Added Updated Readmes, Removed old slides

Author: oskardudycz

EventSourcing.NetCore.sln

@@ -205,6 +205,9 @@ EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Core.Api.Testing", "Core.Api.Testing\Core.Api.Testing.csproj", "{825A40DB-5AB5-4565-AADB-28AC760D0A43}"
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Simple", "Simple", "{11DD4963-5BB4-4E1B-9475-8EB10C822BFC}"
+ProjectSection(SolutionItems) = preProject
+	Sample\EventStoreDB\Simple\README.md = Sample\EventStoreDB\Simple\README.md
+EndProjectSection
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "ECommerce.Api", "Sample\EventStoreDB\Simple\ECommerce.Api\ECommerce.Api.csproj", "{414D1D34-1002-4159-B738-DF3EE042F9FD}"
 EndProject

README.md

@@ -14,6 +14,11 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Core.Api.Testing", "..\..\.
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "ECommerce.Core", "ECommerce.Core\ECommerce.Core.csproj", "{3DF5E171-72BD-4129-B66C-5428029CF932}"
 EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Docs", "Docs", "{6C654A81-F8CF-46DE-9CD8-442162F3F6FD}"
+ProjectSection(SolutionItems) = preProject
+	README.md = README.md
+EndProjectSection
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU

Sample/EventStoreDB/Simple/ECommerce.sln

@@ -0,0 +1,74 @@
+# Simple, practical EventSourcing with EventStoreDB and EntityFramework
+
+The PR is adding a new sample that contains the simple Event Sourcing setup with EventStoreDB. For the Read Model, Postgres and Entity Framework are used.
+
+You can watch the webinar on YouTube when I'm explaining the details of the implementation:
+
+<a href="https://www.youtube.com/watch?v=rqYPVzjoxqI" target="_blank"><img src="https://img.youtube.com/vi/rqYPVzjoxqI/0.jpg" alt="Practical introduction to Event Sourcing with EventStoreDB" width="320" height="240" border="10" /></a>
+
+or read the article explaining the read model part: ["How to build event-driven projections with Entity Framework"](https://event-driven.io/en/how_to_do_events_projections_with_entity_framework/)
+
+## Main assumptions:
+- explain basics of Event Sourcing, both from the write model (EventStoreDB) and read model part (Postgres and EntityFramework),
+- CQRS architecture sliced by business features, keeping code that changes together at the same place. Read more in [How to slice the codebase effectively?](https://event-driven.io/en/how_to_slice_the_codebase_effectively/)
+- no aggregates, just data (records) and functions,
+- clean, composable (pure) functions for command, events, projections, query handling instead of marker interfaces (the only one used internally is `IEventHandler`). Thanks to that testability and easier maintenance.
+- easy to use and self-explanatory fluent API for registering commands and projections with possible fallbacks,
+- registering everything into regular DI containers to integrate with other application services.
+- pushing the type/signature enforcement on edge, so when plugging to DI.
+
+## Overview
+
+It uses:
+- pure data entities, functions and handlers,
+- Stores events from the command handler result  EventStoreDB,
+- Builds read models using [Subscription to `$all`](https://developers.eventstore.com/clients/grpc/subscribing-to-streams/#subscribing-to-all).
+- Read models are stored to Postgres relational tables with [Entity Framework](https://docs.microsoft.com/en-us/ef/core/).
+- App has Swagger and predefined [docker-compose](./docker/docker-compose.yml) to run and play with samples.
+
+## Write Model
+- Sample [ShoppingCart](./ECommerce/ShoppingCarts/ShoppingCart.cs#L34) entity and [events](./ECommerce/ShoppingCarts/ShoppingCart.cs#L6) represent the business workflow. All are stored in the same file to be able to understand flow without jumping from one file to another. It also contains [When](./ECommerce/ShoppingCarts/ShoppingCart.cs#L42) method defining how to apply events to get the entity state. It uses the C#9 switch syntax with records deconstruction.
+- Example [ProductItemsList](./ECommerce/ShoppingCarts/ProductItems/ProductItemsList.cs) value object wrapping the list of product items in the shopping carts. It simplified the main state apply logic and offloaded some of the invariants checks.
+- All commands by convention should be created using the [factory method](./ECommerce/ShoppingCarts/AddingProductItem/AddProductItemToShoppingCart.cs#L13) to enforce the types,
+- Command handlers are defined as static methods in the same file as command definition. Usually, they change together. They are pure functions that take command and/or state and create new events based on the business logic. See sample [Adding Product Item to ShoppingCart](./ECommerce/ShoppingCarts/AddingProductItem/AddProductItemToShoppingCart.cs#L25). This example also shows that you can inject external services to handlers if needed.
+- [Added syntax for self-documenting command handlers registration](./ECommerce/ShoppingCarts/Configuration.cs#L22). See the details of registration in [CommandHandlerExtensions](./ECommerce.Core/Commands/CommandHandler.cs). They differentiate case when [a new entity/stream is created](./Ecommerce.Core/Commands/CommandHandler.cs#L11) from the [update case](./Ecommerce.CoreECommerce.Core/Commands/CommandHandler.cs#L25). Update has to support optimistic concurrency.
+- Added simple [EventStoreDBRepository](./ECommerce.Core/Entities/EventStoreDBRepository.cs) repository to load entity state and store event created by business logic,
+- [New, simplified Core infrastructure](./ECommerce.Core/)
+
+## Read Model
+- Read models are rebuilt with eventual consistency using subscribe to $all stream EventStoreDB feature,
+- Used Entity Framework to store projection data into Postgres tables,
+- Added sample projection for [Shopping cart details](./ECommerce/ShoppingCarts/GettingCartById/ShoppingCartDetails.cs) and slimmed [Shopping cart short info](./ECommerce/ShoppingCarts/GettingCarts/ShoppingCartShortInfo.cs) as an example of different interpretations of the same events. Shopping cart details also contain a nested collection of product items to show more advanced use case. All event handling is done by functions. It enables easier unit and integration testing.
+- [Added syntax for self-documenting projection handlers registration](./ECommerce/ShoppingCarts/Configuration.cs#L49). See the details of registration in [EntityFrameworkProjectionBuilder](./ECommerce.Core/Projections/EntityFrameworkProjection.cs#L28). They differentiate case when [a new read model is created](./ECommerce.Core/Projections/EntityFrameworkProjection.cs#L83) from the [update case](./ECommerce.Core/Projections/EntityFrameworkProjection.cs#L108). Update has to support optimistic concurrency.
+- [example query handlers](./ECommerce/ShoppingCarts/GettingCarts/GetCarts.cs#25) for reading data together with [registration helpers](./ECommerce.Core/Queries/QueryHandler.cs) for EntityFramework querying.
+- Added service [EventStoreDBSubscriptionToAll](./ECommerce.Core/Subscriptions/EventStoreDBSubscriptionToAll.cs) to handle subscribing to all. It handles checkpointing and simple retries when the connection is dropped. Added also general [BackgroundWorker](./ECommerce.Api/Core/BackgroundWorker.cs) to wrap the general `IHostedService` handling
+- Added [ISubscriptionCheckpointRepository](./ECommerce.Core/Subscriptions/ISubscriptionCheckpointRepository.cs) for handling Subscription checkpointing.
+- Added checkpointing to EventStoreDB stream with [EventStoreDBSubscriptionCheckpointRepository](./ECommerce.Core/Subscriptions/EventStoreDBSubscriptionCheckpointRepository.cs),
+- Added custom [EventBus](./ECommerce.Core/Events/EventBus.cs) implementation to not take an additional dependency on external frameworks like MediatR. It's not needed as no advanced pipelining is used here.
+
+## Tests
+API integration tests for:
+- [Initiating shopping cart](./ECommerce.Api.Tests/ShoppingCarts/Initializing/InitializeShoppingCartTests.cs) as an example of creating a new entity,
+- [Confirming shopping cart](./ECommerce.Api.Tests/ShoppingCarts/Confirming/ConfirmShoppingCartTests.cs) as an example of updating an existing entity,
+
+
+## Prerequisities
+
+1. Install git - https://git-scm.com/downloads.
+2. Install .NET Core 5.0 - https://dotnet.microsoft.com/download/dotnet/5.0.
+3. Install Visual Studio 2019, Rider or VSCode.
+4. Install docker - https://docs.docker.com/docker-for-windows/install/.
+5. Open `ECommerce.sln` solution.
+
+## Running
+
+1. Go to [docker](./docker) and run: `docker-compose up`.
+2. Wait until all dockers got are downloaded and running.
+3. You should automatically get:
+    - EventStoreDB UI (for event store): http://localhost:2113/
+    - Postgres DB running (for read models)
+    - PG Admin - IDE for postgres. Available at: http://localhost:5050.
+        - Login: `[email protected]`, Password: `admin`
+        - To connect to server Use host: `postgres`, user: `postgres`, password: `Password12!`
+4. Open, build and run `ECommerce.sln` solution.
+    - Swagger should be available at: http://localhost:5000/index.html