Finding the last index of an array

How do you retrieve the last element of an array in C#?

Solution 1:

LINQ provides Last():

csharp> int[] nums = {1,2,3,4,5};
csharp> nums.Last();              
5

This is handy when you don't want to make a variable unnecessarily.

string lastName = "Abraham Lincoln".Split().Last();

Solution 2:

The array has a Length property that will give you the length of the array. Since the array indices are zero-based, the last item will be at Length - 1.

string[] items = GetAllItems();
string lastItem = items[items.Length - 1];
int arrayLength = array.Length;

When declaring an array in C#, the number you give is the length of the array:

string[] items = new string[5]; // five items, index ranging from 0 to 4.

Solution 3:

With C# 8:

int[] array = { 1, 3, 5 };
var lastItem = array[^1]; // 5

Solution 4:

Use Array.GetUpperBound(0). Array.Length contains the number of items in the array, so reading Length -1 only works on the assumption that the array is zero based.

Solution 5:

New in C# 8.0 you can use the so-called "hat" (^) operator! This is useful for when you want to do something in one line!

var mystr = "Hello World!";
var lastword = mystr.Split(" ")[^1];
Console.WriteLine(lastword);
// World!

instead of the old way:

var mystr = "Hello World";
var split = mystr.Split(" ");
var lastword = split[split.Length - 1];
Console.WriteLine(lastword);
// World!

It doesn't save much space, but it looks much clearer (maybe I only think this because I came from python?). This is also much better than calling a method like .Last() or .Reverse() Read more at MSDN

Edit: You can add this functionality to your class like so:

public class MyClass
{
  public object this[Index indx]
  {
    get
    {
      // Do indexing here, this is just an example of the .IsFromEnd property
      if (indx.IsFromEnd)
      {
        Console.WriteLine("Negative Index!")
      }
      else
      {
        Console.WriteLine("Positive Index!")
      }
    }
  }
}

The Index.IsFromEnd will tell you if someone is using the 'hat' (^) operator