Immediate.Handlers

Creating handlers

Handlers can be created by using the following code:

        [Handler]
public static partial class GetUsersQuery
{
    public record Query;

    private static ValueTask<IEnumerable<User>> HandleAsync(
        Query _,
        UsersService usersService,
        CancellationToken token
	)
    {
        return usersService.GetUsers();
    }
}

This will automatically generate a new class, GetUsersQuery.Handler, which encapsulates the following:

attaching any behaviors which may be relevant for the query
using a class to receive any DI services, such as UsersService

Consuming code can now do the following:

        public class Consumer(GetUsersQuery.Handler handler)
{
	public async Task Consumer(CancellationToken token)
	{
		var response = await handler.HandleAsync(new(), token);
		// do something with response
	}
}

For Command handlers, use a ValueTask, and Immediate.Handlers will insert a return type of ValueTuple to your handler automatically.

        [Handler]
public static partial class CreateUserCommand
{
    public record Command(string Email);

    private static async ValueTask HandleAsync(
        Command command,
        UsersService usersService,
        CancellationToken token
	)
    {
        await usersService.CreateUser(command.Email);
    }
}

public class Consumer(CreateUserCommand.Handler handler)
{
	public async Task Consumer(CancellationToken token)
	{
		await handler.HandleAsync(new(), token);
		// do something with response
	}
}

CancellationTokens are also optional, and may be omitted if unnecessary.

        [Handler]
public static partial class GetHelloResponse
{
    public record Query(string Name);

    private static ValueTask<string> Handle(Query query)
    {
        return ValueTask.FromResult($"Hello {query.Name}!");
    }
}

In case your project layout does not allow direct for references between consumer and handler, the handler will implement the IHandler<TRequest, Response> interface.

        public class Consumer(IHandler<GetUsersQuery.Query, IEnumerable<User>> handler)
{
	public async Task Consumer(CancellationToken token)
	{
		var response = await handler.HandleAsync(new(), token);
		// do something with response
	}
}

Registering with `IServiceCollection`

In your Program.cs, add a call to services.AddXxxHandlers(), where Xxx is the application identifier. By default, this is the short form of the assembly name. For example:

For a project named Web, it will be services.AddWebHandlers()
For a project named Application.Web, it will be services.AddApplicationWebHandlers()

However, this name can be overridden using [assembly: ImmediateAssemblyIdentifierAttribute("SomeIdentifier")].

Calling this AddXxxHandlers() method will register all classes in the assembly marked with [Handler].

Creating handlers

# Registering with IServiceCollection

Registering with `IServiceCollection`