CompareOptions Enumeration
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)
| Member name | Description | |
|---|---|---|
![]() ![]() | None | Indicates the default option settings for string comparisons. |
![]() ![]() | IgnoreCase | Indicates that the string comparison must ignore case. |
![]() ![]() | IgnoreNonSpace | Indicates 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. |
![]() ![]() | IgnoreSymbols | Indicates 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. |
![]() ![]() | IgnoreKanaType | Indicates 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. |
![]() ![]() | IgnoreWidth | Indicates 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. |
![]() ![]() | OrdinalIgnoreCase | String 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. |
![]() ![]() | StringSort | Indicates 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. |
![]() ![]() | Ordinal | Indicates 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. |
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.
Imports System.Collections Imports System.Globalization Public Class Example Private Class MyStringComparer Implements IComparer Private myComp As CompareInfo Private myOptions As CompareOptions = CompareOptions.None ' Constructs a comparer using the specified CompareOptions. Public Sub New(ByVal cmpi As CompareInfo, ByVal options As CompareOptions) myComp = cmpi Me.myOptions = options End Sub 'New ' Compares strings with the CompareOptions specified in the constructor. Public Function Compare(ByVal a As [Object], ByVal b As [Object]) As Integer Implements IComparer.Compare If a = b Then Return 0 End If If a Is Nothing Then Return -1 End If If b Is Nothing Then Return 1 End If Dim sa As [String] = a Dim sb As [String] = b If Not (sa Is Nothing) And Not (sb Is Nothing) Then Return myComp.Compare(sa, sb, myOptions) End If Throw New ArgumentException("a and b should be strings.") End Function 'Compare End Class Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock) ' Creates and initializes an array of strings to sort. Dim myArr() As [String] = {"cant", "bill's", "coop", "cannot", "billet", "can't", "con", "bills", "co-op"} outputBlock.Text &= vbCrLf outputBlock.Text += String.Format("Initially,") & vbCrLf Dim myStr As [String] For Each myStr In myArr outputBlock.Text &= myStr & vbCrLf Next myStr ' Creates and initializes a Comparer to use. 'CultureInfo myCI = new CultureInfo( "en-US", false ); Dim myComp As New MyStringComparer(CompareInfo.GetCompareInfo("en-US"), CompareOptions.None) ' Sorts the array without StringSort. Array.Sort(myArr, myComp) outputBlock.Text &= vbCrLf outputBlock.Text &= "After sorting without CompareOptions.StringSort:" & vbCrLf For Each myStr In myArr outputBlock.Text &= myStr & vbCrLf Next myStr ' Sorts the array with StringSort. myComp = New MyStringComparer(CompareInfo.GetCompareInfo("en-US"), CompareOptions.StringSort) Array.Sort(myArr, myComp) outputBlock.Text &= vbCrLf outputBlock.Text &= "After sorting with CompareOptions.StringSort:" & vbCrLf For Each myStr In myArr outputBlock.Text &= myStr & vbCrLf Next myStr End Sub 'Main End Class 'SamplesCompareOptions '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
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