Comparing strings using the CompareInfo class in .NET C#

It’s important to be aware of the cultural settings in a globalised application when comparing strings. The CompareInfo class and the CompareOptions enumeration provide a useful way to compare strings based on specific cultures.

One way to get hold of the CompareInfo class belonging to a specific culture is through the CultureInfo class:

CultureInfo swedishCulture = new CultureInfo("sv-SE");
CompareInfo swedishCompareInfo = swedishCulture.CompareInfo;

CultureInfo hungarianCulture = new CultureInfo("hu-HU");
CompareInfo hungarianCompareInfo = hungarianCulture.CompareInfo;

CultureInfo germanCulture = new CultureInfo("de-DE");
CompareInfo germanCompareInfo = germanCulture.CompareInfo;

The CompareInfo object has a Compare method which returns 0 if the strings are equal, -1 if the first string is less than the second and 1 if the opposite is the case. The following comparison of two German strings returns -1 as by default the comparison is case-sensitive:

int comparison = germanCompareInfo.Compare("mädchen", "Mädchen");

This is where the CompareOptions enumeration proves useful. Here are the possible values:

  • IgnoreCase: make the comparison case-insensitive
  • IgnoreNonSpace: ignore diacritics, or officially non-spacing combining characters in Unicode. Example: “Madchen” will be equal to “Mädchen” with this flag
  • IgnoreSymbols: ignore symbols, like white-space, #, $, % etc. “Mädch$en” and “M#ädchen” will be considered equal with this flag
  • IgnoreKana and IgnoreWidth: concern mostly the Japanese language
  • None: the default value if the basic overload of Compare is called
  • Ordinal: quick but culture-insensitive comparison based on the Unicode value of each character
  • OrdinalIgnoreCase: same as Ordinal but the comparison is also case-insensitive
  • StringSort: use a sort algorithm where non-alphanumeric symbols, such as ‘-‘ come before the alphanumeric characters

Read all posts related to Globalisation in .NET here.

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About Andras Nemes
I'm a .NET/Java developer living and working in Stockholm, Sweden.

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