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CompareOptions Enumeration

April 12, 2014

Defines the options to use with a number of string comparison methods.

This enumeration has a FlagsAttribute attribute that allows a bitwise combination of its member values.

Namespace:  System.Globalization
Assembly:  mscorlib (in mscorlib.dll)
[FlagsAttribute]
public enum CompareOptions
Member nameDescription
IgnoreCaseIndicates that the string comparison must ignore case.
IgnoreKanaTypeIndicates that the string comparison must ignore the Kana type. Kana type refers to Japanese hiragana and katakana characters, which represent phonetic sounds in the Japanese language. Hiragana is used for native Japanese expressions and words, while katakana is used for words borrowed from other languages, such as "computer" or "Internet". A phonetic sound can be expressed in both hiragana and katakana. If this value is selected, the hiragana character for one sound is considered equal to the katakana character for the same sound.
IgnoreNonSpaceIndicates that the string comparison must ignore nonspacing combining characters, such as diacritics. The Unicode Standard defines combining characters as characters that are combined with base characters to produce a new character. Nonspacing combining characters do not occupy a spacing position by themselves when rendered. For more information on nonspacing combining characters, see The Unicode Standard at the Unicode home page.
IgnoreSymbolsIndicates that the string comparison must ignore symbols, such as white-space characters, punctuation, currency symbols, the percent sign, mathematical symbols, the ampersand, and so on.
IgnoreWidthIndicates that the string comparison must ignore the character width. For example, Japanese katakana characters can be written as full-width or half-width. If this value is selected, the katakana characters written as full-width are considered equal to the same characters written as half-width.
NoneIndicates the default option settings for string comparisons.
OrdinalIndicates that the string comparison must use the Unicode values of each character, leading to a fast comparison but one that is culture-insensitive. A string starting with "U+xxxx" comes before a string starting with "U+yyyy", if xxxx is less than yyyy. This value cannot be combined with other CompareOptions values and must be used alone.
OrdinalIgnoreCaseString comparison must ignore case, then perform an ordinal comparison. This technique is equivalent to converting the string to uppercase using the invariant culture and then performing an ordinal comparison on the result.
StringSortIndicates that the string comparison must use the string sort algorithm. In a string sort, the hyphen and the apostrophe, as well as other nonalphanumeric symbols, come before alphanumeric characters.

The members of the CompareOptions enumeration are used with a number of CompareInfo methods, as well as with several overloads of the Compare method. They denote case sensitivity or the necessity to ignore types of characters.

The .NET Framework uses three distinct ways of sorting: word sort, string sort, and ordinal sort. Word sort performs a culture-sensitive comparison of strings. Certain nonalphanumeric characters might have special weights assigned to them. For example, the hyphen ("-") might have a very small weight assigned to it so that "coop" and "co-op" appear next to each other in a sorted list. String sort is similar to word sort, except that there are no special cases. Therefore, all nonalphanumeric symbols come before all alphanumeric characters. Ordinal sort compares strings based on the Unicode values of each element of the string.

The CompareOptions.StringSort value can be used only with CompareInfo.Compare and the appropriate overloads of Compare. An ArgumentException is thrown if the StringSort value is used with CompareInfo.IsPrefix, CompareInfo.IsSuffix, CompareInfo.IndexOf, or CompareInfo.LastIndexOf.

The following code example shows how sorting with StringSort differs from sorting without StringSort.


using System;
using System.Collections;
using System.Globalization;


public class Example
{

   private class MyStringComparer : IComparer
   {
      private CompareInfo myComp;
      private CompareOptions myOptions = CompareOptions.None;

      // Constructs a comparer using the specified CompareOptions.
      public MyStringComparer(CompareInfo cmpi, CompareOptions options)
      {
         myComp = cmpi;
         this.myOptions = options;
      }

      // Compares strings with the CompareOptions specified in the constructor.
      public int Compare(Object a, Object b)
      {
         if (a == b) return 0;
         if (a == null) return -1;
         if (b == null) return 1;

         String sa = a as String;
         String sb = b as String;
         if (sa != null && sb != null)
            return myComp.Compare(sa, sb, myOptions);
         throw new ArgumentException("a and b should be strings.");

      }
   }

   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {

      // Creates and initializes an array of strings to sort.
      String[] myArr = new String[9] { "cant", "bill's", "coop", "cannot", "billet", "can't", "con", "bills", "co-op" };
      outputBlock.Text += String.Format("\nInitially,") + "\n";
      foreach (String myStr in myArr)
         outputBlock.Text += myStr + "\n";

      // Creates and initializes a Comparer to use.
      //CultureInfo myCI = new CultureInfo( "en-US", false );
      MyStringComparer myComp = new MyStringComparer(CompareInfo.GetCompareInfo("en-US"), CompareOptions.None);

      // Sorts the array without StringSort.
      Array.Sort(myArr, myComp);
      outputBlock.Text += "\nAfter sorting without CompareOptions.StringSort:" + "\n";
      foreach (String myStr in myArr)
         outputBlock.Text += myStr + "\n";

      // Sorts the array with StringSort.
      myComp = new MyStringComparer(CompareInfo.GetCompareInfo("en-US"), CompareOptions.StringSort);
      Array.Sort(myArr, myComp);
      outputBlock.Text += "\nAfter sorting with CompareOptions.StringSort:" + "\n";
      foreach (String myStr in myArr)
         outputBlock.Text += myStr + "\n";

   }

}

/*
This code produces the following output.

Initially,
cant
bill's
coop
cannot
billet
can't
con
bills
co-op

After sorting without CompareOptions.StringSort:
billet
bills
bill's
cannot
cant
can't
con
coop
co-op

After sorting with CompareOptions.StringSort:
bill's
billet
bills
can't
cannot
cant
co-op
con
coop

*/


Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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