Question

Hi all!
I’m trying to synchronize two databases, one local and one remote. The problem is that I have two connections open at once and do not know how. If the two databases I have them locally if I correctly updated because they use the same connection. The problem I have is that the local board to update the program does not see it because the connection is not open, how I can do? This is my code.
Two databases have the same table estructure but user/pass and different database name. Thank you!

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

namespace sincronizacion
{
public partial class Form1 : Form
{
    private string stringConexionLocal ="server=localhost;database=kiosco_m;UID=root;pwd=toor";
    private string stringConexionRemota = "server="ipserverremote";database=grupoorb_kioscom;UID=user_remote;pwd=pass_remote";

    //Instanciado de objetos conexión local
    MySqlConnection conexionLocal;
    MySqlDataAdapter dataAdapterLocal;
    DataSet dataSetLocal;
    MySqlCommandBuilder builderLocal;

    //Instanciado de objetos conexión remota
    MySqlConnection conexionRemota;
    MySqlDataAdapter dataAdapterRemota;
    DataSet dataSetRemoto;
    MySqlCommandBuilder builderRemoto;

    public Form1()
    {
        InitializeComponent();
    }

    private void CargarDatosLocal()
    {
        string Consulta = "SELECT * FROM empresas";
        try
        {
            conexionLocal = new MySqlConnection(this.stringConexionLocal);
            dataAdapterLocal = new MySqlDataAdapter(Consulta, conexionLocal);
            dataSetLocal = new DataSet();
            dataAdapterLocal.Fill(dataSetLocal, "empresas");
            builderLocal = new MySqlCommandBuilder(dataAdapterLocal);
            dataGridView1.DataSource = dataSetLocal;
            dataGridView1.DataMember = "empresas";
        }
        catch (MySqlException ex)
        {
            MessageBox.Show(ex.Message, "Error al intentar conectarse a la BBDD local.", MessageBoxButtons.OK, MessageBoxIcon.Error);
        }

    }

    private void CargarDatosRemoto()
    {
        string Consulta = "SELECT * FROM empresas";
        try
        {
            conexionRemota = new MySqlConnection(this.stringConexionRemota);
            dataAdapterRemota = new MySqlDataAdapter(Consulta, conexionRemota);
            dataSetRemoto = new DataSet();
            dataAdapterRemota.Fill(dataSetRemoto, "empresas");
            builderRemoto = new MySqlCommandBuilder(dataAdapterRemota);
            dataGridView2.DataSource = dataSetRemoto;
            dataGridView2.DataMember = "empresas";

        }
        catch (MySqlException ex)
        {
            MessageBox.Show(ex.Message, "Error al intentar conectarse a la BBDD Remota.", MessageBoxButtons.OK, MessageBoxIcon.Error);
        }

    }

    private void Sincronizar(string miConexionRemota)
    {
        MySqlConnection miConexion = new MySqlConnection(miConexionRemota);
        miConexion.Open();
        MySqlCommand comando = new MySqlCommand();
        MySqlTransaction transaccion;

        // Empieza la transacción
        transaccion = miConexion.BeginTransaction(System.Data.IsolationLevel.ReadCommitted);
        comando.Transaction = transaccion;
        comando.Connection = miConexion;

        try
        {
            comando.CommandText = "UPDATE kiosco_remoto.empresas INNER JOIN kiosco_m.empresas ON kiosco_remoto.empresas.Id = kiosco_m.empresas.Id SET kiosco_remoto.empresas.direccion = kiosco_m.empresas.direccion";
            comando.ExecuteNonQuery();
            transaccion.Commit();
            MessageBox.Show("Se han sincronizado las BBDD correctamente.", "Información", MessageBoxButtons.OK, MessageBoxIcon.Information);
        }
        catch (MySqlException ex)
        {
            transaccion.Rollback();
            MessageBox.Show(ex.Message, "Error al intentar sincronizar.", MessageBoxButtons.OK, MessageBoxIcon.Error);
            //throw ex;

        }
        finally
        {
            CargarDatosLocal();
            CargarDatosRemoto();
            miConexion.Close();
        }

    }

    /* * *
     * 
     * Eventos
     *
     * * */

    private void botonLocal_Click(object sender, EventArgs e)
    {
        CargarDatosLocal();
    }

    private void botonCargaDatosRemoto_Click(object sender, EventArgs e)
    {
        CargarDatosRemoto();
    }

    private void botonGrabarBDLocal_Click(object sender, EventArgs e)
    {
        try
        {
            builderLocal.GetUpdateCommand();
            dataAdapterLocal.Update(dataSetLocal, "empresas");
            CargarDatosLocal();
        }
        catch (NullReferenceException ex)
        {
            MessageBox.Show(ex.Message, "No hay ninguna BBDD abierta.", MessageBoxButtons.OK, MessageBoxIcon.Error);
        }
    }

    private void botonGrabarBDRemota_Click(object sender, EventArgs e)
    {
        try
        {
            builderRemoto.GetUpdateCommand();
            dataAdapterRemota.Update(dataSetRemoto, "empresas");
            CargarDatosRemoto();
        }
        catch (NullReferenceException ex)
        {
            MessageBox.Show(ex.Message, "No hay ninguna BBDD abierta.", MessageBoxButtons.OK, MessageBoxIcon.Error);
        }
    }

    private void Form1_FormClosing(object sender, FormClosingEventArgs e)
    {
        try
        {
            conexionLocal.Close();
            conexionRemota.Close();

            if ((conexionLocal != null) || (conexionRemota != null))
            {
                MessageBox.Show("Se han cerrado todas las conexiones abiertas.", "Información", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
        }
        catch
        {
            // No hago nada.
        }
    }

    private void botonSincro_Click(object sender, EventArgs e)
    {
        Sincronizar(stringConexionRemota);
    }      
}

}

Answer 1

Sadly I don’t quite follow your code as I don’t know the function names, however yes you can have two or more connections to MySQL open.

To synchronize the data is a tricky one, if you want to do a one-way synch then this wouldn’t be difficult to do, but if you wanted a two way then you would have to handle a lot of exceptions for when there is duplicate data.

If you want to get data from local database to a remote database then something like this would work:

string const query = "SELECT * FROM LocalTableName";
using (DbCommand sql =_MySQLConnection.CreateCommand()){
    sql.CommandText = query;
    using (DbDataReader row = sql.ExecuteReader()){
        // the data is sstored in row now upload to remote
        using (DbCommand sql_remote = _MySQLRemote.CreateCommand()){
            sql_remote.CommandText = "INSERT INTO RemoteTableName SET field1 = @p_field1";
            sql.Parameters.Add("@p_field1", row["field1"].toString());
            sql.ExecuteNonQuery();
            sql.Parameters.Clear();
        }
    }
}

sorry it’s untested and may have coding errors as I’m not infront of VS to test