Xamarin.Forms (as of 1.4.2.6359) SearchBar with filter and grouping

cs (codebehind)

// should be able to bind to this in XAML, but haven't found success doing this yet
            search.TextChanged += (sender, args) => { ViewModel.Filter(args.NewTextValue); };

Grouping.cs

using System.Collections.Generic;
using System.Collections.ObjectModel;

// from Xamarin Monkey demo - http://motzcod.es/post/93792500152/custom-listview-viewcells-in-xamarin-forms
namespace Interact.Core.Helper {
    public class Grouping<TKey, TValue> : ObservableCollection<TValue> {
        public TKey Key { get; private set; }
        public Grouping(TKey key, IEnumerable<TValue> items) {
            Key = key;
            foreach (var item in items)
                this.Items.Add(item);
        }
    }
}

ViewModel.cs

        public void Filter(string filter) {
            filteredPeople.Clear();
            if (string.IsNullOrEmpty(filter)) {
                GroupCollections(list); 
            }
            else {
                foreach (var person in people) {
                    if (person.FullName.ToLower().Contains(filter.ToLower())) {
                        filteredPeople.Add(person);
                    }
                }
                GroupCollections(filteredPeople); 
            }           
        }
        
        // the general idea, edited in-situ to make it a bit generic
        private void GroupCollections(ObservableCollection<Detail> ToBeGrouped) {
            peopleGrouped.Clear();
            var sorted = from people in ToBeGrouped
                         orderby people.NameSort
                         group people by people.NameSort into peopleGroup
                         select new Grouping<string, Detail>(peopleGroup.Key, peopleGroup);
            peopleGrouped = new ObservableCollection<Grouping<string, Detail>>(sorted);
        }

XAML

    <SearchBar x:Name="search" Placeholder="Search" />