String..::.Compare Method (String, String)-阿里云开发者社区

String . . :: .Compare Method (String, String)

Updated: November 2007

Compares two specified String objects and returns an integer that indicates their relationship to one another in the sort order.

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

Syntax

Visual Basic (Declaration)

Public Shared Function Compare ( _
    strA As String, _
    strB As String _
) As Integer

Visual Basic (Usage)

Dim strA As String
Dim strB As String
Dim returnValue As Integer

returnValue = (strA, _
    strB)

public static int Compare(
    string strA,
    string strB
)

Visual C++

public:
static int Compare(
    String^ strA, 
    String^ strB
)

public static int Compare(
    String strA,
    String strB
)

JScript

public static function Compare(
    strA : String, 
    strB : String
) : int

Parameters

strA: Type: System..::.String

The first String.

strB: Type: System..::.String

The second String.

Return Value

Type: System..::.Int32

A 32-bit signed integer indicating the lexical relationship between the two comparands.

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

Remarks

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

The comparison is performed using word sort rules. For more information about word, string, and ordinal sorts, see System.Globalization..::.CompareOptions.

One or both comparands can be nullNothingnullptra null reference (Nothing in Visual Basic). By definition, any string, including the empty string (""), 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, then the string with remaining characters is considered greater. The return value is the result of the last comparison performed.

Unexpected results can occur when comparisons are affected by culture-specific casing rules. For example, in Turkish, the following example yields the wrong results because the file system in Turkish does not use linguistic casing rules for the letter 'i' in "file".

Copy Code

 static bool IsFileURI(String path)
 { 
    return ((path, 0, "file:", 0, 5, true) == 0);
 }

Visual Basic

Copy Code

 Shared Function IsFileURI(ByVal path As String) As Boolean
    If (path, 0, "file:", 0, 5, True) = 0 Then
       Return True
    Else
       Return False
    End If
 End Function

Compare the path name to "file" using an ordinal comparison. The correct code to do this is as follows:

Copy Code

 static bool IsFileURI(String path)
 { 
    return ((path, 0, "file:", 0, 5, StringComparison.OrdinalIgnoreCase) == 0);
 }

Visual Basic

Copy Code

Shared Function IsFileURI(ByVal path As String) As Boolean
    If (path, 0, "file:", 0, 5, StringComparison.OrdinalIgnoreCase) = 0 Then
       Return True
    Else
       Return False
    End If
 End Function

Examples

In the following code example, the ReverseStringComparer class demonstrates how you can evaluate two strings with the Compare method.

Visual Basic

Copy Code

Imports System
Imports System.Text
Imports System.Collections



Public Class SamplesArrayList


    Public Shared Sub Main()
        Dim myAL As New ArrayList()
        ' Creates and initializes a new ArrayList.
        myAL.Add("Eric")
        myAL.Add("Mark")
        myAL.Add("Lance")
        myAL.Add("Rob")
        myAL.Add("Kris")
        myAL.Add("Brad")
        myAL.Add("Kit")
        myAL.Add("Bradley")
        myAL.Add("Keith")
        myAL.Add("Susan")

        ' Displays the properties and values of    the    ArrayList.
        Console.WriteLine("Count: {0}", myAL.Count)
        PrintValues("Unsorted", myAL)
        myAL.Sort()
        PrintValues("Sorted", myAL)
        Dim comp as New ReverseStringComparer
        myAL.Sort(comp)
        PrintValues("Reverse", myAL)

        Dim names As String() = CType(myAL.ToArray(GetType(String)), String())
    End Sub 'Main



    Public Shared Sub PrintValues(title As String, myList As IEnumerable)
        Console.Write("{0,10}: ", title)
        Dim sb As New StringBuilder()
        Dim s As String
        For Each s In  myList
            sb.AppendFormat("{0}, ", s)
        Next s
        sb.Remove(sb.Length - 2, 2)
        Console.WriteLine(sb)
    End Sub 'PrintValues
End Class 'SamplesArrayList

Public Class ReverseStringComparer 
  Implements IComparer

     Function Compare(x As Object, y As Object) As Integer implements IComparer.Compare
        Dim s1 As String = CStr (x)
        Dim s2 As String = CStr (y)

        'negate the return value to get the reverse order
        Return - [String].Compare(s1, s2)

    End Function 'Compare
End Class 'ReverseStringComparer

Copy Code

using System;
using System.Text;
using System.Collections;

public class SamplesArrayList  {

    public static void Main()  {
        // Creates and initializes a new ArrayList.
        ArrayList myAL = new ArrayList();
        myAL.Add("Eric");
        myAL.Add("Mark");
        myAL.Add("Lance");
        myAL.Add("Rob");
        myAL.Add("Kris");
        myAL.Add("Brad");
        myAL.Add("Kit");
        myAL.Add("Bradley");
        myAL.Add("Keith");
        myAL.Add("Susan");
    
        // Displays the properties and values of    the    ArrayList.
        Console.WriteLine( "Count: {0}", myAL.Count );
        
        PrintValues ("Unsorted", myAL );
        myAL.Sort();
        PrintValues("Sorted", myAL );
        myAL.Sort(new ReverseStringComparer() );
        PrintValues ("Reverse" , myAL );


        string [] names = (string[]) myAL.ToArray (typeof(string));


    }
    public static void PrintValues(string title, IEnumerable    myList )  {
        Console.Write ("{0,10}: ", title);
        StringBuilder sb = new StringBuilder();
        foreach (string s in myList) {
            sb.AppendFormat( "{0}, ", s);
        }
        sb.Remove (sb.Length-2,2);
        Console.WriteLine(sb);
    }
}
public class ReverseStringComparer : IComparer {
   public int Compare (object x, object y) {
       string s1 = x as string;
       string s2 = y as string;      
       //negate the return value to get the reverse order
       return -  (s1,s2);

   }
}

Visual C++

Copy Code

using namespace System;
using namespace System::Text;
using namespace System::Collections;

ref class ReverseStringComparer: public IComparer
{
public:
   virtual int Compare( Object^ x, Object^ y )
   {
      String^ s1 = dynamic_cast<String^>(x);
      String^ s2 = dynamic_cast<String^>(y);

      //negate the return value to get the reverse order
      return  -String::Compare( s1, s2 );
   }

};

void PrintValues( String^ title, IEnumerable^ myList )
{
   Console::Write( "{0,10}: ", title );
   StringBuilder^ sb = gcnew StringBuilder;
   {
      IEnumerator^ en = myList->GetEnumerator();
      String^ s;
      while ( en->MoveNext() )
      {
         s = en->Current->ToString();
         sb->AppendFormat(  "{0}, ", s );
      }
   }
   sb->Remove( sb->Length - 2, 2 );
   Console::WriteLine( sb );
}

void main()
{
   // Creates and initializes a new ArrayList.
   ArrayList^ myAL = gcnew ArrayList;
   myAL->Add( "Eric" );
   myAL->Add( "Mark" );
   myAL->Add( "Lance" );
   myAL->Add( "Rob" );
   myAL->Add( "Kris" );
   myAL->Add( "Brad" );
   myAL->Add( "Kit" );
   myAL->Add( "Bradley" );
   myAL->Add( "Keith" );
   myAL->Add( "Susan" );

   // Displays the properties and values of the ArrayList.
   Console::WriteLine( "Count: {0}", myAL->Count.ToString() );

   PrintValues( "Unsorted", myAL );

   myAL->Sort();
   PrintValues( "Sorted", myAL );

   myAL->Sort( gcnew ReverseStringComparer );
   PrintValues( "Reverse", myAL );

   array<String^>^names = dynamic_cast<array<String^>^>(myAL->ToArray( String::typeid ));
}

Copy Code

import System.*;
import System.Text.*;
import System.Collections.*;

public class SamplesArrayList
{
    public static void main(String[] args)
    {
        // Creates and initializes a new ArrayList.
        ArrayList myAL = new ArrayList();

        myAL.Add("Eric");
        myAL.Add("Mark");
        myAL.Add("Lance");
        myAL.Add("Rob");
        myAL.Add("Kris");
        myAL.Add("Brad");
        myAL.Add("Kit");
        myAL.Add("Bradley");
        myAL.Add("Keith");
        myAL.Add("Susan");

        // Displays the properties and values of the ArrayList.
        Console.WriteLine("Count: {0}", (Int32)myAL.get_Count());

        PrintValues("Unsorted", myAL);

        myAL.Sort();
        PrintValues("Sorted", myAL);

        myAL.Sort(new ReverseStringComparer());
        PrintValues("Reverse", myAL);

        String names[] = (String[])(myAL.ToArray(String.class.ToType()));
    } //main

    public static void PrintValues(String title, IEnumerable myList)
    {
        Console.Write("{0,10}: ", title);
        StringBuilder sb = new StringBuilder();
        IEnumerator objEnum = myList.GetEnumerator();
        while (objEnum.MoveNext()) {
            String s = System.Convert.ToString(objEnum.get_Current());
            sb.AppendFormat("{0}, ", s);
        }

        sb.Remove(sb.get_Length() - 2, 2);
        Console.WriteLine(sb);
    } //PrintValues
} //SamplesArrayList


public class ReverseStringComparer implements IComparer
{
    public int Compare(Object x, Object y)
    {
        String s1 = System.Convert.ToString(x);
        String s2 = System.Convert.ToString(y);

        //negate the return value to get the reverse order
        return -(s1, s2);
    } //Compare 
} //ReverseStringComparer

JScript

Copy Code

import System;
import System.Text;
import System.Collections;

public class SamplesArrayList  {

    public static function Main() : void {
        // Creates and initializes a new ArrayList.
        var myAL : ArrayList = new ArrayList();
        myAL.Add("Eric");
        myAL.Add("Mark");
        myAL.Add("Lance");
        myAL.Add("Rob");
        myAL.Add("Kris");
        myAL.Add("Brad");
        myAL.Add("Kit");
        myAL.Add("Bradley");
        myAL.Add("Keith");
        myAL.Add("Susan");
    
        // Displays the properties and values of    the    ArrayList.
        Console.WriteLine( "Count: {0}", myAL.Count );
        
        PrintValues ("Unsorted", myAL );
        myAL.Sort();
        PrintValues("Sorted", myAL );
        myAL.Sort(new ReverseStringComparer() );
        PrintValues ("Reverse" , myAL );


        var names : String [] = (String[])(myAL.ToArray (System.String));


    }
    public static function PrintValues(title : String, myList: IEnumerable ) : void {
        Console.Write ("{0,10}: ", title);
        var sb : StringBuilder = new StringBuilder();
        for (var s : String in myList) {
            sb.AppendFormat( "{0}, ", s);
        }
        sb.Remove (sb.Length-2,2);
        Console.WriteLine(sb);
    }
}
public class ReverseStringComparer implements IComparer {
   public function Compare (x, y) : int  {
       //negate the return value to get the reverse order
       return -  (String(x), String(y));
   }
}
SamplesArrayList.Main();

String..::.Compare Method (String, String)

Parameters

Return Value

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