Task Manager — C# / .NET 8 Console Application

A clean, modular task management console application built with C# and .NET 8, demonstrating Object-Oriented Programming principles, the Repository design pattern, and unit testing with xUnit.

🎯 Project Highlights

• Object-Oriented Programming: Classes, interfaces, encapsulation, and polymorphism
• Repository Pattern: Clean separation of data access from business logic
• Dependency Injection: Manual constructor injection for testability
• JSON Persistence: File-based storage using System.Text.Json
• Unit Testing: 14 xUnit tests — 100% pass rate
• Clean Code: XML documentation, input validation, and exception handling

🏗️ Architecture

ConsoleUI          ← User interaction layer
    ↓
TaskService        ← Business logic layer
    ↓
ITaskRepository    ← Abstraction (interface)
    ↓
JsonTaskRepository ← Concrete implementation (JSON persistence)

🛠️ Tech Stack

• Language: C# 12
• Runtime: .NET 8
• Testing Framework: xUnit
• Serialization: System.Text.Json
• IDE: Visual Studio Code

📁 Project Structure

csharp-task-manager/
├── TaskManager/
│   ├── Models/
│   │   ├── TaskItem.cs
│   │   └── TaskPriority.cs
│   ├── Repositories/
│   │   ├── ITaskRepository.cs
│   │   └── JsonTaskRepository.cs
│   ├── Services/
│   │   └── TaskService.cs
│   ├── UI/
│   │   └── ConsoleUI.cs
│   └── Program.cs
└── TaskManager.Tests/
    ├── TaskServiceTests.cs
    └── JsonTaskRepositoryTests.cs

🚀 Getting Started

Prerequisites

• .NET 8 SDK

Build

dotnet build

Run

dotnet run --project TaskManager

Test

dotnet test

✨ Features

• Add tasks with title, description, due date, and priority (Low / Medium / High)
• List all tasks, pending tasks, or filter by priority
• Mark tasks as complete
• Delete tasks
• Persistent storage via JSON — data survives between sessions

🧪 Test Coverage

14 unit tests validating:

• Task creation with valid and invalid input
• Business rule enforcement (empty titles, past due dates)
• Task completion logic
• Priority-based filtering
• Repository CRUD operations
• Data persistence across sessions

💡 Design Decisions

• Repository Pattern enables swapping JSON storage for a database (e.g., SQL Server, PostgreSQL) without changing business logic.
• Interface-based design (ITaskRepository) makes unit testing and future extension straightforward.
• Service layer centralizes validation and business rules, keeping the UI thin.
• Value validation at construction ensures invalid tasks can never exist in the system.

🔮 Future Enhancements

• Migrate persistence to Entity Framework Core with a real database
• Build an ASP.NET Core Web API on top of the service layer
• Add integration tests alongside unit tests
• Introduce a DI container (Microsoft.Extensions.DependencyInjection)
• Add task categories, tags, and reminders

👤 Author

Rajkumar Vijayan
MSc Software Development — University of Limerick
LinkedIn | GitHub