Abstractions

Defines the CQRS handler and validator contracts for the Dosaic plugin framework. This package contains the core interfaces and models that resource handlers must implement — it has no runtime dependencies beyond FluentValidation and the Dosaic persistence/extensions abstractions, making it the right lightweight reference for libraries that need to declare handlers without pulling in full implementations.

Installation

dotnet add package Dosaic.Plugins.Handlers.Abstractions.Cqrs

Features

Handler interfaces (Dosaic.Plugins.Handlers.Abstractions.Cqrs.Handlers)

Interface	Method	Description
IHandler	—	Marker interface; all handlers must implement this
ICreateHandler<TResource>	CreateAsync(TResource, CancellationToken)	Creates a new resource and returns it
IUpdateHandler<TResource>	UpdateAsync(TResource, CancellationToken)	Updates an existing resource and returns it
IDeleteHandler<TResource>	DeleteAsync(IGuidIdentifier, CancellationToken)	Deletes a resource by its identifier
IGetHandler<TResource>	GetAsync(IGuidIdentifier, CancellationToken)	Retrieves a single resource by identifier
IGetListHandler<TResource>	GetListAsync(PagingRequest, CancellationToken)	Returns a paged list of resources

Validator interfaces (Dosaic.Plugins.Handlers.Abstractions.Cqrs.Validators)

Interface	Method	Description
IBaseValidator	—	Marker interface for all validators
ICreateValidator<TResource>	ValidateOnCreate(AbstractValidator<TResource>)	Validation rules applied before create
IUpdateValidator<TResource>	ValidateOnUpdate(AbstractValidator<TResource>)	Validation rules applied before update
IDeleteValidator<TResource>	ValidateOnDelete(AbstractValidator<TResource>)	Validation rules applied before delete
IGetValidator<TResource>	ValidateOnGet(AbstractValidator<TResource>)	Validation rules applied before get
IGetListValidator<TResource>	ValidateOnGetList(AbstractValidator<TResource>)	Validation rules applied before list
GenericValidator<T>	—	Concrete AbstractValidator<T> that delegates rule setup to an Action<AbstractValidator<T>>

Models (Dosaic.Plugins.Handlers.Abstractions.Cqrs.Models)

Type	Description
GuidIdentifier	Record implementing IGuidIdentifier. Has static Empty, New, and Parse(string) factory members

Enum

Type	Values
HandlerAction	Get, GetList, Create, Update, Delete

Usage

1. Define your resource model

Your resource must implement IGuidIdentifier from Dosaic.Plugins.Persistence.Abstractions:

using Dosaic.Plugins.Persistence.Abstractions;

public class Article : IGuidIdentifier
{
    public Guid Id { get; set; }
    public string Title { get; set; }
    public string Body { get; set; }
}

2. Implement a validator

A single class can implement multiple validator interfaces, grouping all validation logic for a resource in one place:

using Dosaic.Plugins.Handlers.Abstractions.Cqrs.Validators;
using FluentValidation;

public class ArticleValidator
    : ICreateValidator<Article>,
      IUpdateValidator<Article>,
      IBaseValidator
{
    public void ValidateOnCreate(AbstractValidator<Article> validator)
    {
        validator.RuleFor(x => x.Title).NotEmpty().MaximumLength(200);
        validator.RuleFor(x => x.Body).NotEmpty();
    }

    public void ValidateOnUpdate(AbstractValidator<Article> validator)
    {
        validator.RuleFor(x => x.Id).NotEmpty();
        validator.RuleFor(x => x.Title).NotEmpty().MaximumLength(200);
    }
}

3. Implement custom handlers

Use the handler interfaces when the built-in SimpleResource implementations (from Dosaic.Plugins.Handlers.Cqrs) do not fit your needs:

using Dosaic.Plugins.Handlers.Abstractions.Cqrs.Handlers;
using Dosaic.Plugins.Persistence.Abstractions;

public class ArticleCreateHandler : ICreateHandler<Article>, IHandler
{
    private readonly IRepository<Article> _repository;
    private readonly ICreateValidator<Article> _validator;

    public ArticleCreateHandler(
        IRepository<Article> repository,
        ICreateValidator<Article> validator)
    {
        _repository = repository;
        _validator = validator;
    }

    public async Task<Article> CreateAsync(Article request, CancellationToken cancellationToken)
    {
        // validate using a GenericValidator that delegates to the injected validator
        var fluentValidator = new GenericValidator<Article>(_validator.ValidateOnCreate);
        await fluentValidator.ValidateOrThrowAsync(request, cancellationToken);

        request.Id = Guid.NewGuid();
        return await _repository.AddAsync(request, cancellationToken);
    }
}

4. Use GuidIdentifier for request objects

GuidIdentifier is a ready-made implementation of IGuidIdentifier that can be used wherever a handler expects just an identifier:

// Create a new random identifier
var id = GuidIdentifier.New;

// Parse from a string (e.g. from a route parameter)
var id = GuidIdentifier.Parse("05a82a17-5a7f-4f28-8ff9-37f35c2cfb5f");

// Represent an empty/null identifier
var empty = GuidIdentifier.Empty;

5. Use the Dosaic.Plugins.Handlers.Cqrs implementation plugin (recommended)

If your resource has a repository registered in the DI container, you can skip writing handlers altogether by adding the CqrsSimpleResourcePlugin from Dosaic.Plugins.Handlers.Cqrs. It automatically registers generic SimpleResource*Handler<T> implementations for all five CQRS operations:

// The plugin detects all IHandler and IBaseValidator implementations in your
// assemblies and registers them, including the generic CRUD handlers.
// No manual registration is required — just run the Dosaic host:
PluginWebHostBuilder.RunDefault(DosaicPluginTypes.All);

Resolved handler types:

Handler interface	Default implementation
ICreateHandler<TResource>	SimpleResourceCreateHandler<TResource>
IUpdateHandler<TResource>	SimpleResourceUpdateHandler<TResource>
IDeleteHandler<TResource>	SimpleResourceDeleteHandler<TResource>
IGetHandler<TResource>	SimpleResourceGetHandler<TResource>
IGetListHandler<TResource>	SimpleResourceGetListHandler<TResource>

Custom implementations registered in your own assemblies take precedence because the plugin scans for types that implement IHandler across all non-framework assemblies and registers them on top of the defaults.

Dependencies

Package	Purpose
Dosaic.Extensions.Abstractions	PagedList<T> used in IGetListHandler
Dosaic.Plugins.Persistence.Abstractions	IGuidIdentifier, PagingRequest
FluentValidation	AbstractValidator<T> used in validator interfaces