using System;
using System.Linq;
using System.Diagnostics.Tracing;
using Microsoft.ApplicationInsights;
using Microsoft.ApplicationInsights.Extensibility;

namespace ConsoleApp1
{
    internal sealed class MyEventListener : EventListener
    {
        public EventSource RichPayloadEventSource;

        protected override void OnEventSourceCreated(EventSource eventSource)
        {
            if (eventSource.Name == "Microsoft-ApplicationInsights-Data")
            {
                RichPayloadEventSource = eventSource;
            }

            base.OnEventSourceCreated(eventSource);
        }
    }

    class Program
    {
        private static string GetEnabledLevels(EventSource eventSource)
            => string.Join('|',
                from EventLevel level in Enum.GetValues(typeof(EventLevel))
                where eventSource.IsEnabled(level, EventKeywords.All)
                select level);

        static void Main(string[] args)
        {
            using (var myListener = new MyEventListener())
            {
                // This has the effect of creating the RichPayloadEventSource.
                // Use an unconfigured TelemetryConfiguration so we don't get the
                // DiagnosticsTelemetryModule added. Note that when config is Disposed,
                // TelemetryConfiguration.Active is reset to null.
                using (var config = new TelemetryConfiguration())
                {
                    new TelemetryClient(config).TrackEvent("Startup");
                }

                // This has the side-effect of creating TelemetryConfiguration.Active with
                // DiagnosticsTelemetryModule added. It hooks up an EventListener for all
                // Microsoft-ApplicationInsights-* event sources, including the
                // RichPayloadEventSource. It's supposed to use EventLevel.Error.
                new TelemetryClient().TrackEvent("Hello!");

                // This prints: LogAlways|Critical|Error|Warning|Informational|Verbose
                // It's supposed to print LogAlways|Critical|Error
                Console.WriteLine(GetEnabledLevels(myListener.RichPayloadEventSource));
            }
        }
    }
}