How to Stop timer if listbox empty or items less than 0 c#

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I am making a windows app.

A button1 which gets the items in listBox1 from server At the start.
A button2 which starts the timer1.
A timer1 which remove items from listBox1 .
A progressBar1 which shows the progress of this process.

Here is the code.

C#

private void button1_Click(object sender, EventArgs e)
{
    jabber.Send("&lt;iq type='get' to='" + textBox1.Text + "@conference.jabber.com' id='qip_1026'&gt;&lt;query xmlns='http://jabber.org/protocol/muc#admin'&gt;&lt;item affiliation='outcast' /&gt;&lt;/query&gt;&lt;/iq&gt;");
}

private void button2_Click(object sender, EventArgs e)
{
    progressBar1.Maximum = listBox1.Items.Count;
    timer1.Start();
    timer1.Interval = 4000;
}

private void timer1_Tick(object sender, EventArgs e)
{
    if (listBox1.Items.Count &gt; 0)
    {
        jabber.Send("&lt;iq type='set' to='" + textBox7.Text + "@conference.jabber.com'&gt;&lt;query xmlns='http://jabber.org/protocol/muc#admin'&gt;&lt;item jid='" + listBox1.Items[0].ToString() + "' affiliation='none'/&gt;&lt;/query&gt;&lt;/iq&gt;");
        listBox1.Items.RemoveAt(0);
        progressBar1.Value += 1;
        label.Text = listBox1.Items.Count.ToString();
    }
    else
    {
        timer1.Enabled = False;
    }
}

The above works well till there is one item left in listBox1.

The error is

System.ArgumentOutOfRangeException was unhandled Message=InvalidArgument=Value of '0' is not valid for 'index'. Parameter name: index

When listBox1 reaches at 0, it raise an error, i want to stop the timer when listbox1 gets no items or 0 items or empty.

Posted 1-Jun-14 4:30am

Member 10579673

Updated 1-Jun-14 4:32am

v3

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Comments

[no name] 1-Jun-14 11:22am

Check the Item count after your RemoveAt.

Sergey Alexandrovich Kryukov 1-Jun-14 13:38pm

Why using timer at all? What did you want to achieve with that?
—SA

Member 10579673 1-Jun-14 14:09pm

Timer changes affiliations of listbox items.and server takes 4 seconds to change a affiliation,thats why used a timer with 4 seconds interval.

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Mike Meinz · Accepted Answer · 2014-06-01T06:33:00

Disable the timer as soon as the timer1_Tick procedure is entered. Re-enable the timer only if there are items left in the ListBox. In your code, if the jabber.Send takes more than four seconds, another timer1_Tick procedure will start running before the previous one has ended. I believe, that is the cause of your error.

Also, do not start the timer until the interval has been set.

C#

private void button1_Click(object sender, EventArgs e)
{
    jabber.Send("<iq type="get" to="" + textBox1.Text + "@conference.jabber.com" id="qip_1026"><query xmlns="http://jabber.org/protocol/muc#admin"><item affiliation="outcast" /></query></iq>");
}
 
private void button2_Click(object sender, EventArgs e)
{
    progressBar1.Maximum = listBox1.Items.Count;
    progressBar1.Value = 0;
    // Set the timer interval to four seconds
    timer1.Interval = 4000;
    // Start the timer
    timer1.Start();
}
 
private void timer1_Tick(object sender, EventArgs e)
{
    // Disable the timer while we are working in this procedure so
    // it doesn't tick while we are working in this procedure
    timer1.Enabled = False;
    // Send only if there are items in the ListBox
    if (listBox1.Items.Count > 0)
    {
        jabber.Send("<iq type="set" to="" + textBox7.Text + "@conference.jabber.com"><query xmlns="http://jabber.org/protocol/muc#admin"><item jid="" + listBox1.Items[0].ToString() + "" affiliation="none" /></query></iq>");
        listBox1.Items.RemoveAt(0);
        progressBar1.Value += 1;
        label.Text = listBox1.Items.Count.ToString();
    }
    // Re-enable only if there are items left in the ListBox
    if (listBox1.Items.Count > 0)
    {
         timer1.Enabled = True;
    }
}