N-Tier Architecture Contacts Management Lab 🏗️

A professional-grade demonstration of the n-Tier Architecture pattern using C# and .NET. This project serves as a technical laboratory for building decoupled, maintainable, and secure database-driven applications.

🏛️ Architectural Design

The solution is strictly divided into multiple distinct layers (n-Tier) to ensure a professional separation of concerns. The primary strength of this project is the multi-presentation capability, where different UI technologies share the exact same logic and data layers.

1. Presentation Layer (Multiple Interfaces)

This project showcases versatility by providing two distinct user interfaces:

• Windows Forms Version (Contacts.WinForms): A rich desktop interface featuring a DataGridView for data management, image handling via PictureBox, and interactive forms for CRUD operations.
• Console Application Version (Contacts.ConsoleApp): A high-performance, command-line interface designed for efficiency. It features formatted text-based tables, colored menus, and robust input validation.

2. Business Logic Layer (Contacts.Business)

• Acts as the central brain and bridge between the UI and Data layers.
• Contains core logic, data validation rules, and business objects (clsContact, clsCountry).
• Shared Logic: This layer serves both the WinForms and Console applications simultaneously, ensuring consistent behavior and centralized maintenance.

3. Data Access Layer (Contacts.Data)

• Dedicated to database communication and CRUD operations.
• Implemented using ADO.NET with secure SQL Parameterized Queries to prevent SQL Injection.
• Handles direct interactions with SQL Server efficiently.

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🛠️ Tech Stack & Patterns

• Language: C# 12.0 / .NET Framework 4.8
• Database: Microsoft SQL Server
• Architectural Pattern: N-Tier / 3-Tier Design
• Data Access: ADO.NET (Connected & Disconnected models)
• UI Technologies: WinForms (GDI+) & System.Console

🚀 Key Technical Features (The Power of This Repo)

• UI Agnostic Design: The ability to swap or run multiple UIs (Console & WinForms) without changing a single line of code in the Business or Data layers.
• Data Integrity: Strict validation within the Business Layer before any persistence occurs.
• Secure Persistence: Fully parameterized queries for all database interactions.
• Clean Code & Scalability: Designed to be easily extended (e.g., adding a Web API or WPF layer would require zero changes to the backend).

⚙️ Getting Started

1. Database Setup: Restore the provided ContactsDB.bak file to your local SQL Server instance.
2. Configuration: Update the connection string in Contacts.Data/clsDataAccessSettings.cs to match your local environment.
3. Run: Choose either Contacts.WinForms or Contacts.ConsoleApp as the startup project and run.

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⚖️ License

This project is open-source and available under the MIT License.