Methods
We are going to see the top 10 most important methods provided by the Array class.
IndexOf
This returns the index of an item inside the array – in our case 2 for lemon 🍋
var fruits = new[] { "melon", "coconut", "lemon" };
var result = Array.IndexOf(fruits, "lemon");
Console.WriteLine(result); // 2
Exists
It checks to see whether or not an item exists in an array (this accepts a Predicate):
var fruits = new[] { "melon", "coconut", "lemon" };
var result = Array.Exists(fruits, fruit => fruit.Contains("l"));
Console.WriteLine(result);
Find
This simply finds an item in an array:
var fruits = new[] { "melon", "coconut", "lemon" };
var result = Array.Find(fruits, fruit => fruit.Contains("l"));
Console.WriteLine(result);
FindLast
As the Find method, but this starts from the end of the array:
var fruits = new[] { "melon", "coconut", "lemon" };
var result = Array.FindLast(fruits, fruit => fruit.Contains("l"));
Console.WriteLine(result);
FindIndex
We can also find the index of an item by using a Predicate:
var fruits = new[] { "melon", "coconut", "lemon" };
var result = Array.FindIndex(fruits, fruit => fruit.Contains("l"));
Console.WriteLine(result);
FindAll
We can find all the items that pass a certain condition:
var fruits = new[] { "melon", "coconut", "lemon" };
var result = Array.FindAll(fruits, fruit => fruit.Contains("l"));
foreach (var fruit in result)
{
Console.WriteLine(fruit);
}
Reverse
We can reverse the items in an array:
var fruits = new[] { "melon", "coconut", "lemon" };
Array.Reverse(fruits);
foreach (var fruit in fruits)
{
Console.WriteLine(fruit);
}
Copy
We can copy the items of an array to another one.
The third argument is to specify how many items you want to copy:
var fruits = new[] { "melon", "coconut", "lemon" };
var fruits2 = new string[fruits.Length];
Array.Copy(fruits, fruits2, 2);
TIP
To copy all the items, just pass fruits.Length as the third argument.
Sort
And one of the most important things is to sort an array:
var fruits = new[] { "melon", "coconut", "lemon" };
Array.Sort(fruits);
foreach (var fruit in fruits)
{
Console.WriteLine(fruit);
}
Maybe we want to reverse the order (descending).
In this case, we need to create a new class which implements the IComparer interface:
public class ReverseComparer : IComparer<String>
{
public int Compare(string x, string y)
{
return y.CompareTo(x);
}
}
And then, just pass an instance of this class as an argument:
var fruits = new[] { "melon", "coconut", "lemon" };
Array.Sort(fruits, new ReverseComparer());
foreach (var fruit in fruits)
{
Console.WriteLine(fruit);
}
BinarySearch
You can search for an element in a sorted array (make sure to sort the array in ascending order before applying this algorithm):
var fruits = new[] { "melon", "coconut", "lemon" };
Array.Sort(fruits);
var index = Array.BinarySearch(fruits, "coconut");
if (index == -1)
Console.WriteLine("nothing");
else
Console.WriteLine(index);
Duplicates
If an array contains duplicate elements (which have the same value), then BinarySearch will return the index of one of those elements.
Next
If you are interested how to implement these methods procedurally (reinventing the wheel), that's coming up next 😉