StringComparer Class
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Represents a string comparison operation that uses specific case and culture-based or ordinal comparison rules.
Assembly: mscorlib (in mscorlib.dll)
The StringComparer type exposes the following members.
| Name | Description | |
|---|---|---|
![]() ![]() | CurrentCulture | Gets a StringComparer object that performs a case-sensitive string comparison using the word comparison rules of the current culture. |
![]() ![]() | CurrentCultureIgnoreCase | Gets a StringComparer object that performs case-insensitive string comparisons using the word comparison rules of the current culture. |
![]() ![]() | InvariantCulture | Gets a StringComparer object that performs a case-sensitive string comparison using the word comparison rules of the invariant culture. |
![]() ![]() | InvariantCultureIgnoreCase | Gets a StringComparer object that performs a case-insensitive string comparison using the word comparison rules of the invariant culture. |
![]() ![]() | Ordinal | Gets a StringComparer object that performs a case-sensitive ordinal string comparison. |
![]() ![]() | OrdinalIgnoreCase | Gets a StringComparer object that performs a case-insensitive ordinal string comparison. |
| Name | Description | |
|---|---|---|
![]() | Compare(Object, Object) | When overridden in a derived class, compares two objects and returns an indication of their relative sort order. |
![]() | Compare(String, String) | When overridden in a derived class, compares two strings and returns an indication of their relative sort order. |
![]() ![]() | Create | Creates a StringComparer object that compares strings according to the rules of a specified culture. |
![]() | Equals(Object) | Determines whether the specified Object is equal to the current Object. (Inherited from Object.) |
![]() | Equals(Object, Object) | When overridden in a derived class, indicates whether two objects are equal. |
![]() | Equals(String, String) | When overridden in a derived class, indicates whether two strings are equal. |
![]() | Finalize | Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.) |
![]() | GetHashCode | Serves as a hash function for a particular type. (Inherited from Object.) |
![]() | GetHashCode(Object) | When overridden in a derived class, gets the hash code for the specified object. |
![]() | GetHashCode(String) | When overridden in a derived class, gets the hash code for the specified string. |
![]() | GetType | Gets the Type of the current instance. (Inherited from Object.) |
![]() | MemberwiseClone | Creates a shallow copy of the current Object. (Inherited from Object.) |
![]() | ToString | Returns a string that represents the current object. (Inherited from Object.) |
An object derived from the StringComparer class embodies string-based comparison, equality, and hash code operations that take into account both case and culture-specific comparison rules. You can use the StringComparer class to create a type-specific comparison to sort the elements in a generic collection.
A comparison operation that is represented by the StringComparer class is defined to be either case-sensitive or case-insensitive, and use either word (culture-sensitive) or ordinal (culture-insensitive) comparison rules. For more information about word and ordinal comparison rules, see System.Globalization.CompareOptions.
Implemented Properties
You might be confused about how to use the StringComparer class properties because of a seeming contradiction. The StringComparer class is declared abstract (MustInherit in Visual Basic), which means its members can be invoked only on an object of a class derived from the StringComparer class. The contradiction is that each property of the StringComparer class is declared static (Shared in Visual Basic), which means the property can be invoked without first creating a derived class.
You can call a StringComparer property directly because each property actually returns an instance of an anonymous class that is derived from the StringComparer class. Consequently, the type of each property value is StringComparer, which is the base class of the anonymous class, not the type of the anonymous class itself. Each StringComparer class property returns a StringComparer object that supports predefined case and comparison rules.
The following code example demonstrates the properties and the Create method of the StringComparer class. The example illustrates how different StringComparer objects sort three versions of the Latin letter I.
' This code example demonstrates members of the System.StringComparer class. Imports System.Collections Imports System.Collections.Generic Imports System.Globalization Imports System.Threading Class Example Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock) ' Create a list of string. Dim list As New List(Of String) ' Get the tr-TR (Turkish-Turkey) culture. Dim turkish As New CultureInfo("tr-TR") ' Get the culture that is associated with the current thread. Dim thisCulture As CultureInfo = Thread.CurrentThread.CurrentCulture ' Get the standard StringComparers. Dim invCmp As StringComparer = StringComparer.InvariantCulture Dim invICCmp As StringComparer = StringComparer.InvariantCultureIgnoreCase Dim currCmp As StringComparer = StringComparer.CurrentCulture Dim currICCmp As StringComparer = StringComparer.CurrentCultureIgnoreCase Dim ordCmp As StringComparer = StringComparer.Ordinal Dim ordICCmp As StringComparer = StringComparer.OrdinalIgnoreCase ' Create a StringComparer that uses the Turkish culture and ignores case. Dim turkICComp As StringComparer = StringComparer.Create(turkish, True) ' Define three strings consisting of different versions of the letter I. ' LATIN CAPITAL LETTER I (U+0049) Dim capitalLetterI As String = "I" ' LATIN SMALL LETTER I (U+0069) Dim smallLetterI As String = "i" ' LATIN SMALL LETTER DOTLESS I (U+0131) Dim smallLetterDotlessI As String = "ı" ' Add the three strings to the list. list.Add(capitalLetterI) list.Add(smallLetterI) list.Add(smallLetterDotlessI) ' Display the original list order. Display(outputBlock, list, "The original order of the list entries...") ' Sort the list using the invariant culture. list.Sort(invCmp) Display(outputBlock, list, "Invariant culture...") list.Sort(invICCmp) Display(outputBlock, list, "Invariant culture, ignore case...") ' Sort the list using the current culture. outputBlock.Text += String.Format("The current culture is ""{0}"".", thisCulture.Name) & vbCrLf list.Sort(currCmp) Display(outputBlock, list, "Current culture...") list.Sort(currICCmp) Display(outputBlock, list, "Current culture, ignore case...") ' Sort the list using the ordinal value of the character code points. list.Sort(ordCmp) Display(outputBlock, list, "Ordinal...") list.Sort(ordICCmp) Display(outputBlock, list, "Ordinal, ignore case...") ' Sort the list using the Turkish culture, which treats LATIN SMALL LETTER ' DOTLESS I differently than LATIN SMALL LETTER I. list.Sort(turkICComp) Display(outputBlock, list, "Turkish culture, ignore case...") End Sub 'Main Public Shared Sub Display(ByVal outputBlock As System.Windows.Controls.TextBlock, ByVal lst As List(Of String), ByVal title As String) Dim c As Char Dim s As String Dim codePoint As Integer outputBlock.Text &= title & vbCrLf For Each s In lst c = s(0) codePoint = Convert.ToInt32(c) outputBlock.Text += String.Format("0x{0:x}", codePoint) & vbCrLf Next s outputBlock.Text &= vbCrLf End Sub 'Display End Class 'Sample ' 'This code example produces the following results: ' 'The original order of the list entries... '0x49 '0x69 '0x131 ' 'Invariant culture... '0x69 '0x49 '0x131 ' 'Invariant culture, ignore case... '0x49 '0x69 '0x131 ' 'The current culture is "en-US". 'Current culture... '0x69 '0x49 '0x131 ' 'Current culture, ignore case... '0x49 '0x69 '0x131 ' 'Ordinal... '0x49 '0x69 '0x131 ' 'Ordinal, ignore case... '0x69 '0x49 '0x131 ' 'Turkish culture, ignore case... '0x131 '0x49 '0x69 '



