isDeleteItem.cs

using Microsoft.Practices.Prism.Mvvm;
using Reactive.Bindings;
using Reactive.Bindings.Extensions;
using System;
using System.Collections.ObjectModel;
using System.Linq;
using System.Reactive.Linq;
using System.Threading;

namespace RxPropEdu
{
    class Program
    {
        static void Main(string[] args)
        {
            SynchronizationContext.SetSynchronizationContext(new SynchronizationContext());

            var deleted = new ObservableCollection<Person>();
            var c = new ObservableCollection<Person>(
                Enumerable.Range(1, 10).Select(x => new Person { Name = "tanaka" + x }));

            c.ObserveElementProperty(x => x.IsDelete)
                .Subscribe(x =>
                {
                    if (x.Value)
                    {
                        deleted.Add(x.Instance);
                    }
                    else
                    {
                        deleted.Remove(x.Instance);
                    }
                });
            c.ObserveAddChangedItems()
                .Merge(c.ObserveReplaceChangedItems().Select(xs => xs.NewItem))
                .Subscribe(xs =>
                {
                    foreach (var p in xs)
                    {
                        if (p.IsDelete) { deleted.Add(p); }
                    }
                });
            c.ObserveRemoveChangedItems()
                .Merge(c.ObserveReplaceChangedItems().Select(xs => xs.OldItem))
                .Subscribe(xs =>
                {
                    foreach (var x in xs) { deleted.Remove(x); }
                });

            var isDeleted = deleted.CollectionChangedAsObservable()
                .Select(_ => deleted.Count != 0)
                .ToReactiveProperty();

            Console.WriteLine(isDeleted);

            c[0].IsDelete = true;

            Console.WriteLine(isDeleted);

            c.RemoveAt(0);

            Console.WriteLine(isDeleted);
        }
    }

    class Person : BindableBase
    {
        private string name;

        public string Name
        {
            get { return this.name; }
            set { this.SetProperty(ref this.name, value); }
        }

        private bool isDelete;

        public bool IsDelete
        {
            get { return this.isDelete; }
            set { this.SetProperty(ref this.isDelete, value); }
        }

    }
}