C#

label.Visible = false

label.Visible = true

public class ClassS
   {

       #region variable et propriété
       private   int codemessage;
       /// <summary>
       /// le code du message qui détérmine les propriétés
       /// </summary>
       public int Codemessage
       {
           get { return codemessage; }
           set { codemessage = value; }
       }


       #endregion

BuzyOperationDelegate del = new BuzyOperationDelegate(BuzyOperation);
IAsyncResult result = del.BeginInvoke(null,null);
while (result.IsCompleted == false)
{
   //progress bar shown here...
}

private int BuzyOperation()
 {
         Form2 frm2 = new Form2();
         frm2.Show();//this will take 5sec.
         return 1;
 }

serialPort1 = new SerialPort("COM3", 19200, Parity.None, 8, StopBits.One);<br />
            serialPort1.ReadTimeout = 1000;<br />
            serialPort1.Handshake = Handshake.None;<br />
            serialPort1.ReceivedBytesThreshold = 1;<br />
          if (serialPort1.IsOpen)<br />
                serialPort1.Close();<br />
                serialPort1.Open();<br />
                byte[] request1 = new byte[] {(byte)'P', 4, 19, 6, (byte)'@'};<br />
                serialPort1.Write(request1, 0, request1.Length);<br />
                serialPort1.DataReceived += new SerialDataReceivedEventHandler(serialPort1_DataReceived);     <br />
private void serialPort1_DataReceived(object sender, SerialDataReceivedEventArgs e)<br />
        {<br />
            this.Invoke(new EventHandler(DoUpdate));<br />
        }<br />
        private void DoUpdate(object s, EventArgs e)<br />
        {<br />
            while (serialPort1.BytesToRead > 0)<br />
            {<br />
                textBox1.Text = serialPort1.BytesToRead.ToString();<br />
            }<br />
        }