CompareTo Method (String)
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String.CompareTo Method (String)

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

Compares this instance with a specified String object and indicates whether this instance precedes, follows, or appears in the same position in the sort order as the specified String.

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

'Declaration
Public Function CompareTo ( _
	strB As String _
) As Integer

Parameters

strB
Type: System.String
The string to compare with this instance.

Return Value

Type: System.Int32
A 32-bit signed integer that indicates whether this instance precedes, follows, or appears in the same position in the sort order as the value parameter.

Value

Condition

Less than zero

This instance precedes strB.

Zero

This instance has the same position in the sort order as strB.

Greater than zero

This instance follows strB.

-or-

strB is Nothing.

Implements

IComparable(Of T).CompareTo(T)

This method performs a word (case-sensitive and culture-sensitive) comparison using the current culture. For more information about word, string, and ordinal sorts, see System.Globalization.CompareOptions.

Caution noteCaution:

The CompareTo(String) 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.

For more information about the behavior of this method, see the Remarks section of the Compare(String, String) method.

This method implements the System.IComparable(Of T) interface, and performs slightly better than the String.CompareTo method because it does not have to determine whether the value argument is a mutable value type that must be boxed, and it does not have to cast its parameter from an Object to a String.

The following example demonstrates how you can use the CompareTo method with another String.




Public Class Example

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      Dim strFirst As String = "Goodbye"
      Dim strSecond As String = "Hello"
      Dim strThird As String = "a small string"
      Dim strFourth As String = "goodbye"


      ' compare a string to itself
      outputBlock.Text += String.Format(CompareStrings(strFirst, strFirst)) & vbCrLf

      outputBlock.Text += String.Format(CompareStrings(strFirst, strSecond)) & vbCrLf
      outputBlock.Text += String.Format(CompareStrings(strFirst, strThird)) & vbCrLf

      ' compare a string to another string that varies only by case
      outputBlock.Text += String.Format(CompareStrings(strFirst, strFourth)) & vbCrLf
      outputBlock.Text += String.Format(CompareStrings(strFourth, strFirst)) & vbCrLf
   End Sub 'Main


   Private Shared Function CompareStrings(ByVal str1 As String, ByVal str2 As String) As String
      Dim cmpVal As Integer = str1.CompareTo(str2)
      If cmpVal = 0 Then

         ' compare the values, using the CompareTo method on the first string

         ' the values are the same
         Return "The strings have the same value!"
      Else
         If cmpVal > 0 Then

            ' the first value is greater than the second value
            Return "The first string is greater than the second string!"
         Else

            ' the second string is greater than the first string
            Return "The second string is greater than the first string!"
         End If
      End If
   End Function 'CompareStrings
End Class 'CompareToTest


' This code example displays the following:
'
' The strings have the same value!
' The second string is greater than the first string!
' The first string is greater than the second string!
' The first string is greater than the second string!
' The second string is greater than the first string!


The following example demonstrates generic and non-generic versions of the CompareTo method for several value and reference types.


' This example demonstrates the generic and non-generic versions of the 
' CompareTo method for several base types.
' The non-generic version takes a parameter of type Object, while the generic
' version takes a type-specific parameter, such as Boolean, Int32, or Double.


Class Example
   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      Dim nl As String = vbCrLf
      Dim msg As String = _
          "{0}The following is the result of using the generic and non-generic{0}" & _
          "versions of the CompareTo method for several base types:{0}"

      Dim now As DateTime = DateTime.Now
      ' Time span = 11 days, 22 hours, 33 minutes, 44 seconds
      Dim tsX As New TimeSpan(11, 22, 33, 44)
      ' Version = 1.2.333.4
      Dim versX As New Version("1.2.333.4")
      ' Guid = CA761232-ED42-11CE-BACD-00AA0057B223
      Dim guidX As New Guid("{CA761232-ED42-11CE-BACD-00AA0057B223}")

      Dim a1 As [Boolean] = True, a2 As [Boolean] = True
      Dim b1 As [Byte] = 1, b2 As [Byte] = 1
      Dim c1 As Int16 = -2, c2 As Int16 = 2
      Dim d1 As Int32 = 3, d2 As Int32 = 3
      Dim e1 As Int64 = 4, e2 As Int64 = -4
      Dim f1 As [Decimal] = -5.5D, f2 As [Decimal] = 5.5D
      Dim g1 As [Single] = 6.6F, g2 As [Single] = 6.6F
      Dim h1 As [Double] = 7.7, h2 As [Double] = -7.7
      Dim i1 As [Char] = "A"c, i2 As [Char] = "A"c
      Dim j1 As String = "abc", j2 As String = "abc"
      Dim k1 As DateTime = now, k2 As DateTime = now
      Dim l1 As TimeSpan = tsX, l2 As TimeSpan = tsX
      Dim m1 As Version = versX, m2 As New Version("2.0")
      Dim n1 As Guid = guidX, n2 As Guid = guidX

      ' The following types are not CLS-compliant.
      ' SByte, UInt16, UInt32, UInt64

      outputBlock.Text &= String.Format(msg, nl) & vbCrLf
      Try
         ' The second and third Show method call parameters are automatically boxed because
         ' the second and third Show method declaration arguments expect type Object.

         Show(outputBlock, "Boolean:  ", a1, a2, a1.CompareTo(a2), a1.CompareTo(CObj(a2)))
         Show(outputBlock, "Byte:     ", b1, b2, b1.CompareTo(b2), b1.CompareTo(CObj(b2)))
         Show(outputBlock, "Int16:    ", c1, c2, c1.CompareTo(c2), c1.CompareTo(CObj(c2)))
         Show(outputBlock, "Int32:    ", d1, d2, d1.CompareTo(d2), d1.CompareTo(CObj(d2)))
         Show(outputBlock, "Int64:    ", e1, e2, e1.CompareTo(e2), e1.CompareTo(CObj(e2)))
         Show(outputBlock, "Decimal:  ", f1, f2, f1.CompareTo(f2), f1.CompareTo(CObj(f2)))
         Show(outputBlock, "Single:   ", g1, g2, g1.CompareTo(g2), g1.CompareTo(CObj(g2)))
         Show(outputBlock, "Double:   ", h1, h2, h1.CompareTo(h2), h1.CompareTo(CObj(h2)))
         Show(outputBlock, "Char:     ", i1, i2, i1.CompareTo(i2), i1.CompareTo(CObj(i2)))
         Show(outputBlock, "String:   ", j1, j2, j1.CompareTo(j2), j1.CompareTo(CObj(j2)))
         Show(outputBlock, "DateTime: ", k1, k2, k1.CompareTo(k2), k1.CompareTo(CObj(k2)))
         Show(outputBlock, "TimeSpan: ", l1, l2, l1.CompareTo(l2), l1.CompareTo(CObj(l2)))
         Show(outputBlock, "Version:  ", m1, m2, m1.CompareTo(m2), m1.CompareTo(CObj(m2)))
         Show(outputBlock, "Guid:     ", n1, n2, n1.CompareTo(n2), n1.CompareTo(CObj(n2)))
         '
         outputBlock.Text &= String.Format("{0}The following types are not CLS-compliant:", nl) & vbCrLf
         outputBlock.Text &= String.Format("SByte, UInt16, UInt32, UInt64") & vbCrLf

      Catch e As Exception
         outputBlock.Text &= e.GetType().Name & vbCrLf
      End Try
   End Sub 'Main

   Public Shared Sub Show(ByVal outputBlock As System.Windows.Controls.TextBlock, ByVal caption As String, ByVal var1 As [Object], ByVal var2 As [Object], _
                          ByVal resultGeneric As Integer, ByVal resultNonGeneric As Integer)
      Dim relation As String

      outputBlock.Text &= caption
      If resultGeneric = resultNonGeneric Then
         If resultGeneric < 0 Then
            relation = "less than"
         ElseIf resultGeneric > 0 Then
            relation = "greater than"
         Else
            relation = "equal to"
         End If
         outputBlock.Text &= String.Format("{0} is {1} {2}", var1, relation, var2) & vbCrLf

         ' The following condition will never occur because the generic and non-generic
         ' CompareTo methods are equivalent.

      Else
         outputBlock.Text &= String.Format("Generic CompareTo = {0}; non-generic CompareTo = {1}", _
                            resultGeneric, resultNonGeneric) & vbCrLf
      End If
   End Sub 'Show
End Class 'Sample
'
'This example produces the following results:
'
'The following is the result of using the generic and non-generic versions of the
'CompareTo method for several base types:
'
'Boolean:  True is equal to True
'Byte:     1 is equal to 1
'Int16:    -2 is less than 2
'Int32:    3 is equal to 3
'Int64:    4 is greater than -4
'Decimal:  -5.5 is less than 5.5
'Single:   6.6 is equal to 6.6
'Double:   7.7 is greater than -7.7
'Char:     A is equal to A
'String:   abc is equal to abc
'DateTime: 12/1/2003 5:37:46 PM is equal to 12/1/2003 5:37:46 PM
'TimeSpan: 11.22:33:44 is equal to 11.22:33:44
'Version:  1.2.333.4 is less than 2.0
'Guid:     ca761232-ed42-11ce-bacd-00aa0057b223 is equal to ca761232-ed42-11ce-bacd-00
'aa0057b223
'
'The following types are not CLS-compliant:
'SByte, UInt16, UInt32, UInt64
'


Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

Show:
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