List(Of T).LastIndexOf Method (T, 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 extends from the first element to the specified index.

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

'Declaration
Public Function LastIndexOf ( _
	item As T, _
	index As Integer _
) As Integer

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.

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 extends from the first element to index, if found; otherwise, –1.

ExceptionCondition
ArgumentOutOfRangeException

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

The List(Of T) is searched backward starting at index and ending at the first element.

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 the number of elements from the beginning of the List(Of T) to index.

The following 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 four 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

.NET Framework

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

.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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