Annular.Modules 0.1.2-dev

Annular Modules

Trying to imitate Angular Modules in a way that makes sense for dotnet with IServiceCollection and IConfiguration.

Modules are registerd as IOptions and you can use the IOptions patterns to access them. By default the module is also registerd as a Scoped service and retrieves it's value from the IOptionsMonitor.CurrentValue.

What remains to be added is maybe a special method with a configuration object instead of only IConfiguration that can be used from the module to decide what to register in the service provider.

Usage

Simple

Create a class implementing the IModule interface:

public sealed class WeatherModule : IModule
{
    // This is called only once allowing us to register what we need
    // no matter if we are imported from another module.
    public static void Add(IServiceCollection services, IConfiguration configuration)
    {
        // register services
        services.AddScoped<IWeatherService, InternalWeatherService>();
        // ...
    }
}

Register the module:

// In Program.cs
// this will execute the `Add(IServiceCollection, IConfiguration)` method This is executed only once.
builder.Services.AddModule<WeatherModule>(builder.Configuration);

Validation

Implement IValidModule interface:

public sealed class WeatherModule : IModule, IValidModule
{
    public string ConnectionString {get; set;} = string.Empty;

    // This is called only once allowing us to register what we need
    // no matter if we are imported from another module.
    public static void Add(IServiceCollection services, IConfiguration configuration)
    {
        // register services
        services.AddScoped<IWeatherService, InternalWeatherService>();
        services.AddDbContext<>();
        // ...
    }

    public ValidateOptionsResult Validate()
    {
        return string.IsNullOrWhiteSpace(ConnectionString)
            ? ValidateOptionsResult.Fail("Connection string is not valid")
            : ValidateOptionsResult.Success;
    }
}

DbContext implementation

public class WeatherDbContext : DbContext
{
    // Weather module is registerd as scoped
    public WeatherDbContext(WeatherModule module)
    {
    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlServer(module.ConnectionString);
        // You could even provide a callback here
        // allowing for arbitary databases, connection strings etc.
    }
}

Advanced

Let's say we have a complex solution called Broker that is responsible to deliver all kinds of messages to our users using various ways like Email, SMS etc.

Our modules are:

• Data provides a way to talk to our database.
• Publisher provides ways to publish messages to a bus.
• REST API provides the REST API which internal services will use.
• Dashboard displays UI to see what is going on in our system database.
• Consumer provides ways to consume messages from a bus.

Module implementations:

public sealed class BrokerDataModule : IModule, IValidModule
{
    public string ConnectionString { get; set; } = string.Empty;

    public static void Add(IServiceCollection services, IConfiguration configuration)
    {
        // The project contains all Database Models etc and implements it in any way it
        // makes sense for it. When this is called all these services/handlers etc are registered.
    }

    public ValidateOptionsResult Validate()
    {
        return string.IsNullOrWhiteSpace(ConnectionString)
            ? ValidateOptionsResult.Fail("Connection string is not valid")
            : ValidateOptionsResult.Success;
    }
}

public sealed class BrokerPublisherModule : IModule
{
    public static void Add(IServiceCollection services, IConfiguration configuration)
    {
        services.AddModule<BrokerDataModule>(configuration);
        // we could also only focus on publishing and the consumer could focus on saving to the db
        // here we assume we want to save some details to the database before publishing to the bus.
    }
}

public sealed class BrokerRestApiModule : IModule
{
    public static void Add(IServiceCollection services, IConfiguration configuration)
    {
        // Register any services like caching, authorization policies etc.

        // Here we register the Data module since we will use the services to access the database data.
        services.AddModule<BrokerDataModule>(configuration);

        // Our API will provide endpoints to publish messages to internal services so we need the publishing services.
        services.AddModule<BrokerPublisherModule>(configuration);
    }
}

public sealed class BrokerDashboardModule : IModule
{
    public string ClientId { get; set; } = string.Empty;

    public string ApiUrl { get; set; } = string.Empty;

    public static void Add(IServiceCollection services, IConfiguration configuration)
    {
        // Register dashboard services like HttpClients, and OAuth.
        // this one assumes the dashboard is a SPA application served statically
        // on which we will provide the ClientId and ApiUrl since it might be server from anywhere.
    }
}

public sealed class BrokerConsumerModule : IModule
{
    public static void Add(IServiceCollection services, IConfiguration configuration)
    {
        // Register services needed so that you can consume messages from the bus.

        // Register the data module so that you can access and update the database.
        services.AddModule<BrokerDataModule>(configuration);
    }
}

This way all modules will register once while those that have validations will throw and make users provide their options. Since Configure is used internally you can also bind all of the modules to certain sections. This demonstrates that modules can use other modules.