Allegro.Extensions.Cqrs.Abstractions 1.0.0

Allegro.Extensions.Cqrs

Believe that there is no need to describe it once more and point you to authority:

https://martinfowler.com/bliki/CQRS.html

In this package our custom implementation of tools and markers are delivered.

Allegro.Extensions.Cqrs.Abstractions

Contains common CQRS set of markers and abstractions like ICommand, IQuery<>, ICommandDispatcher, IQueryDispatcher, ICommandHandler, IQueryHandler.

Additionally we introduce some additonaly things like ICommandValidator, ICommandExecutionActions and Decorator.

ICommandValidator

In more sophisticated validation cases, that simple DataAnnotations are not enough we introduce ICommandValidator<ICommand> to enables adding some validation logic before command execution.

internal class SampleCommandValidator : ICommandValidator<SampleCommand>
{
    public Task Validate(SampleCommand command)
    {
       // validation logic
    }
}

Sample

ICommandExecutionActions

To be able to run some additional actions before and after command execution (like unit of work, collect metrics, diagnostics etc.) without messing business logic code in handler we introduce ICommandExecutionActions<> interface. We can easily split business logic from some technical noise.

internal class SampleCommandActions : ICommandExecutionActions<SampleCommand>
{
    public Task Before(SampleCommand command)
    {
       ...
    }

    public Task After(SampleCommand command)
    {
       ...
    }
}

Sample

Decorators

To be able to use decorator pattern we introduced DecoratorAttribute. Each handler marked with it wont be registered automatically in services by our extensions and give opportunity to Decorate handlers with any custom code.

Example:

[Decorator]
internal class CommandHandlerDecorator<T> : ICommandHandler<T> where T : ICommand
{
...
}

Registration with Scrutor:

    services.TryDecorate(typeof(ICommandHandler<>), typeof(CommandHandlerDecorator<>));

Remember to first register all commands handlers and than register custom decorator.

Samples

Some sample usage could be found:

• commands
• queries

Allegro.Extensions.Cqrs

This package contains:

• default implementation of ICommandDispatcher and IQueryDispatcher
• automatic registrations of all ICommandHandler, IQueryHandler, ICommandValidator, ICommandExecutionActions

For registrations Scrutor packages is uses as a tool.