using System;

using System.Linq;

using System.Text.Json;

using System.Collections;

using System.Collections.Generic;

using System.Timers;

using System.Diagnostics;

​

public enum AlarmSeverityLevel

{

    Unknown = 0,

    Bad = 1,

    ReallyBad = 2,

    ReallyReallyBad = 3,

    ReallyReallyReallyBad = 3,

}

​

public class Program

{

    public static void Main()

    {

        var stopwatch = new Stopwatch();

        stopwatch.Start();

​

        int count = 0;

        Foo((o) => {count += o.Count;});

        stopwatch.Stop();

        var timeSpan = stopwatch.Elapsed;

        Console.WriteLine("Total elapsed Timespan = {0}, count = {1}", timeSpan, count);

    }

    static void Foo(Action<IList> businessLogicFunction)

    {

#if false

        var alarms = from healthIssue in _context.HealthIssues.AsNoTracking()

            join asset in _context.Assets.AsNoTracking() on healthIssue.AssetNumber equals asset.SerialNumber into joinedTable

            from data in joinedTable.DefaultIfEmpty()

            select new

        {

            ID = 101,

            AssetNumber = 202,                                                         

            AlarmName = "flarb", 

            Crew = "my crew"; 

        };

        var alarmsViewModelList = await alarms.ToListAsync();

#else

        var alarms = Enumerable.Range(0, 30000).Select(i =>

                                                       new

                                                       {

                                                           ID = 101,

                                                           AssetNumber = 202 + (i % 12000),                                                         

                                                           AlarmName = "flarb", 

                                                           Crew = "no idea what this is",

                                                           AlarmSeverityLevel = (AlarmSeverityLevel)((i + 1) % 5),

                                                           AlarmLastUpdatedTime = 10101L + i,

                                                       });

        var alarmsViewModelList = alarms.ToList();

#endif      

        var groupedData = alarmsViewModelList

            .Where(c => c.AlarmSeverityLevel != AlarmSeverityLevel.Unknown)

            .GroupBy(c => new { c.AssetNumber, c.AlarmName })

            .Select(g => g.Select(c =>

                                  new {

                                      HealthIssueID = c.ID,

                                      AlarmLastUpdateDateTime = DateTimeHelpers.FromEpochSecondsUTC(c.AlarmLastUpdatedTime),

                                      AlarmSeverityLevel = c.AlarmSeverityLevel,

                                  }).OrderByDescending(c =>c.AlarmLastUpdateDateTime).ToList())

            .Where(l => l.Count > 0);

        foreach (var alarmList in groupedData)

            businessLogicFunction(alarmList);

    }

}

​

public static class DateTimeHelpers

{

    public static DateTime FromEpochSecondsUTC(long seconds) => DateTime.UtcNow; // Some dummy method for compilation purposes.

}

​