timer on form to blink message

Question

4.17/5 (3 votes)

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Hi,
In my windows form project, every time there is a call to a long running method, I show a small form which has a label control that says, please wait and then after the long running call I hide that form . i.e.

C#

ShowForm();
LongRunningMethod();
HideForm();

Question:
How can I make the label control to blink every second while the showForm is being shown?
Thanks

Posted 5-Feb-12 21:59pm

arkiboys

Updated 5-Feb-12 22:06pm

CPallini

v2

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Sergey Alexandrovich Kryukov 6-Feb-12 4:15am

Just a note: this code would be serious abuse of... I don't know, pretty much everything. Please see my solution.
--SA

3 solutions

Solution 2

You should call your LongRunningMethod in a separate thread and use a timer in the main thread to blink the label.
See "Threading Tutorial (C#)"[^].

Posted 5-Feb-12 22:09pm

CPallini

Comments

Sergey Alexandrovich Kryukov 6-Feb-12 4:21am

Good point, but I'm not fully agree with the timer. Also, it depends on the type of timer. (I voted 4).

For explanation, please see my comment to the answer by Griff and my own answer.
--SA

thatraja 6-Feb-12 13:29pm

5!

Solution 1

Set a timer in the form:

C#

            Timer blinkTimer = new Timer();
            blinkTimer.Interval = 1000;
            blinkTimer.Tick += new EventHandler(blinkTimer_Tick);
            blinkTimer.Start();

...

        void blinkTimer_Tick(object sender, EventArgs e)
            {
            myBlinkingLabel.Visible = !myBlinkingLabel.Visible;
            }

Posted 5-Feb-12 22:08pm

OriginalGriff

Comments

Sergey Alexandrovich Kryukov 6-Feb-12 4:19am

Griff, did you try it? It is not unusual when blinking made using System.Windows.Forms.Timer does not look periodic, due to low priority and hence accuracy of this timer type. This timer is useful sometimes, but a human eye can easily see this flaw of this timer in wanna-be-periodic action. I saw it a number of times.
(I did not vote.)

Please see my solution -- more complex but robust.
--SA

arkiboys 6-Feb-12 4:30am

Following what you mentioned.
But the label does not blink.

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Sergey Alexandrovich Kryukov · Accepted Answer · 2012-02-05T22:14:00

My first advice is: don't make anything blinking! Most users will be highly irritated by this.

If you don't want to listen to this good friendly advice, better use a separate thread with Thread.Sleep. At least don't use System.Windows.Forms.Timer. Due to low priority (fool-proof feature, I think), it is so inaccurate that your blinking won't even look periodic sometimes. Better use other types of timers.

The problem is this: with those other timers and thread, you will have to notify the UI thread form non-UI thread to change color or visibility of some control to blink, etc. But you cannot call anything related to UI from non-UI thread. Instead, you need to use the method Invoke or BeginInvoke of System.Windows.Threading.Dispatcher (for both Forms or WPF) or System.Windows.Forms.Control (Forms only).

You will find detailed explanation of how it works and code samples in my past answers:
Control.Invoke() vs. Control.BeginInvoke()[^],
Problem with Treeview Scanner And MD5[^].

Wait a minute! How about LongRunningMethod? Oh no! You are about to commit a crime (against yourself, I guess). Never ever run anything "long running" in the UI thread. Do it in the separate thread, and also use invocation.

See also more references on threading:
How to get a keydown event to operate on a different thread in vb.net[^],
Control events not firing after enable disable + multithreading[^].

—SA

timer on form to blink message

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