How to get MainActivity for Intent created in another Xamarin.Droid class of the project?

Question

Android

I want to set an alarm for a Xamarin.Droid project. To do this, I use DependencyService to define platform-specific functions. I define an interface with a function signature

namespace ExampleProgram.Droid
{
    public interface IRunAlarm
    {
        Intent setIntent();
        ...
    }
}

and a class with an implementation.

[assembly: Dependency(typeof(ExampleProgram.Droid.RunAlarm))]
    namespace ExampleProgram.Droid
    {
        public class RunAlarm: MainActivity, IRunAlarm
        {
            public Intent setIntent()
            {
                Intent i = new Intent(this, typeof(AlarmReceiver));
                return i;
            }
            ...
        }
    }

When I run the program, an exception occurs

Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference

on this line:

Intent i = new Intent(this, typeof(AlarmReceiver));

AndroidManifest.xml:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" android:versionCode="3" android:versionName="3" package="com.example.exampleprogram">
    <uses-sdk android:minSdkVersion="15" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.MEDIA_CONTENT_CONTROL" />
    <uses-permission android:name="android.permission.WAKE_LOCK" />
    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
    <application android:label="exampleprogram" android:icon="@drawable/appicon"></application>
</manifest>

How to handle this exception, and how can MainActivity be correctly retrieved in this case?