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Array.LastIndexOf Method (Array, Object)

Searches for the specified object and returns the index of the last occurrence within the entire one-dimensional Array.

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

'Declaration
Public Shared Function LastIndexOf ( _
	array As Array, _
	value As Object _
) As Integer

Parameters

array
Type: System.Array

The one-dimensional Array to search.

value
Type: System.Object

The object to locate in array.

Return Value

Type: System.Int32
The index of the last occurrence of value within the entire array, if found; otherwise, the lower bound of the array minus 1.

ExceptionCondition
ArgumentNullException

array is Nothing.

RankException

array is multidimensional.

The one-dimensional Array is searched backward starting at the last element and ending at the first element.

The elements are compared to the specified value using the Object.Equals method. If the element type is a nonintrinsic (user-defined) type, the Equals implementation of that type is used.

Since most arrays will have a lower bound of zero, this method would generally return –1 when value is not found. In the rare case that the lower bound of the array is equal to Int32.MinValue and value is not found, this method returns Int32.MaxValue, which is System.Int32.MinValue - 1.

This method is an O(n) operation, where n is the Length of array.

In the .NET Framework version 2.0, this method uses the Equals and CompareTo methods of the Array to determine whether the Object specified by the value parameter exists. In the earlier versions of the .NET Framework, this determination was made by using the Equals and CompareTo methods of the value Object itself.

CompareTo methods of the item parameter on the objects in the collection.

The following code example shows how to determine the index of the last occurrence of a specified element in an array.

Imports System
Imports Microsoft.VisualBasic

Public Class SamplesArray    

    Public Shared Sub Main()

        ' Creates and initializes a new Array with three elements of 
        ' the same value. 
        Dim myArray As Array = Array.CreateInstance(GetType(String), 12)
        myArray.SetValue("the", 0)
        myArray.SetValue("quick", 1)
        myArray.SetValue("brown", 2)
        myArray.SetValue("fox", 3)
        myArray.SetValue("jumps", 4)
        myArray.SetValue("over", 5)
        myArray.SetValue("the", 6)
        myArray.SetValue("lazy", 7)
        myArray.SetValue("dog", 8)
        myArray.SetValue("in", 9)
        myArray.SetValue("the", 10)
        myArray.SetValue("barn", 11)

        ' Displays the values of the Array.
        Console.WriteLine("The Array contains the following values:")
        PrintIndexAndValues(myArray)

        ' Searches for the last occurrence of the duplicated value. 
        Dim myString As String = "the" 
        Dim myIndex As Integer = Array.LastIndexOf(myArray, myString)
        Console.WriteLine("The last occurrence of ""{0}"" is at index {1}.", _
           myString, myIndex)

        ' Searches for the last occurrence of the duplicated value in the first 
        ' section of the Array.
        myIndex = Array.LastIndexOf(myArray, myString, 8)
        Console.WriteLine("The last occurrence of ""{0}"" between the start " _
           + "and index 8 is at index {1}.", myString, myIndex)

        ' Searches for the last occurrence of the duplicated value in a section 
        ' of the Array.  Note that the start index is greater than the end 
        ' index because the search is done backward.
        myIndex = Array.LastIndexOf(myArray, myString, 10, 6)
        Console.WriteLine("The last occurrence of ""{0}"" between index 5 " _
           + "and index 10 is at index {1}.", myString, myIndex)
    End Sub 


    Public Shared Sub PrintIndexAndValues(myArray As Array)
        Dim i As Integer 
        For i = myArray.GetLowerBound(0) To myArray.GetUpperBound(0)
            Console.WriteLine(ControlChars.Tab + "[{0}]:" + ControlChars.Tab _
               + "{1}", i, myArray.GetValue(i))
        Next i
    End Sub 
End Class 

' This code produces the following output. 
'  
' The Array contains the following values: 
'     [0]:    the 
'     [1]:    quick 
'     [2]:    brown 
'     [3]:    fox 
'     [4]:    jumps 
'     [5]:    over 
'     [6]:    the 
'     [7]:    lazy 
'     [8]:    dog 
'     [9]:    in 
'     [10]:    the 
'     [11]:    barn 
' The last occurrence of "the" is at index 10. 
' The last occurrence of "the" between the start and index 8 is at index 6. 
' The last occurrence of "the" between index 5 and index 10 is at index 10. 

.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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