Windows form closes after System.Threading.Timer elaples-CodePudding

I'm building an alarm clock application and using System.Threading.Timer. After the timer is elapsed I wanna show usercontrol to allow user to choose either to wake up or to snooze. After adding a new control or form in callback the form is just closing.

private void setTimerButton_Click(object sender, EventArgs e)
    {
        try
        {
            alarmDate = setAlarmDateTimePicker.Value - DateTime.Now;
            var alarmClock = new System.Threading.Timer(AlarmCallback, null, alarmDate, TimeSpan.Zero);
            addedAlarmTextBox.Text = setAlarmDateTimePicker.Text;
        }
        catch
        {}
        finally
        {
            setAlarmDateTimePicker.Value = DateTime.Now;
        }
    }
    private void AlarmCallback(object state)
    {
            this.Controls.Add(new AlarmBeepsForm());
    }

As far as I know, it has something with the threads, but I'm quite new to programming and I don't understand what's wrong. How can I change the code to successfully add the control or should I use another type of timer?

CodePudding user response：

Unless you set Control.CheckForIllegalCrossThreadCalls to false, you should call Control.Invoke to switch to the thread that created the control handle.

private void setTimerButton_Click(object sender, EventArgs e)
{
   try
   {
      alarmDate = setAlarmDateTimePicker.Value - DateTime.Now;
      var alarmClock = new System.Threading.Timer(AlarmCallback, null, alarmDate, TimeSpan.Zero);
      addedAlarmTextBox.Text = setAlarmDateTimePicker.Text;
   }
   catch
   {}
   finally
   {
      setAlarmDateTimePicker.Value = DateTime.Now;
   }
}
private void AlarmCallback(object state)
{
    this.Invoke(new Action(() => this.Controls.Add(new AlarmBeepsForm()));
}