C
C#•3w ago
SWEETPONY

✅ How to make static field required to use from interface?

I have this interface: 
public interface IEventProcessor
{
    public static IReadOnlyCollection<string> HandledEvents { get; } = [];
}
public interface IEventProcessor
{
    public static IReadOnlyCollection<string> HandledEvents { get; } = [];
}
HandledEvents is static because I can easily read values from it using reflection and without Activator.CreateInstance Processor example: 
public sealed class FlightEventProcessor(JsonSerializerOptions serializerOptions): IEventProcessor
{
    public static string[] HandledEvents => ["FlightAdded", "FlightUpdated"];
}
public sealed class FlightEventProcessor(JsonSerializerOptions serializerOptions): IEventProcessor
{
    public static string[] HandledEvents => ["FlightAdded", "FlightUpdated"];
}
the main problem HandledEvents can be easily removed from FlightEventProcessor and nothing will happens. compilator allows me to not implement this array inside every classes that inherit IEventProcessor
4 Replies
SWEETPONY
SWEETPONYOP•3w ago
thanks!
SleepWellPupper
SleepWellPupper•3w ago
because I can easily read values from it using reflection
You should rethink your design imo. Why do these need to be static anyway?
SWEETPONY
SWEETPONYOP•3w ago
because I don't want to create instance of the class to read values 
public sealed class EventProcessorFactory(IServiceProvider provider): IEventProcessorFactory
{
    private static readonly Lazy<Dictionary<string, Type>> processors = new(DiscoverEventProcessors);

    public IEventProcessor? GetProcessor(string eventName)
    {
        if(!processors.Value.TryGetValue(eventName, out var type))
            return null;

        return (IEventProcessor)provider.GetRequiredService(type);
    }

    private static Dictionary<string, Type> DiscoverEventProcessors()
    {
        var processorTypes = Assembly.GetExecutingAssembly().GetTypes()
            .Where(t => typeof(IEventProcessor).IsAssignableFrom(t) && t.IsClass)
            .ToArray();

        var discoverEventProcessors = new Dictionary<string, Type>();

        foreach(var processorType in processorTypes)
        {
            var handledEvents = processorType
                .GetProperty(nameof(IEventProcessor.HandledEvents))
                ?.GetValue(null) as IReadOnlyCollection<string>;

            foreach(var handledEvent in handledEvents ?? [])
                discoverEventProcessors[handledEvent] = processorType;
        }

        return discoverEventProcessors;
    }
}
public sealed class EventProcessorFactory(IServiceProvider provider): IEventProcessorFactory
{
    private static readonly Lazy<Dictionary<string, Type>> processors = new(DiscoverEventProcessors);

    public IEventProcessor? GetProcessor(string eventName)
    {
        if(!processors.Value.TryGetValue(eventName, out var type))
            return null;

        return (IEventProcessor)provider.GetRequiredService(type);
    }

    private static Dictionary<string, Type> DiscoverEventProcessors()
    {
        var processorTypes = Assembly.GetExecutingAssembly().GetTypes()
            .Where(t => typeof(IEventProcessor).IsAssignableFrom(t) && t.IsClass)
            .ToArray();

        var discoverEventProcessors = new Dictionary<string, Type>();

        foreach(var processorType in processorTypes)
        {
            var handledEvents = processorType
                .GetProperty(nameof(IEventProcessor.HandledEvents))
                ?.GetValue(null) as IReadOnlyCollection<string>;

            foreach(var handledEvent in handledEvents ?? [])
                discoverEventProcessors[handledEvent] = processorType;
        }

        return discoverEventProcessors;
    }
}
333fred
333fred•3w ago
Because no shadowing is involved They're just entirely unrelated, period

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