Good morning Steve,
Before we look at the two questions in the post, I'd like to first
introduce three different timer classes in the .NET Class Library:
System.Windows. Forms.Timer
System.Timers.T imer
System.Threadin g.Timer
The first two classes appear in the Visual Studio.NET toolbox window,
allowing us to drag and drop them directly onto a Windows Forms designer or
a component class designer. System.Threadin g.Timer does not appear in the
toolbox, but it exposes several more advanced features. Alex Calvo [MSFT]
wrote a good article, going through the differences between the three in
detail.
Comparing the Timer Classes in the .NET Framework Class Library
http://msdn.microsoft.com/en-us/magazine/cc164015.aspx
>Does the code in a Timer control.tick event run on a different thread
to the main Application thread (UI Thread)?
If the timer is the control dragged from the toolbox into the winform
designer, control.tick event handler would run on the same thread as the UI
thread. It can be proved with this piece of code:
// in the winform, (e.g. Form_Load), we dump the UI thread ID:
Debug.Print("UI Thread: " +
Thread.CurrentT hread.ManagedTh readId.ToString ());
// in the timer's tick event handler, we dump the ID of the thread that
runs the handler:
private void timer1_Tick(obj ect sender, EventArgs e)
{
Debug.Print("Ti ck: " +
Thread.CurrentT hread.ManagedTh readId.ToString ());
}
>In some of the timers I update some UI controls e.g statusbar.label s
and I am wondering if I should be doing this if the code is running in
a different thread
If the timer belongs to System.Windows. Forms.Timer, or System.Timers.T imer
whose SynchronizingOb ject is set to the winform object (for example:
Dim tmrTimersTimer As New System.Timers.T imer();
tmrTimersTimer. SynchronizingOb ject = Me 'Synchronize with the current form
the timer's tick event will run in the UI thread, and we can directly
operate on the UI control (e.g. statusbar.label s).
However, if the timer belongs to System.Threadin g.Timer, or
System.Timers.T imer whose SynchronizingOb ject is NOT set to the winform
object, the ticket event will run in a different thread, and we need to
call either Control.Invoke or Control.BeginIn voke to operate on the UI
controls. For example:
// Created on UI thread
private Label lblStatus;
// Doesn't run on UI thread
private void RunsOnWorkerThr ead() {
DoSomethingSlow ();
// Do UI update on UI thread
object[] pList = { this, System.EventArg s.Empty };
lblStatus.Begin Invoke(
new System.EventHan dler(UpdateUI), pList);
}
// Code to be run back on the UI thread
// (using System.EventHan dler signature
// so we don't need to define a new
// delegate type here)
private void UpdateUI(object o, System.EventArg s e) {
// Now OK - this method will be called via
// Control.Invoke, so we are allowed to do
// things to the UI.
lblStatus.Text = "Finished!" ;
}
For simplicity, we usually write a wrapper function, e.g
public void ShowProgress(st ring msg, int percentDone) {
if (InvokeRequired ) {
// As before
} else {
// We're already on the UI thread just
// call straight through.
UpdateUI(this, new MyProgressEvent s(msg,
PercentDone));
}
}
For more details, please refer to the MSDN magazine article:
Give Your .NET-based Application a Fast and Responsive UI with Multiple
Threads
http://msdn.microsoft.com/zh-cn/maga...29(en-us).aspx
Is the above information helpful to you? If you have any other questions or
concerns, please feel free to let me know.
Have a very nice day!
Regards,
Jialiang Ge (ji****@online. microsoft.com, remove 'online.')
Microsoft Online Community Support
Delighting our customers is our #1 priority. We welcome your comments and
suggestions about how we can improve the support we provide to you. Please
feel free to let my manager know what you think of the level of service
provided. You can send feedback directly to my manager at:
ms****@microsof t.com.
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