> 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/crud/update-example.md).

# Update Example

## Overview

This document demonstrates the complete **Update flow** using the **UpdateOrder** feature from the EBusiness application. The flow starts with a PUT request to the controller and ends with event publishing and subscriber processing.

## Complete Flow Architecture

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

### **Detailed Flow Breakdown**

```
1. PUT Request
   ↓
2. Controller (API Entry Point)
   ↓
3. Service Layer (Business Orchestration)
   ↓
4. PreBus Processing (Validation Pipeline)
   ├── UpdateOrderSequence (Plugin Registration)
   ├── UpdateOrderDataPacket (Validation Context)
   └── IsValidOrder 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**: `OrdersController_UpdateOrder.cs`

```csharp
[HttpPut]
[Route("UpdateOrder")]
[ProducesResponseType(typeof(BadRequestResult), 400)]
[ProducesResponseType(typeof(string), 200)]
public async Task<IActionResult> UpdateOrder([FromBody]UpdateOrderDto dto)
{
    return await RunService(200, dto, _processOrdersService.UpdateOrder);
}
```

**What Happens:**

* **HTTP Method**: `PUT /api/Orders/UpdateOrder`
* **Input**: `UpdateOrderDto` from request body
* **Action**: Calls the service layer to process the order update
* **Response**: HTTP 200 OK with success status

### 2. **Service Layer** - Business Orchestration

**File**: `ProcessOrdersService_UpdateOrder.cs`

```csharp
public async Task<CommandResult> UpdateOrder(UpdateOrderDto dto)
{
    var packet = await ProcessBusinessRuleSequence<UpdateOrderDataPacket, UpdateOrderSequence, UpdateOrderDto, FlexAppContextBridge>(dto);

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

        await ProcessCommand(cmd);

        CommandResult cmdResult = new CommandResult(Status.Success);

        UpdateOrderResultModel outputResult = new UpdateOrderResultModel();
        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 `UpdateOrderCommand` with DTO
* **Command Processing**: Calls the command handler
* **Result**: Returns success status

### 2.1. **PreBus Business Rule Sequence** - Validation Pipeline

**File**: `UpdateOrderSequence.cs`

```csharp
public class UpdateOrderSequence : FlexiBusinessRuleSequenceBase<UpdateOrderDataPacket>
{
    public UpdateOrderSequence()
    {
        this.Add<IsValidOrder>(); 
    }
}
```

**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**: `UpdateOrderDataPacket.cs`

```csharp
public partial class UpdateOrderDataPacket : FlexiFlowDataPacketWithDtoBridge<UpdateOrderDto, FlexAppContextBridge>
{
    protected readonly ILogger<UpdateOrderDataPacket> _logger;

    public UpdateOrderDataPacket(ILogger<UpdateOrderDataPacket> 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**: `IsValidOrder.cs`

```csharp
public partial class IsValidOrder : FlexiBusinessRuleBase, IFlexiBusinessRule<UpdateOrderDataPacket>
{
    public override string Id { get; set; } = "3a1cd500a49d178e88f75ed6bccaed88";
    public override string FriendlyName { get; set; } = "IsValidOrder";

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

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

    public virtual async Task Validate(UpdateOrderDataPacket 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**: `UpdateOrderHandler.cs`

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

    _model = _repoFactory.GetRepo().FindAll<Order>().Where(m=>m.Id == cmd.Dto.Id).FirstOrDefault();
    
    if (_model != null)
    {
        _model.UpdateOrder(cmd);
        _repoFactory.GetRepo().InsertOrUpdate(_model);

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

        await this.Fire(EventCondition, serviceBusContext);
    }
}
```

**What Happens:**

* **Context Setup**: Initializes application context and repository
* **Entity Lookup**: Finds existing order by ID
* **Null Check**: Ensures order exists before updating
* **Domain Logic**: Calls domain model to process business rules
* **Database Save**: Updates the order in database
* **Logging**: Logs success/failure of database operation
* **Event Publishing**: Fires events for subscribers

### 4. **Domain Model** - Business Logic

**File**: `Order/UpdateOrder.cs`

```csharp
public virtual Order UpdateOrder(UpdateOrderCommand cmd)
{
    Guard.AgainstNull("Order model cannot be empty", cmd);

    this.Convert(cmd.Dto);
    this.LastModifiedBy = cmd.Dto.GetAppContext()?.UserId;

    //Map any other field not handled by Automapper config

    this.SetModified();

    //Set your appropriate SetModified for the inner object here

    return this;
}
```

**What Happens:**

* **Validation**: Guards against null commands
* **Data Mapping**: Converts DTO to domain model
* **Audit Fields**: Sets last modified by user
* **State Management**: Marks entity as modified
* **Child Objects**: Processes child object updates

### 5. **NServiceBus Handler** - Message Processing

**File**: `UpdateOrderNsbHandler.cs`

```csharp
public class UpdateOrderNsbHandler : NsbCommandHandler<UpdateOrderCommand>
{
    readonly ILogger<UpdateOrderNsbHandler> _logger;
    readonly IFlexHost _flexHost;
    readonly IUpdateOrderHandler _handler;

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

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

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

**What Happens:**

* **Message Reception**: Receives `UpdateOrderCommand` 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**: `OrderUpdatedEvent`

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

**What Happens:**

* **Event Creation**: FlexBase creates event with order data
* **Message Bus**: Event is published to message bus
* **Subscriber Notification**: All subscribers are notified

### 7. **Event Subscribers** - Side Effects

**File**: `UpdateManagerOnUpdateOrder.cs`

```csharp
public partial class UpdateManagerOnUpdateOrder : IUpdateManagerOnUpdateOrder
{
    protected readonly ILogger<UpdateManagerOnUpdateOrder> _logger;
    protected string EventCondition = "";

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

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

        //TODO: Write your business logic here:
        // - Notify managers of order changes
        // - Update inventory levels
        // - Send update notifications
        // - Update analytics

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

**What Happens:**

* **Event Reception**: Receives `OrderUpdatedEvent` from message bus
* **Side Effects**: Executes business logic (notifications, inventory updates, etc.)
* **Additional Events**: Can fire more events if needed

## Data Transfer Objects (DTOs)

### **Input DTO**: `UpdateOrderDto`

```csharp
public partial class UpdateOrderDto : DtoBridge 
{
    public string Id { get; set; }
    
}
```

### **Command**: `UpdateOrderCommand`

```csharp
public class UpdateOrderCommand : FlexCommandBridge<UpdateOrderDto, FlexAppContextBridge>
{
    // Command data is automatically populated by FlexBase
}
```

## Key Differences from Insert Flow

### **Update-Specific Characteristics**

1. **Entity Lookup**: Must find existing entity before updating
2. **Null Check**: Validates entity exists before processing
3. **State Management**: Uses `SetModified()` instead of `SetAdded()`
4. **Audit Fields**: Updates `LastModifiedBy` instead of `CreatedBy`
5. **HTTP Method**: Uses `PUT` instead of `POST`
6. **Response Code**: Returns `200 OK` instead of `201 Created`

### **PreBus Validation Focus**

* **IsValidOrder**: Validates order exists and is in updatable state
* **Business Rules**: Ensures order can be modified (not shipped, not cancelled)
* **Data Integrity**: Validates update doesn't violate business constraints

## Flow Summary

### **Synchronous Flow (Immediate Response)**

1. **PUT Request** → Controller receives request
2. **Service Processing** → Business orchestration and PreBus validation
3. **PreBus Plugins** → Sequential validation of business rules
4. **Command Handler** → Entity lookup and data processing
5. **Domain Logic** → Business rules and state management
6. **Response** → HTTP 200 OK with success status

### **Asynchronous Flow (Event Processing)**

1. **Event Publishing** → OrderUpdatedEvent published to message bus
2. **Subscriber Processing** → UpdateManagerOnUpdateOrder executes
3. **Side Effects** → Manager notifications, inventory updates, analytics

## Key Benefits

* **Data Integrity**: Ensures entity exists before updating
* **Audit Trail**: Tracks who made changes and when
* **Business Rules**: Validates update is allowed
* **Event-Driven**: Notifies other systems of changes
* **Testable**: Each component can be tested independently
* **Maintainable**: Clear separation of concerns

***

**This UpdateOrder example demonstrates how FlexBase enables clean, maintainable, and scalable update operations with proper validation, audit trails, and event-driven architecture!** 🚀