> For the complete documentation index, see [llms.txt](https://docs.flexbase.in/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.flexbase.in/solution-structure/getting-started/features/use-case.md).

# Use Case

## Overview

The **EBusiness** application is a comprehensive e-commerce solution built using FlexBase Framework, demonstrating real-world implementation of enterprise features. This application showcases how to build scalable, maintainable business applications following Domain-Driven Design (DDD) principles and Clean Architecture patterns.

## Application Architecture

### **Domain Focus**

* **E-Commerce Business**: Complete online shopping platform
* **Multi-Tenant Support**: Serve multiple customers with isolated data
* **Event-Driven Architecture**: Asynchronous processing for scalability
* **CQRS Pattern**: Separate read and write operations for performance

### **Key Business Capabilities**

* **Order Management**: Complete order lifecycle from creation to fulfillment
* **Product Catalog**: Product management with inventory tracking
* **Customer Management**: User registration, authentication, and profile management
* **Payment Processing**: Secure payment handling and transaction management
* **Inventory Management**: Stock tracking and low inventory alerts
* **Reporting & Analytics**: Business intelligence and reporting capabilities

## Feature Implementation List

### 1. **Order Management Features**

#### **Command Features (Data Modification)**

* **AddOrder** - Create new customer orders
  * **Flow**: `POST /api/Orders/AddOrder`
  * **Handler**: `AddOrderHandler.cs`
  * **Event**: `OrderCreatedEvent` (Eventual)
  * **Use Case**: Customer places order, inventory reserved, confirmation sent
* **UpdateOrder** - Modify existing orders
  * **Flow**: `PUT /api/Orders/UpdateOrder`
  * **Handler**: `UpdateOrderHandler.cs`
  * **Event**: `OrderUpdatedEvent` (Eventual)
  * **Use Case**: Update order details, change shipping address
* **CancelOrder** - Cancel pending orders
  * **Flow**: `PUT /api/Orders/CancelOrder`
  * **Handler**: `CancelOrderHandler.cs`
  * **Event**: `OrderCancelledEvent` (Eventual)
  * **Use Case**: Customer cancels order, inventory released
* **ProcessOrder** - Process order for fulfillment
  * **Flow**: `PUT /api/Orders/ProcessOrder`
  * **Handler**: `ProcessOrderHandler.cs`
  * **Event**: `OrderProcessedEvent` (Eventual)
  * **Use Case**: Warehouse processes order, shipping label generated

#### **Query Features (Data Retrieval)**

* **GetOrderById** - Retrieve specific order details
  * **Flow**: `GET /api/Orders/GetOrderById/{id}`
  * **Query**: `GetOrderByIdQuery.cs`
  * **Use Case**: Customer views order details, admin order lookup
* **GetOrders** - List all orders with filtering
  * **Flow**: `GET /api/Orders/GetOrders`
  * **Query**: `GetOrdersQuery.cs`
  * **Use Case**: Admin order management, customer order history
* **GetOrdersPaged** - Paginated order list
  * **Flow**: `GET /api/Orders/GetOrdersPaged`
  * **Query**: `GetOrdersPagedQuery.cs`
  * **Use Case**: Large order lists with pagination support
* **GetCustomerOrders** - Orders for specific customer
  * **Flow**: `GET /api/Orders/GetCustomerOrders/{customerId}`
  * **Query**: `GetCustomerOrdersQuery.cs`
  * **Use Case**: Customer order history, account management

### 2. **Product Management Features**

#### **Command Features (Data Modification)**

* **AddProduct** - Create new products
  * **Flow**: `POST /api/Products/AddProduct`
  * **Handler**: `AddProductHandler.cs`
  * **Event**: `ProductCreatedEvent` (Eventual)
  * **Use Case**: Admin adds new product to catalog
* **UpdateProduct** - Modify product information
  * **Flow**: `PUT /api/Products/UpdateProduct`
  * **Handler**: `UpdateProductHandler.cs`
  * **Event**: `ProductUpdatedEvent` (Eventual)
  * **Use Case**: Update product details, pricing, descriptions
* **UpdateInventory** - Adjust product stock levels
  * **Flow**: `PUT /api/Products/UpdateInventory`
  * **Handler**: `UpdateInventoryHandler.cs`
  * **Event**: `InventoryUpdatedEvent` (Eventual)
  * **Use Case**: Stock adjustments, receiving shipments
* **DeactivateProduct** - Soft delete products
  * **Flow**: `PUT /api/Products/DeactivateProduct`
  * **Handler**: `DeactivateProductHandler.cs`
  * **Event**: `ProductDeactivatedEvent` (Eventual)
  * **Use Case**: Discontinue products, seasonal items

#### **Query Features (Data Retrieval)**

* **GetProductById** - Retrieve specific product
  * **Flow**: `GET /api/Products/GetProductById/{id}`
  * **Query**: `GetProductByIdQuery.cs`
  * **Use Case**: Product detail pages, admin product management
* **GetProducts** - List products with filtering
  * **Flow**: `GET /api/Products/GetProducts`
  * **Query**: `GetProductsQuery.cs`
  * **Use Case**: Product catalog browsing, search results
* **GetProductsPaged** - Paginated product list
  * **Flow**: `GET /api/Products/GetProductsPaged`
  * **Query**: `GetProductsPagedQuery.cs`
  * **Use Case**: Large product catalogs with pagination
* **SearchProducts** - Product search functionality
  * **Flow**: `GET /api/Products/SearchProducts`
  * **Query**: `SearchProductsQuery.cs`
  * **Use Case**: Customer product search, admin product lookup

### 3. **Customer Management Features**

#### **Command Features (Data Modification)**

* **RegisterCustomer** - Create new customer accounts
  * **Flow**: `POST /api/Customers/RegisterCustomer`
  * **Handler**: `RegisterCustomerHandler.cs`
  * **Event**: `CustomerRegisteredEvent` (Eventual)
  * **Use Case**: New customer registration, welcome email sent
* **UpdateCustomer** - Modify customer information
  * **Flow**: `PUT /api/Customers/UpdateCustomer`
  * **Handler**: `UpdateCustomerHandler.cs`
  * **Event**: `CustomerUpdatedEvent` (Eventual)
  * **Use Case**: Profile updates, address changes
* **DeactivateCustomer** - Soft delete customer accounts
  * **Flow**: `PUT /api/Customers/DeactivateCustomer`
  * **Handler**: `DeactivateCustomerHandler.cs`
  * **Event**: `CustomerDeactivatedEvent` (Eventual)
  * **Use Case**: Account closure, compliance requirements

#### **Query Features (Data Retrieval)**

* **GetCustomerById** - Retrieve specific customer
  * **Flow**: `GET /api/Customers/GetCustomerById/{id}`
  * **Query**: `GetCustomerByIdQuery.cs`
  * **Use Case**: Customer profile pages, admin customer lookup
* **GetCustomers** - List customers with filtering
  * **Flow**: `GET /api/Customers/GetCustomers`
  * **Query**: `GetCustomersQuery.cs`
  * **Use Case**: Admin customer management, customer support
* **GetCustomersPaged** - Paginated customer list
  * **Flow**: `GET /api/Customers/GetCustomersPaged`
  * **Query**: `GetCustomersPagedQuery.cs`
  * **Use Case**: Large customer databases with pagination

### 4. **Payment Processing Features**

#### **Command Features (Data Modification)**

* **ProcessPayment** - Handle payment transactions
  * **Flow**: `POST /api/Payments/ProcessPayment`
  * **Handler**: `ProcessPaymentHandler.cs`
  * **Event**: `PaymentProcessedEvent` (Eventual)
  * **Use Case**: Credit card processing, order payment
* **RefundPayment** - Process payment refunds
  * **Flow**: `POST /api/Payments/RefundPayment`
  * **Handler**: `RefundPaymentHandler.cs`
  * **Event**: `PaymentRefundedEvent` (Eventual)
  * **Use Case**: Order cancellations, returns processing

#### **Query Features (Data Retrieval)**

* **GetPaymentById** - Retrieve payment details
  * **Flow**: `GET /api/Payments/GetPaymentById/{id}`
  * **Query**: `GetPaymentByIdQuery.cs`
  * **Use Case**: Payment verification, transaction lookup
* **GetPayments** - List payments with filtering
  * **Flow**: `GET /api/Payments/GetPayments`
  * **Query**: `GetPaymentsQuery.cs`
  * **Use Case**: Financial reporting, transaction history

### 5. **Inventory Management Features**

#### **Command Features (Data Modification)**

* **AdjustInventory** - Modify stock levels
  * **Flow**: `PUT /api/Inventory/AdjustInventory`
  * **Handler**: `AdjustInventoryHandler.cs`
  * **Event**: `InventoryAdjustedEvent` (Eventual)
  * **Use Case**: Stock adjustments, receiving shipments
* **ReserveInventory** - Reserve stock for orders
  * **Flow**: `PUT /api/Inventory/ReserveInventory`
  * **Handler**: `ReserveInventoryHandler.cs`
  * **Event**: `InventoryReservedEvent` (Eventual)
  * **Use Case**: Order processing, stock allocation

#### **Query Features (Data Retrieval)**

* **GetInventoryLevels** - Check stock levels
  * **Flow**: `GET /api/Inventory/GetInventoryLevels`
  * **Query**: `GetInventoryLevelsQuery.cs`
  * **Use Case**: Stock monitoring, low inventory alerts
* **GetLowStockItems** - Identify items needing restocking
  * **Flow**: `GET /api/Inventory/GetLowStockItems`
  * **Query**: `GetLowStockItemsQuery.cs`
  * **Use Case**: Purchasing decisions, inventory alerts

## Event-Driven Processing

### **Event Subscribers**

* **OrderCreatedSubscriber** - Handles order creation events
  * **Actions**: Send confirmation email, reserve inventory, update analytics
* **PaymentProcessedSubscriber** - Handles payment events
  * **Actions**: Update order status, send receipt, trigger fulfillment
* **InventoryLowSubscriber** - Handles low inventory events
  * **Actions**: Send alerts to purchasing, update product status
* **CustomerRegisteredSubscriber** - Handles customer registration
  * **Actions**: Send welcome email, create customer profile, update marketing

## Technology Implementation

### **Framework Components**

* **FlexBase Framework**: Core enterprise framework
* **Entity Framework Core**: Data access and ORM
* **NServiceBus**: Message bus and event handling
* **ASP.NET Core**: Web API and controllers
* **AutoMapper**: Object mapping and DTOs

### **Database Support**

* **SQL Server**: Primary database
* **MySQL**: Alternative database option
* **PostgreSQL**: Cross-platform database support
* **Multi-Tenant**: Isolated data per customer

### **Message Bus Options**

* **RabbitMQ**: High-performance messaging
* **Azure Service Bus**: Cloud-native messaging
* **SQL Server Transport**: Database-based messaging
* **Learning Transport**: Development and testing

## Business Value

### **Scalability**

* **Horizontal Scaling**: Add more instances as needed
* **Database Scaling**: Separate read/write databases
* **Message Bus Scaling**: Handle high message volumes

### **Maintainability**

* **Clear Separation**: Commands vs Queries
* **Domain Focus**: Business logic in domain layer
* **Testability**: Each component can be tested independently

### **Performance**

* **CQRS**: Optimized read and write operations
* **Event Sourcing**: Track all changes for audit
* **Caching**: Fast data retrieval for frequently accessed data

***

**This EBusiness application demonstrates how FlexBase Framework enables rapid development of enterprise-grade applications with clean architecture, scalable design, and maintainable code!** 🚀