public class BloggingContext : DbContext
        {
            public BloggingContext(DbContextOptions<BloggingContext> options) : base(options){ }

            public virtual DbSet<Blog> Blogs { get; set; }
            public virtual DbSet<Post> Posts { get; set; }
        }

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

            public ICollection<Post> Posts { 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; }
        }

private readonly BloggingContext db;

        public ValuesController(BloggingContext db)
        {
            this.db = db;
        }

        // GET api/values
        [HttpGet]
        public ActionResult<IEnumerable<Blog>> Get()
        {
            return db.Blogs.ToList();
        }

var connection = @"Server=(localdb)mssqllocaldb;Database=EFGetStarted.AspNetCore.NewDb;Trusted_Connection=True;ConnectRetryCount=0";
            services.AddDbContext<Models.Model.BloggingContext>
                (options => options.UseSqlServer(connection));

Blogs Table Result
__________________
BlogId  |   Url
1       |   asdasd1
2       |   asdas2

Posts Table Result
__________
PostId  |   Title   |   Content |   BlogId
1       |   asdasd  |   fdg     |   1
2       |   fsg     |   asda    |   1
3       |   dsgfsdg |   sgf     |   2

[
  {
    "blogId": 1,
    "url": "asdasd1",
    "posts": null
  },
  {
    "blogId": 2,
    "url": "asdas2",
    "posts": null
  },
  {
    "blogId": 3,
    "url": "asdsad3",
    "posts": null
  }
]

[
  {
    "blogId": 1,
    "url": "asdasd1",
    "posts": [
      {
        "PostId": 1,
        "Title": "asdasd",
        "Content": "fdg"
      },
      {
        "PostId": 2,
        "Title": "fsg",
        "Content": "asda"
      }
    ]
  },
  {
    "blogId": 2,
    "url": "asdas2",
    "posts": {
      "PostId": 2,
      "Title": "fsg",
      "Content": "asda"
    }
  },
  {
    "blogId": 3,
    "url": "asdsad3",
    "posts": null
  }
]