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String.Compare Method (String, String)

Compares two specified String objects and returns an integer that indicates their relative position in the sort order.

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

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

Parameters

strA
Type: System.String

The first string to compare.

strB
Type: System.String

The second string to compare.

Return Value

Type: System.Int32
A 32-bit signed integer that indicates 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.

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.

Caution noteCaution

When comparing strings, you should call the Compare(String, String, StringComparison) method, which requires that you explicitly specify the type of string comparison that the method uses. For more information, see Best Practices for Using Strings in the .NET Framework.

One or both comparands can be Nothing. 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".

Shared Function IsFileURI(ByVal path As String) As Boolean 
    If String.Compare(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:

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

Notes to Callers

Character sets include ignorable characters. The Compare(String, String) method does not consider such characters when it performs a culture-sensitive comparison. For example, if the following code is run on the .NET Framework 4 or later, a culture-sensitive comparison of "animal" with "ani-mal" (using a soft hyphen, or U+00AD) indicates that the two strings are equivalent.

Module Example
   Public Sub Main()
      Dim s1 As String = "ani" + ChrW(&h00AD) + "mal" 
      Dim s2 As String = "animal"

      Console.WriteLine("Comparison of '{0}' and '{1}': {2}", 
                        s1, s2, String.Compare(s1, s2))
  End Sub 
End Module 
' The example displays the following output: 
'       Comparison of 'ani-mal' and 'animal': 0

To recognize ignorable characters in a string comparison, call the Compare(String, String, StringComparison) method and supply a value of either CompareOptions.Ordinal or CompareOptions.OrdinalIgnoreCase for the comparisonType parameter.

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

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

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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