public sealed class CreateLogCommand : ICommand { }
public sealed class CreateUserCommand : ICommand<int> { }

public sealed class GetUserQuery : IQuery<UserDto> { }

services.AddScoped<IDispatcher, Dispatcher>();

// Command (no return)
services.AddScoped<ICommandHandler<CreateLogCommand>, CreateLogHandler>();

// Command (with return)
services.AddScoped<ICommandHandler<CreateUserCommand, int>, CreateUserHandler>();

// Query
services.AddScoped<IQueryHandler<GetUserQuery, UserDto>, GetUserHandler>();

public sealed class CreateLogCommand : ICommand
{
    public string Message { get; init; } = string.Empty;
}

public sealed class CreateLogHandler : ICommandHandler<CreateLogCommand>
{
    public Task HandleAsync(CreateLogCommand cmd, CancellationToken ct = default)
    {
        Console.WriteLine($"LOG: {cmd.Message}");
        return Task.CompletedTask;
    }
}

await dispatcher.SendAsync(new CreateLogCommand { Message = "Hello!" });

public sealed class CreateUserCommand : ICommand<int>
{
    public string Email { get; init; } = string.Empty;
}

public sealed class CreateUserHandler : ICommandHandler<CreateUserCommand, int>
{
    private static int _nextId = 1;

    public Task<int> HandleAsync(CreateUserCommand cmd, CancellationToken ct = default)
    {
        return Task.FromResult(_nextId++);
    }
}

int id = await dispatcher.SendAsync(new CreateUserCommand { Email = "demo@test.com" });

public sealed class GetUserQuery : IQuery<UserDto>
{
    public int UserId { get; init; }
}

public sealed class GetUserHandler : IQueryHandler<GetUserQuery, UserDto>
{
    public Task<UserDto> HandleAsync(GetUserQuery query, CancellationToken ct = default)
    {
        return Task.FromResult(new UserDto { UserId = query.UserId });
    }
}

var user = await dispatcher.QueryAsync(new GetUserQuery { UserId = 10 });

[Fact]
public async Task SendAsync_CommandWithReturn_Should_Return_Id()
{
    var id = await dispatcher.SendAsync(new CreateUserCommand { Email = "abc@test.com" });
    Assert.True(id > 0);
}