Practice Projects - Apply Your Collections Knowledge in Real C# Scenarios

Vaibhav • September 10, 2025

The best way to master arrays and collections is to use them in real projects. This article gives you a set of practical, beginner-friendly mini-projects that reinforce everything you’ve learned in Chapter 7. Each project includes a clear goal, suggested steps, and sample code snippets to help you get started. You’ll use List<string>, Dictionary<string,int>, HashSet<string>, arrays, and more-just like in professional C# code.

Project 1: Unique Word Counter

Goal: Read a sentence from the user, split it into words, and count how many unique words appear.

• Use HashSet<string> for uniqueness.
• Use Split and Trim for basic text processing.

Console.WriteLine("Enter a sentence:");
string input = Console.ReadLine();
string[] words = input.Split(' ', StringSplitOptions.RemoveEmptyEntries);

var uniqueWords = new HashSet<string>();
foreach (string w in words)
    uniqueWords.Add(w.Trim().ToLower());

Console.WriteLine("Unique word count: " + uniqueWords.Count);

Project 2: Simple Contact Book

Goal: Store names and phone numbers, allow adding, searching, and listing all contacts.

• Use Dictionary<string,string> for fast lookups.
• Use TryGetValue for safe searching.

var contacts = new Dictionary<string, string>();

contacts["Alice"] = "555-1234";
contacts["Bob"] = "555-5678";

// Search
Console.WriteLine("Enter name to search:");
string name = Console.ReadLine();
if (contacts.TryGetValue(name, out string phone))
    Console.WriteLine(name + ": " + phone);
else
    Console.WriteLine("Contact not found.");

// List all
foreach (var kv in contacts)
    Console.WriteLine(kv.Key + ": " + kv.Value);

Project 3: Top Scores Tracker

Goal: Store a list of scores, sort them, and display the top 3.

• Use List<int> and Sort.
• Use Count and index-based access.

var scores = new List<int> { 90, 85, 100, 78, 88 };
scores.Sort();
scores.Reverse(); // highest first

for (int i = 0; i < Math.Min(3, scores.Count); i++)
    Console.WriteLine("Top " + (i+1) + ": " + scores[i]);

Project 4: Grocery List Manager

Goal: Add items to a grocery list, remove items, and print the final list.

• Use List<string> for dynamic management.
• Use Add, Remove, and foreach.

var groceries = new List<string>();

groceries.Add("Milk");
groceries.Add("Eggs");
groceries.Add("Bread");

groceries.Remove("Eggs");

foreach (string item in groceries)
    Console.WriteLine(item);

Project 5: Attendance Tracker

Goal: Track which students attended a class, and print only those who were present.

• Use HashSet<string> for attendance.
• Use Contains for membership checks.

var allStudents = new List<string> { "Alice", "Bob", "Charlie", "Dana" };
var present = new HashSet<string> { "Alice", "Dana" };

foreach (string student in allStudents)
    if (present.Contains(student))
        Console.WriteLine(student + " was present.");

Tips for Success

• Start with a small, clear goal and build up.
• Use initializers for sample data, and foreach for easy iteration.
• Test edge cases: empty lists, missing keys, duplicate entries.
• Refactor your code to use best practices from previous articles.

Summary

These practice projects help you apply everything you’ve learned about arrays and collections in C#. By building simple tools like word counters, contact books, and score trackers, you’ll gain confidence and fluency with the most important data structures in real-world programming. Keep experimenting, and revisit these projects as you learn new features in future chapters!