Repeat ping every 30 seconds

Question

I created a Windows Forms application to ping a list of Ip addresses, then i used a Timer to repeat the ping every 30 seconds. This is the code i used:

private System.Timers.Timer timer;

    public Form1()
    {
        InitializeComponent();

        timer = new System.Timers.Timer();
        timer.Interval = 30000;
        timer.Enabled = true;
        timer.Elapsed += button1_Click;

    }

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
    {
        pingResults.Clear();
        ipAddress.Add("10.100.1.1");
        ipAddress.Add("10.100.1.2");
        ipAddress.Add("10.100.1.3");
        ipAddress.Add("10.100.1.4");
        ipAddress.Add("10.100.1.5");
        ipAddress.Add("10.100.1.100");

        for (int i = 1; i < 7; i++)
        {
            pictureBoxList.Add((PictureBox)Controls.Find("pictureBox" + i, true)[0]);
        }

        Parallel.For(0, ipAddress.Count(), (i, loopState) =>
        {
            Ping ping = new Ping();
            PingReply pingReply = ping.Send(ipAddress[i].ToString());

            this.BeginInvoke((Action)delegate()
            {
                pictureBoxList[i].BackColor = (pingReply.Status == IPStatus.Success) ? Color.Green : Color.Red;
            });

        });

    }
private void button1_Click(object sender,ElapsedEventArgs e )
    {            
      backgroundWorker1.RunWorkerAsync();                      
    }

But i got this error message:

Error 1 No overload for 'button1_Click' matches delegate 'System.EventHandler'

I tried a lot of examples but i didn't get how to use the Timer. what is the problem here or is there any other way to repeat the Ping?

Answer 1

Looking on the definition of System.EventHandler (at https://learn.microsoft.com/en-us/dotnet/api/system.eventhandler?view=netframework-4.8), we see that it's:

[System.Runtime.InteropServices.ComVisible(true)]
[System.Serializable]
public delegate void EventHandler(object sender, EventArgs e);

It's a delegate, which takes one parameter of type System.EventArgs and one of type object. Looking on your code:

private void button1_Click(object sender, ElapsedEventArgs e)

We see that your event handler receives an object and an ElapsedEventArgs, which is a subclass of EventArgs. But you can't use it, since the compiler expect EventArgs (the opposite, superclass instead of subclass, of course allowed). This is the meaning of the error message:

Error 1 No overload for 'button1_Click' matches delegate 'System.EventHandler'

I (the compiler) expected a method matches the signature of System.EventHandler, but didn't got.

Answer 2

Please, note that Button.Clicked and Timer.Elapsed have different signatures; you, probably, want

public Form1()
{
    InitializeComponent();

    timer = new System.Timers.Timer();
    timer.Interval = 30000;
    timer.Enabled = true;
    timer.Elapsed += timer_Elapsed; // not button1_Click
}

...

private void timer_Elapsed(object sender, ElapsedEventArgs e)
{            
    backgroundWorker1.RunWorkerAsync();                      
}

private void button1_Click(object sender, EventArgs e) 
{  
    backgroundWorker1.RunWorkerAsync();
}

Or you can get rid of timer_Elapsed at all with a help of lambda function:

public Form1()
{
    InitializeComponent();

    timer = new System.Timers.Timer();
    timer.Interval = 30000;
    timer.Enabled = true;
    timer.Elapsed += (s, e) => {backgroundWorker1.RunWorkerAsync();}; 
}

...

private void button1_Click(object sender, EventArgs e) 
{  
    backgroundWorker1.RunWorkerAsync();
}

Answer 3

Your idea with the timer is a perfect idea. Anyhow now you try to activate the timer with a button which will not work properly.

Try this example from the microsoft documentation

https://learn.microsoft.com/en-us/dotnet/api/system.timers.timer?view=netframework-4.8