con = new OleDbConnection("Provider=Microsoft.ACE.Oledb.12.0;Data Source=isim.accdb");
con.Open();
OleDbCommand command = new OleDbCommand();
command.Connection = con;
command.CommandText = "select* from okul";
OleDbDataReader reader = command.ExecuteReader();
while (reader.Read())
{
comboBox1.Items.Add(reader["no"]);
}
con.Close();