CSharp-DatabaseAdvanced - ExamPrep I

 public static string ImportPosts(InstagraphContext context, string xmlString)
        {
            StringBuilder sb = new StringBuilder();

            // защо не се десериализират с вградения метод за десерилизация:
            //var serializer = new XmlSerializer(typeof(PostDto[]), new XmlRootAttribute("posts"));
            //var deserializedPosts = (PostDto[])serializer.Deserialize(new MemoryStream(Encoding.UTF8.GetBytes(xmlString)));


            var xml = XDocument.Parse(xmlString);
            var deserializedPosts = xml.Root.Elements();

            var validPosts = new List<Post>();

            foreach (var post in deserializedPosts)
            {
                string caption = post.Element("caption")?.Value;
                string user = post.Element("user")?.Value;
                string picture = post.Element("picture")?.Value;

                bool isValid = !String.IsNullOrWhiteSpace(caption) &&
                                !String.IsNullOrWhiteSpace(user) &&
                                !String.IsNullOrWhiteSpace(picture);

                if (!isValid)
                {
                    sb.AppendLine(errorMsg);
                    continue;
                }

                bool isUserExists = context.Users.Any(u => u.Username == user);
                bool isPicureExists = context.Pictures.Any(u => u.Path == picture);

                Post currPost = null;
                if (isPicureExists && isUserExists)
                {
                    var currUser= context.Users.FirstOrDefault(u => u.Username == user);
                    var currPicure = context.Pictures.FirstOrDefault(u => u.Path == picture);
                    currPost = new Post()
                    {
                        Caption = caption,
                        User = currUser,
                        Picture = currPicure
                    };
                    validPosts.Add(currPost);
                    sb.AppendLine(String.Format(successMsg, $"Post {currPost.Caption}"));
                }
                else
                {
                    sb.AppendLine(errorMsg);
                    continue;
                }

            }
            context.Posts.AddRange(validPosts);
            context.SaveChanges();

            return sb.ToString().TrimEnd();
        }