EF6.x | Same context instance to different databases

Demo.cs

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

namespace ConsoleApplication1
{
    class Program
    {
        private static string connection_one = "Server=(localdb)\\mssqllocaldb;Database=Blogging_One;Trusted_Connection=True;";
        private static string connection_two = "Server=(localdb)\\mssqllocaldb;Database=BLogging_Two;Trusted_Connection=True;";

        static void Main(string[] args)
        {
            SetupTestData();

            using (var db = new TestContext())
            {
                db.Database.Connection.ConnectionString = connection_one;
                var blog = db.Blogs.First();
                blog.Url += "/modified";

                db.Database.Connection.ConnectionString = connection_two;
                db.SaveChanges();
            }
        }

        private static void SetupTestData()
        {
            var blog = new Blog { Url = "http://sample.com", BlogId = new Guid() };

            using (var db = new TestContext())
            {
                db.Database.Connection.ConnectionString = connection_one;
                db.Database.CreateIfNotExists();
                db.Blogs.Add(blog);
                db.SaveChanges();
            }

            using (var db = new TestContext())
            {
                db.Database.Connection.ConnectionString = connection_two;
                db.Database.CreateIfNotExists();
                db.Blogs.Add(blog);
                db.SaveChanges();
            }
        }
    }

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

    public class Blog
    {
        public Guid BlogId { get; set; }
        public string Url { get; set; }
    }
}