Event Driven Design Playground

How to use different technologies to achieve a event publish subscriber system

Leverage on the following technologies

• Delegates
• Events
• Mediator Design Pattern
• Event Bus
• CQRS using MediatR
• Docker Containers
• RabbitMQ
• CQRS with RabbitMQ
• SignalR
• Background Service
• WebRTC
• Data Streaming
• Event Brokers/ Stores Interface like RabbitMQ/ Kafka/ Redis

CQRS using MediatR guide

Step by step

• install swagger
• install mediatr
• create classes for entities > repositories
• create classes for dto models like CarResponseModel and CarRequestModel
• add using MediatR; on top of files from here on
• create classes for requests like GetCarsQuery and CreateCarCommand, then extend IRequest<TResponse> where TResponse is response object type
• create classes for handlers like GetCarsQueryHandler and CreateCarCommandHandler, then extend IRequestHandler<IRequest,TResponse>
• example for the above will be GetCarsQuery : IRequest<CarResponseModel> and CreateCarCommandHandler : IRequestHandler<GetCarsQuery,CarResponseModel>. Note that CarResponseModel can be int, bool, string etc
• In Program.cs add builder.Services.AddMediatR(typeof(Program).GetTypeInfo().Assembly); to reqister MediatR in DI container
• In the controler add private IMediator _mediator;
• write controller action

Observations

• Query and Command are refered to as Request in MediatR
• Event is refered to as Notification in MediatR
• A Request should be immutable so the setter property removed i.e { get; }
• Request pipeline: Controller > Query or Command Tresponse > Handler Trequest,Tresponse > Repository. Here Trequest is the Query/Command type.

Nuget Packages

dotnet add package MediatR --version 10.0.1
dotnet add package MediatR.Extensions.Microsoft.DependencyInjection --version 10.0.1