C#

private void Main_Load(object sender, EventArgs e)
{ 
    port = new SerialPort("COM1", 9600, Parity.None, 8, StopBits.One);
    port.DataReceived += new s system.IO.Ports.SerialDataReceivedEventHandler(Recepcion);

    if (port.IsOpen == false)
    {
      try
      {
         port.Open();
      }
      catch (Exception oex)
      {
          MessageBox.Show(oex.ToString());
      }
    }
}

private void Actualizar(object s, EventArgs e)
{
   //I try this
   lblMSG.Text = ExtractDecimalFromString(port.ReadLine()).ToString();
   port.DiscardInBuffer();

   //Also I try this
   lblMSG.Text = ExtractDecimalFromString(port.ReadExisting()).ToString();
   port.DiscardInBuffer();
}

private void Recepcion(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
  try
  {
     this.Invoke(new EventHandler(Actualizar));
  }
  catch { }
}

 port.DataReceived -= new System.IO.Ports.SerialDataReceivedEventHandler(Recepcion);

GC.Collect();   //also i try to remark this
port.Close();
port.Dispose();
this.Close();