HOW TO UPDATE UI FROM THREAD

Form1.cs

public Form1()
{
    InitializeComponent();
    serialPort1.PortName = "COM2";
    serialPort1.BaudRate = 9600;
    serialPort1.Open();
    Thread oThread = new Thread(new ThreadStart(recvThread));
    oThread.Start();
}

private void recvThread()
{
    while (true)
    {
        byte b = (byte)serialPort1.ReadByte(); /* wait a byte from COM port */
        label1.Text = b.ToString(); /* error! */
    }
}