C# | Array.LastIndexOf<T>(T[], T) Method (original) (raw)

Last Updated : 06 Oct, 2021

Array.LastIndexOf(T[], T) Method is used to search for the specified object. It returns the index of the last occurrence within the entire Array.

Syntax:

public static int LastIndexOf(T[] array, T value);

Parameters:

array: It is a one-dimensional, zero-indexed array to search.
value: Element whose index of last occurrence is to be returned.

Return Value: It returns the zero-based index of type System.Int32 of the last occurrence of value within the entire array, if found otherwise it returns -1.
Exceptions This method will give ArgumentNullException if the array is null.
Below examples illustrate the use of above-discussed method:
Example 1:

CSHARP `

// C# program to demonstrate // Array.LastIndexOf(T[], value) // Method using System;

class Geeks {

// Main Method
public static void Main()
{

    // Creates and initializes a new 
    // Array with three elements of the
    // same value.
    string[] str = {"C", "C++", "C#", "Java", 
                      "Python", "C#", "C++", 
                                 "C#", "CSS"};
    
    // printing the Elements of an Array
    Console.WriteLine("Elements of Array: ");
    Console.WriteLine();
    foreach(string str1 in str)
    {
        Console.WriteLine(str1);
    }
    
    
    Console.Write("\nLast Occurrence of C#: ");
    
    // printing the last index of C# 
    // using Array.LastIndexOf<T>(T[],
    // value<T>) Method
    Console.Write(Array.LastIndexOf(str, "C#"));
    
    
    Console.Write("\nLast Occurrence of C++: ");
    
    // printing the last index of C++ 
    // using Array.LastIndexOf<T>(T[],
    // value<T>) Method
    Console.Write(Array.LastIndexOf(str, "C++"));
}

}

`

Output:

Elements of Array:

C C++ C# Java Python C# C++ C# CSS

Last Occurrence of C#: 7 Last Occurrence of C++: 6

Example 2:

CSHARP `

// C# program to demonstrate // Array.LastIndexOf(T[], value) // Method using System;

class Geeks {

// Main Method
public static void Main()
{

    // creating and initializing an array
    int[] arr = {1, 2, 3, 4, 1, 2,
                   3, 4, 2, 4, 2};
    
    // printing the Elements of an Array
    Console.WriteLine("Elements of Array: ");
    Console.WriteLine();
    foreach(int i in arr)
    {
        Console.WriteLine(i);
    }
    
    // using Array.LastIndexOf<T>(T[],
    // value<T>) Method
    // it will give runtime error as 
    // array parameter is null
    Console.Write(Array.LastIndexOf(null, 1));
    

}

}

`

Runtime Error:

Unhandled Exception:
System.ArgumentNullException: Value cannot be null.
Parameter name: array