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mohamed Tayel
mohamed Tayel

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Introduction to Arrays

#csharp #arrays #collections #dotnet

Arrays are one of the most fundamental collection types in C#. They allow you to store multiple related values in a single, ordered collection. Whether you're managing days of the week, student grades, or product prices, arrays make data organization and manipulation more efficient.

In this article, we’ll cover:

  1. What arrays are.
  2. How to create and initialize them.
  3. Accessing, modifying, and enumerating array elements.
  4. A practical example: Building a Weekly Task Manager.

1. What Is an Array?

An array is:

  • A fixed-size collection: Once created, the size cannot change.
  • Ordered: Each item in an array has a specific position (index).
  • Zero-indexed: The first element is at index 0, the second at 1, and so on.

2. Creating and Initializing Arrays

Example: Storing Days of the Week 

string[] daysOfWeek = { "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday" };
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Here:

  • string[] specifies that the array stores strings.
  • { ... } contains the array’s initial values.

Accessing Items 

Console.WriteLine(daysOfWeek[0]); // Output: Monday
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Modifying Items 

daysOfWeek[2] = "Weds"; // Updates Wednesday to Weds
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3. Enumerating an Array

You can iterate through an array using a foreach loop:

Example 

foreach (string day in daysOfWeek) { Console.WriteLine(day); }
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This prints:

Monday Tuesday Wednesday Thursday Friday Saturday Sunday
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4. A Practical Example: Weekly Task Manager

Let’s build a Weekly Task Manager. The program will:

  1. Store tasks for each day of the week.
  2. Allow the user to view or update tasks.
  3. Display all tasks for the week.

Step 1: Create the Array

We’ll use a string array to store tasks for each day.

string[] tasks = new string[7]; // 7 days in a week
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Step 2: Initialize with Default Tasks

Let’s initialize the array with some default tasks:

tasks[0] = "Gym in the morning"; tasks[1] = "Team meeting"; tasks[2] = "Work on project report"; tasks[3] = "Grocery shopping"; tasks[4] = "Dinner with friends"; tasks[5] = "Family outing"; tasks[6] = "Relax and read a book";
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Step 3: Build the Menu

The program will display a menu for the user to:

  1. View tasks.
  2. Update tasks.
  3. Display all tasks.

Step 4: Implement the Program

Here’s the full code:

using System; class WeeklyTaskManager { static void Main() { // Initialize tasks string[] tasks = { "Gym in the morning", "Team meeting", "Work on project report", "Grocery shopping", "Dinner with friends", "Family outing", "Relax and read a book" }; while (true) { Console.WriteLine("\n=== Weekly Task Manager ==="); Console.WriteLine("1. View Task"); Console.WriteLine("2. Update Task"); Console.WriteLine("3. Display All Tasks"); Console.WriteLine("4. Exit"); Console.Write("Choose an option: "); int option = int.Parse(Console.ReadLine()); if (option == 4) break; switch (option) { case 1: ViewTask(tasks); break; case 2: UpdateTask(tasks); break; case 3: DisplayAllTasks(tasks); break; default: Console.WriteLine("Invalid option. Please try again."); break; } } } static void ViewTask(string[] tasks) { Console.Write("Enter the day number (1 for Monday, 7 for Sunday): "); int day = int.Parse(Console.ReadLine()) - 1; if (day >= 0 && day < tasks.Length) { Console.WriteLine($"Task for {GetDayName(day)}: {tasks[day]}"); } else { Console.WriteLine("Invalid day number."); } } static void UpdateTask(string[] tasks) { Console.Write("Enter the day number (1 for Monday, 7 for Sunday): "); int day = int.Parse(Console.ReadLine()) - 1; if (day >= 0 && day < tasks.Length) { Console.Write($"Enter the new task for {GetDayName(day)}: "); tasks[day] = Console.ReadLine(); Console.WriteLine("Task updated successfully."); } else { Console.WriteLine("Invalid day number."); } } static void DisplayAllTasks(string[] tasks) { Console.WriteLine("\n=== Weekly Tasks ==="); for (int i = 0; i < tasks.Length; i++) { Console.WriteLine($"{GetDayName(i)}: {tasks[i]}"); } } static string GetDayName(int index) { string[] daysOfWeek = { "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday" }; return daysOfWeek[index]; } }
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How It Works

  1. View Task:

    • User inputs a day number.
    • Program retrieves and displays the task for that day.

  2. Update Task:

    • User inputs a day number and a new task.
    • Program updates the corresponding array element.

  3. Display All Tasks:

    • The program iterates through the array and prints each task with its day.

Sample Output

Menu: 

=== Weekly Task Manager === 1. View Task 2. Update Task 3. Display All Tasks 4. Exit Choose an option:
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View Task:

Input: 1

Output: Task for Monday: Gym in the morning

Update Task:

Input: 2, then 7, then Plan next week

Output: Task updated successfully.

Display All Tasks: 

=== Weekly Tasks === Monday: Gym in the morning Tuesday: Team meeting Wednesday: Work on project report Thursday: Grocery shopping Friday: Dinner with friends Saturday: Family outing Sunday: Plan next week
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Key Takeaways

  • Arrays are a great choice for managing fixed-size, ordered data.
  • Use foreach for enumeration and square brackets ([]) for accessing and modifying elements.
  • Arrays can power real-world applications like task managers, schedules, and more.

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