Arrays

An array is a container that holds multiple values of the same type. Think of it like a row of lockers — each locker has a number (index), and each holds one item.

Declaring and Initializing Arrays

Use square brackets to say "this is an array." You can set the size upfront or let C# count the elements for you.

using System;

class Program {
  static void Main() {
    int[] numbers = new int[5];
    numbers[0] = 10;
    numbers[1] = 20;
    numbers[2] = 30;
    numbers[3] = 40;
    numbers[4] = 50;
    Console.WriteLine(numbers[2]);
  }
}
    

Array Initializer Syntax

Shorter way: provide all values in curly braces and skip the size. C# figures out the length.

using System;

class Program {
  static void Main() {
    int[] numbers = { 10, 20, 30, 40, 50 };
    Console.WriteLine(numbers[0]);
    Console.WriteLine(numbers[numbers.Length - 1]);
  }
}
    

Array Length

The Length property tells you how many elements are in the array. Remember: indices go from 0 to Length - 1.

using System;

class Program {
  static void Main() {
    string[] names = { "Alice", "Bob", "Charlie" };
    Console.WriteLine("Array size: " + names.Length);
  }
}
    

Looping Through Arrays

Use a for loop with the index, or a foreach loop to go through each element automatically.

using System;

class Program {
  static void Main() {
    int[] nums = { 2, 4, 6, 8, 10 };
    
    for (int i = 0; i < nums.Length; i++) {
      Console.WriteLine("Index " + i + ": " + nums[i]);
    }
    
    int sum = 0;
    foreach (int n in nums) {
      sum += n;
    }
    Console.WriteLine("Sum: " + sum);
  }
}
    

Arrays Are Fixed Size

Once you set the size, it can't change. If you need a growable collection, look at List<T> instead.

using System;

class Program {
  static void Main() {
    int[] nums = { 1, 2, 3 };
    Console.WriteLine("Fixed at " + nums.Length + " elements");
  }
}