Array.Exists

This C# method tests a condition. It returns true if an element matches that condition. It returns false otherwise. We pass a predicate method instance to Array.Exists.

Method notes

When we call Array.Exists, we are calling a loop in a declarative way. This can reduce some issues with maintaining a lot of loops.

Exists example

To start, this example program creates a string array of 2 string literals. Then it invokes the Array.Exists method 3 times.

using System;

string[] array = { "cat", "bird" };

// Version 1: test for cat.
bool a = Array.Exists(array, element => element == "cat");
Console.WriteLine(a);

// Version 2: test for python.
bool b = Array.Exists(array, element => element == "python");
Console.WriteLine(b);

// Version 3: see if anything starts with "d."
bool c = Array.Exists(array, element => element.StartsWith("d"));
Console.WriteLine(c);
True
False
False

Method example

For Array.Exists, we can pass the name of a static method that receives the type of the array elements and returns a bool. We do not need to use lambda syntax.

using System;

class Program
{
    static bool IsLowNumber(int number)
    {
        return number <= 20;
    }

    static void Main()
    {
        Console.WriteLine(Array.Exists(new int[]{ 200, 300, 400 }, IsLowNumber));
    }
}
False

Discussion

How does the Array.Exists method work? It contains a for-loop that iterates through every array element calls the predicate function on each element.

Summary

Array.Exists() searches for an element that matches a certain predicate condition. It involves some overhead and performance drawbacks.