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String.LastIndexOf Method (String, Int32, Int32)

Updated: July 2008

Reports the index position of the last occurrence of a specified String within this instance. The search starts at a specified character position and examines a specified number of character positions.

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

'Declaration
Public Function LastIndexOf ( _
	value As String, _
	startIndex As Integer, _
	count As Integer _
) As Integer
'Usage
Dim instance As String 
Dim value As String 
Dim startIndex As Integer 
Dim count As Integer 
Dim returnValue As Integer 

returnValue = instance.LastIndexOf(value, _
	startIndex, count)

Parameters

value
Type: System.String

The String to seek.

startIndex
Type: System.Int32

The search starting position.

count
Type: System.Int32

The number of character positions to examine.

Return Value

Type: System.Int32
The index position of value if that string is found, or -1 if it is not found or if the current instance equals String.Empty. If value is Empty, the return value is startIndex.

ExceptionCondition
ArgumentNullException

value is Nothing.

ArgumentOutOfRangeException

The current instance does not equal String.Empty and count or startIndex is negative.

-or-

startIndex is greater than the length of this instance.

-or-

startIndex + 1 - count specifies a position that is not within this instance.

Index numbering starts from zero. That is, the first character in the string is at index zero and the last is at Length - 1.

The search begins at the startIndex character position of this instance and proceeds backward toward the beginning until either value is found or count character positions have been examined. For example, if startIndex is Length - 1, the method searches backward count characters from the last character in the string.

This method performs a word (case-sensitive and culture-sensitive) search using the current culture.

The following example finds the index of all occurrences of a string in substring, working from the end of the substring to the start of the substring.

' Sample for String.LastIndexOf(String, Int32, Int32) 
Imports System
 _

Class Sample

   Public Shared Sub Main()

      Dim br1 As String = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-" 
      Dim br2 As String = "0123456789012345678901234567890123456789012345678901234567890123456" 
      Dim str As String = "Now is the time for all good men to come to the aid of their party." 
      Dim start As Integer 
      Dim at As Integer 
      Dim count As Integer 
      Dim [end] As Integer

      start = str.Length - 1
      [end] = start / 2 - 1
      Console.WriteLine("All occurrences of 'he' from position {0} to {1}.", start, [end])
      Console.WriteLine("{1}{0}{2}{0}{3}{0}", Environment.NewLine, br1, br2, str)
      Console.Write("The string 'he' occurs at position(s): ")

      count = 0
      at = 0
      While start > - 1 And at > - 1
         count = start - [end] 'Count must be within the substring.
         at = str.LastIndexOf("he", start, count)
         If at > - 1 Then
            Console.Write("{0} ", at)
            start = at - 1
         End If 
      End While
      Console.Write("{0}{0}{0}", Environment.NewLine)
   End Sub 'Main 
End Class 'Sample

'This example produces the following results: 
'All occurrences of 'he' from position 66 to 32. 
'0----+----1----+----2----+----3----+----4----+----5----+----6----+- 
'0123456789012345678901234567890123456789012345678901234567890123456 
'Now is the time for all good men to come to the aid of their party. 

'The string 'he' occurs at position(s): 56 45 

'

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

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

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

Date

History

Reason

July 2008

Added exception information.

Content bug fix.

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