Csharp/C Sharp/Database ADO.net/OleDbDataReader

Execute complicated SQL query

using System;
using System.Data;
using System.Data.OleDb;
public class ExtractInfo {    
 public static void Main () { 
   String connect = "Provider=Microsoft.JET.OLEDB.4.0;data source=.\\Employee.mdb";
   OleDbConnection con = new OleDbConnection(connect);
   con.Open();  
   Console.WriteLine("Made the connection to the Sales database");
   OleDbCommand cmd = con.CreateCommand();
   
   cmd.rumandText = "SELECT DISTINCT CustomerName "
            + "FROM Customer, Item, Orders, OrderItem "
            + "WHERE Customer.CustomerID = Orders.CustomerID "
            + "AND Orders.OrderNumber = OrderItem.OrderNumber "
            + "AND OrderItem.ItemNumber = Item.ItemNumber "
            + "AND Description = "computer"";
   OleDbDataReader reader = cmd.ExecuteReader();
   while(reader.Read())
     Console.WriteLine(reader.GetString(0));
   reader.Close();

   con.Close();
 }
}

Format Data from OleDbDataReader

using System;
using System.Data; 
using System.Data.OleDb; 
class OleDbProvider{
   static void Main(string[] args)  {
      String connString = "provider=sqloledb;server=(local)\\SQLEXPRESS;database=MyDatabase;Integrated Security=SSPI";
    
    String sql = "select firstname, lastname from Employee";
      OleDbConnection conn = null;
      OleDbDataReader reader = null;
      try {
         conn = new OleDbConnection(connString);
         conn.Open();
         OleDbCommand cmd = new OleDbCommand(sql, conn);
         reader = cmd.ExecuteReader();
         Console.WriteLine("Querying database {0} with query {1}\n"
                           , conn.Database
                           , cmd.rumandText);
         Console.WriteLine("First Name\tLast Name\n");
         while(reader.Read()){
            Console.WriteLine(
               "{0} | {1}" 
               , reader["FirstName"].ToString().PadLeft(10) 
               , reader[1].ToString().PadLeft(10)
               );
         }
      } catch (Exception e) {
         Console.WriteLine("Error: " + e);
      } finally {
         reader.Close();
         conn.Close();
      }
   }
}

Map database column name to OleDbDataReader

using System;
using System.Data.OleDb;
public class ReadFromOleDb
{
  [STAThread]
  static void Main(string[] args)
  {
    String sConn = "provider=sqloledb;server=(local)\\SQLEXPRESS;database=MyDatabase;Integrated Security=SSPI";
    
    String sSQL = "select id, firstname, lastname from Employee";
    OleDbConnection oConn = new OleDbConnection(sConn);
    oConn.Open();
    OleDbCommand oCmd = new OleDbCommand(sSQL, oConn);
    OleDbDataReader oReader = oCmd.ExecuteReader();
    int idxID = oReader.GetOrdinal("id");
    int idxFirstName = oReader.GetOrdinal("firstname");
    int idxLastName = oReader.GetOrdinal("lastname");
    while(oReader.Read()) {
      Console.WriteLine("{0} {1} {2}",
        oReader.GetValue(idxID),
        oReader.GetValue(idxFirstName),
        oReader.GetValue(idxLastName));
    }
  }
}

Query more columns and read result set

using System;
using System.Data;
using System.Data.OleDb;
public class ExtractInfo {    
 public static void Main () { 
   String connect = "Provider=Microsoft.JET.OLEDB.4.0;data source=.\\Employee.mdb";
   OleDbConnection con = new OleDbConnection(connect);
   con.Open();  
   Console.WriteLine("Made the connection to the Sales database");
   OleDbCommand cmd = con.CreateCommand();
   cmd.rumandText = "SELECT First_Name, Last_Name FROM Employee ORDER BY First_Name"; 
   OleDbDataReader reader = cmd.ExecuteReader();
   Console.WriteLine("First_Name\t\tLast_Name");  
   while(reader.Read()) 
     Console.WriteLine("{0}\t{1}",reader.GetString(0), reader.GetString(1));
   reader.Close();
   
   con.Close();
 }
}

Read result set containing all columns

using System;
using System.Data;
using System.Data.OleDb;
public class ExtractInfo {    
 public static void Main () { 
   String connect = "Provider=Microsoft.JET.OLEDB.4.0;data source=.\\Employee.mdb";
   OleDbConnection con = new OleDbConnection(connect);
   con.Open();  
   Console.WriteLine("Made the connection to the Sales database");
   OleDbCommand cmd = con.CreateCommand();
   
   cmd.rumandText = "SELECT * FROM Employee";
   OleDbDataReader reader = cmd.ExecuteReader();
   Console.WriteLine();
   Console.WriteLine("ID\tFirstName\tLastName\tSalary");  
   while (reader.Read())
     Console.WriteLine("{0}\t\t{1}\t\t{2}\t{3}",reader.GetInt32(0),reader.GetString(1),reader.GetString(2), reader.GetDecimal(3));
   reader.Close();

   con.Close();
 }
}

Read value using OleDbDataReader

using System;
using System.Data;
using System.Data.OleDb;
public class Prepare {    
 public static void Main () { 
   String connect = "Provider=Microsoft.JET.OLEDB.4.0;data source=.\\Employee.mdb";
   OleDbConnection con = new OleDbConnection(connect);
   con.Open();  
   Console.WriteLine("Made the connection to the database");
   OleDbCommand cmd2 = con.CreateCommand();
   cmd2.rumandText = "SELECT First_name FROM Employee "
                                  + "WHERE ID > ?"; 
   OleDbParameter p3 = new OleDbParameter();
   cmd2.Parameters.Add(p3);
   p3.Value = new Decimal(0.0);
   OleDbDataReader reader = cmd2.ExecuteReader();
   while(reader.Read()) 
     Console.WriteLine("{0}", reader.GetString(0));
   reader.Close();

   con.Close();
 }
}

Reference data in OleDbDataReader by column name

    using System;
    using System.Data.OleDb;
  class MapOleDbReader
  {
    static void Main(string[] args)
    {
        String sConn = "provider=sqloledb;server=(local)\\SQLEXPRESS;database=MyDatabase;Integrated Security=SSPI";
        String sSQL = "select id, firstname, lastname from Employee";
      OleDbConnection oConn = new OleDbConnection(sConn);
      oConn.Open();
      OleDbCommand oCmd = new OleDbCommand(sSQL, oConn);
      OleDbDataReader oReader = oCmd.ExecuteReader();
      while(oReader.Read()) 
      {
        Console.WriteLine("{0} {1} {2}",
          oReader["id"],
          oReader["firstname"],
          oReader["lastname"]);
      }
    }
  }