项目
11/18/2011

String.Compare Method (String, String, CultureInfo, CompareOptions)

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Compares two specified String objects using the specified comparison options and culture-specific information to influence the comparison, and returns an integer that indicates the relationship of the two strings to one another in the sort order.

Namespace: System
Assembly: mscorlib (in mscorlib.dll)

Syntax

'Declaration
Public Shared Function Compare ( _
    strA As String, _
    strB As String, _
    culture As CultureInfo, _
    options As CompareOptions _
) As Integer

public static int Compare(
    string strA,
    string strB,
    CultureInfo culture,
    CompareOptions options
)

Parameters

strA
Type: System.String
The first string.

strB
Type: System.String
The second string.

culture
Type: System.Globalization.CultureInfo
The culture that supplies culture-specific comparison information.

options
Type: System.Globalization.CompareOptions
Options, such as ignoring case or symbols, to use when performing the comparison.

Return Value

Type: System.Int32
A 32-bit signed integer that indicates the lexical relationship between strA and strB.

Value	Condition
Less than zero	strA is less than strB.
Zero	strA equals strB.
Greater than zero	strA is greater than strB.

Exceptions

Exception	Condition
ArgumentException	options is not a CompareOptions value.
ArgumentNullException	culture is nulla null reference (Nothing in Visual Basic).

Remarks

The comparison uses the culture parameter to obtain culture-specific information, such as casing rules and the alphabetic order of individual characters. For example, a particular culture could specify that certain combinations of characters be treated as a single character, that uppercase and lowercase characters be compared in a particular way, or that the sort order of a character depends on the characters that precede or follow it.

Caution:
The Compare(String, String, CultureInfo, CompareOptions) method is designed primarily for use in sorting or alphabetizing operations. It should not be used when the primary purpose of the method call is to determine whether two strings are equivalent (that is, when the purpose of the method call is to test for a return value of zero). To determine whether two strings are equivalent, call the Equals method.

The Compare(String, String, CultureInfo, CompareOptions) method is designed primarily for use in sorting or alphabetizing operations. It should not be used when the primary purpose of the method call is to determine whether two strings are equivalent (that is, when the purpose of the method call is to test for a return value of zero). To determine whether two strings are equivalent, call the Equals method.

The comparison can be further specified by the options parameter, which consists of one or more members of the CompareOptions enumeration. However, because the purpose of this method is to conduct a culture-sensitive string comparison, the CompareOptions.Ordinal and CompareOptions.OrdinalIgnoreCase values have no effect.

Either or both comparands can be nulla null reference (Nothing in Visual Basic). By definition, any string, including String.Empty, compares greater than a null reference, and two null references compare equal to each other.

The comparison terminates when an inequality is discovered or both strings have been compared. However, if the two strings compare equal to the end of one string, and the other string has characters remaining, the string with the remaining characters is considered greater.

Examples

The following example compares two strings in three different ways: using linguistic comparison for the en-US culture; using linguistic case-sensitive comparison for the en-US culture; and using an ordinal comparison. It illustrates how the three methods of comparison produce three different results.

Imports System.Globalization

Public Module Example
   Public Sub Demo(ByVal outputBlock As TextBlock)
      Dim string1 As String = "brother"
      Dim string2 As String = "Brother"
      Dim relation As String
      Dim result As Integer

      ' Cultural (linguistic) comparison.
      result = String.Compare(string1, string2, _
                              New CultureInfo("en-US"), CompareOptions.None)
      If result > 0 Then
         relation = "comes after"
      ElseIf result = 0 Then
         relation = "is the same as"
      Else
         relation = "comes before"
      End If
      outputBlock.Text &= String.Format("'{0}' {1} '{2}'.", string1, relation, string2)
      outputBlock.Text &= vbCrLf

      ' Cultural (linguistic) case-insensitive comparison.
      result = String.Compare(string1, string2, _
                              New CultureInfo("en-US"), CompareOptions.IgnoreCase)
      If result > 0 Then
         relation = "comes after"
      ElseIf result = 0 Then
         relation = "is the same as"
      Else
         relation = "comes before"
      End If
      outputBlock.Text &= String.Format("'{0}' {1} '{2}'.", string1, relation, string2)
      outputBlock.Text &= vbCrLf

      ' Culture-insensitive ordinal comparison.
      result = String.CompareOrdinal(string1, string2)
      If result > 0 Then
         relation = "comes after"
      ElseIf result = 0 Then
         relation = "is the same as"
      Else
         relation = "comes before"
      End If
      outputBlock.Text &= String.Format("'{0}' {1} '{2}'.", string1, relation, string2)
   End Sub
End Module
' The example produces the following output:
'    'brother' comes before 'Brother'.   
'    'brother' is the same as 'Brother'.
'    'brother' comes after 'Brother'.

using System;
using System.Globalization;

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      string string1 = "brother";
      string string2 = "Brother";
      string relation;
      int result;

      // Cultural (linguistic) comparison.
      result = String.Compare(string1, string2, new CultureInfo("en-US"), 
                              CompareOptions.None);
      if (result > 0)
         relation = "comes after";
      else if (result == 0)
         relation = "is the same as";
      else
         relation = "comes before";

      outputBlock.Text += String.Format("'{0}' {1} '{2}'.\n", 
                                        string1, relation, string2);

      // Cultural (linguistic) case-insensitive comparison.
      result = String.Compare(string1, string2, new CultureInfo("en-US"), 
                              CompareOptions.IgnoreCase);
      if (result > 0)
         relation = "comes after";
      else if (result == 0)
         relation = "is the same as";
      else
         relation = "comes before";

      outputBlock.Text += String.Format("'{0}' {1} '{2}'.\n", 
                                        string1, relation, string2);

       // Culture-insensitive ordinal comparison.
      result = String.CompareOrdinal(string1, string2);
      if (result > 0)
         relation = "comes after";
      else if (result == 0)
         relation = "is the same as";
      else
         relation = "comes before";

      outputBlock.Text += String.Format("'{0}' {1} '{2}'.\n", 
                                        string1, relation, string2);
   }
}
// The example produces the following output:
//    'brother' comes before 'Brother'.   
//    'brother' is the same as 'Brother'.
//    'brother' comes after 'Brother'.

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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