For a Code Review exercise

CodeReviewExercise

using System.Collections.Generic;
using System.Linq;
 
namespace CodeReviewExercise
{
    using System;
    using Serilog;
 
    public class Customer
    {
        // when a customer gets to an interesting place we'd better tell
        // Globodex head office!
        public void UpdatePlace(string sessionGuid, double[] readings)
        {
  
            if (sessionGuid = "")
                throw new NotAGuidException();
 
            //calculates a value we will treat as a hash of the readings
            var h = readings.Where(r => r/3.14 > 3.14/2).Average();
 
            var newPlace = new Location(h);
            newPlace.Customer = this;
  
            int i;
  
            foreach (var read in readings)
            {
                var potentialPlace = this.LocateReadingOnTheMap(read, "com.demo");
                newPlace.PotentialPlaces.Add(potentialPlace);
                ++i;
            }
  
            Log.Information(
            "A new reading has been placed: " + newPlace.Id + " at " + DateTime.Now);
  
            CommunicationService.SendEmail(
                "Customer placed on a location!",
                "A new placed has been found: " + newPlace.Id + " at " + DateTime.Now,
                "locateriser@omniplex.io", "locationSupport@globodex.de");
        }
 
        /// <summary>
        /// This loads the map from disk, finds the reading on it and reutrns a place to represent that
        /// </summary>
        /// <param name="read">the Long that represents a reading</param>
        /// <param name="mapId"></param>
        /// <returns></returns>
        private Place LocateReadingOnTheMap(double read, string mapId)
        {
            //snip...
        }
    }
 
    internal class Place
    {
        //snip...
    }
 
    internal class Location
    {
        public double LocationHash { get; set; }
 
        public Location(double h)
        {
            LocationHash = h;
        }
 
        /// <summary>
        /// the customer
        /// </summary>
        public Customer Customer { get; set; }
 
        /// <summary>
        /// A string ID
        /// </summary>
        public Guid Id { get; set; }
 
        public List<Place> PotentialPlaces { get; set; }
    }
 
    public class NotAGuidException : Exception
    {
    }
}