Is there a C# equivalent of PHP's array_key_exists?

Sorry, but dynamic arrays like PHP are not supported in C#. What you can do it create a Dictionary<TKey, TValue>(int, int) and add using .Add(int, int)

using System.Collections.Generic;...Dictionary<int, int> dict = new Dictionary<int, int>();dict.Add(5, 4);dict.Add(7, 8);if (dict.ContainsKey(5)){    // [5, int] exists    int outval = dict[5];    // outval now contains 4}

An array in C# has a fixed size, so you would declare an array of 8 integers

int[] array = new int[8];

You then only need to check the length

if(array.Length > 2){    Debug.WriteLine( array[2] );}

That's fine for value types, but if you have an array of reference types, e.g.

Person[] array = new Person[8];

then you'll need to check for null as in

if(array.Length > 2 && array[2] != null){    Debug.WriteLine( array[2].ToString() );}

In C# when you declare a new array, you have to provide it a size for memory allocation. If you're creating an array of int, values are pre-populated at instantiation, so the keys will always exist.

int[] array = new int[10];Console.WriteLine(array[0]); //outputs 0.

If you want a dynamically sized array, you can use a List.

List<int> array = new List<int>array.push(0);if (array.Length > 5)   Console.WriteLine(array[5]);