Csharp/CSharp Tutorial/ADO.Net/Oracle

A connection string using integrated security for Oracle database

Data Source=ORCL;Integrated Security=yes;

A connection string without integrated security for Oracle database

Data Source=ORCL;User Id=hr;Password=password;

Connecting to an Oracle Database with OracleConnection

using System;
using System.Data.OracleClient;
using System.Data.OleDb;
using System.Data.Odbc;
    class Program
    {
        static void Main(string[] args)
        {
            string oracleConnectString ="Data Source=ORCL;User Id=hr;Password=password;";
            using (OracleConnection connection = new OracleConnection(oracleConnectString))
            {
                connection.Open(  );
                Console.WriteLine("---Microsoft .NET Provider for Oracle---");
                Console.WriteLine("ConnectionString = {0}\n", oracleConnectString);
                Console.WriteLine("State = {0}", connection.State);
                Console.WriteLine("DataSource = {0}", connection.DataSource);
                Console.WriteLine("ServerVersion = {0}", connection.ServerVersion);
            }

        }
    }

Connection String for Oracle database

using System;
using System.Data;
using System.Data.OracleClient;

class Class1{
    static void Main(string[] args)
    {
      string connstr = "User Id=scott; Password=tiger; Data Source=oranet";
      OracleConnection con = new OracleConnection();
      con.ConnectionString = connstr;
      Console.WriteLine("Connection String 1: {0}", con.ConnectionString);
      con.Open();
      Console.WriteLine("Connection String 2: {0}", con.ConnectionString);
      con.Close();
      Console.WriteLine("Connection String 3: {0}", con.ConnectionString);
      con.Dispose();
    }
}

Connect to an Oracle Database using .NET data provider for OLE DB

using System;
using System.Data.OracleClient;
using System.Data.OleDb;
using System.Data.Odbc;
    class Program
    {
        static void Main(string[] args)
        {
            string oledbConnectString = "Provider=MSDAORA;Data Source=ORCL;User Id=hr;Password=password;";
            
            using (OleDbConnection connection = new OleDbConnection(oledbConnectString))
            {
                connection.Open(  );
                Console.WriteLine("ConnectionString = {0}\n", oledbConnectString);
                Console.WriteLine("State = {0}", connection.State);
                Console.WriteLine("DataSource = {0}", connection.DataSource);
                Console.WriteLine("ServerVersion = {0}", connection.ServerVersion);
            }
        }
    }

Connect to an Oracle Database using OdbcConnection

using System;
using System.Data.OracleClient;
using System.Data.OleDb;
using System.Data.Odbc;
    class Program
    {
        static void Main(string[] args)
        {
            string odbcConnectString = "Driver={Oracle in OraDb10g_home1};Server=ORCL;uid=hr;pwd=password;";
            using (OdbcConnection connection = new OdbcConnection(odbcConnectString))
            {
                connection.Open(  );
                Console.WriteLine("ConnectionString = {0}\n", odbcConnectString);
                Console.WriteLine("State = {0}", connection.State);
                Console.WriteLine("DataSource = {0}", connection.DataSource);
                Console.WriteLine("ServerVersion = {0}", connection.ServerVersion);
            }
        }
    }

Do a delete command to Oracle database

using System;
using System.Drawing;
using System.Collections;
using System.ruponentModel;
using System.Windows.Forms;
using System.Data;
using System.Data.OracleClient;
  public class MainClass
  {
    public static void Main()
    {
      OracleConnection oraConn = new OracleConnection();
      string connString = "User Id=oranetuser; Password=demo; Data Source=oranet";
      if (oraConn.State != ConnectionState.Open)
      {
        try
        {
          oraConn.ConnectionString = connString;
          oraConn.Open();
          MessageBox.Show(oraConn.ConnectionString, "Successful Connection");
        }
        catch (Exception ex)
        {
          MessageBox.Show(ex.Message,"Exception Caught");
        }
      }

      if (oraConn.State == ConnectionState.Open)
      {
        string sqlDelete = "delete from PlayerTable where player_num = :p_num";
        OracleCommand cmdDelete = new OracleCommand();
        cmdDelete.rumandText = sqlDelete;
        cmdDelete.Connection = oraConn;
        OracleParameter pPlayerNum = new OracleParameter();
        pPlayerNum.DbType = DbType.Decimal;
        pPlayerNum.Value = 1;
        pPlayerNum.ParameterName = "p_num";
        cmdDelete.Parameters.Add(pPlayerNum);
        cmdDelete.ExecuteNonQuery();
        cmdDelete.Dispose();
      }
    }
  }

Do an insert command to Oracle database

using System;
using System.Drawing;
using System.Collections;
using System.ruponentModel;
using System.Windows.Forms;
using System.Data;
using System.Data.OracleClient;
public class MainClass
{
    public static void Main()
    {
        OracleConnection oraConn = new OracleConnection();
        string connString = "User Id=oranetuser; Password=demo; Data Source=oranet";
        if (oraConn.State != ConnectionState.Open)
        {
            try
            {
                oraConn.ConnectionString = connString;
                oraConn.Open();
                MessageBox.Show(oraConn.ConnectionString, "Successful Connection");
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message, "Exception Caught");
            }
        }
        if (oraConn.State == ConnectionState.Open)
        {
            string sqlInsert = "insert into PlayerTable (player_num, last_name, first_name, position, club) ";
            sqlInsert += "values (:p_num, :p_last, :p_first, :p_pos, :p_club)";
            OracleCommand cmdInsert = new OracleCommand();
            cmdInsert.rumandText = sqlInsert;
            cmdInsert.Connection = oraConn;
            OracleParameter pPlayerNum = new OracleParameter();
            pPlayerNum.DbType = DbType.Decimal;
            pPlayerNum.Value = 10;
            pPlayerNum.ParameterName = "p_num";
            OracleParameter pLastName = new OracleParameter();
            pLastName.Value = "Last";
            pLastName.ParameterName = "p_last";
            OracleParameter pFirstName = new OracleParameter();
            pFirstName.Value = "FirstName";
            pFirstName.ParameterName = "p_first";
            OracleParameter pPosition = new OracleParameter();
            pPosition.Value = "A";
            pPosition.ParameterName = "p_pos";
            OracleParameter pClub = new OracleParameter();
            pClub.Value = "abc";
            pClub.ParameterName = "p_club";
            cmdInsert.Parameters.Add(pPlayerNum);
            cmdInsert.Parameters.Add(pLastName);
            cmdInsert.Parameters.Add(pFirstName);
            cmdInsert.Parameters.Add(pPosition);
            cmdInsert.Parameters.Add(pClub);
            cmdInsert.ExecuteNonQuery();
            cmdInsert.Dispose();
        }
    }
}

Do an update to Oracle database

using System;
using System.Drawing;
using System.Collections;
using System.ruponentModel;
using System.Windows.Forms;
using System.Data;
using System.Data.OracleClient;
  public class MainClass
  {
    public static void Main()
    {
      OracleConnection oraConn = new OracleConnection();
      string connString = "User Id=oranetuser; Password=demo; Data Source=oranet";
      if (oraConn.State != ConnectionState.Open)
      {
        try
        {
          oraConn.ConnectionString = connString;
          oraConn.Open();
          MessageBox.Show(oraConn.ConnectionString, "Successful Connection");
        }
        catch (Exception ex)
        {
          MessageBox.Show(ex.Message,"Exception Caught");
        }
      }

      if (oraConn.State == ConnectionState.Open)
      {
        string sqlUpdate = "update PlayerTable ";
        sqlUpdate += "set last_name = :p_last, ";
        sqlUpdate += "first_name = :p_first, ";
        sqlUpdate += "position = :p_pos, ";
        sqlUpdate += "club = :p_club " ;
        sqlUpdate += "where player_num = :p_num";
        OracleCommand cmdUpdate = new OracleCommand();
        cmdUpdate.rumandText = sqlUpdate;
        cmdUpdate.Connection = oraConn;
        OracleParameter pPlayerNum = new OracleParameter();
        pPlayerNum.DbType = DbType.Decimal;
        pPlayerNum.Value = 10;
        pPlayerNum.ParameterName = "p_num";
        OracleParameter pLastName = new OracleParameter();
        pLastName.Value = "Tom";
        pLastName.ParameterName = "p_last";
        OracleParameter pFirstName = new OracleParameter();
        pFirstName.Value = "Gib";
        pFirstName.ParameterName = "p_first";
        OracleParameter pPosition = new OracleParameter();
        pPosition.Value = "a";
        pPosition.ParameterName = "p_pos";
  
        OracleParameter pClub = new OracleParameter();
        pClub.Value = "abc";
        pClub.ParameterName = "p_club";
        cmdUpdate.Parameters.Add(pLastName);
        cmdUpdate.Parameters.Add(pFirstName);
        cmdUpdate.Parameters.Add(pPosition);
        cmdUpdate.Parameters.Add(pClub);
        cmdUpdate.Parameters.Add(pPlayerNum);
        cmdUpdate.ExecuteNonQuery();
        MessageBox.Show("Record Updated Successfully" , "Record Updated");
        cmdUpdate.Dispose();
      }    
    }
}

Get connection state and server version

using System;
using System.Data.OracleClient;
  class Class1
  {
    static void Main(string[] args)
      {
            String connString = "User Id=oranetuser;Password=demo";
            OracleConnection oraConn = new OracleConnection(connString);
            try
            {
                oraConn.Open();
                Console.WriteLine(oraConn.ConnectionString.ToString() + "\n");
                Console.WriteLine(oraConn.State.ToString() + "\n");
                Console.WriteLine(oraConn.ServerVersion.ToString());
            }
            catch (Exception ex)
            {
                Console.WriteLine("Error occured: " + ex.Message);
            }
            finally
            {
                if (oraConn.State == System.Data.ConnectionState.Open)
                {
                    oraConn.Close();
                }
            }
    }
  }

how to use an OleDbConnection object to connect to an Oracle database

using System;
using System.Data;
using System.Data.OleDb;
class OleDbConnectionOracle {
    public static void Main() {
        string connectionString = "provider=MSDAORA;data source=ORCL;user id=SCOTT;password=TIGER";
        OleDbConnection myOleDbConnection = new OleDbConnection(connectionString);
        OleDbCommand myOleDbCommand = myOleDbConnection.CreateCommand();
        myOleDbCommand.rumandText =
          "SELECT empno, ename, sal " +
          "FROM emp " +
          "WHERE empno = 7369";
        myOleDbConnection.Open();
        OleDbDataReader myOleDbDataReader = myOleDbCommand.ExecuteReader();
        myOleDbDataReader.Read();
        Console.WriteLine("myOleDbDataReader[\" empno\"] = " + myOleDbDataReader["empno"]);
        Console.WriteLine("myOleDbDataReader[\" ename\"] = " + myOleDbDataReader["ename"]);
        Console.WriteLine("myOleDbDataReader[\" sal\"] = " + myOleDbDataReader["sal"]);
        myOleDbDataReader.Close();
        myOleDbConnection.Close();
    }
}

Manual Loopup for Oracle database

using System;
using System.Drawing;
using System.Collections;
using System.ruponentModel;
using System.Windows.Forms;
using System.Data;
using System.Data.OracleClient;
  public class MainClass
  {
    public static void Main()
    {
      OracleConnection oraConn = new OracleConnection();
      string connString = "User Id=oranetuser; Password=demo; Data Source=oranet";
      if (oraConn.State != ConnectionState.Open)
      {
        try
        {
          oraConn.ConnectionString = connString;
          oraConn.Open();
          MessageBox.Show(oraConn.ConnectionString, "Successful Connection");
        }
        catch (Exception ex)
        {
          MessageBox.Show(ex.Message,"Exception Caught");
        }
      }
      if (oraConn.State == ConnectionState.Open)
      {
        string sqlLookup = "select last_name, first_name, from PlayerTable ";
        sqlLookup += "where player_num = :player_num";
        OracleCommand cmdLookup = new OracleCommand();
        cmdLookup.rumandText = sqlLookup;
        cmdLookup.Connection = oraConn;
        OracleParameter pPlayerNum = new OracleParameter();
        pPlayerNum.DbType = DbType.Decimal;
        pPlayerNum.Value = 10;
        pPlayerNum.ParameterName = "player_num";
        cmdLookup.Parameters.Add(pPlayerNum);
        OracleDataReader dataReader = cmdLookup.ExecuteReader();
        if (dataReader.Read()){
          Console.WriteLine(dataReader.GetString(0));
          Console.WriteLine(dataReader.GetString(1));
          Console.WriteLine(dataReader.GetString(2));
          Console.WriteLine(dataReader.GetString(3));
        }else{
          MessageBox.Show("No record for Player Number Found" , "No Record Found");
        }
        dataReader.Close();
        dataReader.Dispose();
        cmdLookup.Dispose();
      }
    }
  }

No Connection Pooling

using System;
using System.Data.OracleClient;

  class Class1
  {
    static void Main(string[] args)
    {
      string l_connect = "User Id=oranetuser;Password=demo;Data Source=oranet;pooling=false";
      OracleConnection conn_1 = new OracleConnection(l_connect);
      conn_1.Open();
      conn_1.Dispose();
      OracleConnection conn_2 = new OracleConnection(l_connect);
      conn_2.Open();
      conn_2.Dispose();
    }
  }

Read decimal from OracleDataReader

using System;
using System.Drawing;
using System.Collections;
using System.ruponentModel;
using System.Windows.Forms;
using System.Data;
using System.Data.OracleClient;
  public class Form1 : System.Windows.Forms.Form
  {
    private System.Windows.Forms.Button btnConnect;
    private System.Windows.Forms.Button btnGetIDs;
    private System.Windows.Forms.Label label1;
    private System.Windows.Forms.ruboBox cbEmpIds;
    private System.Windows.Forms.Label lblFirstName;
    private System.Windows.Forms.Label lblLastName;
    private System.Windows.Forms.Label label4;
    private System.Windows.Forms.Label label5;
    private System.Windows.Forms.Button btnLookup1;
    private System.Windows.Forms.Button btnLookup2;
    private System.Windows.Forms.Label lblEmail;
    private System.Windows.Forms.Label lblPhone;
    private System.Windows.Forms.Label lblEmailText;
    private System.Windows.Forms.Label lblPhoneText;
    private System.Windows.Forms.Button btnReset;
    private System.Windows.Forms.Button btnNoBinds;
    private System.Data.OracleClient.OracleConnection oraConn;
    private System.Data.OracleClient.OracleCommand cmdGetIDs;
    private System.Data.OracleClient.OracleCommand cmdLookup1;
    private System.Data.OracleClient.OracleCommand cmdLookup2;
    private System.Data.OracleClient.OracleCommand cmdNoBinds1;
    private System.Data.OracleClient.OracleCommand cmdNoBinds2;
    public Form1()
    {
      this.btnConnect = new System.Windows.Forms.Button();
      this.btnGetIDs = new System.Windows.Forms.Button();
      this.cbEmpIds = new System.Windows.Forms.ruboBox();
      this.label1 = new System.Windows.Forms.Label();
      this.lblFirstName = new System.Windows.Forms.Label();
      this.lblLastName = new System.Windows.Forms.Label();
      this.label4 = new System.Windows.Forms.Label();
      this.label5 = new System.Windows.Forms.Label();
      this.btnLookup1 = new System.Windows.Forms.Button();
      this.btnLookup2 = new System.Windows.Forms.Button();
      this.lblEmail = new System.Windows.Forms.Label();
      this.lblPhone = new System.Windows.Forms.Label();
      this.lblEmailText = new System.Windows.Forms.Label();
      this.lblPhoneText = new System.Windows.Forms.Label();
      this.btnReset = new System.Windows.Forms.Button();
      this.btnNoBinds = new System.Windows.Forms.Button();
      this.oraConn = new System.Data.OracleClient.OracleConnection();
      this.cmdGetIDs = new System.Data.OracleClient.OracleCommand();
      this.cmdLookup1 = new System.Data.OracleClient.OracleCommand();
      this.cmdLookup2 = new System.Data.OracleClient.OracleCommand();
      this.cmdNoBinds1 = new System.Data.OracleClient.OracleCommand();
      this.cmdNoBinds2 = new System.Data.OracleClient.OracleCommand();
      this.SuspendLayout();
      this.btnConnect.Location = new System.Drawing.Point(32, 44);
      this.btnConnect.Text = "C&onnect";
      this.btnConnect.Click += new System.EventHandler(this.btnConnect_Click);
      this.btnGetIDs.Location = new System.Drawing.Point(32, 80);
      this.btnGetIDs.Text = "&Get IDs";
      this.btnGetIDs.Click += new System.EventHandler(this.btnGetIDs_Click);
      this.cbEmpIds.DropDownStyle = System.Windows.Forms.ruboBoxStyle.DropDownList;
      this.cbEmpIds.Location = new System.Drawing.Point(144, 44);
      this.cbEmpIds.Size = new System.Drawing.Size(68, 21);
      this.label1.Location = new System.Drawing.Point(144, 24);
      this.label1.Size = new System.Drawing.Size(72, 16);
      this.label1.Text = "&Employee ID:";
      this.lblFirstName.Location = new System.Drawing.Point(228, 48);
      this.lblFirstName.Size = new System.Drawing.Size(116, 16);
      this.lblLastName.Location = new System.Drawing.Point(364, 48);
      this.lblLastName.Size = new System.Drawing.Size(128, 16);
      this.label4.Location = new System.Drawing.Point(228, 24);
      this.label4.Size = new System.Drawing.Size(100, 16);
      this.label4.Text = "&First Name:";
      this.label5.Location = new System.Drawing.Point(364, 24);
      this.label5.Size = new System.Drawing.Size(100, 16);
      this.label5.Text = "&Last Name:";
      this.btnLookup1.Location = new System.Drawing.Point(32, 116);
      this.btnLookup1.Text = "Lookup &1";
      this.btnLookup1.Click += new System.EventHandler(this.btnLookup1_Click);
      this.btnLookup2.Location = new System.Drawing.Point(32, 152);
      this.btnLookup2.Text = "Lookup &2";
      this.btnLookup2.Click += new System.EventHandler(this.btnLookup2_Click);
      this.lblEmail.Location = new System.Drawing.Point(228, 88);
      this.lblEmail.Size = new System.Drawing.Size(100, 16);
      this.lblEmail.Text = "E&mail:";
      this.lblPhone.Location = new System.Drawing.Point(364, 88);
      this.lblPhone.Size = new System.Drawing.Size(100, 16);
      this.lblPhone.Text = "Phone &Number:";
      this.lblEmailText.Location = new System.Drawing.Point(228, 112);
      this.lblEmailText.Size = new System.Drawing.Size(116, 16);
      this.lblPhoneText.Location = new System.Drawing.Point(364, 112);
      this.lblPhoneText.Size = new System.Drawing.Size(128, 16);
      this.btnReset.Location = new System.Drawing.Point(32, 224);
      this.btnReset.Text = "&Reset";
      this.btnReset.Click += new System.EventHandler(this.btnReset_Click);
      this.btnNoBinds.Location = new System.Drawing.Point(32, 188);
      this.btnNoBinds.Text = "No &Binds";
      this.btnNoBinds.Click += new System.EventHandler(this.btnNoBinds_Click);
      this.oraConn.ConnectionString = "user id=hr;data source=oranet;password=demo";
      this.cmdGetIDs.rumandText = "SELECT EMPLOYEE_ID FROM EMPLOYEES ORDER BY EMPLOYEE_ID";
      this.cmdGetIDs.Connection = this.oraConn;
      this.cmdLookup1.rumandText = "SELECT FIRST_NAME, LAST_NAME FROM EMPLOYEES WHERE (EMPLOYEE_ID = :p_id)";
      this.cmdLookup1.Connection = this.oraConn;
      this.cmdLookup1.Parameters.Add(new System.Data.OracleClient.OracleParameter(":p_id", System.Data.OracleClient.OracleType.Number, 0, System.Data.ParameterDirection.Input, false, ((System.Byte)(6)), ((System.Byte)(0)), "EMPLOYEE_ID", System.Data.DataRowVersion.Current, null));
      this.cmdLookup2.rumandText = "SELECT EMAIL, PHONE_NUMBER FROM EMPLOYEES WHERE (FIRST_NAME = :p_first) AND (LAST" +
        "_NAME = :p_last)";
      this.cmdLookup2.Connection = this.oraConn;
      this.cmdLookup2.Parameters.Add(new System.Data.OracleClient.OracleParameter(":p_first", System.Data.OracleClient.OracleType.VarChar, 20, "FIRST_NAME"));
      this.cmdLookup2.Parameters.Add(new System.Data.OracleClient.OracleParameter(":p_last", System.Data.OracleClient.OracleType.VarChar, 25, "LAST_NAME"));
      this.cmdNoBinds1.Connection = this.oraConn;
      this.cmdNoBinds2.Connection = this.oraConn;
      this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
      this.ClientSize = new System.Drawing.Size(534, 264);
      this.Controls.Add(this.btnNoBinds);
      this.Controls.Add(this.btnReset);
      this.Controls.Add(this.lblPhoneText);
      this.Controls.Add(this.lblEmailText);
      this.Controls.Add(this.lblPhone);
      this.Controls.Add(this.lblEmail);
      this.Controls.Add(this.btnLookup2);
      this.Controls.Add(this.btnLookup1);
      this.Controls.Add(this.label5);
      this.Controls.Add(this.label4);
      this.Controls.Add(this.lblLastName);
      this.Controls.Add(this.lblFirstName);
      this.Controls.Add(this.label1);
      this.Controls.Add(this.cbEmpIds);
      this.Controls.Add(this.btnGetIDs);
      this.Controls.Add(this.btnConnect);
      this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.Fixed3D;
      this.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen;
      this.Load += new System.EventHandler(this.Form1_Load);
      this.ResumeLayout(false);
    }
    static void Main() 
    {
      Application.Run(new Form1());
    }
    private void btnConnect_Click(object sender, System.EventArgs e)
    {
      if (oraConn.State != ConnectionState.Open)
      {
         oraConn.Open();
         MessageBox.Show(oraConn.ConnectionString, "Successful Connection");
      }
    }
    private void btnGetIDs_Click(object sender, System.EventArgs e)
    {
        OracleDataReader dataReader = cmdGetIDs.ExecuteReader();
        while (dataReader.Read())
        {
          cbEmpIds.Items.Add(dataReader.GetDecimal(0));
        }
    }
    private void Form1_Load(object sender, System.EventArgs e)
    {
    }
    private void btnLookup1_Click(object sender, System.EventArgs e)
    {
      object selectedItem = cbEmpIds.SelectedItem;
      if (selectedItem != null)
      {
        cmdLookup1.Parameters[0].Value = Convert.ToDecimal(selectedItem.ToString());
        OracleDataReader dataReader = cmdLookup1.ExecuteReader();
        if (dataReader.Read())
        {
          lblFirstName.Text = dataReader.GetString(0);
          lblLastName.Text = dataReader.GetString(1);
        }
        dataReader.Close();
        dataReader.Dispose();
      }
    }
    private void btnLookup2_Click(object sender, System.EventArgs e)
    {
      cmdLookup2.Parameters[0].Value = lblFirstName.Text;
      cmdLookup2.Parameters[1].Value = lblLastName.Text;
      OracleDataReader dataReader = cmdLookup2.ExecuteReader();
      if (dataReader.Read())
      {
        lblEmailText.Text = dataReader.GetString(0);
        lblPhoneText.Text = dataReader.GetString(1);
      }
      dataReader.Close();
      dataReader.Dispose();
    }
    private void btnReset_Click(object sender, System.EventArgs e)
    {
      cbEmpIds.SelectedIndex = -1;
      lblFirstName.Text = "";
      lblLastName.Text = "";
      lblEmailText.Text = "";
      lblPhoneText.Text = "";
    }
    private void btnNoBinds_Click(object sender, System.EventArgs e)
    {
      object selectedItem = cbEmpIds.SelectedItem;
      if (selectedItem != null)
      {
        OracleDataReader dataReader;
        cmdNoBinds1.rumandText = "select first_name, last_name from employees where employee_id = " + selectedItem.ToString();
        dataReader = cmdNoBinds1.ExecuteReader();
        if (dataReader.Read())
        {
          lblFirstName.Text = dataReader.GetString(0);
          lblLastName.Text = dataReader.GetString(1);
        }
        dataReader.Close();
        cmdNoBinds2.rumandText = "select email, phone_number from employees where first_name = "" + lblFirstName.Text + "" and last_name = "" + lblLastName.Text +""";
        dataReader = cmdNoBinds2.ExecuteReader();
        if (dataReader.Read())
        {
          lblEmailText.Text = dataReader.GetString(0);
          lblPhoneText.Text = dataReader.GetString(1);
        }
        dataReader.Close();
        dataReader.Dispose();
      }
    }
  }

Read string from OracleDataReader

using System;
using System.Drawing;
using System.Collections;
using System.ruponentModel;
using System.Windows.Forms;
using System.Data;
using System.Data.OracleClient;
  public class Form1 : System.Windows.Forms.Form
  {
    private System.Windows.Forms.Button btnConnect;
    private System.Windows.Forms.Button btnGetIDs;
    private System.Windows.Forms.Label label1;
    private System.Windows.Forms.ruboBox cbEmpIds;
    private System.Windows.Forms.Label lblFirstName;
    private System.Windows.Forms.Label lblLastName;
    private System.Windows.Forms.Label label4;
    private System.Windows.Forms.Label label5;
    private System.Windows.Forms.Button btnLookup1;
    private System.Windows.Forms.Button btnLookup2;
    private System.Windows.Forms.Label lblEmail;
    private System.Windows.Forms.Label lblPhone;
    private System.Windows.Forms.Label lblEmailText;
    private System.Windows.Forms.Label lblPhoneText;
    private System.Windows.Forms.Button btnReset;
    private System.Windows.Forms.Button btnNoBinds;
    private System.Data.OracleClient.OracleConnection oraConn;
    private System.Data.OracleClient.OracleCommand cmdGetIDs;
    private System.Data.OracleClient.OracleCommand cmdLookup1;
    private System.Data.OracleClient.OracleCommand cmdLookup2;
    private System.Data.OracleClient.OracleCommand cmdNoBinds1;
    private System.Data.OracleClient.OracleCommand cmdNoBinds2;
    public Form1()
    {
      this.btnConnect = new System.Windows.Forms.Button();
      this.btnGetIDs = new System.Windows.Forms.Button();
      this.cbEmpIds = new System.Windows.Forms.ruboBox();
      this.label1 = new System.Windows.Forms.Label();
      this.lblFirstName = new System.Windows.Forms.Label();
      this.lblLastName = new System.Windows.Forms.Label();
      this.label4 = new System.Windows.Forms.Label();
      this.label5 = new System.Windows.Forms.Label();
      this.btnLookup1 = new System.Windows.Forms.Button();
      this.btnLookup2 = new System.Windows.Forms.Button();
      this.lblEmail = new System.Windows.Forms.Label();
      this.lblPhone = new System.Windows.Forms.Label();
      this.lblEmailText = new System.Windows.Forms.Label();
      this.lblPhoneText = new System.Windows.Forms.Label();
      this.btnReset = new System.Windows.Forms.Button();
      this.btnNoBinds = new System.Windows.Forms.Button();
      this.oraConn = new System.Data.OracleClient.OracleConnection();
      this.cmdGetIDs = new System.Data.OracleClient.OracleCommand();
      this.cmdLookup1 = new System.Data.OracleClient.OracleCommand();
      this.cmdLookup2 = new System.Data.OracleClient.OracleCommand();
      this.cmdNoBinds1 = new System.Data.OracleClient.OracleCommand();
      this.cmdNoBinds2 = new System.Data.OracleClient.OracleCommand();
      this.SuspendLayout();
      this.btnConnect.Location = new System.Drawing.Point(32, 44);
      this.btnConnect.Text = "C&onnect";
      this.btnConnect.Click += new System.EventHandler(this.btnConnect_Click);
      this.btnGetIDs.Location = new System.Drawing.Point(32, 80);
      this.btnGetIDs.Text = "&Get IDs";
      this.btnGetIDs.Click += new System.EventHandler(this.btnGetIDs_Click);
      this.cbEmpIds.DropDownStyle = System.Windows.Forms.ruboBoxStyle.DropDownList;
      this.cbEmpIds.Location = new System.Drawing.Point(144, 44);
      this.cbEmpIds.Size = new System.Drawing.Size(68, 21);
      this.label1.Location = new System.Drawing.Point(144, 24);
      this.label1.Size = new System.Drawing.Size(72, 16);
      this.label1.Text = "&Employee ID:";
      this.lblFirstName.Location = new System.Drawing.Point(228, 48);
      this.lblFirstName.Size = new System.Drawing.Size(116, 16);
      this.lblLastName.Location = new System.Drawing.Point(364, 48);
      this.lblLastName.Size = new System.Drawing.Size(128, 16);
      this.label4.Location = new System.Drawing.Point(228, 24);
      this.label4.Size = new System.Drawing.Size(100, 16);
      this.label4.Text = "&First Name:";
      this.label5.Location = new System.Drawing.Point(364, 24);
      this.label5.Size = new System.Drawing.Size(100, 16);
      this.label5.Text = "&Last Name:";
      this.btnLookup1.Location = new System.Drawing.Point(32, 116);
      this.btnLookup1.Text = "Lookup &1";
      this.btnLookup1.Click += new System.EventHandler(this.btnLookup1_Click);
      this.btnLookup2.Location = new System.Drawing.Point(32, 152);
      this.btnLookup2.Text = "Lookup &2";
      this.btnLookup2.Click += new System.EventHandler(this.btnLookup2_Click);
      this.lblEmail.Location = new System.Drawing.Point(228, 88);
      this.lblEmail.Size = new System.Drawing.Size(100, 16);
      this.lblEmail.Text = "E&mail:";
      this.lblPhone.Location = new System.Drawing.Point(364, 88);
      this.lblPhone.Size = new System.Drawing.Size(100, 16);
      this.lblPhone.Text = "Phone &Number:";
      this.lblEmailText.Location = new System.Drawing.Point(228, 112);
      this.lblEmailText.Size = new System.Drawing.Size(116, 16);
      this.lblPhoneText.Location = new System.Drawing.Point(364, 112);
      this.lblPhoneText.Size = new System.Drawing.Size(128, 16);
      this.btnReset.Location = new System.Drawing.Point(32, 224);
      this.btnReset.Text = "&Reset";
      this.btnReset.Click += new System.EventHandler(this.btnReset_Click);
      this.btnNoBinds.Location = new System.Drawing.Point(32, 188);
      this.btnNoBinds.Text = "No &Binds";
      this.btnNoBinds.Click += new System.EventHandler(this.btnNoBinds_Click);
      this.oraConn.ConnectionString = "user id=hr;data source=oranet;password=demo";
      this.cmdGetIDs.rumandText = "SELECT EMPLOYEE_ID FROM EMPLOYEES ORDER BY EMPLOYEE_ID";
      this.cmdGetIDs.Connection = this.oraConn;
      this.cmdLookup1.rumandText = "SELECT FIRST_NAME, LAST_NAME FROM EMPLOYEES WHERE (EMPLOYEE_ID = :p_id)";
      this.cmdLookup1.Connection = this.oraConn;
      this.cmdLookup1.Parameters.Add(new System.Data.OracleClient.OracleParameter(":p_id", System.Data.OracleClient.OracleType.Number, 0, System.Data.ParameterDirection.Input, false, ((System.Byte)(6)), ((System.Byte)(0)), "EMPLOYEE_ID", System.Data.DataRowVersion.Current, null));
      this.cmdLookup2.rumandText = "SELECT EMAIL, PHONE_NUMBER FROM EMPLOYEES WHERE (FIRST_NAME = :p_first) AND (LAST" +
        "_NAME = :p_last)";
      this.cmdLookup2.Connection = this.oraConn;
      this.cmdLookup2.Parameters.Add(new System.Data.OracleClient.OracleParameter(":p_first", System.Data.OracleClient.OracleType.VarChar, 20, "FIRST_NAME"));
      this.cmdLookup2.Parameters.Add(new System.Data.OracleClient.OracleParameter(":p_last", System.Data.OracleClient.OracleType.VarChar, 25, "LAST_NAME"));
      this.cmdNoBinds1.Connection = this.oraConn;
      this.cmdNoBinds2.Connection = this.oraConn;
      this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
      this.ClientSize = new System.Drawing.Size(534, 264);
      this.Controls.Add(this.btnNoBinds);
      this.Controls.Add(this.btnReset);
      this.Controls.Add(this.lblPhoneText);
      this.Controls.Add(this.lblEmailText);
      this.Controls.Add(this.lblPhone);
      this.Controls.Add(this.lblEmail);
      this.Controls.Add(this.btnLookup2);
      this.Controls.Add(this.btnLookup1);
      this.Controls.Add(this.label5);
      this.Controls.Add(this.label4);
      this.Controls.Add(this.lblLastName);
      this.Controls.Add(this.lblFirstName);
      this.Controls.Add(this.label1);
      this.Controls.Add(this.cbEmpIds);
      this.Controls.Add(this.btnGetIDs);
      this.Controls.Add(this.btnConnect);
      this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.Fixed3D;
      this.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen;
      this.Load += new System.EventHandler(this.Form1_Load);
      this.ResumeLayout(false);
    }
    static void Main() 
    {
      Application.Run(new Form1());
    }
    private void btnConnect_Click(object sender, System.EventArgs e)
    {
      if (oraConn.State != ConnectionState.Open)
      {
         oraConn.Open();
         MessageBox.Show(oraConn.ConnectionString, "Successful Connection");
      }
    }
    private void btnGetIDs_Click(object sender, System.EventArgs e)
    {
        OracleDataReader dataReader = cmdGetIDs.ExecuteReader();
        while (dataReader.Read())
        {
          cbEmpIds.Items.Add(dataReader.GetDecimal(0));
        }
    }
    private void Form1_Load(object sender, System.EventArgs e)
    {
    }
    private void btnLookup1_Click(object sender, System.EventArgs e)
    {
      object selectedItem = cbEmpIds.SelectedItem;
      if (selectedItem != null)
      {
        cmdLookup1.Parameters[0].Value = Convert.ToDecimal(selectedItem.ToString());
        OracleDataReader dataReader = cmdLookup1.ExecuteReader();
        if (dataReader.Read())
        {
          lblFirstName.Text = dataReader.GetString(0);
          lblLastName.Text = dataReader.GetString(1);
        }
        dataReader.Close();
        dataReader.Dispose();
      }
    }
    private void btnLookup2_Click(object sender, System.EventArgs e)
    {
      cmdLookup2.Parameters[0].Value = lblFirstName.Text;
      cmdLookup2.Parameters[1].Value = lblLastName.Text;
      OracleDataReader dataReader = cmdLookup2.ExecuteReader();
      if (dataReader.Read())
      {
        lblEmailText.Text = dataReader.GetString(0);
        lblPhoneText.Text = dataReader.GetString(1);
      }
      dataReader.Close();
      dataReader.Dispose();
    }
    private void btnReset_Click(object sender, System.EventArgs e)
    {
      cbEmpIds.SelectedIndex = -1;
      lblFirstName.Text = "";
      lblLastName.Text = "";
      lblEmailText.Text = "";
      lblPhoneText.Text = "";
    }
    private void btnNoBinds_Click(object sender, System.EventArgs e)
    {
      object selectedItem = cbEmpIds.SelectedItem;
      if (selectedItem != null)
      {
        OracleDataReader dataReader;
        cmdNoBinds1.rumandText = "select first_name, last_name from employees where employee_id = " + selectedItem.ToString();
        dataReader = cmdNoBinds1.ExecuteReader();
        if (dataReader.Read())
        {
          lblFirstName.Text = dataReader.GetString(0);
          lblLastName.Text = dataReader.GetString(1);
        }
        dataReader.Close();
        cmdNoBinds2.rumandText = "select email, phone_number from employees where first_name = "" + lblFirstName.Text + "" and last_name = "" + lblLastName.Text +""";
        dataReader = cmdNoBinds2.ExecuteReader();
        if (dataReader.Read())
        {
          lblEmailText.Text = dataReader.GetString(0);
          lblPhoneText.Text = dataReader.GetString(1);
        }
        dataReader.Close();
        dataReader.Dispose();
      }
    }
  }

Rollback for Oracle database

using System;
using System.Data;
using System.Data.OracleClient;
  class Class1{
    static void Main(string[] args)
    {
      string connStr = "User Id=oranetuser; Password=demo; Data Source=oranet";
      OracleConnection oraConn = new OracleConnection(connStr);
      oraConn.Open();
      testRollback(oraConn);
      oraConn.Close();
      oraConn.Dispose();
    }
    private static void testRollback(OracleConnection con)
    {
      string sqlUpdate = "update trans_test ";
      sqlUpdate += "set balance = balance + :amount ";
      sqlUpdate += "where acct_id = :acct_id";
      string sqlSelect = "select acct_id, balance ";
      sqlSelect += "from trans_test ";
      sqlSelect += "where acct_id = :acct_id";
      OracleParameter amount = new OracleParameter();
      amount.DbType = DbType.Decimal;
      amount.Precision = 12;
      amount.Scale = 2;
      amount.Value = 500;
      amount.ParameterName = "amount";
      OracleParameter acct_id = new OracleParameter();
      acct_id.DbType = DbType.Decimal;
      acct_id.Precision = 2;
      acct_id.Value = 2;
      acct_id.ParameterName = "acct_id";
      OracleCommand cmdUpdate = new OracleCommand();
      cmdUpdate.Connection = con;
      cmdUpdate.rumandText = sqlUpdate;
      cmdUpdate.Parameters.Add(amount);
      cmdUpdate.Parameters.Add(acct_id);
      OracleTransaction trans = con.BeginTransaction();
      cmdUpdate.Transaction = trans;
      cmdUpdate.ExecuteNonQuery();
      OracleCommand cmdSelect = new OracleCommand();
      cmdSelect.Connection = con;
      cmdSelect.rumandText = sqlSelect;
      cmdSelect.Transaction = trans;
      OracleParameter acct_id2 = new OracleParameter();
      acct_id2.DbType = DbType.Decimal;
      acct_id2.Precision = 2;
      acct_id2.Value = 2;
      acct_id2.ParameterName = "acct_id";
      cmdSelect.Parameters.Add(acct_id2);
      OracleDataReader reader = cmdSelect.ExecuteReader();
      if (reader.Read())
      {
        Console.WriteLine(reader.GetDecimal(0).ToString());
        Console.WriteLine(reader.GetDecimal(1).ToString());
      }
      trans.Rollback();
      reader.Close();
      reader = cmdSelect.ExecuteReader();
      if (reader.Read())
      {
        Console.WriteLine(reader.GetDecimal(0).ToString());
        Console.WriteLine(reader.GetDecimal(1).ToString());
      }
    }
  }

Runs the CustomerAdd stored procedure.

using System;
using System.Data;
using System.Data.SqlClient;
public class AddCustomer
{
    public static void Main() 
    {
        string connectionString = "Data Source=localhost;Initial Catalog=store;Integrated Security=SSPI";
        string procedure = "CustomerAdd";
        SqlConnection con = new SqlConnection(connectionString);
        SqlCommand cmd = new SqlCommand(procedure, con);
        cmd.rumandType = CommandType.StoredProcedure;
        SqlParameter param;
        param = cmd.Parameters.Add("@FullName", SqlDbType.NVarChar, 50);
        param.Value = "AAA";
        param = cmd.Parameters.Add("@Email", SqlDbType.NVarChar, 50);
        param.Value = "j@my.ru";
        param = cmd.Parameters.Add("@Password", SqlDbType.NVarChar, 50);
        param.Value = "password";
        param = cmd.Parameters.Add("@CustomerID", SqlDbType.Int);
        param.Direction = ParameterDirection.Output;
        con.Open();
        cmd.ExecuteNonQuery();
        con.Close();
        Console.WriteLine(param.Value);
    }
}

Use OracleConnection to connect to Oracle database

using System;
using System.Data.OracleClient;
  class Class1
  {
    [STAThread]
    static void Main(string[] args)
    {
      String connString = "User Id=oranetuser;Password=demo;Data Source=oranet";
      OracleConnection oraConnection = new OracleConnection(connString);
        oraConnection.Open();
        Console.WriteLine("Connection String: ");
        Console.WriteLine(oraConnection.ConnectionString.ToString() + "\n");
        Console.WriteLine("Current Connection State: ");
        Console.WriteLine(oraConnection.State.ToString() + "\n");
        Console.WriteLine("Oracle Database Server Version: ");
        Console.WriteLine(oraConnection.ServerVersion.ToString());
    }
  }

Using OracleCommandBuilder

using System;
using System.Drawing;
using System.Collections;
using System.ruponentModel;
using System.Windows.Forms;
using System.Data;
using System.Data.OracleClient;
  public class Form1 : System.Windows.Forms.Form
  {
    public Form1()
    {
      this.btnConnect = new System.Windows.Forms.Button();
      this.btnClear = new System.Windows.Forms.Button();
      this.btnLoad = new System.Windows.Forms.Button();
      this.dgPlayerTable = new System.Windows.Forms.DataGrid();
      this.btnUpdate = new System.Windows.Forms.Button();
      this.btnBind = new System.Windows.Forms.Button();
      ((System.ruponentModel.ISupportInitialize)(this.dgPlayerTable)).BeginInit();
      this.SuspendLayout();
      this.btnConnect.Location = new System.Drawing.Point(16, 12);
      this.btnConnect.Text = "C&onnect";
      this.btnConnect.Click += new System.EventHandler(this.btnConnect_Click);
      this.btnClear.Location = new System.Drawing.Point(16, 84);
      this.btnClear.Text = "&Clear Grid";
      this.btnClear.Click += new System.EventHandler(this.btnClear_Click);
      this.btnLoad.Location = new System.Drawing.Point(16, 120);
      this.btnLoad.Text = "&Load Grid";
      this.btnLoad.Click += new System.EventHandler(this.btnLoad_Click);
      this.dgPlayerTable.DataMember = "";
      this.dgPlayerTable.HeaderForeColor = System.Drawing.SystemColors.ControlText;
      this.dgPlayerTable.Location = new System.Drawing.Point(108, 12);
      this.dgPlayerTable.Size = new System.Drawing.Size(476, 244);
      this.btnUpdate.Location = new System.Drawing.Point(16, 156);
      this.btnUpdate.Text = "U&pdate";
      this.btnUpdate.Click += new System.EventHandler(this.btnUpdate_Click);
      this.btnBind.Location = new System.Drawing.Point(16, 48);
      this.btnBind.Text = "&Bind";
      this.btnBind.Click += new System.EventHandler(this.btnBind_Click);
      this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
      this.ClientSize = new System.Drawing.Size(594, 266);
      this.Controls.Add(this.btnBind);
      this.Controls.Add(this.btnUpdate);
      this.Controls.Add(this.dgPlayerTable);
      this.Controls.Add(this.btnLoad);
      this.Controls.Add(this.btnClear);
      this.Controls.Add(this.btnConnect);
      this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.Fixed3D;
      this.Name = "Form1";
      this.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen;
      this.Text = "OracleDataAdapter Sample";
      this.Load += new System.EventHandler(this.Form1_Load);
      ((System.ruponentModel.ISupportInitialize)(this.dgPlayerTable)).EndInit();
      this.ResumeLayout(false);
    }
    static void Main() 
    {
      Application.Run(new Form1());
    }
    private System.Windows.Forms.Button btnConnect;
    private System.Windows.Forms.Button btnClear;
    private System.Windows.Forms.Button btnLoad;
    private System.Windows.Forms.DataGrid dgPlayerTable;
    private System.Windows.Forms.Button btnUpdate;
    private System.Windows.Forms.Button btnBind;
    public OracleConnection oraConn;
    public OracleDataAdapter oraAdapter;
    public OracleCommandBuilder oraBuilder;
    public DataSet dsPlayerTable;
    private void btnConnect_Click(object sender, System.EventArgs e)
    {
      string connString = "User Id=oranetuser; Password=demo; Data Source=oranet";
      if (oraConn.State != ConnectionState.Open)
      {
        try
        {
          oraConn.ConnectionString = connString;
          oraConn.Open();
          MessageBox.Show(oraConn.ConnectionString, "Successful Connection");
        }
        catch (Exception ex)
        {
          MessageBox.Show(ex.Message,"Exception Caught");
        }
      }    
    }
    private void Form1_Load(object sender, System.EventArgs e)
    {
      oraConn = new OracleConnection();
    }
    private void btnBind_Click(object sender, System.EventArgs e)
    {
      if (oraConn.State == ConnectionState.Open)
      {
        string strSelect = "select player_num, last_name, first_name, from PlayerTable order by player_num";
        oraAdapter = new OracleDataAdapter(strSelect, oraConn);
        oraBuilder = new OracleCommandBuilder(oraAdapter);
        dsPlayerTable = new DataSet("dsPlayerTable");
        oraAdapter.Fill(dsPlayerTable,"PlayerTable");
        dgPlayerTable.SetDataBinding(dsPlayerTable,"PlayerTable");
        btnBind.Enabled = false;
      }
    }
    private void btnClear_Click(object sender, System.EventArgs e)
    {
      dsPlayerTable.Clear();
      dgPlayerTable.SetDataBinding(null,null);
    }
    private void btnLoad_Click(object sender, System.EventArgs e)
    {
      btnClear_Click(sender, e);
      oraAdapter.Fill(dsPlayerTable,"PlayerTable");
      dgPlayerTable.SetDataBinding(dsPlayerTable,"PlayerTable");      
    }
    private void btnUpdate_Click(object sender, System.EventArgs e)
    {
      oraAdapter.Update(dsPlayerTable,"PlayerTable");
    }
  }

Using OracleCommand to do query

using System;
using System.Drawing;
using System.Collections;
using System.ruponentModel;
using System.Windows.Forms;
using System.Data;
using System.Data.OracleClient;
  public class Form1 : System.Windows.Forms.Form
  {
    private System.Windows.Forms.Button btnConnect;
    private System.Windows.Forms.Button btnRetrieve;
    private System.Windows.Forms.ListBox listJobs;
    public Form1()
    {
      this.btnConnect = new System.Windows.Forms.Button();
      this.btnRetrieve = new System.Windows.Forms.Button();
      this.listJobs = new System.Windows.Forms.ListBox();
      this.SuspendLayout();
      this.btnConnect.Location = new System.Drawing.Point(12, 28);
      this.btnConnect.Text = "C&onnect";
      this.btnConnect.Click += new System.EventHandler(this.btnConnect_Click);
      this.btnRetrieve.Location = new System.Drawing.Point(12, 64);
      this.btnRetrieve.Text = "&Retrieve";
      this.btnRetrieve.Click += new System.EventHandler(this.btnRetrieve_Click);
      this.listJobs.Font = new System.Drawing.Font("Courier New", 9F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((System.Byte)(0)));
      this.listJobs.ItemHeight = 15;
      this.listJobs.Location = new System.Drawing.Point(100, 28);
      this.listJobs.Size = new System.Drawing.Size(524, 244);
      this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
      this.ClientSize = new System.Drawing.Size(634, 284);
      this.Controls.Add(this.listJobs);
      this.Controls.Add(this.btnRetrieve);
      this.Controls.Add(this.btnConnect);
      this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.Fixed3D;
      this.MaximizeBox = false;
      this.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen;
      this.Text = "TableDirect Sample";
      this.Load += new System.EventHandler(this.Form1_Load);
      this.ResumeLayout(false);
    }
    static void Main() 
    {
      Application.Run(new Form1());
    }
    private void btnConnect_Click(object sender, System.EventArgs e)
    {
      string connString = "User Id=hr; Password=demo; Data Source=oranet";
      if (oraConn.State != ConnectionState.Open)
      {
        try
        {
          oraConn.ConnectionString = connString;
          oraConn.Open();
          MessageBox.Show(oraConn.ConnectionString, "Successful Connection");
        }
        catch (Exception ex)
        {
          MessageBox.Show(ex.Message,"Exception Caught");
        }
      }
    }
    private OracleConnection oraConn;
    private void Form1_Load(object sender, System.EventArgs e)
    {
      oraConn = new OracleConnection();
    }
    private void btnRetrieve_Click(object sender, System.EventArgs e)
    {
      OracleCommand cmdEmployees = new OracleCommand();
      cmdEmployees.Connection = oraConn;
      cmdEmployees.rumandType = CommandType.Text;
      cmdEmployees.rumandText = "SELECT * FROM JOBS";
      string headText = "Job".PadRight(12);
      headText += "Title".PadRight(37);
      headText += "Min Salary".PadRight(12);
      headText += "Max Salary".PadRight(12);
      string headSep = "----";
      if (oraConn.State == ConnectionState.Open)
      {
        try
        {
          OracleDataReader dataReader = cmdEmployees.ExecuteReader();
          listJobs.Items.Add(headText);
          listJobs.Items.Add(headSep);
          string textLine = "";
          while (dataReader.Read())
          {
            textLine = dataReader.GetString(0);
            textLine += dataReader.GetString(1);
            textLine += dataReader.GetDecimal(2).ToString();
            textLine += dataReader.GetDecimal(3).ToString();
            listJobs.Items.Add(textLine);
          }
        }
        catch (Exception ex)
        {
          MessageBox.Show(ex.Message,"Exception Caught");
        }
      }
      cmdEmployees.Dispose();
    }
  }

Using OracleCommand to do the query sql

using System;
using System.Data;
using System.Data.OracleClient;
class Class1{
    static void Main(string[] args)
    {
      string connstr = "User Id=scott; Password=tiger; Data Source=oranet";
      OracleConnection con = new OracleConnection(connstr);
      con.Open();
      string sql = "select empno, ename from emp";
      OracleCommand cmd = new OracleCommand(sql, con);
      OracleDataReader dr = cmd.ExecuteReader();
      while (dr.Read())
      {
        Console.Write(dr[0].ToString() + "\t");
        Console.Write(dr[1].ToString() + "\t");
        Console.Write(dr[2].ToString() + "\t");
        Console.WriteLine(dr[3].ToString());
      }
      // close and dispose the objects
      dr.Close();
      dr.Dispose();
      cmd.Dispose();
      con.Close();
      con.Dispose();
    }
}

Using OracleDataAdapter

using System;
using System.Drawing;
using System.Collections;
using System.ruponentModel;
using System.Windows.Forms;
using System.Data;
using System.Data.OracleClient;
  public class Form1 : System.Windows.Forms.Form
  {
    public Form1()
    {
      this.btnConnect = new System.Windows.Forms.Button();
      this.btnClear = new System.Windows.Forms.Button();
      this.btnLoad = new System.Windows.Forms.Button();
      this.dgPlayerTable = new System.Windows.Forms.DataGrid();
      this.btnUpdate = new System.Windows.Forms.Button();
      this.btnBind = new System.Windows.Forms.Button();
      ((System.ruponentModel.ISupportInitialize)(this.dgPlayerTable)).BeginInit();
      this.SuspendLayout();
      this.btnConnect.Location = new System.Drawing.Point(16, 12);
      this.btnConnect.Text = "C&onnect";
      this.btnConnect.Click += new System.EventHandler(this.btnConnect_Click);
      this.btnClear.Location = new System.Drawing.Point(16, 84);
      this.btnClear.Text = "&Clear Grid";
      this.btnClear.Click += new System.EventHandler(this.btnClear_Click);
      this.btnLoad.Location = new System.Drawing.Point(16, 120);
      this.btnLoad.Text = "&Load Grid";
      this.btnLoad.Click += new System.EventHandler(this.btnLoad_Click);
      this.dgPlayerTable.DataMember = "";
      this.dgPlayerTable.HeaderForeColor = System.Drawing.SystemColors.ControlText;
      this.dgPlayerTable.Location = new System.Drawing.Point(108, 12);
      this.dgPlayerTable.Size = new System.Drawing.Size(476, 244);
      this.btnUpdate.Location = new System.Drawing.Point(16, 156);
      this.btnUpdate.Text = "U&pdate";
      this.btnUpdate.Click += new System.EventHandler(this.btnUpdate_Click);
      this.btnBind.Location = new System.Drawing.Point(16, 48);
      this.btnBind.Text = "&Bind";
      this.btnBind.Click += new System.EventHandler(this.btnBind_Click);
      this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
      this.ClientSize = new System.Drawing.Size(594, 266);
      this.Controls.Add(this.btnBind);
      this.Controls.Add(this.btnUpdate);
      this.Controls.Add(this.dgPlayerTable);
      this.Controls.Add(this.btnLoad);
      this.Controls.Add(this.btnClear);
      this.Controls.Add(this.btnConnect);
      this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.Fixed3D;
      this.Name = "Form1";
      this.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen;
      this.Text = "OracleDataAdapter Sample";
      this.Load += new System.EventHandler(this.Form1_Load);
      ((System.ruponentModel.ISupportInitialize)(this.dgPlayerTable)).EndInit();
      this.ResumeLayout(false);
    }
    static void Main() 
    {
      Application.Run(new Form1());
    }
    private System.Windows.Forms.Button btnConnect;
    private System.Windows.Forms.Button btnClear;
    private System.Windows.Forms.Button btnLoad;
    private System.Windows.Forms.DataGrid dgPlayerTable;
    private System.Windows.Forms.Button btnUpdate;
    private System.Windows.Forms.Button btnBind;
    public OracleConnection oraConn;
    public OracleDataAdapter oraAdapter;
    public OracleCommandBuilder oraBuilder;
    public DataSet dsPlayerTable;
    private void btnConnect_Click(object sender, System.EventArgs e)
    {
      string connString = "User Id=oranetuser; Password=demo; Data Source=oranet";
      if (oraConn.State != ConnectionState.Open)
      {
        try
        {
          oraConn.ConnectionString = connString;
          oraConn.Open();
          MessageBox.Show(oraConn.ConnectionString, "Successful Connection");
        }
        catch (Exception ex)
        {
          MessageBox.Show(ex.Message,"Exception Caught");
        }
      }    
    }
    private void Form1_Load(object sender, System.EventArgs e)
    {
      oraConn = new OracleConnection();
    }
    private void btnBind_Click(object sender, System.EventArgs e)
    {
      if (oraConn.State == ConnectionState.Open)
      {
        string strSelect = "select player_num, last_name, first_name, from PlayerTable order by player_num";
        oraAdapter = new OracleDataAdapter(strSelect, oraConn);
        oraBuilder = new OracleCommandBuilder(oraAdapter);
        dsPlayerTable = new DataSet("dsPlayerTable");
        oraAdapter.Fill(dsPlayerTable,"PlayerTable");
        dgPlayerTable.SetDataBinding(dsPlayerTable,"PlayerTable");
        btnBind.Enabled = false;
      }
    }
    private void btnClear_Click(object sender, System.EventArgs e)
    {
      dsPlayerTable.Clear();
      dgPlayerTable.SetDataBinding(null,null);
    }
    private void btnLoad_Click(object sender, System.EventArgs e)
    {
      btnClear_Click(sender, e);
      oraAdapter.Fill(dsPlayerTable,"PlayerTable");
      dgPlayerTable.SetDataBinding(dsPlayerTable,"PlayerTable");      
    }
    private void btnUpdate_Click(object sender, System.EventArgs e)
    {
      oraAdapter.Update(dsPlayerTable,"PlayerTable");
    }
  }

Using OracleDataReader to read from Oracle database

using System;
using System.Data;
using System.Data.OracleClient;
  class Class1
  {
    static void Main(string[] args)
    {
      string connString = "User Id=" + args[0].ToString() + ";";
      connString += "Password=" + args[1].ToString() + ";";
      connString += "Data Source=" + args[2].ToString();
      OracleConnection oraConn = new OracleConnection();
      oraConn.ConnectionString = connString;
      string sqlStatement = "select * from " + args[3].ToString();
      int fieldCount = 0;
      int i = 0;
      oraConn.Open();
      if (oraConn.State == ConnectionState.Open)
      {
          OracleCommand cmdSQL = new OracleCommand(sqlStatement,oraConn);
          OracleDataReader dataReader = cmdSQL.ExecuteReader();
          fieldCount = dataReader.FieldCount;
          for (i = 0; i < fieldCount; i++)
          {
            Console.Write(dataReader.GetName(i));
            if (i < fieldCount - 1)
            {
              Console.Write(",");
            }
          }
          Console.WriteLine();
          while (dataReader.Read())
          {
            for (i = 0; i < fieldCount; i++)
            {
              if (!dataReader.IsDBNull(i))
              {
                Console.Write(dataReader[i].ToString());
              }
              else
              {
                Console.Write("(null)");
              }
              if (i < fieldCount - 1)
              {
                Console.Write(",");
              }
            }
          }
      }
      if (oraConn.State == ConnectionState.Open)
      {
        oraConn.Close();
      }
      oraConn.Dispose();
    }
  }

Using OracleParameter

using System;
using System.Drawing;
using System.Collections;
using System.ruponentModel;
using System.Windows.Forms;
using System.Data;
using System.Data.OracleClient;

  public class Form1 : System.Windows.Forms.Form
  {
    private System.Windows.Forms.Button btnConnect;
    private System.Windows.Forms.Button btnGetIDs;
    private System.Windows.Forms.Label label1;
    private System.Windows.Forms.ruboBox cbEmpIds;
    private System.Windows.Forms.Label lblFirstName;
    private System.Windows.Forms.Label lblLastName;
    private System.Windows.Forms.Label label4;
    private System.Windows.Forms.Label label5;
    private System.Windows.Forms.Button btnLookup1;
    private System.Windows.Forms.Button btnLookup2;
    private System.Windows.Forms.Label lblEmail;
    private System.Windows.Forms.Label lblPhone;
    private System.Windows.Forms.Label lblEmailText;
    private System.Windows.Forms.Label lblPhoneText;
    private System.Windows.Forms.Button btnReset;
    private System.Windows.Forms.Button btnNoBinds;
    private System.ruponentModel.Container components = null;
    public Form1()
    {
      this.btnConnect = new System.Windows.Forms.Button();
      this.btnGetIDs = new System.Windows.Forms.Button();
      this.cbEmpIds = new System.Windows.Forms.ruboBox();
      this.label1 = new System.Windows.Forms.Label();
      this.lblFirstName = new System.Windows.Forms.Label();
      this.lblLastName = new System.Windows.Forms.Label();
      this.label4 = new System.Windows.Forms.Label();
      this.label5 = new System.Windows.Forms.Label();
      this.btnLookup1 = new System.Windows.Forms.Button();
      this.btnLookup2 = new System.Windows.Forms.Button();
      this.lblEmail = new System.Windows.Forms.Label();
      this.lblPhone = new System.Windows.Forms.Label();
      this.lblEmailText = new System.Windows.Forms.Label();
      this.lblPhoneText = new System.Windows.Forms.Label();
      this.btnReset = new System.Windows.Forms.Button();
      this.btnNoBinds = new System.Windows.Forms.Button();
      this.SuspendLayout();
      this.btnConnect.Location = new System.Drawing.Point(32, 44);
      this.btnConnect.Text = "C&onnect";
      this.btnConnect.Click += new System.EventHandler(this.btnConnect_Click);
      this.btnGetIDs.Location = new System.Drawing.Point(32, 80);
      this.btnGetIDs.Text = "&Get IDs";
      this.btnGetIDs.Click += new System.EventHandler(this.btnGetIDs_Click);
      this.cbEmpIds.DropDownStyle = System.Windows.Forms.ruboBoxStyle.DropDownList;
      this.cbEmpIds.Location = new System.Drawing.Point(144, 44);
      this.cbEmpIds.Size = new System.Drawing.Size(68, 21);
      this.label1.Location = new System.Drawing.Point(144, 24);
      this.label1.Size = new System.Drawing.Size(72, 16);
      this.label1.Text = "&Employee ID:";
      this.lblFirstName.Location = new System.Drawing.Point(228, 48);
      this.lblFirstName.Size = new System.Drawing.Size(116, 16);
      this.lblLastName.Location = new System.Drawing.Point(364, 48);
      this.lblLastName.Size = new System.Drawing.Size(128, 16);
      this.label4.Location = new System.Drawing.Point(228, 24);
      this.label4.Size = new System.Drawing.Size(100, 16);
      this.label4.Text = "&First Name:";
      this.label5.Location = new System.Drawing.Point(364, 24);
      this.label5.Size = new System.Drawing.Size(100, 16);
      this.label5.Text = "&Last Name:";
      this.btnLookup1.Location = new System.Drawing.Point(32, 116);
      this.btnLookup1.Text = "Lookup &1";
      this.btnLookup1.Click += new System.EventHandler(this.btnLookup1_Click);
      this.btnLookup2.Location = new System.Drawing.Point(32, 152);
      this.btnLookup2.Text = "Lookup &2";
      this.btnLookup2.Click += new System.EventHandler(this.btnLookup2_Click);
      this.lblEmail.Location = new System.Drawing.Point(228, 88);
      this.lblEmail.Size = new System.Drawing.Size(100, 16);
      this.lblEmail.Text = "E&mail:";
      this.lblPhone.Location = new System.Drawing.Point(364, 88);
      this.lblPhone.Size = new System.Drawing.Size(100, 16);
      this.lblPhone.Text = "Phone &Number:";
      this.lblEmailText.Location = new System.Drawing.Point(228, 112);
      this.lblEmailText.Size = new System.Drawing.Size(116, 16);
      this.lblPhoneText.Location = new System.Drawing.Point(364, 112);
      this.lblPhoneText.Size = new System.Drawing.Size(128, 16);
      this.btnReset.Location = new System.Drawing.Point(32, 224);
      this.btnReset.Text = "&Reset";
      this.btnReset.Click += new System.EventHandler(this.btnReset_Click);
      this.btnNoBinds.Location = new System.Drawing.Point(32, 188);
      this.btnNoBinds.Text = "No &Binds";
      this.btnNoBinds.Click += new System.EventHandler(this.btnNoBinds_Click);
      this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
      this.ClientSize = new System.Drawing.Size(534, 264);
      this.Controls.Add(this.btnNoBinds);
      this.Controls.Add(this.btnReset);
      this.Controls.Add(this.lblPhoneText);
      this.Controls.Add(this.lblEmailText);
      this.Controls.Add(this.lblPhone);
      this.Controls.Add(this.lblEmail);
      this.Controls.Add(this.btnLookup2);
      this.Controls.Add(this.btnLookup1);
      this.Controls.Add(this.label5);
      this.Controls.Add(this.label4);
      this.Controls.Add(this.lblLastName);
      this.Controls.Add(this.lblFirstName);
      this.Controls.Add(this.label1);
      this.Controls.Add(this.cbEmpIds);
      this.Controls.Add(this.btnGetIDs);
      this.Controls.Add(this.btnConnect);
      this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.Fixed3D;
      this.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen;
      this.Text = "Oracle Parameter Sample";
      this.Load += new System.EventHandler(this.Form1_Load);
      this.ResumeLayout(false);
    }
    static void Main() 
    {
      Application.Run(new Form1());
    }
    private OracleConnection oraConn;
    private void btnConnect_Click(object sender, System.EventArgs e)
    {
      string connString = "User Id=hr; Password=demo; Data Source=oranet";
      if (oraConn.State != ConnectionState.Open)
      {
        try
        {
          oraConn = new OracleConnection(connString);
          oraConn.Open();
          MessageBox.Show(oraConn.ConnectionString, "Successful Connection");
        }
        catch (Exception ex)
        {
          MessageBox.Show(ex.Message,"Exception Caught");
        }
      }
    }
    private void btnGetIDs_Click(object sender, System.EventArgs e)
    {
      OracleCommand cmdEmpId = new OracleCommand();
      cmdEmpId.rumandText = "select employee_id from employees order by employee_id";
      cmdEmpId.Connection = oraConn;
      try
      {
        OracleDataReader dataReader = cmdEmpId.ExecuteReader();
        while (dataReader.Read())
        {
          cbEmpIds.Items.Add(dataReader.GetDecimal(0));
        }
        dataReader.Dispose();
      }
      catch (Exception ex)
      {
        MessageBox.Show(ex.Message,"Exception Caught");
      }
      finally
      {
        cmdEmpId.Dispose();
      }
    }
    private void Form1_Load(object sender, System.EventArgs e)
    {
      oraConn = new OracleConnection();
    }
    private void btnLookup1_Click(object sender, System.EventArgs e)
    {
      object selectedItem = cbEmpIds.SelectedItem;
      if (selectedItem != null)
      {
        OracleCommand cmdEmpName = new OracleCommand();
        cmdEmpName.rumandText = "select first_name, last_name from employees where employee_id = :p_id";
    
        cmdEmpName.Connection = oraConn;
        OracleParameter p_id = new OracleParameter();
        p_id.DbType = DbType.Decimal;
        p_id.Value = Convert.ToDecimal(selectedItem.ToString());
        p_id.ParameterName = "p_id";
        cmdEmpName.Parameters.Add(p_id);
        OracleDataReader dataReader = cmdEmpName.ExecuteReader();
        if (dataReader.Read())
        {
          lblFirstName.Text = dataReader.GetString(0);
          lblLastName.Text = dataReader.GetString(1);
        }
        dataReader.Close();
        dataReader.Dispose();
        cmdEmpName.Dispose();
      }    
    }
    private void btnLookup2_Click(object sender, System.EventArgs e)
    {
      OracleCommand cmdEmpInfo = new OracleCommand();
      cmdEmpInfo.rumandText = "select email, phone_number from employees where first_name = :p_first and last_name = :p_last";
      cmdEmpInfo.Connection = oraConn;
      OracleParameter p1 = new OracleParameter();
      OracleParameter p2 = new OracleParameter();
      p1.ParameterName = "p_first";
      p2.ParameterName = "p_last";
      p1.Value = lblFirstName.Text;
      p2.Value = lblLastName.Text;
      cmdEmpInfo.Parameters.Add(p2);
      cmdEmpInfo.Parameters.Add(p1);
      OracleDataReader dataReader = cmdEmpInfo.ExecuteReader();
      if (dataReader.Read())
      {
        lblEmailText.Text = dataReader.GetString(0);
        lblPhoneText.Text = dataReader.GetString(1);
      }
      dataReader.Close();
      dataReader.Dispose();
      cmdEmpInfo.Dispose();
    }
    private void btnReset_Click(object sender, System.EventArgs e)
    {
      cbEmpIds.SelectedIndex = -1;
      lblFirstName.Text = "";
      lblLastName.Text = "";
      lblEmailText.Text = "";
      lblPhoneText.Text = "";
    }
    private void btnNoBinds_Click(object sender, System.EventArgs e)
    {
      object selectedItem = cbEmpIds.SelectedItem;
      if (selectedItem != null)
      {
        OracleCommand cmdNoBinds = new OracleCommand();
        cmdNoBinds.Connection = oraConn;
        OracleDataReader dataReader;
        cmdNoBinds.rumandText = "select first_name, last_name from employees where employee_id = " + selectedItem.ToString();
        dataReader = cmdNoBinds.ExecuteReader();
        if (dataReader.Read())
        {
          lblFirstName.Text = dataReader.GetString(0);
          lblLastName.Text = dataReader.GetString(1);
        }
        dataReader.Close();
        cmdNoBinds.rumandText = "select email, phone_number from employees where first_name = "" + lblFirstName.Text + "" and last_name = "" + lblLastName.Text +""";
        dataReader = cmdNoBinds.ExecuteReader();
        if (dataReader.Read())
        {
          lblEmailText.Text = dataReader.GetString(0);
          lblPhoneText.Text = dataReader.GetString(1);
        }
        dataReader.Close();
        dataReader.Dispose();
        cmdNoBinds.Dispose();
      }
    }
  }