Delete Example

Overview

This document demonstrates the complete Delete flow using the DeleteProduct feature from the EBusiness application. The flow starts with a DELETE request to the controller and ends with event publishing and subscriber processing.

Complete Flow Architecture

DELETE Request → Controller → Service → PreBus Plugins → Command Handler → Domain Model → Database → Event Publishing → Subscribers

Detailed Flow Breakdown

1. DELETE Request
   ↓
2. Controller (API Entry Point)
   ↓
3. Service Layer (Business Orchestration)
   ↓
4. PreBus Processing (Validation Pipeline)
   ├── DeleteProductSequence (Plugin Registration)
   ├── DeleteProductDataPacket (Validation Context)
   └── IsValidProduct Plugin (Business Rules)
   ↓
5. Command Handler (Data Processing)
   ↓
6. Domain Model (Business Logic)
   ↓
7. Database (Data Persistence)
   ↓
8. Event Publishing (Asynchronous Processing)
   ↓
9. Subscribers (Side Effects)

Step-by-Step Implementation

1. API Controller - The Entry Point

File: ProductsController_DeleteProduct.cs

[HttpDelete()]
[Route("DeleteProduct/{id}")]
public async Task<IActionResult> DeleteProduct(string id)
{
    DeleteProductDto dto = new DeleteProductDto();
    dto.Id = id;
    return await RunService(200, dto, _processProductsService.DeleteProduct);
}

What Happens:

• HTTP Method: DELETE /api/Products/DeleteProduct/{id}

• Input: Product ID from URL parameter

• DTO Creation: Creates DeleteProductDto with the ID

• Action: Calls the service layer to process the product deletion

• Response: HTTP 200 OK with success status

2. Service Layer - Business Orchestration

File: ProcessProductsService_DeleteProduct.cs

public async Task<CommandResult> DeleteProduct(DeleteProductDto dto)
{
    var packet = await ProcessBusinessRuleSequence<DeleteProductDataPacket, DeleteProductSequence, DeleteProductDto, FlexAppContextBridge>(dto);

    if (packet.HasError)
    {
        return new CommandResult(Status.Failed, packet.Errors());
    }
    else
    {
        dto.SetGeneratedId(_pkGenerator.GenerateKey());
        DeleteProductCommand cmd = new DeleteProductCommand
        {
            Dto = dto,
        };

        await ProcessCommand(cmd);

        CommandResult cmdResult = new CommandResult(Status.Success);

        YourOutputResultModel outputResult = new YourOutputResultModel();
        cmdResult.result = outputResult;
        return cmdResult;
    }
}

What Happens:

• PreBus Processing: Executes business rule sequences (plugins)

• Validation: Processes business rule sequences

• ID Generation: Generates unique key for tracking

• Command Creation: Creates DeleteProductCommand with DTO

• Command Processing: Calls the command handler

• Result: Returns success status

2.1. PreBus Business Rule Sequence - Validation Pipeline

File: DeleteProductSequence.cs

public class DeleteProductSequence : FlexiBusinessRuleSequenceBase<DeleteProductDataPacket>
{
    public DeleteProductSequence()
    {
        this.Add<IsValidProduct>(); 
    }
}

What Happens:

• Plugin Registration: Registers validation plugins in execution order

• Sequential Processing: Executes plugins one by one

• Error Collection: Collects validation errors from all plugins

• Early Exit: Stops processing if any plugin fails

2.2. PreBus Data Packet - Validation Context

File: DeleteProductDataPacket.cs

public partial class DeleteProductDataPacket : FlexiFlowDataPacketWithDtoBridge<DeleteProductDto, FlexAppContextBridge>
{
    protected readonly ILogger<DeleteProductDataPacket> _logger;

    public DeleteProductDataPacket(ILogger<DeleteProductDataPacket> logger)
    {
        _logger = logger;
    }

    #region "Properties
    //Models and other properties goes here
    #endregion
}

What Happens:

• Context Container: Holds DTO and application context

• Error Collection: Collects validation errors from plugins

• Data Sharing: Allows plugins to share data during validation

• Logging: Provides logging capabilities for plugins

2.3. PreBus Validation Plugin - Business Rules

File: IsValidProduct.cs

public partial class IsValidProduct : FlexiBusinessRuleBase, IFlexiBusinessRule<DeleteProductDataPacket>
{
    public override string Id { get; set; } = "3a1cd5b1fa98b4c63378de9607706082";
    public override string FriendlyName { get; set; } = "IsValidProduct";

    protected readonly ILogger<IsValidProduct> _logger;
    protected readonly RepoFactory _repoFactory;

    public IsValidProduct(ILogger<IsValidProduct> logger, RepoFactory repoFactory)
    {
        _logger = logger;
        _repoFactory = repoFactory;
    }

    public virtual async Task Validate(DeleteProductDataPacket packet)
    {
        //Uncomment the below line if validating against a db data using your repo
        //_repoFactory.Init(packet.Dto);

        //If any validation fails, uncomment and use the below line of code to add error to the packet
        //packet.AddError("key", "ErrorMessage");

        await Task.CompletedTask; //If you have any await in the validation, remove this line
    }
}

What Happens:

• Business Rule Validation: Implements specific validation logic

• Database Access: Can access repository for data validation

• Error Reporting: Adds errors to the data packet if validation fails

• Async Support: Supports asynchronous validation operations

• Dependency Injection: Receives logger and repository factory

3. Command Handler - Data Processing

File: DeleteProductHandler.cs

public virtual async Task Execute(DeleteProductCommand cmd, IFlexServiceBusContext serviceBusContext)
{
    _flexAppContext = cmd.Dto.GetAppContext();
    _repoFactory.Init(cmd.Dto);

    _model = _flexHost.GetDomainModel<Product>().DeleteProduct(cmd);

    if (_model != null)
    {
        _repoFactory.GetRepo().InsertOrUpdate(_model);

        int records = await _repoFactory.GetRepo().SaveAsync();
        if (records > 0)
        {
            _logger.LogDebug("{} with {} deleted from Database: ", typeof(Product).Name, _model.Id);
        }
        else
        {
            _logger.LogWarning("No records deleted for {} with {}", typeof(Product).Name, _model.Id);
        }

        //EventCondition = CONDITION_ONSUCCESS;
    }
    else
    {
        //you may raise an event here to notify about the error
        //EventCondition = CONDITION_ONFAILED;
    }
    await this.Fire(EventCondition, serviceBusContext);
}

What Happens:

• Context Setup: Initializes application context and repository

• Domain Logic: Calls domain model to process business rules

• Null Check: Handles case where product doesn't exist

• Database Save: Updates the product in database (soft delete)

• Logging: Logs success/failure of database operation

• Event Publishing: Fires events for subscribers

4. Domain Model - Business Logic

File: Product/DeleteProduct.cs

public virtual Product DeleteProduct(DeleteProductCommand cmd)
{
    Guard.AgainstNull("Product model cannot be empty", cmd);

    this.Id = cmd.Dto.Id;
    this.SetDeleted();

    //Set your appropriate SetDeleted for the inner object here

    return this;
}

What Happens:

• Validation: Guards against null commands

• ID Assignment: Sets the product ID from DTO

• State Management: Marks entity as deleted (soft delete)

• Child Objects: Processes child object deletions

5. NServiceBus Handler - Message Processing

File: DeleteProductNsbHandler.cs

public class DeleteProductNsbHandler : NsbCommandHandler<DeleteProductCommand>
{
    readonly ILogger<DeleteProductNsbHandler> _logger;
    readonly IFlexHost _flexHost;
    readonly IDeleteProductHandler _handler;

    public DeleteProductNsbHandler(ILogger<DeleteProductNsbHandler> logger, IFlexHost flexHost, IDeleteProductHandler handler)
    {
        _logger = logger;
        _flexHost = flexHost;
        _handler = handler;
    }

    public override async Task Handle(DeleteProductCommand message, IMessageHandlerContext context)
    {
        _logger.LogTrace($"Executing {nameof(DeleteProductNsbHandler)}");

        await _handler.Execute(message, new NsbHandlerContextBridge(context));
    }
}

What Happens:

• Message Reception: Receives DeleteProductCommand from message bus

• Logging: Logs handler execution

• Delegation: Calls the actual command handler

• Context Bridge: Converts NServiceBus context to FlexBase context

6. Event Publishing - Asynchronous Processing

Event: ProductDeletedEvent (if implemented)

public class ProductDeletedEvent : FlexEventBridge<FlexAppContextBridge>
{
    // Event data is automatically populated by FlexBase
}

What Happens:

• Event Creation: FlexBase creates event with product data

• Message Bus: Event is published to message bus

• Subscriber Notification: All subscribers are notified

7. Event Subscribers - Side Effects

File: NotifyInventoryOnProductDeleted.cs (if implemented)

public partial class NotifyInventoryOnProductDeleted : INotifyInventoryOnProductDeleted
{
    protected readonly ILogger<NotifyInventoryOnProductDeleted> _logger;
    protected string EventCondition = "";

    public NotifyInventoryOnProductDeleted(ILogger<NotifyInventoryOnProductDeleted> logger)
    {
        _logger = logger;
    }

    public virtual async Task Execute(ProductDeletedEvent @event, IFlexServiceBusContext serviceBusContext)
    {
        _flexAppContext = @event.AppContext;

        //TODO: Write your business logic here:
        // - Update inventory levels
        // - Notify suppliers
        // - Update analytics
        // - Archive related data

        await this.Fire<NotifyInventoryOnProductDeleted>(EventCondition, serviceBusContext);
    }
}

What Happens:

• Event Reception: Receives ProductDeletedEvent from message bus

• Side Effects: Executes business logic (inventory updates, notifications, etc.)

• Additional Events: Can fire more events if needed

Data Transfer Objects (DTOs)

Input DTO: DeleteProductDto

public partial class DeleteProductDto : DtoBridge 
{
    public string Id { get; set; }
}

Command: DeleteProductCommand

public class DeleteProductCommand : FlexCommandBridge<DeleteProductDto, FlexAppContextBridge>
{
    // Command data is automatically populated by FlexBase
}

Key Differences from Insert/Update Flow

Delete-Specific Characteristics

1. URL Parameter: ID comes from URL path instead of request body

2. DTO Creation: Controller creates DTO with ID from URL

3. Soft Delete: Uses SetDeleted() instead of SetAdded() or SetModified()

4. State Management: Marks entity as deleted (soft delete pattern)

5. HTTP Method: Uses DELETE instead of POST or PUT

6. Minimal Data: Only requires ID for deletion

PreBus Validation Focus

• IsValidProduct: Validates product exists and can be deleted

• Business Rules: Ensures product can be removed (not in use, not referenced)

• Data Integrity: Validates deletion doesn't violate business constraints

Soft Delete Pattern

• Database: Entity is marked as deleted, not physically removed

• Queries: Soft-deleted entities are filtered out of normal queries

• Recovery: Deleted entities can be restored if needed

• Audit Trail: Maintains complete history of deletions

Flow Summary

Synchronous Flow (Immediate Response)

1. DELETE Request → Controller receives request with ID

2. Service Processing → Business orchestration and PreBus validation

3. PreBus Plugins → Sequential validation of business rules

4. Command Handler → Data processing and soft delete

5. Domain Logic → Business rules and state management

6. Response → HTTP 200 OK with success status

Asynchronous Flow (Event Processing)

1. Event Publishing → ProductDeletedEvent published to message bus

2. Subscriber Processing → NotifyInventoryOnProductDeleted executes

3. Side Effects → Inventory updates, supplier notifications, analytics

Key Benefits

• Data Safety: Soft delete preserves data for recovery

• Business Rules: Validates deletion is allowed

• Audit Trail: Tracks who deleted what and when

• Event-Driven: Notifies other systems of deletions

• Testable: Each component can be tested independently

• Maintainable: Clear separation of concerns

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This DeleteProduct example demonstrates how FlexBase enables clean, maintainable, and scalable delete operations with proper validation, soft delete patterns, and event-driven architecture! 🚀