How to fill an array with data in C#?

Question

C++ / C#

I was advised in C# to use classes to describe the data structure. Here is a description of my data.

namespace DBSync.Model

{
   public  class UserData
    {
        public string Id { get; set; }
        public string Guid { get; set; }
        public string Name { get; set; }
        public byte[] UserBlob { get; set; }
        public string FL { get; set; }

     
    };
}

In the database class, I do the following:
private UserData ud = new UserData(); // created an instance
Fill in:

public UserData GetData()
        {
            try
            {
                string sql = @"SELECT id, guid, username, userblob, ""FL"" FROM ""USERS"" WHERE ""FL""=10;";

                NpgsqlCommand command = new NpgsqlCommand(sql, (NpgsqlConnection)Connection);

                NpgsqlDataReader dr = command.ExecuteReader(); // here exception
                if (!dr.HasRows)
                {
                    Console.ForegroundColor = ConsoleColor.Cyan;
                    Console.WriteLine("[INFO] PostgreSQL do not have data with FL=10");
                    Console.ResetColor();
                }
                int i = 0;
                while (dr.Read())
                {
                    // UserData ud = new UserData();
                    ud.Id = dr[0].ToString();
                    ud.Guid = (dr[1].ToString());
                    ud.Name = (dr[2].ToString());
                    ud.UserBlob = (byte[])dr[3];
                    ud.FL = dr[4].ToString();
                    i++;
                }
                Console.ForegroundColor = ConsoleColor.Green;
                Console.WriteLine("[INFO] Syncronisated PG->SQLite rows: {0}", i);
                Console.ResetColor();
                dr.Dispose(); // releases connection
                try
                {
                    sqllite.Connect();
                    sqllite.InsertData(ud);
                    string sqlUpdate = @"UPDATE ""USERS"" SET ""FL""=11 WHERE ""FL""=10;";
                    //NpgsqlCommand commandUpdate = new NpgsqlCommand(sql, (NpgsqlConnection)Connection);
                    NpgsqlCommand cmd = new NpgsqlCommand(sqlUpdate, (NpgsqlConnection)Connection);
                    cmd.ExecuteNonQuery();

                    if (i > 0)
                    {
                        Console.WriteLine("Flags in PostgreSQL set to 11 (waiting for sync)");
                    }
                        
                    sqllite.CloseConnect();
                    Console.ReadKey();

                }
                catch (Exception e)
                {
                    Console.WriteLine(e.Message);
                    Console.WriteLine("Can't insert data to SQLite");
                }
                

            }

            catch (Exception e)
            {
                Console.WriteLine("SelectDataForSync function");
                Console.WriteLine(e.Message);
            }

            return ud;
        }

But the problem is that only the latest data will get into my copy here. It's not an array of instances, but one instance. How to be then?
I need to take the data and then insert what I collected into another database.

Answer 1

you need to use List
For each entry create a new instance and add (Add() method) it to the list
UPD: something like this

List<UserData> usersList = new List<UserData>(); //создали список
while (dr.Read())
{
   UserData ud = new UserData(); //создаем один экземпляр
   ud.Id = dr[0].ToString(); //наполняем его
   ud.Guid = (dr[1].ToString());
   ud.Name = (dr[2].ToString());
   ud.UserBlob = (byte[])dr[3];
   ud.FL = dr[4].ToString();

   usersList.Add(ud); //добавляем в список
}

int usersCount = usersList.Count; //количество элементов в списке
Console.WriteLine("[INFO] Syncronisated PG->SQLite rows: {0}", usersCount);

Answer 2

smsc.ru

Answer 3

Where / to whom to send is not very clear?