Question

I am trying to connect to a mysql database, my credentials(username, password, database name… etc) are all correct to my knowledge. I got stuck at coonection.open() statement which displays an error of the connection being already opened.

I searched for help at other sites, it has been reported as a bug… http://support.microsoft.com/kb/823401

While searching for alternative solutions I came across

   using ( connection = MySqlConnection(connectionString))

I was unable to proceed with it. Any help with it would be really appreciated.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using MySql.Data.MySqlClient;
using System.Windows.Forms;

namespace HotelManagement
{
class DBConnect
{
    private MySqlConnection connection;
    private string server;
    private string database;
    private string uid;
    private string password;

    //constructor
    public DBConnect()
    {
        Initialize();
    }

    private void Initialize()
    {
        server = "localhost";
        database = "hm";
        uid = "root";
        password = "password";
        string connectionString;
        connectionString = "SERVER=" + server + ";" + "DATABASE=" + database + ";" +    "UID=" + uid + ";" + "PASSWORD=" + password + ";";

        connection = new MySqlConnection(connectionString);
    }

    public bool openConnection()
    {
        try
        {
            connection.Open();  //*SHOWS ERROR InvalidOperationUnhandled: Conection already open*
            return true;

        }
        catch (MySqlException e)
        {
            //error 0: Cannot Connect to the server
            switch (e.Number)
            {
                case 0: MessageBox.Show("Cannot Connect to the server");
                    break;
                case 1045: MessageBox.Show("invalid username/password");
                    break;
            }
            return false;
        }
    }

    public bool closeConnection()
    {
        try
        {
            connection.Close();
            return true;
        }
        catch (MySqlException e)
        {
            MessageBox.Show(e.Message);
            return false;
        }
    }

    public void insert()
    {
        string query = "insert into test (i) values (10)";
        if (this.openConnection() == true)
        {
            //creating command and connections
            MySqlCommand cmd = new MySqlCommand(query, connection);
            cmd.ExecuteNonQuery();
            this.closeConnection();
        }
    }

    }

}

Answer 1

You must close your connection , you have not closed connection (Maybe after first debug)

You can use

connection.Close();

Best Practise :

I suggest you to use using block, in order to ensure that you clean non managed object in the end of treatment

using(var connection = new MySqlConnection(...))
{
  ...
}