Chapter 24: Building Applications
Up until now, we’ve been writing console apps (great for learning), but now we’re going to explore the real-world power of C# and .NET:
- Console Applications – perfect for practice projects and tools
- ASP.NET Core – build modern Web APIs, MVC websites, and Razor Pages
- .NET MAUI – create cross-platform desktop & mobile apps (Windows, macOS, Android, iOS)
- Blazor – build interactive web apps using C# instead of JavaScript
- Unity – create professional games for PC, mobile, consoles, VR…
I’m going to explain each path very slowly, step by step, with real-life examples, project ideas, and code snippets — just like we’re sitting together in Hyderabad looking at the same screen. Let’s dive in! 🚀
1. Console Applications – Practice Projects (The Best Way to Master C#)
Why start here? Console apps are simple, fast to build, and perfect for practicing everything we’ve learned (OOP, collections, LINQ, async, file I/O, etc.).
Recommended Practice Projects (Start Small → Go Bigger)
- Personal Finance Tracker
- Features: Add income/expense, categorize, show monthly summary, save/load from JSON
- Practice: Classes, Lists, Dictionary, JSON serialization, LINQ
- To-Do List Manager (with file persistence)
- Features: Add task, mark done, delete, search, priority levels
- Practice: Records, async file I/O, pattern matching
- Weather CLI Tool
- Features: Enter city → show current weather (use free API)
- Practice: async/await, HttpClient, JSON deserialization
- File Organizer
- Features: Scan folder → organize files by type (images, documents…)
- Practice: File I/O, Directory class, Parallel.ForEach
- Text Adventure Game
- Features: Rooms, items, inventory, commands (go north, take key…)
- Practice: Classes, inheritance, dictionaries, switch pattern matching
Example – Simple To-Do Console App (with JSON save/load)
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// Program.cs (top-level statements) using System.Text.Json; record TodoItem(string Task, bool IsDone = false, DateTime Created = default); List<TodoItem> todos = LoadTodos() ?? new(); while (true) { Console.Clear(); Console.WriteLine("=== My To-Do List ===\n"); for (int i = 0; i < todos.Count; i++) { var t = todos[i]; Console.WriteLine($"{i + 1}. {(t.IsDone ? "[DONE]" : "[ ]")} {t.Task}"); } Console.WriteLine("\nCommands: add <task> | done <number> | save | exit"); string input = Console.ReadLine()?.Trim().ToLower() ?? ""; if (input.StartsWith("add ")) { string task = input[4..].Trim(); if (!string.IsNullOrWhiteSpace(task)) todos.Add(new TodoItem(task, false, DateTime.Now)); } else if (input.StartsWith("done ") && int.TryParse(input[5..], out int num) && num > 0 && num <= todos.Count) { var item = todos[num - 1]; todos[num - 1] = item with { IsDone = true }; } else if (input == "save") { File.WriteAllText("todos.json", JsonSerializer.Serialize(todos, new JsonSerializerOptions { WriteIndented = true })); Console.WriteLine("Saved!"); } else if (input == "exit") break; Console.WriteLine("\nPress any key to continue..."); Console.ReadKey(); } static List<TodoItem>? LoadTodos() { if (File.Exists("todos.json")) { string json = File.ReadAllText("todos.json"); return JsonSerializer.Deserialize<List<TodoItem>>(json); } return null; } |
Tip: Build 3–5 console projects like this → you’ll become very strong in C# fundamentals!
2. ASP.NET Core – Web APIs, MVC, Razor Pages
ASP.NET Core is the modern web framework for building:
- Web APIs (RESTful services for mobile apps, React/Angular, etc.)
- MVC (Model-View-Controller) – traditional websites
- Razor Pages – page-focused web apps (simpler than MVC)
Quick Setup (2026 style):
- Install .NET 10 SDK
- Run in terminal: dotnet new webapi -o MyApidotnet new mvc -o MyMvcAppdotnet new razor -o MyRazorApp
Example – Simple Web API (Weather Forecast)
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// WeatherForecast.cs public record WeatherForecast(DateOnly Date, int TemperatureC, string? Summary) { public int TemperatureF => 32 + (int)(TemperatureC / 0.5556); } // WeatherForecastController.cs [ApiController] [Route("[controller]")] public class WeatherForecastController : ControllerBase { private static readonly string[] Summaries = ["Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching"]; [HttpGet(Name = "GetWeatherForecast")] public IEnumerable<WeatherForecast> Get() { return Enumerable.Range(1, 5).Select(index => new WeatherForecast ( DateOnly.FromDateTime(DateTime.Now.AddDays(index)), Random.Shared.Next(-20, 55), Summaries[Random.Shared.Next(Summaries.Length)] )) .ToArray(); } } |
Run → dotnet run → open https://localhost:5001/weatherforecast → see JSON!
3. .NET MAUI – Cross-Platform Desktop & Mobile Apps
.NET MAUI (Multi-platform App UI) lets you write one codebase for:
- Windows
- macOS
- Android
- iOS
Setup:
- Install .NET 10 SDK
- Install Visual Studio 2026 → select .NET Multi-platform App UI development workload
Example – Simple MAUI Counter App
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// MainPage.xaml <ContentPage ...> <VerticalStackLayout> <Label Text="{Binding Count}" FontSize="Large" /> <Button Text="Click me" Command="{Binding IncreaseCount}" /> </VerticalStackLayout> </ContentPage> // MainPage.xaml.cs public partial class MainPage : ContentPage { int count = 0; public int Count => count; public Command IncreaseCount { get; } public MainPage() { InitializeComponent(); BindingContext = this; IncreaseCount = new Command(() => { count++; OnPropertyChanged(nameof(Count)); }); } } |
Deploy:
- Windows → Run directly
- Android → Connect phone or emulator
- iOS → Need Mac + Xcode
4. Blazor – C# in the Browser (Web Apps with C#)
Blazor lets you build interactive web UIs using C# instead of JavaScript.
Two flavors:
- Blazor Server – runs on server, uses SignalR (real-time)
- Blazor WebAssembly – runs in browser (offline capable)
Setup: dotnet new blazorserver -o MyBlazorApp or dotnet new blazorwasm -o MyBlazorWasm
Example – Counter Component
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@page "/counter" <h1>Counter</h1> <p>Current count: @currentCount</p> <button @onclick="IncrementCount">Click me</button> @code { private int currentCount = 0; private void IncrementCount() { currentCount++; } } |
Run: dotnet run → open https://localhost:5001/counter → click away!
5. Unity – Game Development with C#
Unity is the most popular game engine for indie and mobile games (Pokémon GO, Among Us, Cuphead…)
Setup:
- Download Unity Hub (free)
- Install Unity 2023 LTS or latest
- Create new 2D/3D project
- Use Visual Studio 2026 as editor (install Unity extension)
Example – Simple Player Controller (C# Script)
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using UnityEngine; public class PlayerController : MonoBehaviour { public float speed = 5f; void Update() { float moveX = Input.GetAxis("Horizontal"); float moveZ = Input.GetAxis("Vertical"); Vector3 movement = new Vector3(moveX, 0, moveZ).normalized * speed * Time.deltaTime; transform.Translate(movement); } } |
- Attach this script to your player object
- Play → use WASD / arrow keys to move!
Tip: Unity has tons of free assets and tutorials on Unity Learn.
Your Next Steps – Choose Your Path!
| Goal | Recommended Path | First Project Idea |
|---|---|---|
| Learn & practice C# deeply | Console Applications | To-Do List + Finance Tracker |
| Build web services / APIs | ASP.NET Core Web API | Todo API + Swagger |
| Build modern websites | ASP.NET Core MVC or Razor Pages | Personal Blog |
| Mobile + Desktop apps | .NET MAUI | Weather App or Notes App |
| Interactive web apps with C# | Blazor WebAssembly / Server | Todo App or Chat App |
| Make games | Unity | 2D Platformer or Endless Runner |
My advice (2026): Start with 3–5 solid console projects → then pick one of the above paths and build one real project (portfolio piece).
You’re now ready to build anything with C#! 🎉
Your Homework (Super Fun & Practical!)
- Choose one path from above
- Build a small but complete project:
- Console → To-Do List with JSON save/load
- Web API → Simple Todo API
- MAUI → Basic Counter + Weather display
- Blazor → Interactive Todo list
- Unity → Simple 2D character that moves
- Share what you built (screenshot, GitHub link) – I’d love to see it!
Congratulations! You’ve gone from zero to building real applications! 🎊 You’re officially a C# developer now!
Any path exciting you the most? Want help setting up any of them? Just tell me — I’m right here for you! 💙
