Array.FindLastIndex Method

Definition

Overloads

Examples

The following code example demonstrates all three overloads of the FindLastIndex generic method. An array of strings is created, containing 8 dinosaur names, two of which (at positions 1 and 5) end with "saurus". The code example also defines a search predicate method named EndsWithSaurus, which accepts a string parameter and returns a Boolean value indicating whether the input string ends in "saurus".

The FindLastIndex(T[], Predicate) method overload traverses the array backward from the end, passing each element in turn to the EndsWithSaurus method. The search stops when the EndsWithSaurus method returns true for the element at position 5.

The FindLastIndex(T[], Int32, Predicate) method overload is used to search the array beginning at position 4 and continuing backward to the beginning of the array. It finds the element at position 1. Finally, the FindLastIndex(T[], Int32, Int32, Predicate) method overload is used to search the range of three elements beginning at position 4 and working backward (that is, elements 4, 3, and 2). It returns -1 because there are no dinosaur names in that range that end with "saurus".

using System;

public class Example
{
    public static void Main()
    {
        string[] dinosaurs = { "Compsognathus",
            "Amargasaurus",   "Oviraptor",      "Velociraptor",
            "Deinonychus",    "Dilophosaurus",  "Gallimimus",
            "Triceratops" };

        Console.WriteLine();
        foreach(string dinosaur in dinosaurs)
        {
            Console.WriteLine(dinosaur);
        }

        Console.WriteLine(
            "\nArray.FindLastIndex(dinosaurs, EndsWithSaurus): {0}",
            Array.FindLastIndex(dinosaurs, EndsWithSaurus));

        Console.WriteLine(
            "\nArray.FindLastIndex(dinosaurs, 4, EndsWithSaurus): {0}",
            Array.FindLastIndex(dinosaurs, 4, EndsWithSaurus));

        Console.WriteLine(
            "\nArray.FindLastIndex(dinosaurs, 4, 3, EndsWithSaurus): {0}",
            Array.FindLastIndex(dinosaurs, 4, 3, EndsWithSaurus));
    }

    // Search predicate returns true if a string ends in "saurus".
    private static bool EndsWithSaurus(String s)
    {
        if ((s.Length > 5) &&
            (s.Substring(s.Length - 6).ToLower() == "saurus"))
        {
            return true;
        }
        else
        {
            return false;
        }
    }
}

/* This code example produces the following output:

Compsognathus
Amargasaurus
Oviraptor
Velociraptor
Deinonychus
Dilophosaurus
Gallimimus
Triceratops

Array.FindLastIndex(dinosaurs, EndsWithSaurus): 5

Array.FindLastIndex(dinosaurs, 4, EndsWithSaurus): 1

Array.FindLastIndex(dinosaurs, 4, 3, EndsWithSaurus): -1
 */

open System

// Search predicate returns true if a string ends in "saurus".
let endsWithSaurus (s: string) =
    s.Length > 5 && s.Substring(s.Length - 6).ToLower() = "saurus"

let dinosaurs =
    [| "Compsognathus"; "Amargasaurus"
       "Oviraptor"; "Velociraptor"
       "Deinonychus"; "Dilophosaurus"
       "Gallimimus"; "Triceratops" |]

printfn ""
for dino in dinosaurs do
    printfn $"{dino}"

Array.FindLastIndex(dinosaurs, endsWithSaurus)
|> printfn "\nArray.FindLastIndex(dinosaurs, EndsWithSaurus): %i"

Array.FindLastIndex(dinosaurs, 4, endsWithSaurus)
|> printfn "\nArray.FindLastIndex(dinosaurs, 4, EndsWithSaurus): %i"

Array.FindLastIndex(dinosaurs, 4, 3, endsWithSaurus)
|> printfn "\nArray.FindLastIndex(dinosaurs, 4, 3, EndsWithSaurus): %i"


// This code example produces the following output:
//
//     Compsognathus
//     Amargasaurus
//     Oviraptor
//     Velociraptor
//     Deinonychus
//     Dilophosaurus
//     Gallimimus
//     Triceratops
//
//     Array.FindLastIndex(dinosaurs, EndsWithSaurus): 5
//
//     Array.FindLastIndex(dinosaurs, 4, EndsWithSaurus): 1
//
//     Array.FindLastIndex(dinosaurs, 4, 3, EndsWithSaurus): -1

Public Class Example

    Public Shared Sub Main()

        Dim dinosaurs() As String = { "Compsognathus", _
            "Amargasaurus",   "Oviraptor",      "Velociraptor", _
            "Deinonychus",    "Dilophosaurus",  "Gallimimus", _
            "Triceratops" }

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

        Console.WriteLine(vbLf & _
            "Array.FindLastIndex(dinosaurs, AddressOf EndsWithSaurus): {0}", _
            Array.FindLastIndex(dinosaurs, AddressOf EndsWithSaurus))

        Console.WriteLine(vbLf & _
            "Array.FindLastIndex(dinosaurs, 4, AddressOf EndsWithSaurus): {0}", _
            Array.FindLastIndex(dinosaurs, 4, AddressOf EndsWithSaurus))

        Console.WriteLine(vbLf & _
            "Array.FindLastIndex(dinosaurs, 4, 3, AddressOf EndsWithSaurus): {0}", _
            Array.FindLastIndex(dinosaurs, 4, 3, AddressOf EndsWithSaurus))

    End Sub

    ' Search predicate returns true if a string ends in "saurus".
    Private Shared Function EndsWithSaurus(ByVal s As String) _
        As Boolean

        ' AndAlso prevents evaluation of the second Boolean
        ' expression if the string is so short that an error
        ' would occur.
        If (s.Length > 5) AndAlso _
            (s.Substring(s.Length - 6).ToLower() = "saurus") Then
            Return True
        Else
            Return False
        End If
    End Function
End Class

' This code example produces the following output:
'
'Compsognathus
'Amargasaurus
'Oviraptor
'Velociraptor
'Deinonychus
'Dilophosaurus
'Gallimimus
'Triceratops
'
'Array.FindLastIndex(dinosaurs, AddressOf EndsWithSaurus): 5
'
'Array.FindLastIndex(dinosaurs, 4, AddressOf EndsWithSaurus): 1
'
'Array.FindLastIndex(dinosaurs, 4, 3, AddressOf EndsWithSaurus): -1

public:
generic 
 static int FindLastIndex(cli::array  ^ array, Predicate ^ match);

public static int FindLastIndex(T[] array, Predicate match);

static member FindLastIndex : 'T[] * Predicate<'T> -> int

Public Shared Function FindLastIndex(Of T) (array As T(), match As Predicate(Of T)) As Integer

public:
generic 
 static int FindLastIndex(cli::array  ^ array, int startIndex, Predicate ^ match);

public static int FindLastIndex(T[] array, int startIndex, Predicate match);

static member FindLastIndex : 'T[] * int * Predicate<'T> -> int

Public Shared Function FindLastIndex(Of T) (array As T(), startIndex As Integer, match As Predicate(Of T)) As Integer

public:
generic 
 static int FindLastIndex(cli::array  ^ array, int startIndex, int count, Predicate ^ match);

public static int FindLastIndex(T[] array, int startIndex, int count, Predicate match);

static member FindLastIndex : 'T[] * int * int * Predicate<'T> -> int

Public Shared Function FindLastIndex(Of T) (array As T(), startIndex As Integer, count As Integer, match As Predicate(Of T)) As Integer