A modern, lightweight, and extensible .NET framework for building event-sourced applications using Domain-Driven Design (DDD) principles and Command Query Responsibility Segregation (CQRS) patterns.

SourceFlow.Net empowers developers to build scalable, maintainable applications by providing a complete toolkit for event sourcing, domain modeling, and command/query separation. Built from the ground up for .NET 9.0 with performance and developer experience as core priorities.

• 🏗️ Domain-Driven Design Support - First-class support for aggregates, entities, value objects
• ⚡ CQRS Implementation - Complete command/query separation with optimized read models
• 📊 Event Sourcing Foundation - Event-first design with full audit trail
• 🧱 Clean Architecture - Clear separation of concerns and dependency management
• 💾 Flexible Persistence - Multiple storage options including Entity Framework Core
• 🔄 Event Replay - Built-in command replay for debugging and state reconstruction
• 🎯 Type Safety - Strongly-typed commands, events, and projections
• 📦 Dependency Injection - Seamless integration with .NET DI container
• 📈 OpenTelemetry Integration - Built-in distributed tracing and metrics for operations at scale
• ⚡ Memory Optimization - ArrayPool-based optimization for extreme throughput scenarios
• 🛡️ Resilience Patterns - Polly integration for fault tolerance with retry policies and circuit breakers

Aggregates

• An Aggregate encapsulates a root domain entity within a bounded context (microservice)
• Changes to aggregates are initiated by publishing commands
• Aggregates subscribe to events to react to external changes from other sagas or workflows that may affect their state

Sagas

• A Saga represents a long-running transaction that orchestrates complex business processes
• Sagas subscribe to commands and execute the actual updates to aggregate entities
• They manage both success and failure flows to ensure data consistency and preserve aggregate state
• Sagas can publish commands to themselves or other sagas to coordinate multi-step workflows
• Events can be raised by sagas during command handling to notify other components of state changes

Events

• Events are published to interested subscribers when state changes occur
• Two primary event subscribers exist in the framework:
  • Aggregates: React to events from external workflows that impact their domain state
  • Views: Project event data into optimized read models for query operations

Views

• Views subscribe to events and transform domain data into denormalized view models
• View models provide optimized read access for consumers such as UIs or reporting systems
• Data in view models follows eventual consistency patterns

Command Dispatcher

• Dispatches commands to cloud-based message queues for distributed processing
• Targets specific command queues based on bounded context routing
• Configured using the Bus Configuration System fluent API

Command Queue

• A dedicated queue for each bounded context (microservice)
• Routes incoming commands to the appropriate subscribing sagas within the domain

Event Dispatcher

• Publishes domain events to cloud-based topics for cross-service communication
• Enables event-driven architecture across distributed systems
• Configured using the Bus Configuration System fluent API

Event Listeners

• Bootstrap components that listen to subscribed event topics
• Dispatch received events to the appropriate aggregates and views within each domain context
• Enable seamless integration across bounded contexts

Bus Configuration System

• Code-first fluent API for configuring command and event routing
• Automatic resource creation (queues, topics, subscriptions)
• Type-safe configuration with compile-time validation
• Simplified setup using short names instead of full URLs/ARNs
• See Cloud Configuration Guide for details

Click on Architecture for more details on how to extend SourceFlow.Net for bespoke requirements.

Package	Version	Release Date	Details	.Net Frameworks
SourceFlow	v2.0.0	15th Mar 2026	v1.0.0 Core functionality with integrated cloud abstractions. Cloud.Core consolidated into main package. Breaking changes: namespace updates from SourceFlow.Cloud.Core.* to SourceFlow.Cloud.*
SourceFlow	v1.0.0	29th Nov 2025	Initial stable release with event sourcing and CQRS
SourceFlow.Stores.EntityFramework	v2.0.0	29th Nov 2025	v1.0.0 Core EF store implementations with new cloud idempotency provider implementation.
SourceFlow.Stores.EntityFramework	v1.0.0	29th Nov 2025	Provides store implementation using EF. Can configure different (types of ) databases for each store.
SourceFlow.Cloud.AWS	v2.0.0	15th Mar 2026	Provides support for AWS cloud with cross domain boundary command and Event publishing & subscription. Includes comprehensive testing framework with LocalStack integration, performance benchmarks, security validation, and resilience testing.
SourceFlow.Cloud.Azure	v2.0.0	(TBC)	Provides support for Azure cloud with cross domain boundary command and Event publishing & subscription. Includes comprehensive testing framework with Azurite integration, performance benchmarks, security validation, and resilience testing.

From Problems to Patterns — Domain-Driven Design and Event Sourcing in .NET By Najaf A. Shaikh · First Edition, 2026

The complete, runnable companion code for all 32 chapters of the book is available in the dd-event-sourcing-dotnet-samples repository. Every code example builds and all tests pass. The code evolves chapter by chapter through a single Bank Account domain — starting from a naive CRUD implementation and ending with a containerised, observable, event-sourced system built on SourceFlow.Net.

add nuget packages for SourceFlow.Net

• dotnet add package SourceFlow.Net
• dotnet add package SourceFlow.Stores.EntityFramework
• dotnet add package SourceFlow.Cloud.AWS
• add custom implementation for stores, and extend for your cloud.

When deploying SourceFlow.Net applications to the cloud with AWS or Azure, idempotency is crucial for handling duplicate messages in distributed systems.

For single-instance deployments, SourceFlow automatically uses an in-memory idempotency service:

services.UseSourceFlow();

services.UseSourceFlowAws(
    options => { options.Region = RegionEndpoint.USEast1; },
    bus => bus
        .Send.Command<CreateOrderCommand>(q => q.Queue("orders.fifo"))
        .Listen.To.CommandQueue("orders.fifo"));

For multi-instance deployments, use the SQL-based idempotency service to ensure duplicate detection across all instances:

services.UseSourceFlow();

// Register Entity Framework stores with SQL-based idempotency
services.AddSourceFlowEfStores(connectionString);
services.AddSourceFlowIdempotency(
    connectionString: connectionString,
    cleanupIntervalMinutes: 60);

// Configure cloud integration (AWS or Azure)
services.UseSourceFlowAws(
    options => { options.Region = RegionEndpoint.USEast1; },
    bus => bus
        .Send.Command<CreateOrderCommand>(q => q.Queue("orders.fifo"))
        .Listen.To.CommandQueue("orders.fifo"));

Benefits of SQL-Based Idempotency:

• ✅ Distributed duplicate detection across multiple instances
• ✅ Automatic cleanup of expired records
• ✅ Database-backed persistence for reliability
• ✅ Supports SQL Server, PostgreSQL, MySQL, SQLite

For more details, see:

• AWS Cloud Integration
• SQL-Based Idempotency Service
• Cloud Integration Testing guide

This comprehensive guide provides detailed information about the SourceFlow.Net framework, covering everything from basic concepts to advanced implementation patterns and troubleshooting guidelines.

Please click on Developer Guide for complete details.

If you are having problems, please let me know by raising a new issue.

This project is licensed with the MIT license.

We welcome contributions! Please see our Contributing Guide for details.

• 🐛 Bug Reports - Create an issue
• 💡 Feature Requests - Start a discussion
• 📝 Documentation - Help improve our docs
• 💻 Code - Submit pull requests

Thank you for reading. Please fork, explore, contribute and report. Happy Coding !! :)