分组查询时无法使用ExecuteReader（）检索数据

Question

I need to retrieve the information stored in a database of some thousand items. If I go one by one by this way it takes a large amount of time (tac is a 8-character string):

string connectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=DataBase\IMEIDB.accdb";
using (OleDbConnection connection = new OleDbConnection(connectionString))
{
    connection.Open();
    using (OleDbCommand command = connection.CreateCommand())
    {
        OleDbDataReader reader;
        command.CommandText = "SELECT TAC, Name, Model, Year, Manufacturer, LTE FROM Terminales WHERE TAC = @tac";
        command.Parameters.AddWithValue("@tac", tac);
        reader = command.ExecuteReader();
        while (reader.Read())
        {
            ulong tac = Convert.ToUInt64(reader.GetString(0));
            if (this.DiccionarioTerminales.ContainsKey(tac))
            {
                DiccionarioTerminales[tac].inDB = true;
                DiccionarioTerminales[tac].Name = reader.GetValue(1).ToString();
                DiccionarioTerminales[tac].Manufacturer = reader.GetValue(2).ToString();
                DiccionarioTerminales[tac].Model = reader.GetValue(3).ToString();
                DiccionarioTerminales[tac].Year = reader.GetValue(4).ToString();
                DiccionarioTerminales[tac].LTE = reader.GetValue(5).ToString();
            }
        }
        command.Dispose();
    }
    connection.Dispose();
}

It works well (I know I must use ExecuteNonQuery() if it's only one record, but this example is only a test), but if I try to group the tac 10 by 10 (now tac is a string like 'xxxxxxxx','xxxxxxxx','xxxxxxxx','xxxxxxxx'... ) with the next changes in my code...

OleDbDataReader reader;
command.CommandText = "SELECT TAC, Name, Model, Year, Manufacturer, LTE FROM Terminales WHERE TAC IN (@tac)";
command.Parameters.AddWithValue("@tac", tac);

It doesn't enter in the while loop and I don't know why...

Is there something that am I missing or maybe I need to use another method to retrieve those data?

EDIT : Change the format due to the Soner Gönül answer

Answer 1

Because when you use this string in IN clause, it will seems like;

IN (xxxxxxxx,xxxxxxxx,xxxxxxxx,xxxxxxxx)

but the right syntax should be

IN ('xxxxxxxx','xxxxxxxx','xxxxxxxx','xxxxxxxx')

That's why it doesn't work. One solution might be, you can split your string with , , format them with using single quotes and join them , again.

var str = "xxxxxxxx,xxxxxxxx,xxxxxxxx,xxxxxxxx";
var result = string.Join(",", str.Split(',').Select(s => string.Format("'{0}'", s)));

result will be 'xxxxxxxx','xxxxxxxx','xxxxxxxx','xxxxxxxx' and you can use it in your IN clause like;

...TAC IN (@tac)

and

command.Parameters.AddWithValue("@tac", result);

Also don't use AddWithValue as much as you can. It may generate unexpected and surprising results sometimes . Use Add method overload to specify your parameter type and it's size.

Related: Parameterize an SQL IN clause