Err.ChangeTracking.SourceGenerator 0.4.0

Err.ChangeTracking Solution (Full Documentation)

A complete, high-performance, AOT-friendly solution to track changes on POCO models — combining runtime efficiency and compile-time generation.

📚 Introduction

Managing changes on POCO models is a common but tedious problem. Manually tracking modifications leads to verbose code, maintenance headaches, and runtime inefficiency.

Err.ChangeTracking provides:

• A lightweight runtime library.
• A powerful Roslyn Source Generator to automate everything at compile time.

Result?
⚡ Lightning-fast, zero-reflection change tracking ready for Blazor, NativeAOT, Cloud, Web, and Mobile.

🚨 Problem Statement

✅ How to detect if a POCO model has been modified?
✅ How to rollback changes easily?
✅ How to track changes without relying on slow reflection or dynamic proxies?

Conventional solutions introduce runtime overhead and are not AOT-friendly.

🛠 Manual Implementation Example (Using Only Err.ChangeTracking Runtime)

using System;
using Err.ChangeTracking;

public partial class Person : ITrackable<Person>
{
    private IChangeTracking<Person> _changeTracker;
    public IChangeTracking<Person> GetChangeTracker() => _changeTracker ??= new ChangeTracking<Person>(this);

    private string _firstName;
    public partial string FirstName
    {
        get => _firstName;
        set { _changeTracker?.RecordChange(nameof(FirstName), _firstName, value); _firstName = value; }
    }

    private int _age;
    public partial int Age
    {
        get => _age;
        set { _changeTracker?.RecordChange(nameof(Age), _age, value); _age = value; }
    }
}

Explanation:

• _changeTracker monitors the original values.
• RecordChange is called manually inside each setter.
• IsDirty, Rollback, and AcceptChanges become available.

✅ Powerful — but ✋ very repetitive and error-prone for large models.

🤖 With Err.ChangeTracking.SourceGenerator (Recommended)

Instead of manually writing setters, just annotate your class:

[Trackable]
public partial class Person
{
    public partial string FirstName { get; set; }
    public partial int Age { get; set; }
}

The source generator will auto-generate the backing fields, tracking logic, and setter wrappers.

✅ Keep your models clean, readable, and efficient.

✨ How the Generator Works

• Class must be marked as [Trackable]
• Class must be partial
• Public, partial properties are eligible
• Attributes control behavior:

🧪 Examples From Unit Tests

Tracking simple properties

var person = new Person { FirstName = "Alice", Age = 30 }.AsTrackable();
person.FirstName = "Bob";

Assert.True(person.GetChangeTracker().IsDirty);
Assert.True(person.GetChangeTracker().HasChanged(x => x.FirstName));

Rollback a single property

person.GetChangeTracker().Rollback(x => x.FirstName);
Assert.Equal("Alice", person.FirstName);

Tracking collections

[Trackable]
public partial class Order
{
    [TrackCollection]
    public partial List<string> Items { get; set; }
}

var order = new Order { Items = new List<string>() }.AsTrackable();
order.Items.AsTrackable().Add("New Item");

Assert.True(order.GetChangeTracker().IsDirty);

TrackingMode OnlyMarked with [TrackOnly]

[Trackable(Mode = TrackingMode.OnlyMarked)]
public partial class Invoice
{
    [TrackOnly]
    public partial string InvoiceNumber { get; set; }

    public partial string Comment { get; set; }
}

var invoice = new Invoice { InvoiceNumber = "INV001", Comment = "Test" }.AsTrackable();

invoice.InvoiceNumber = "INV002";
invoice.Comment = "Changed Comment";

Assert.True(invoice.GetChangeTracker().HasChanged(x => x.InvoiceNumber));
Assert.False(invoice.GetChangeTracker().HasChanged(x => x.Comment));

🚀 Typical Use Cases

• Change tracking in CRUD applications
• Undo/Redo features
• Form validation and dirty detection
• Optimizing entity update operations

📦 Requirements

IMPORTANT: This package uses C# 13 feature Patrial properties and requires either:

• .NET 9.0 or higher, OR
• .NET 8.0 with LangVersion set to "preview" in your project file

If you're using .NET 8.0, add the following to your project file:

<PropertyGroup>
    <LangVersion>preview</LangVersion>
</PropertyGroup>

! Without this configuration, the source generator will not work correctly.

📦 Installation

dotnet add package Err.ChangeTracking

dotnet add package Err.ChangeTracking.SourceGenerator

📋 License

Licensed under the MIT License.

🔥 Related Projects

• Err.ChangeTracking — Runtime library
• Err.ChangeTracking.SourceGenerator — Roslyn code generator

🙌 Contributions

Contributions are welcome!
Fork the repository, submit a PR, or open an issue to suggest improvements!

Built with ❤️ by ERRADIL