AlarmManager not working after device is rebooted

I am insert multiple Alarms ,but after mobile restart its not working.

TodoActivity.cs

                 {
            Intent alarmIntent1 = new Intent(context, typeof(AlarmReceiver));
                  alarmManager = (AlarmManager)context.GetSystemService(Context.AlarmService);   
                  var dtBasis = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc); 
                  Intent alarmIntent = new Intent(context, typeof(AlarmReceiver));
                  alarmIntent.PutExtra("title", "To Do");
                   alarmIntent.PutExtra("message", Notifi.Description.ToString()); 
                    var dateString = AlaramDateTime.ToString("hh:mm tt, dddd dd MMMM");
                  alarmIntent.PutExtra("date", dateString);
                  var dateString1 = AlaramGetDueDateTime.ToString("hh:mm tt, dddd dd MMMM");
                   alarmIntent.PutExtra("duedatetime", dateString1);
                   alarmIntent.PutExtra("AlarmID", Notifi.NotificationId.ToString());                                                             
                   PendingIntent pendingIntent = PendingIntent.GetBroadcast(context, Notifi.NotificationId, alarmIntent, PendingIntentFlags.UpdateCurrent);
                    var firstTime = (long)Notifi.NotificationDateTime.ToUniversalTime().Subtract(dtBasis).TotalMilliseconds;
                    alarmManager.Set(AlarmType.RtcWakeup, firstTime, pendingIntent);
          }

AlarmReceiver.cs

      [BroadcastReceiver]
        [IntentFilter(new[] { Intent.ActionBootCompleted })]
         public class AlarmReceiver : BroadcastReceiver
        {
            DateTime date, date1;
            private static Intent notIntent;
            public static List<LanguageCode> Language = new List<LanguageCode>();
            private static List<Timeformat> timeformat = new List<Timeformat>();

            public override void OnReceive(Context context, Intent intent)
            {

                try
                {

                    if ((intent.Action != null) && (intent.Action == Intent.ActionBootCompleted))
                    {
                        logger.Trace("ALARAM ActionBootCompleted");
                     // context.StartService(new Intent(context, typeof(AlarmService)));

                    }     
                    logger.Trace("ALARAM");
                    Context mContext = Android.App.Application.Context;
                    AppPreferences ap = new AppPreferences(mContext);

                    var message = intent.GetStringExtra("message");
                    var title = intent.GetStringExtra("title");
                    var MediID = intent.GetStringExtra("MediID");
                    var Time = intent.GetStringExtra("date");
                    var Alarmid = intent.GetStringExtra("AlarmID");
                    var dueTime = intent.GetStringExtra("duedatetime"); 

                        notIntent = new Intent(context, typeof(MainActivity));
                        id = Resource.Drawable.ic_blkreminder;
                        notIntent.PutExtra("Title", title);
                        notIntent.PutExtra("Message", message);
                        notIntent.PutExtra("AlarmTime", Time);
                        notIntent.PutExtra("MedicineAlarmID", Alarmid);
                        notIntent.PutExtra("DueDateTime", dueTime);


                    PendingIntent contentIntent = PendingIntent.GetActivity(context, 0, notIntent, PendingIntentFlags.CancelCurrent);
                    Notification.Builder builder;
                    Notification.BigTextStyle textStyle = new Notification.BigTextStyle();

                        builder = new Notification.Builder(context)
                                  .SetSmallIcon(id)
                                  .SetContentTitle(alatit)
                                  .SetDefaults(NotificationDefaults.Sound)
                                  .SetContentText(message)
                                  .SetAutoCancel(true)
                                  .SetContentIntent(contentIntent);


                    builder.SetStyle(textStyle); 
                    builder.SetSound(RingtoneManager.GetDefaultUri(RingtoneType.Ringtone));
                    builder.SetLargeIcon(BitmapFactory.DecodeResource(context.Resources, Resource.Drawable.SmdLogo));

                    Notification notification = builder.Build(); 
                    NotificationManager mNotificationManager = (NotificationManager)context.GetSystemService(Context.NotificationService); 
                    // Turn on vibrate:
                    notification.Flags |= NotificationFlags.Insistent; 

                    mNotificationManager.Notify(1, notification);
                }
                catch(Exception ex)
                {
                    logger.Trace(ex.ToString());
                }
            }
        }

AndroidManifest.xml

    <?xml version="1.0" encoding="utf-8"?>
    <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.Smart.Smart" android:versionCode="1" android:versionName="1.0" android:installLocation="internalOnly">
        <uses-sdk android:minSdkVersion="16" />
        <uses-permission android:name="android.permission.WAKE_LOCK" />
        <uses-permission android:name="com.android.alarm.permission.SET_ALARM" />
        <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
        <uses-permission android:name="android.permission.READ_CALENDAR" />
        <uses-permission android:name="android.permission.WRITE_CALENDAR" />
        <uses-permission android:name="android.permission.INTERNET" />
        <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
        <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
        <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
        <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
        <application 
        android:label="Smart"
        android:icon="@drawable/SMART"
        android:hardwareAccelerated="false"
        android:largeHeap="true">
        <!--<service android:name=".AlarmService"/>-->
         <!--<receiver android:name=".AlarmReceiver"></receiver>--> 
         <receiver android:name=".AlarmReceiver" android:enabled="true" >
         <intent-filter>
           <action android:name="android.intent.action.BOOT_COMPLETED" />
           <category android:name="android.intent.category.DEFAULT" />
           <action android:name="android.intent.action.QUICKBOOT_POWERON"/>
        </intent-filter>
        </receiver> 
        </application>
    </manifest>