InMemory creates new row for modified entries that do not exist

[rowanmiller]

The code below gives the following output, meaning that a new row gets created for the modified state entry even though no row with that key exists.

Modified
22 - blogs.msdn.com/dotnet
Press any key to continue . . .

using Microsoft.Data.Entity;
using System;
using System.Linq;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            using (var db = new BloggingContext())
            {
                db.Blogs.Update(new Blog { Id = 22, Url = "blogs.msdn.com/dotnet" });
                Console.WriteLine(db.ChangeTracker.Entries().Single().State);
                db.SaveChanges();
            }

            using (var db = new BloggingContext())
            {
                foreach (var item in db.Blogs)
                {
                    Console.WriteLine($"{item.Id} - {item.Url}");
                }
            }
        }
    }

    public class Blog
    {
        public int Id { get; set; }
        public string Url { get; set; }
    }

    public class BloggingContext : DbContext
    {
        public DbSet<Blog> Blogs { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseInMemoryDatabase();
        }
    }
}

[rowanmiller]

Make sure we also test the delete case from #4515

[ajcvickers]

Already fixed as part of #4680