How to use Asynch in C# correctly?

Question

I have a demo application from the supplier. This demo application allows me to connect to a RFID reader via a network connection. Once the connection is established I can then scan for RFID tags and the tag data is then displayed on the application.

The eventhandler is raised whenever the CAlienServer receives a message from the RFID reader.

private void addServerEvents(int idx)
{
    mServers[idx].ServerMessageReceived += new CAlienServer.ServerMessageReceivedEventHandler(mServer_ServerMessageReceived);
    mServers[idx].ServerConnectionEstablished += new CAlienServer.ServerConnectionEstablishedEventHandler(mServer_ServerConnectionEstablished);
    mServers[idx].ServerConnectionEnded += new CAlienServer.ServerConnectionEndedEventHandler(mServer_ServerConnectionEnded);
    mServers[idx].ServerSocketError += new CAlienServer.ServerSocketErrorEventHandler(mServer_ServerSocketError);
}

private void mServer_ServerMessageReceived(string msg)
{
    if (msg != null)
    {
        displayText(msg.Insert(msg.IndexOf(" ") + 1, "\r\n"));
    }    
}

private void displayText(String data)
{
    try
    {
        if (this.InvokeRequired)
        {
            object[] temp = {data};
            this.Invoke(new displayMessageDlgt(displayText),temp);
            return;
        }
        else
        {
            txtNotifications.Text += data.Replace("\0","") + "\r\n";
            Task task = insert(data);
            NotifyInfo ni = null;
            AlienUtils.ParseNotification(data, out ni);
            if (ni != null)
            {
                lblReaderName.Text = ni.ReaderName;
            }
        }
    }
    catch(Exception ex)
    {
        Debug.WriteLine("Exception in the DiscplayText(): " + ex.Message);
    }
}

I want to know run another function that stores the data in the variable 'data' or 'msg' into a database. I know calling a synchronous function will not work because what if the programming is running the insertion of the data into the database function and the reader picks up new tags. Hence a synchronous function will not work. I am thinking of using an asynchronous function instead. So my database insertion function is. Is this the correct way to go about it?

private async Task insert(string rfid)
{
   await Task.Factory.StartNew(()=>
   {
      using (var connection = new MySqlConnection("server=localhost;user id='" + username_mysql + "';database=new;password='" + password_mysql + "'"))
      {
        connection.Open();

        try
        {
           string sql = "INSERT INTO `data` (`RFID TAG`) VALUE (@rfid)";

           MySqlCommand cmd = new MySqlCommand(sql, connection);

           cmd.Parameters.Add("@rfid", MySqlDbType.VarChar).Value = rfid;

           if (cmd.ExecuteNonQuery() == 1)
           {
             

           }
        }
        catch (Exception ex)
        {
            
        }
    }
   });
}

Error 1:

Update:

Code:

    private void insert(string rfid)
    {
        using (var connection = new MySqlConnection("server=localhost;user id='" + username_mysql + "';database=alien;password='" + password_mysql + "'"))
        {
            connection.Open();

            try
            {
                string sql = "INSERT INTO `data` (`DATA`) VALUE (@data)";

                MySqlCommand cmd = new MySqlCommand(sql, connection);

                cmd.Parameters.Add("@data", MySqlDbType.VarChar).Value = rfid;

                if (cmd.ExecuteNonQuery() == 1)
                {
                    Debug.WriteLine("Successfull: " + rfid);
                    textBox2.BackColor = Color.Green;

                }
            }
            catch (Exception ex)
            {
                Debug.WriteLine("Exception in the insert(): " + ex.Message);
            }
        }
    }

private void displayText(String data)
{
    try
    {
            if (this.InvokeRequired)
            {
                object[] temp = {data};
                this.Invoke(new displayMessageDlgt(displayText), temp);
                return;
            }
            else
            {
                txtNotifications.Text += data.Replace("\0","") + "\r\n";
                //await Task.Run(() => insert(data));
                insert(data);
                textBox2.BackColor = Color.Red;

                NotifyInfo ni = null;
                AlienUtils.ParseNotification(data, out ni);
                if (ni != null)
                {
                    lblReaderName.Text = ni.ReaderName;
                }
            }
        }
        catch(Exception ex)
        {
            Debug.WriteLine("Exception in the DisplayText(): " + ex.Message);
        }
  }

SERVER MESSAGE is from the mServer_ServerMessageReceived(string msg) method Succesfull is from the insert() method.

This clearly shows that all of that tag data is been inserted in the database.

Debug output:

SERVER MESSAGE: 00:1B:5F:00:F9:B4 0004,3,1

SERVER MESSAGE: 00:1B:5F:00:F9:B4 A123 0001,3,1

Successfull: 00:1B:5F:00:F9:B4 0004,3,1

SERVER MESSAGE: 00:1B:5F:00:F9:B4 A641 2541,3,1

Successfull: 00:1B:5F:00:F9:B4 A123 0001,3,1

SERVER MESSAGE: 00:1B:5F:00:F9:B4 0014,3,1

Successfull: 00:1B:5F:00:F9:B4 A641 2541,3,1

SERVER MESSAGE: 00:1B:5F:00:F9:B4 5253 7AB2 0200 0000 0000 1002,3,1

Successfull: 00:1B:5F:00:F9:B4 0014,3,1

SERVER MESSAGE: 00:1B:5F:00:F9:B4 A064 0001 0601,3,1

Successfull: 00:1B:5F:00:F9:B4 5253 7AB2 0200 0000 0000 1002,3,1

SERVER MESSAGE: 00:1B:5F:00:F9:B4 0000 0000,3,1

SERVER MESSAGE: 00:1B:5F:00:F9:B4 0001,3,1

SERVER MESSAGE: 00:1B:5F:00:F9:B4 2123 6521,3,1

SERVER MESSAGE: 00:1B:5F:00:F9:B4 0016,3,1

Successfull: 00:1B:5F:00:F9:B4 A064 0001 0601,3,1

Successfull: 00:1B:5F:00:F9:B4 0000 0000,3,1

Successfull: 00:1B:5F:00:F9:B4 0001,3,1

Successfull: 00:1B:5F:00:F9:B4 2123 6521,3,1

Successfull: 00:1B:5F:00:F9:B4 0016,3,1

Answer 1

You should probably use ExecuteNonQueryAsync instead. Note that this may or may not actually exectue asynchronous.

For Oracles MySql connector all async method execute synchronously. MySqlConnector claims to provide true async support, but I have not tested this. ( Thanks to Bradley Grainger for additional information.)

Is you determine that the query is actually running synchronous it might be reasonable to run the query on a background thread to avoid blocking the UI (if it is a UI application). If so, it would probably be best to first make a synchronous method.

private void insert(string rfid){
    ...
}

And then call it like

private async Task displayText(String data){
    ....
    await Task.Run(() => insert(rfid));
    ...
}

If you do this you need to guarantee that the method is thread safe. If you cannot guarantee this, you should not run it on another thread. Note that you should ensure exceptions are handled correctly. I.e.

• Avoid en empty catch, all exceptions should be handled somehow. If you could not insert the required data the user should probably be informed.
• All tasks should be awaited, otherwise any exceptions will be lost.
• Avoid using async void since this makes it impossible for the caller await, and therefore cannot receive any exceptions.
• For event handlers (i.e. pressing a button) you will need to use async void, in this case you should ensure that any exceptions are caught and take appropriate action. Probably informing the user of the failure, and/or terminating the application.