ErikLieben.FA.ES.EventStreamManagement 2.0.0-preview.17

ErikLieben.FA.ES

A lightweight, AOT-friendly Event Sourcing toolkit for .NET. Build aggregates, append and read events, create snapshots, upcast historical data, and integrate with Azure storage and Functions.

A Friendly Note

This is an opinionated library built primarily for my own projects and coding style. You're absolutely free to use it (it's MIT licensed!), but please don't expect free support or feature requests. If it works for you, great! If not, there are many other excellent libraries in the .NET ecosystem. For commercially supported event-sourcing platforms, consider EventStoreDB or AxonIQ's Axon Server/Framework.

That said, I do welcome bug reports and thoughtful contributions. If you're thinking about a feature or change, please open an issue first to discuss it.

Getting Started

The fastest way to explore the library is to run the TaskFlow demo application, a full-stack Aspire app showcasing aggregates, projections, Minimal APIs, and Azure Functions.

Prerequisites

• .NET 10 SDK
• Docker Desktop or Podman (for Azurite and CosmosDB emulators)

Run the Demo

# Clone the repository
git clone https://github.com/eriklieben/ErikLieben.FA.ES.git
cd ErikLieben.FA.ES

# Run the Aspire demo
dotnet run --project demo/src/TaskFlow.AppHost

This starts:

• API - ASP.NET Core Minimal API with event-sourced aggregates
• Functions - Azure Functions with EventStream and Projection bindings
• Frontend - Angular app (optional, at demo/taskflow-web)
• Azurite - Azure Storage emulator for blobs/tables/queues
• CosmosDB Emulator - For CosmosDB-backed event streams (optional)

Open the Aspire dashboard (URL shown in console) to see all services and explore.

Optional: Persist Storage

To keep data across restarts:

dotnet run --project demo/src/TaskFlow.AppHost -- --PersistStorage=true

Key Features

Packages

# Core library
dotnet add package ErikLieben.FA.ES

# CLI tool (local)
dotnet new tool-manifest
dotnet tool install ErikLieben.FA.ES.CLI --local

# Storage providers
dotnet add package ErikLieben.FA.ES.AzureStorage
dotnet add package ErikLieben.FA.ES.CosmosDb

# Integrations
dotnet add package ErikLieben.FA.ES.AspNetCore.MinimalApis
dotnet add package ErikLieben.FA.ES.Azure.Functions.Worker.Extensions

# Testing
dotnet add package ErikLieben.FA.ES.Testing

Requirements: .NET 9.0 or .NET 10.0

Documentation

Exception Reference

Structured error codes are documented in docs/exceptions/.

Quick Example

// Define an aggregate
public partial class Customer(IEventStream stream) : Aggregate(stream)
{
    public string? Name { get; private set; }

    public Task Register(string name)
    {
        ArgumentNullException.ThrowIfNull(name);
        return Stream.Session(ctx => Fold(ctx.Append(new CustomerRegistered(name))));
    }

    private void When(CustomerRegistered e) => Name = e.Name;
}

// Define an event
[EventName("Customer.Registered")]
public record CustomerRegistered(string Name);

// Generate supporting code
// dotnet tool run faes

See the demo/src/TaskFlow.Domain folder for complete aggregate and projection examples.

License

MIT License - see the LICENSE file for details.