Bartender is a CQRS propose without any dependencies and available for all netstandard 1.1 compliant platform.
PM> Install-Package Bartender
- Synchronous/Asynchronous message dispatching
- Suit well with IoC
- Simple Publish-Subscribe mode
- Automatic validation
First thing you have to do with Bartender is to implement the IDependencyContainer interface and register it with a IoC container.
You also need to register your handlers (IHandler, IAsyncHandler, ICancellableAsyncHandler) and bind dispatch interfaces (IDispatcher, IAsyncDispatcher, ICancellableAsyncDispatcher) to the Dispatcher class.
This step really depend on which IoC container you use in your project. Check out project samples, you can find dependencies registration with StructureMap here
A message is just an implementation of the IMessage interface. You can consider the interface to work as a marker and it never impose to write specific code. When mark as IMessage an Object can be dispatched with the library. For exemple if you want to retreive informations of a person who's got an identifier, you can define a message like this :
public class GetPersonByIdQuery : IMessage
{
public int Id { get; }
public GetPersonById(int id)
{
Id = id;
}
}By convention in CQRS when you define a message to read data it have to be suffix with Query and by opposition Command define a write operation message. The library don't force you to respect this principle but it is a good way to organise your project.
When your message is define, you have to write an handler for it. Handler can be implement with synchronous or ascynchronous execution :
//Synchronous handler
public class GetPersonByIdQueryHandler : IHandler<GetPersonByIdQuery, GetPersonReadModel>
{
public GetPersonReadModel Handle(GetPersonByIdQuery message)
{
//add you logic code here
}
}
//Asynchronous handler
public class GetPersonByIdQueryHandler : IAsyncHandler<GetPersonByIdQuery, GetPersonReadModel>
{
public GetPersonReadModel HandleAsync(GetPersonByIdQuery message)
{
//add you logic code here
}
}The nature of queries is to retreive data, but for a command you can define to return an object or not (for Fire & Forget operation). To deal with this case, IHandler can be implement without return :
public class CreatePersonCommandHandler : IHandler<CreatePersonCommand>
{
public void Handle(CreatePersonCommand message)
{
//add you logic code here
}
}When handlers are register with IoC and can be finded by your IDependencyContainer implementation, the message is dispatchable :
IDispatcher dispatcher = new Dispatcher();
dispatcher.Dispatch<GetPersonByIdQuery, GetPersonReadModel>(new GetPersonByIdQuery(1));If your define an asynchronous handler, dispatch it with IAsyncHandler :
IAsyncDispatcher dispatcher = new Dispatcher();
await dispatcher.DispatchAsync<CreatePersonCommand>(new CreatePersonCommand(1, "Name"));As you certainly notice, Dispatcher explicitly implement dispatching interfaces. This type of implementation force developer to use the instance as interface and suit well with IoC too :)
MIT