using System;

using System.Collections.Generic;

using System.Linq;

using Microsoft.EntityFrameworkCore;

​

​

  public class BloggingContext : DbContext

    {

        public DbSet<Blog> Blogs { get; set; }

        public DbSet<Post> Posts { get; set; }

        public DbSet<Author> Authors { get; set; }

​

        // The following configures EF to create a Sqlite database file as `C:\blogging.db`.

        // For Mac or Linux, change this to `/tmp/blogging.db` or any other absolute path.

        protected override void OnConfiguring(DbContextOptionsBuilder options) 

            => options.UseSqlServer(@"Server=.\SQLEXPRESS;Database=SchoolDB;Trusted_Connection=True;");

        protected override void OnModelCreating(ModelBuilder modelBuilder)

        {

            base.OnModelCreating(modelBuilder);

        }

​

    }

​

    public class Author {

      public int AuthorId {get; set;}

      public string Name {get; set;}

    }

    public class Blog

    {

        public int AuthorId {get; set;}

        public int BlogId { get; set; }

        public string Url { get; set; }

​

        public List<Post> Posts { get;  set; } = new List<Post>();

        public Author Author {get; set;}

    }

​

    public class Post

    {

        public int PostId { get; set; }

        public string Title { get; set; }

        public string Content { get; set; }

​

        public int BlogId { get; set; }

        public Blog Blog { get; set; }

    }

​

​

​

public class Program

{

    public static void Main()

    {

        using var context = new BloggingContext();

        var blog = new Blog { BlogId = 1, Url = "aaa" };

        context.Blogs.Attach(blog);

        blog.Url = "bbb";

        blog.Author = new Author { Name = "Daniel Turan" };

        var changedEntries = context.ChangeTracker

                .Entries<Blog>() //detects changes

                .Where(e => e.State != EntityState.Unchanged)

                .ToArray();

​

​

           foreach (var entry in changedEntries.Where(e => e.State == EntityState.Modified))

        {  

           foreach(var p in entry.Properties.Where(p => p.IsModified)) 

           {

               Console.WriteLine($"{p.Metadata.Name}: {p.CurrentValue}");

           }

        } 

​

    }

}