DataAccessLayer.DataBase.GetAllPosts C# (CSharp) Method

        public List<Post> GetAllPosts()
        {
            string queryString =
                "SELECT [dbo].posts.postid, posts.postname, posts.source, posts.createdtime, posts.accountid, posts.rating, posts.[text], [dbo].accounts.[login], tag, [dbo].posts.mimetype " +
                "FROM [dbo].posts, [dbo].tags, [dbo].accounts " +
                "WHERE (([dbo].tags.postid = [dbo].posts.postid) AND ([dbo].posts.accountid = [dbo].accounts.accountid))";

            List<Post> _list;

            using (SqlConnection connection = new SqlConnection(_connectionString))
            {
                var command = new SqlCommand(queryString, connection);

                connection.Open();
                var reader = command.ExecuteReader();

                if (reader == null)
                {
                    return null;
                }

                _list = new List<Post>();

                while (reader.Read())
                {
                    _list.Add(new Post()
                    {
                        PostId = (Guid)reader[0],
                        NamePost = (string)reader[1],
                        Image = (byte[])reader[2],
                        CreatedTime = (DateTime)reader[3],
                        AccountId = (Guid)reader[4],
                        Rating = (int)reader[5],
                        Text = (string)reader[6],
                        AuthorName = (string)reader[7],
                        Tags = ((string)reader[8]).Split(','),
                        MimeType = (string)reader[9]
                    });
                    var exec = _list;
                }

                return _list;
            }
        }