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C# Academy · Lesson

Arrays, slicing, List<T>, Dictionary<TKey,TValue>

Create and use arrays, copy a slice, and work with List and Dictionary for dynamic items and key-based lookups.

Lesson overview

Goal: Pick the right container.

  • Array: fixed size, fast indexing
  • List<T>: grows/shrinks
  • Dictionary<TKey,TValue>: fast key lookup
  • Simple array slice via copy

Array basics

Arrays are fixed-size and indexable. Use Length and zero-based indices.

using System;

public class Program
{
  public static void Main(string[] args)
  {
    int[] nums = new int[] { 10, 20, 30 };
    Console.WriteLine("Length = " + nums.Length);
    Console.WriteLine("First = " + nums[0]);
    Console.WriteLine("Last = " + nums[nums.Length - 1]);

    // Update by index
    nums[1] = 25;
    Console.WriteLine("Updated middle = " + nums[1]);
  }
}

All lessons in this course

  1. Arrays, slicing, List , Dictionary
  2. foreach patterns; collection initializers
  3. LINQ preview: Where, Select, OrderBy, Take/Skip; deferred execution
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