SRenerCq 26.1.17

SRenerCQ

SRenerCQ is a simple CQRS implementation focused on using Dependency Injection to decouple commands and queries.

How to Use

Enabling SRenerCQ

Before using, it's important to enable SRenerCQ at the application by registering it in the service collection:

using SRenerCQ;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddSRenerCQ();

...

Using SRenerCQ

After implementing commands/queries as described below, invoking them is done using the ISender interface by Dependency Injection. To use them:

public class MyInjectedClass(ISender sender) : IMyInjectedClass
{
    public async Task ProcessCommand(){
        MyCommand command = new("Foo");
        await sender.Command(command);
    }

    public async Task ProcessQuery(){
        MyQuery query = new("Foo");
        string result = await sender.Query(query);

        Console.WriteLine(result);
    }
}

By convention, queries return data and commands perform state changes. This library allows commands to return a result (e.g., an identifier) — if you prefer strict CQRS, treat commands as void/Task and return read-model results via queries.

Commands

Commands could or could not return a value and are reserved to instructions that has the main goal of changing a piece of data. To use then:

Implement an ICommand and the corresponding ICommandHandler

public record MyCommand(string Name) : ICommand;

public class MyCommandHandler : ICommandHandler<MyCommand>
{
    public async Task Handle(MyCommand command, CancellationToken cancellationToken)
    {
        Console.WriteLine($"Hello {command.Name}");
    }
}

or, when it needs to return a value:

public record MyCommand(string Name) : ICommand<string>;

public class MyCommandHandler : ICommandHandler<MyCommand, string>
{
    public async Task<string> Handle(MyCommand command, CancellationToken cancellationToken)
    {
        return $"Hello {command.Name}";
    }
}

Queries

Queries are responsible to search and return a certain kind of data from the system. To accomplish that:

public record MyQuery(string Name) : IQuery<string>;

public class MyQueryHandler : IQueryHandler<MyQuery, string>
{
    public async Task<string> Handle(MyQuery query, CancellationToken cancellationToken)
    {
        return $"Hello {query.Name}";
    }
}