xamarin SetAlarm on a DateTime - xamarin

Question

I wish to set the alarm so that it sends a notification whenever the alarm is fired. The below code which I have, the alarmDate.Millisecond returns 0 (because it was never set). It should return the correct millis for the alarm to work - I think it takes the milliseconds for UTC - But the time has to be GMT/DST in the UK.
Code:
private void InitBroadcast()
{
// Build the intents
var intent = new Intent(this, typeof(MyReceiver));
var pendingIntent = PendingIntent.GetBroadcast(this, 0, intent, 0);
var alarmManager = (AlarmManager)GetSystemService(AlarmService);
// Build the dates
var currentDate = DateTime.Now;
var alarmDate = new DateTime(currentDate.Year, currentDate.Month, currentDate.Day, 5, 29, 0, DateTimeKind.Local);
// If the alarm time has already past, set the alarm date to tomorrow
if (DateTime.Compare(currentDate, alarmDate) < 0) {
alarmDate.AddDays(1);
}
alarmManager.SetRepeating(AlarmType.RtcWakeup, alarmDate.Millisecond, millisInADay, pendingIntent);
textView.SetText(string.Format("Alarm set for {0}", alarmDate.ToString()), TextView.BufferType.Normal);
}

Answer 1

Check the docs: https://learn.microsoft.com/en-us/dotnet/api/system.datetime.millisecond?view=netframework-4.7.2#System_DateTime_Millisecond
The milliseconds component, expressed as a value between 0 and 999.
So alarmDate.Millisecond does not return 0 because it was never set, it returns 0 because it was set to zero then you created the DateTime object with alarmDate = new DateTime(currentDate.Year, currentDate.Month, currentDate.Day, 5, 29, 0, DateTimeKind.Local);
See: https://learn.microsoft.com/en-us/dotnet/api/system.datetime.-ctor?view=netframework-4.7.2#System_DateTime__ctor_System_Int32_System_Int32_System_Int32_System_Int32_System_Int32_System_Int32_System_DateTimeKind_
You are setting the time to the current date at 5:29 am ( with 0 for the seconds, so the 0 for milliseconds is implied).
alarmDate.Ticks would give you the umber of "Ticks" (1/10,000 of a millisecond) that have elapsed since the beginning of the twenty-first century. But do keep in mind what SushiHangover said in the so link in his comment
Android's AlarmManager is based upon Android/Linux Epoch milliseconds
not .NET DateTime ticks. Epoch milliseconds are the number of milliseconds that have elapsed since January 1, 1970 at 00:00:00 GMT (1970-01-01 00:00:00 GMT).
So instead of passing in alarmDate.Millisecond to the alarmManager.SetRepeating method, use a TimeSpan between the current time and Jan 1, 1970 midnight GMT to get the epoch milliseconds and pass that in instead, e.g.:
var epochMs = (alarmDate - new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc)).TotalMilliseconds;
alarmManager.SetRepeating(AlarmType.RtcWakeup, (Int64)epochMs, millisInADay, pendingIntent);