C#

TcpClient SmtpServ = new TcpClient("smtp.my.com", 25);
            string Data;
            byte[] szData;
            string CRLF = "\r\n";
 
            try
            {
                // initialization
                NetworkStream NetStrm = SmtpServ.GetStream();
                StreamReader RdStrm = new StreamReader(SmtpServ.GetStream());
                Console.WriteLine(RdStrm.ReadLine());
 
                // say hello to server and send response into log report
                Data = "HELO server" + CRLF;
                szData = System.Text.Encoding.ASCII.GetBytes(Data.ToCharArray());
                NetStrm.Write(szData, 0, szData.Length);
                Console.WriteLine(RdStrm.ReadLine());
                // send sender data
                Data = "MAIL From:" + " me@test.com" + CRLF;
                szData = System.Text.Encoding.ASCII.GetBytes(Data.ToCharArray());
                NetStrm.Write(szData, 0, szData.Length);
                Console.WriteLine(RdStrm.ReadLine());
 
                // send receiver data
                Data = "RCPT TO: " + "me@my.net" + CRLF;
                szData = System.Text.Encoding.ASCII.GetBytes(Data.ToCharArray());
                NetStrm.Write(szData, 0, szData.Length);
                Console.WriteLine(RdStrm.ReadLine());
 
                // send DATA
                Data = "DATA" + CRLF;
                szData = System.Text.Encoding.ASCII.GetBytes(Data.ToCharArray());
                NetStrm.Write(szData, 0, szData.Length);
                Console.WriteLine(RdStrm.ReadLine());
 
                // send content data
                Data = "SUBJECT: my subject\r\n\r\n";
                Data += "Hello there!\r\n";
                Data += ".\r\n";
                szData = System.Text.Encoding.ASCII.GetBytes(Data.ToCharArray());
                NetStrm.Write(szData, 0, szData.Length);
                Console.WriteLine(RdStrm.ReadLine());
 

                // quit from server SMTP
                Data = "QUIT" + CRLF;
                szData = System.Text.Encoding.ASCII.GetBytes(Data.ToCharArray());
                NetStrm.Write(szData, 0, szData.Length);
                Console.WriteLine(RdStrm.ReadLine());
 
                // close connection
                NetStrm.Close();
                RdStrm.Close();
                Console.WriteLine("Close connection");
                Console.WriteLine("Send mail successly..");
 
            }
            catch (InvalidOperationException err)
            {
                Console.WriteLine("Error: " + err.ToString());
            }

--  Connect.cs file.
public static void connectDB()
    {
        try
        {
                conn.ConnectionString = connection;
                conn.Open();
        }
        catch
        {
            //closeConnectDB();
        }
    }
    public static void closeConnectDB()
    {
        //conn.Dispose();
            conn.Close();
        //conn.Dispose();
    }
    public static int ExecuteQuery(string SQL)
    {
        try
        {
            connectDB();
            NpgsqlCommand cmd = new NpgsqlCommand(SQL, conn);
            return cmd.ExecuteNonQuery();
        }
        catch
        {
            closeConnectDB();
            return 0;
        }
        
    }

    public static DataSet SelectQuery(string SQL)
    {
        DataSet ds = new DataSet();
        try
        {
            connectDB();
            NpgsqlDataAdapter nDa = new NpgsqlDataAdapter(SQL, conn);
            
            nDa.Fill(ds);
            // closeConnectDB();
            return ds;
        }
        catch
        {
            closeConnectDB();
            return ds;
        }
        
    }

--- calling functions files.
try
                        {
                            string strTest = "Select * from abc where .. ";
                            DataSet ds1 = new DataSet();
                            ds1 = Connect.SelectQuery(strTest);
                            if (ds1.Tables[0].Rows.Count > 0)
                            {
                                
                            }
                            else
                            {
                                int kq = Connect.ExecuteQuery(strInsert);
                                if (kq > 0)
                                {
                                    int kk = Connect.ExecuteQuery(strUpdate);
                                    kk = Connect.ExecuteQuery(strUpdate2);
                                    
                                    strHTML = "OK";
                                }
                            }
                        }
                        catch
                        {
                            strHTML = "errors.";
                        }
                        finally
                        {
                            int kk = Connect.ExecuteQuery(strUpdate);
                            kk = Connect.ExecuteQuery(strUpdate2);
                            
                            strHTML += "-- Sub Finally";
                        }

private WebResponse webPOST(string URLextension, string Parameters)
{
    HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(BASE_URL + URLextension);
    request.ContentType = "application/x-www-form-urlencoded";
    request.Method = "POST";
    request.Headers.Add("X-Requested-With: C# Interface");
    request.CookieContainer = _cookieJar;
    request.Timeout = 3600000;  //1 HOUR TIMEOUT
    if (_proxy != string.Empty)
    {
        request.Proxy = new System.Net.WebProxy(_proxy, false);
        request.Proxy.Credentials = new 
            NetworkCredential(_proxyUser.ConvertToUnsecureString(), _proxyPass.ConvertToUnsecureString());
    }
    byte[] buffer = Encoding.GetEncoding("UTF-8").GetBytes(Parameters);
    Stream reqstr = request.GetRequestStream();
    reqstr.Write(buffer, 0, buffer.Length);
    reqstr.Close();
    return request.GetResponse();
}