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List(Of T).LastIndexOf Method (T, Int32, Int32)

Searches for the specified object and returns the zero-based index of the last occurrence within the range of elements in the List(Of T) that contains the specified number of elements and ends at the specified index.

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

'Declaration
Public Function LastIndexOf ( _
	item As T, _
	index As Integer, _
	count As Integer _
) As Integer
'Usage
Dim instance As List 
Dim item As T
Dim index As Integer 
Dim count As Integer 
Dim returnValue As Integer 

returnValue = instance.LastIndexOf(item, _
	index, count)

Parameters

item
Type: T

The object to locate in the List(Of T). The value can be Nothing for reference types.

index
Type: System.Int32

The zero-based starting index of the backward search.

count
Type: System.Int32

The number of elements in the section to search.

Return Value

Type: System.Int32
The zero-based index of the last occurrence of item within the range of elements in the List(Of T) that contains count number of elements and ends at index, if found; otherwise, –1.

ExceptionCondition
ArgumentOutOfRangeException

index is outside the range of valid indexes for the List(Of T).

-or-

count is less than 0.

-or-

index and count do not specify a valid section in the List(Of T).

The List(Of T) is searched backward starting at index and ending at index minus count plus 1, if count is greater than 0.

This method determines equality using the default equality comparer EqualityComparer(Of T).Default for T, the type of values in the list.

This method performs a linear search; therefore, this method is an O(n) operation, where n is count.

The following code example demonstrates all three overloads of the LastIndexOf method. A List(Of T) of strings is created, with one entry that appears twice, at index location 0 and index location 5. The LastIndexOf(T) method overload searches the entire list from the end, and finds the second occurrence of the string. The LastIndexOf(T, Int32) method overload is used to search the list backward beginning with index location 3 and continuing to the beginning of the list, so it finds the first occurrence of the string in the list. Finally, the LastIndexOf(T, Int32, Int32) method overload is used to search a range of 4 entries, beginning at index location 4 and extending backward (that is, it searches the items at locations 4, 3, 2, and 1); this search returns –1 because there are no instances of the search string in that range.

Imports System
Imports System.Collections.Generic

Public Class Example

    Public Shared Sub Main()

        Dim dinosaurs As New List(Of String)

        dinosaurs.Add("Tyrannosaurus")
        dinosaurs.Add("Amargasaurus")
        dinosaurs.Add("Mamenchisaurus")
        dinosaurs.Add("Brachiosaurus")
        dinosaurs.Add("Deinonychus")
        dinosaurs.Add("Tyrannosaurus")
        dinosaurs.Add("Compsognathus")

        Console.WriteLine()
        For Each dinosaur As String In dinosaurs
            Console.WriteLine(dinosaur)
        Next

        Console.WriteLine(vbLf & _
            "LastIndexOf(""Tyrannosaurus""): {0}", _
            dinosaurs.LastIndexOf("Tyrannosaurus"))

        Console.WriteLine(vbLf & _
            "LastIndexOf(""Tyrannosaurus"", 3): {0}", _
            dinosaurs.LastIndexOf("Tyrannosaurus", 3))

        Console.WriteLine(vbLf & _
            "LastIndexOf(""Tyrannosaurus"", 4, 4): {0}", _
            dinosaurs.LastIndexOf("Tyrannosaurus", 4, 4))

    End Sub 
End Class 

' This code example produces the following output: 

'Tyrannosaurus 
'Amargasaurus 
'Mamenchisaurus 
'Brachiosaurus 
'Deinonychus 
'Tyrannosaurus 
'Compsognathus 

'LastIndexOf("Tyrannosaurus"): 5 

'LastIndexOf("Tyrannosaurus", 3): 0 

'LastIndexOf("Tyrannosaurus", 4, 4): -1

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

.NET Compact Framework

Supported in: 3.5, 2.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

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