CartesianView.cs

public ObservableCollection<TemperatureReading> ChartDataSource
        {
            get { return _datasource; }
            set
            {
                if (value != null)
                {
                    if (value.Count == 0)
                    {
                        _datasource = value;
                        _datasource.CollectionChanged += Datasource_CollectionChanged;
                    }
                    else if (value.Count > 0)
                    {
                        // we are reentering
                        var item = value.ElementAt(0);;
                        InitializeChart(item.SensorData.Keys.Count);
                        InitializeChartPalette();
                    }
                }

                if (HorizontalAxis == null)
                    InitializeHorizontalAxis();

                if (VerticalAxis == null)
                    InitializeVerticalAxis();
            }
        }

        void Datasource_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
        {
            if (e.NewItems != null && e.NewItems.Count > 0)
            {
                if (_temperatureChartValueCollection == null)
                {
                    var item = ChartDataSource.ElementAt(0);        // need to determine how many sensors are coming in

                    _temperatureChartValueCollection = new Com.Telerik.Android.Common.ObservableCollection();
                    InitializeChart(item.SensorData.Keys.Count);
                    InitializeChartPalette();
                }

                _temperatureChartValueCollection.Add(new TemperatureReadingChartValue((TemperatureReading)e.NewItems[0]));
            }

            if (e.Action == NotifyCollectionChangedAction.Remove)
            {
                // at this stage the first index is the one that is always being removed
                _temperatureChartValueCollection.Remove(0);
            }
        }