Xamarin - phone call events / state

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C#

Xamarin

Hi,
I'm very new to Xamarin and mobile development, but have an experience with C#.
Following is my attempt to take some code from the web and adjusting it to Xamarin.
The code fails on exception, while placing a call.
I, actually, can't reach breakpoints in my CallReceiver / PhonecallReceiver classes.
I'm running VS2017 community, API23, arm phone.
What I'm missing?

What I have tried:

MainActivity:

using System;
using Android.App;
using Android.Content;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Android.OS;
using Android.Telephony;
using Java.Lang;
using String = System.String;
using System.Collections.Generic;
using Java.Util;
using Javax.Security.Auth;

namespace CallManipulation
{
    public abstract class PhonecallReceiver : BroadcastReceiver
    {
    private static CallState lastState = CallState.Idle;
    private static DateTime callStartTime;
    private static bool isIncoming;
    private static String savedNumber;


    public override void OnReceive(Context context, Intent intent)
    {
        if (intent.Action.Equals("android.intent.action.NEW_OUTGOING_CALL"))
        {
            savedNumber = intent.Extras.GetString("android.intent.extra.PHONE_NUMBER");
        }
        else
        {
            String stateStr = intent.Extras.GetString(TelephonyManager.ExtraState);
            String number = intent.Extras.GetString(TelephonyManager.ExtraIncomingNumber);
            CallState state = CallState.Idle;

            if (stateStr.Equals(TelephonyManager.ExtraStateIdle))
            {
                state = CallState.Idle;
            }
            else if (stateStr.Equals(TelephonyManager.ExtraStateOffhook))
            {
                state = CallState.Offhook;
            }
            else if (stateStr.Equals(TelephonyManager.ExtraStateRinging))
            {
                state = CallState.Ringing;
            }

            OnCallStateChanged(context, state, number);
        }
    }

    protected virtual void onIncomingCallStarted(Context ctx, String number, DateTime start) { }
    protected virtual void onOutgoingCallStarted(Context ctx, String number, DateTime start) { }
    protected virtual void onIncomingCallEnded(Context ctx, String number, DateTime start, DateTime end) { }
    protected virtual void onOutgoingCallEnded(Context ctx, String number, DateTime start, DateTime end) { }
    protected virtual void onMissedCall(Context ctx, String number, DateTime start) { }

        public void OnCallStateChanged(Context context, CallState state, string number)
        {
            if (lastState == state)
                return;
            switch (state)
            {
                case CallState.Ringing:
                    isIncoming = true;
                    callStartTime = new DateTime().Date;
                    savedNumber = number;
                    onIncomingCallStarted(context, number, callStartTime);
                    break;
                case CallState.Offhook:
                    if (lastState != CallState.Ringing)
                    {
                        isIncoming = false;
                        callStartTime = new DateTime().Date;
                        onOutgoingCallStarted(context, savedNumber, callStartTime);
                    }
                    break;
                case CallState.Idle:
                    if (lastState == CallState.Ringing)
                        onMissedCall(context, savedNumber, callStartTime);
                    else if (isIncoming)
                        onIncomingCallEnded(context, savedNumber, callStartTime, new DateTime().Date);
                    else
                        onOutgoingCallEnded(context, savedNumber, callStartTime, new DateTime().Date);
                    break;
            }
            lastState = state;
        }
    }

    public class CallReceiver : PhonecallReceiver
    {
        protected override void onIncomingCallStarted(Context ctx, string number, DateTime start)
        {
        }

        protected override void onOutgoingCallStarted(Context ctx, string number, DateTime start)
        {
        }

        protected override void onIncomingCallEnded(Context ctx, string number, DateTime start, DateTime end)
        {
        }

        protected override void onOutgoingCallEnded(Context ctx, string number, DateTime start, DateTime end)
        {
        }

        protected override void onMissedCall(Context ctx, string number, DateTime start)
        {
        }
    }

    [Activity(Label = "CallManipulation", MainLauncher = true, Icon = "@drawable/icon")]
    public class MainActivity : Activity
    {
        int count = 1;


        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);
        }
    }
}

Manifest:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="CallManipulation.CallManipulation" android:versionCode="1" android:versionName="1.0">
  <uses-sdk android:minSdkVersion="16" />
  <uses-permission android:name="android.permission.READ_PHONE_STATE" />
  <uses-permission android:name="android.permission.PROCESS_OUTGOING_CALLS"/>
  <application android:label="CallManipulation">
    <!--This part is inside the application-->
    <receiver android:name=".CallReceiver" >
      <intent-filter>
        <action android:name="android.intent.action.PHONE_STATE" />
      </intent-filter>
      <intent-filter>
        <action android:name="android.intent.action.NEW_OUTGOING_CALL" />
      </intent-filter>
    </receiver>
  </application>
</manifest>