C# | Check if an array contain the elements that match the specified conditions

Array.Exists(T[], Predicate<T>) Method is used to check whether the specified array contains elements that match the conditions defined by the specified predicate. Syntax:

public static bool Exists<T> (T[] array, Predicate<T> match);

Parameters:

array: It is a one-dimensional, zero-based Array to search. match: It is a Predicate that defines the conditions of the elements to search for. Where T is a type of the elements present in the array.

Return Value: The return type of this method is System.Boolean. It return true if array contains one or more elements that match the conditions defined by the specified predicate. Otherwise, return false. Exception: This method will give ArgumentNullException if the value of array is null, or if the value of match is null. Below given are some examples to understand the implementation in a better way: Example 1:

CSharp

// C# program to illustrate the
// Array.Exists(T[], Predicate<T>) Method
using System;

class GFG {

    // Main method
    static public void Main()
    {

        // Create and initialize array
        string[] language = {"Ruby", "C", "C++", "Java",
                            "Perl", "C#", "Python", "PHP"};

        // Display language array
        Console.WriteLine("Display the array:");
        foreach(string i in language)
        {
            Console.WriteLine(i);
        }

        // Display and check the given elements
        // present in the array or not

        // Using Exists() method
        Console.WriteLine("Is Ruby part of language: {0}",
                        Array.Exists(language, element => element == "Ruby"));

        Console.WriteLine("Is VB part of language: {0}",
                        Array.Exists(language, element => element == "VB"));
    }
}

Output:

Display the array:
Ruby
C
C++
Java
Perl
C#
Python
PHP
Is Ruby part of language: True
Is VB part of language: False

Example 2:

CSharp

// C# program to illustrate the
// Array.Exists(T[], Predicate<T>) Method
using System;

public class GFG {

// Main method
static public void Main()
{

    // Create and initialize array
    string[] ds = {"Array", "Queue", "LinkedList",
                            "Stack", "Graph" };

    // Display ds array
    Console.WriteLine("Given Array: ");

    foreach(string i in ds)
    {
        Console.WriteLine(i);
    }

    // Display and check the given elements with the
    // specified letter is present in the array or not
    // Using Exists() method
    Console.WriteLine("Is element start with L letter is present in array: {0}",
                    Array.Exists(ds, element => element.StartsWith("L")));

    Console.WriteLine("Is element start with O letter is present in array: {0}",
                    Array.Exists(ds, element => element.StartsWith("O")));
}
}

Output:

Given Array: 
Array
Queue
LinkedList
Stack
Graph
Is element start with L letter is present in array: True
Is element start with O letter is present in array: False

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

Space complexity: O(n) where n is the size of the array

Reference: https://docs.microsoft.com/en-us/dotnet/api/system.array.exists?view=netcore-2.1#definition