SampleApp

Complex Manual Mapping Example with Expression-Bodied Static Classes

This project demonstrates a comprehensive manual mapping system using static classes and methods with expression-bodied syntax in C# 13.0 and .NET 9.

Features

🎯 Expression-Bodied Mapping Methods

All mapping methods use modern C# expression-bodied member syntax (=>) for concise, readable code.

🏗️ Complex Entity Relationships

• Person with nested Address, PhoneNumbers collection, and Orders collection
• Order with OrderItems collection
• Multiple enum types with automatic conversion
• Bi-directional mapping (Entity ↔ DTO)

📦 Static Mapper Classes

PersonMapper

• Entity to DTO and DTO to Entity mapping
• Bulk operations with IEnumerable<T>
• Safe null-aware mapping
• Partial update functionality

AddressMapper

• Property name transformation (e.g., StreetAddress → Street)
• Address formatting utilities
• Validation helpers

PhoneMapper

• Enum to string conversion with switch expressions
• Phone number formatting and cleaning
• Type-safe phone type parsing

OrderMapper

• Order status enum handling
• Advanced filtering by date ranges and status
• Total value calculations
• Comprehensive validation

OrderItemMapper

• Line total calculations
• Discount calculations
• High-value item filtering
• Aggregation operations (sum, average, count)

🚀 Advanced Mapping Service

The MappingService provides:

• Generic mapping with Func<TSource, TDestination>
• Safe null-aware mapping with generic constraints
• Business rule-based filtering
• Summary mapping with selective data inclusion
• Statistical calculations (lifetime value, order counts)

Key Expression-Bodied Examples

Simple Property Mapping

public static PersonDto ToDto(Person entity) => new()
{
    Id = entity.PersonId,
    FirstName = entity.FirstName,
    LastName = entity.LastName,
    Email = entity.EmailAddress,
    // ... more properties
};

Collection Mapping

public static IEnumerable<PersonDto> ToDtoList(IEnumerable<Person> entities) =>
    entities.Select(ToDto);

Conditional Logic with Switch Expressions

public static string GetPhoneTypeString(PhoneType phoneType) => phoneType switch
{
    PhoneType.Mobile => "Mobile",
    PhoneType.Home => "Home",
    PhoneType.Work => "Work",
    PhoneType.Fax => "Fax",
    _ => "Unknown"
};

Complex Filtering and Transformations

public static IEnumerable<OrderDto> GetRecentOrders(IEnumerable<Order> orders, int days) =>
    orders.Where(o => o.CreatedDate >= DateTime.Now.AddDays(-days))
          .Select(ToDto);

Business Logic with Pattern Matching

public static bool IsActiveOrder(Order order) =>
    order.OrderStatus is not OrderStatus.Cancelled and not OrderStatus.Delivered;

Demonstration Features

The program demonstrates:

1. Basic Entity-DTO Mapping - Converting between domain entities and DTOs
2. Reverse Mapping - Converting DTOs back to entities
3. Phone Number Processing - Formatting, validation, and cleaning
4. Order Calculations - Total values, item counts, validation
5. Advanced Service Operations - Customer lifetime value, filtering
6. Bulk Operations - Mapping collections efficiently
7. Conditional Mapping - Adult persons, active orders
8. Summary Mapping - Selective data inclusion
9. Advanced Filtering - High-value items, product-specific items
10. Statistical Analysis - Averages, totals, counts

Technical Highlights

• C# 13.0 Features: Expression-bodied members, pattern matching, switch expressions
• .NET 9: Modern runtime with performance optimizations
• Static Classes: No instantiation needed, purely functional approach
• Generic Methods: Type-safe operations with compile-time checking
• LINQ Integration: Seamless collection transformations
• Null Safety: Proper null handling throughout
• Validation: Comprehensive business rule validation
• Formatting: User-friendly string representations

Sample Output

The demonstration produces detailed output showing:

• Person details with formatted addresses and phone numbers
• Order processing with calculations and validation
• Advanced filtering and statistical operations
• Performance metrics and validation results

This example showcases how to build robust, maintainable mapping systems using modern C# features while maintaining clean, readable code through expression-bodied syntax.