Persistence.cs

private static void Main(string[] args)
{
    DbContextOptionsBuilder<MyContext> builder = new DbContextOptionsBuilder<MyContext>();
    builder.UseSqlServer("<connection string>");
    Guid blogId;
    Guid postIdToRemove;

	  // Let's create the Aggregate root first i.e. Blog
    using(var ctx = new MyContext(builder.Options))
    {
        var blog = new Blog("Aman'sThoughts.com");
        ctx.Blogs.Add(blog);
        ctx.SaveChanges();
        blogId = blog.Id;
    }

	  // Now let's publish some posts in the blog
    using (var ctx = new MyContext(builder.Options))
    {
        var blog = ctx.Blogs.Where(x => x.Id == blogId).Include(x => x.Posts).FirstOrDefault();
        blog.CreatePost("Migrating from EF Core 2. to EF Core 3.0", "Its a bit broken!");
        blog.CreatePost("Migrating from .NET Core 2.2 to NET Core 3.1", "Went kinda ok!");
        ctx.SaveChanges(); // <--- this is where it blows up!
    }
}