004 12 29 344136 aspx

User · Answer

Here is an example where string equality comparison using InvariantCultureIgnoreCase and OrdinalIgnoreCase will not give the same results   string str     xC4     A with umlaut     string A   str Normalize NormalizationForm FormC     Length is 1  this will contain the single A with umlaut character      string B   str Normalize NormalizationForm FormD     Length is 2  this will contain an uppercase A followed by an umlaut combining character bool equals1   A Equals B  StringComparison OrdinalIgnoreCase   bool equals2   A Equals B  StringComparison InvariantCultureIgnoreCase     If you run this  equals1 will be false  and equals2 will be true

User · Answer

No need to use fancy unicode char exmaples to show the difference  Here s one simple example I found out today which is surprising  consisting of only ASCII characters   According to the ASCII table  0  0x48  is smaller than    0x95  when compared ordinally  InvariantCulture would say the opposite  PowerShell code below    PS gt   System StringComparer   Ordinal Compare       0   47 PS gt   System StringComparer   InvariantCulture Compare       0   -1

User · Answer

It does matter  for example - there is a thing called character expansion  var s1    Strasse   var s2    Stra  e    s1 Equals s2  StringComparison Ordinal               false s1 Equals s2  StringComparison InvariantCulture      true   With InvariantCulture the    character gets expanded to ss

User · Answer

No need to use fancy unicode char exmaples to show the difference  Here s one simple example I found out today which is surprising  consisting of only ASCII characters   According to the ASCII table  0  0x48  is smaller than    0x95  when compared ordinally  InvariantCulture would say the opposite  PowerShell code below    PS gt   System StringComparer   Ordinal Compare       0   47 PS gt   System StringComparer   InvariantCulture Compare       0   -1

User · Answer

It does matter  for example - there is a thing called character expansion  var s1    Strasse   var s2    Stra  e    s1 Equals s2  StringComparison Ordinal               false s1 Equals s2  StringComparison InvariantCulture      true   With InvariantCulture the    character gets expanded to ss

User · Answer

Invariant is a linguistically appropriate type of comparison  Ordinal is a binary type of comparison   faster  See http   www siao2 com 2004 12 29 344136 aspx

User · Answer

Another handy difference  in English where accents are uncommon  is that an InvariantCulture comparison compares the entire strings by case-insensitive first  and then if necessary  and requested  distinguishes by case after first comparing only on the distinct letters    You can also do a case-insensitive comparison  of course  which won t distinguish by case    Corrected  Accented letters are considered to be another flavor of the same letters and the string is compared first ignoring accents and then accounting for them if the general letters all match  much as with differing case except not ultimately ignored in a case-insensitive compare    This groups accented versions of the otherwise same word near each other instead of completely separate at the first accent difference   This is the sort order you would typically find in a dictionary  with capitalized words appearing right next to their lowercase equivalents  and accented letters being near the corresponding unaccented letter   An ordinal comparison compares strictly on the numeric character values  stopping at the first difference   This sorts capitalized letters completely separate from the lowercase letters  and accented letters presumably separate from those   so capitalized words would sort nowhere near their lowercase equivalents   InvariantCulture also considers capitals to be greater than lower case  whereas Ordinal considers capitals to be less than lowercase  a holdover of ASCII from the old days before computers had lowercase letters  the uppercase letters were allocated first and thus had lower values than the lowercase letters added later    For example  by Ordinal   0   lt   9   lt   A   lt   Ab   lt   Z   lt   a   lt   aB   lt   ab   lt   z   lt        lt     b   lt        lt     b   And by InvariantCulture   0   lt   9   lt   a   lt   A   lt        lt        lt   ab   lt   aB   lt   Ab   lt     b   lt     b   lt   z   lt   Z

User · Answer

Another handy difference  in English where accents are uncommon  is that an InvariantCulture comparison compares the entire strings by case-insensitive first  and then if necessary  and requested  distinguishes by case after first comparing only on the distinct letters    You can also do a case-insensitive comparison  of course  which won t distinguish by case    Corrected  Accented letters are considered to be another flavor of the same letters and the string is compared first ignoring accents and then accounting for them if the general letters all match  much as with differing case except not ultimately ignored in a case-insensitive compare    This groups accented versions of the otherwise same word near each other instead of completely separate at the first accent difference   This is the sort order you would typically find in a dictionary  with capitalized words appearing right next to their lowercase equivalents  and accented letters being near the corresponding unaccented letter   An ordinal comparison compares strictly on the numeric character values  stopping at the first difference   This sorts capitalized letters completely separate from the lowercase letters  and accented letters presumably separate from those   so capitalized words would sort nowhere near their lowercase equivalents   InvariantCulture also considers capitals to be greater than lower case  whereas Ordinal considers capitals to be less than lowercase  a holdover of ASCII from the old days before computers had lowercase letters  the uppercase letters were allocated first and thus had lower values than the lowercase letters added later    For example  by Ordinal   0   lt   9   lt   A   lt   Ab   lt   Z   lt   a   lt   aB   lt   ab   lt   z   lt        lt     b   lt        lt     b   And by InvariantCulture   0   lt   9   lt   a   lt   A   lt        lt        lt   ab   lt   aB   lt   Ab   lt     b   lt     b   lt   z   lt   Z

User · Answer

Pointing to Best Practices for Using Strings in the  NET Framework    Use StringComparison Ordinal or StringComparison OrdinalIgnoreCase for comparisons as your safe default for culture-agnostic string matching  Use comparisons with StringComparison Ordinal or StringComparison OrdinalIgnoreCase for better performance  Use the non-linguistic StringComparison Ordinal or StringComparison OrdinalIgnoreCase values instead of string operations based on CultureInfo InvariantCulture when the comparison is linguistically irrelevant  symbolic  for example     And finally    Do not use string operations based on StringComparison InvariantCulture in most cases  One of the few exceptions is when you are persisting linguistically meaningful but culturally agnostic data

User · Answer

Here is an example where string equality comparison using InvariantCultureIgnoreCase and OrdinalIgnoreCase will not give the same results   string str     xC4     A with umlaut     string A   str Normalize NormalizationForm FormC     Length is 1  this will contain the single A with umlaut character      string B   str Normalize NormalizationForm FormD     Length is 2  this will contain an uppercase A followed by an umlaut combining character bool equals1   A Equals B  StringComparison OrdinalIgnoreCase   bool equals2   A Equals B  StringComparison InvariantCultureIgnoreCase     If you run this  equals1 will be false  and equals2 will be true

User · Answer

Although the question is about equality  for quick visual reference  here the order of some strings sorted using a couple of cultures illustrating some of the idiosyncrasies out there   Ordinal          0 9 A Ab a aB aa ab ss      b         b           A IgnoreCase       0 9 a A aa ab Ab aB ss         b   b              A -------------------------------------------------------------------- InvariantCulture 0 9 a A A       aa ab aB Ab   b   b ss              IgnoreCase       0 9 A a A       aa Ab aB ab   b   b    ss           -------------------------------------------------------------------- da-DK            0 9 a A A ab aB Ab ss            b   b aa           IgnoreCase       0 9 A a A Ab aB ab    ss         b   b aa           -------------------------------------------------------------------- de-DE            0 9 a A A       aa ab aB Ab   b   b    ss           IgnoreCase       0 9 A a A       aa Ab aB ab   b   b ss              -------------------------------------------------------------------- en-US            0 9 a A A       aa ab aB Ab   b   b    ss           IgnoreCase       0 9 A a A       aa Ab aB ab   b   b ss              -------------------------------------------------------------------- ja-JP            0 9 a A A       aa ab aB Ab   b   b    ss           IgnoreCase       0 9 A a A       aa Ab aB ab   b   b ss                Observations     de-DE  ja-JP  and en-US sort the same way Invariant only sorts ss and    differently from the above three cultures da-DK sorts quite differently the IgnoreCase flag matters for all sampled cultures   The code used to generate above table   var l   new List lt string gt         0    9    A    Ab    a    aB    aa    ab    ss                        b            b                        A           foreach  var comparer in new         StringComparer Ordinal      StringComparer OrdinalIgnoreCase      StringComparer InvariantCulture      StringComparer InvariantCultureIgnoreCase      StringComparer Create new CultureInfo  da-DK    false       StringComparer Create new CultureInfo  da-DK    true       StringComparer Create new CultureInfo  de-DE    false       StringComparer Create new CultureInfo  de-DE    true       StringComparer Create new CultureInfo  en-US    false       StringComparer Create new CultureInfo  en-US    true       StringComparer Create new CultureInfo  ja-JP    false       StringComparer Create new CultureInfo  ja-JP    true            l Sort comparer       Console WriteLine string Join      l

User · Answer

Always try to use InvariantCulture in those string methods that accept it as overload  By using  InvariantCulture you are on a safe side  Many  NET programmers may not use this functionality but if your software will be used by different cultures  InvariantCulture is an extremely handy feature

[c#] Difference between InvariantCulture and Ordinal string comparison

InvariantCulture

Ordinal

Examples related to c#

Examples related to .net

Examples related to string-comparison

Examples related to ordinal