图片框图像在C＃中不变

Question

I want to change picture's box image when my board(a USB module) is joined or disjoined to computer. But I think my thread will execute just one time. And picture box's image won't change.

my code:

bool boardjoined = false;
void BoardConnecion()
{
    foreach (var item in SerialPort.GetPortNames())
    {
        if (item == "COM3")
        {
            boardjoined = true;
            DisplayImage(_pic_usb, "on.png");
        }
        else
        {
            boardjoined = false;
            DisplayImage(_pic_usb, "off.png");
        }

    }
}

public Form1()
{
    InitializeComponent();

}

private void Form1_Load(object sender, EventArgs e)
{
    _pic_usb.Image = Bitmap.FromFile(Application.StartupPath + @"\off.png");

    new Thread(new ThreadStart(BoardConnecion)).Start();

}

private void DisplayImage(PictureBox pic, string picName)
{
    pic.Invoke(new EventHandler(delegate
    {
        pic.Image = Bitmap.FromFile(Application.StartupPath +@"\" + picName);
    }));
}

Answer 1

You can do a never ending loop in the BoardConnection.

    void BoardConnecion()
    {
        while(true)
        {
            foreach (var item in SerialPort.GetPortNames())
            {
                if (item == "COM3")
                {
                    boardjoined = true;
                    DisplayImage(_pic_usb, "on.png");
                }
                else
                {
                    boardjoined = false;
                    DisplayImage(_pic_usb, "off.png");
                }

            }
            Thread.Sleep(500);
        }
    }

You should proabably add a safety switch to get out of the loop to. =)

Answer 2

you can use below mentioned code

private System.Timers.Timer timerClock = new System.Timers.Timer();    
timerClock.Elapsed += new ElapsedEventHandler(OnTimer);
timerClock.Interval = 1000;
timerClock.Enabled = true;

public void OnTimer( Object source, ElapsedEventArgs e )
{
    foreach (var item in SerialPort.GetPortNames())
        {
            if (item == "COM3")
            {
                boardjoined = true;
                DisplayImage(_pic_usb, "on.png");
            }
            else
            {
                boardjoined = false;
                DisplayImage(_pic_usb, "off.png");
            }

        } 
}