C# Discussion Boards - CodeProject

AlexZieg7127-Sep-07 9:45

27-Sep-07 9:45

Yes, I think so (?), because the main thread runs as STA.

The timer is stopped and disposed when the form closes (Form.Closing event). Do you think it is a problem, that the form is closed from the main thread or that the main thread manipulates the progress-value in the progress-bar form?

Judah Gabriel Himango27-Sep-07 11:50

Judah Gabriel Himango

27-Sep-07 11:50

AlexZieg71 wrote:
Yes, I think so (?), because the main thread runs as STA.

The second thread won't automatically be in the correct apartment state. Here's code that sets the right apartment state:

Thread myThread = new Thread(new ThreadStart(someFunctionThatCreatesControlsOrWindows));
myThread.SetApartmentState(ApartmentState.STA);
myThread.Start();

Remember, STA is required only if that thread will be creating windows or controls. If the thread is just doing background work, don't worry about apartment state.

Also remember: when you create a new thread yourself (or use one from the thread pool via the ThreadPool.QueueUserWorkItem method), the thread will be in the MTA state by default.

Regarding your timer stuff, it's almost certain it's a threading issue -- the main form thread is manipulating values (e.g. changing shared state) in the 2nd thread; this is dangerous. Also, closing the progress form from the main form thread is dangerous.

Fortunately, there's a simple solution to both of these problems:

Instead of modifying variables shared between threads, just have the main thread tell the progress form to do it for you. That way, the progress form alone is king, and doesn't have to worry about sharing variables and state with the main thread. To do this, do something like:

// On the main form thread.
ThreadStart functionThatUpdatesSomeProgressFormVariables = new ThreadStart(...);
progressForm.BeginInvoke(functionThatUpdatesSomeProgressFormVariables);

Same with closing the progress form. Instead of closing the progress form from the main thread, just have the main thread tell the progress form to close:

// On the main form thread.
ThreadStart closeTheProgressFormFunction = new ThreadStart(CloseTheProgressForm);
progressForm.BeginInvoke(closeTheProgressFormFunction);

...

void CloseTheProgressForm()
{
    progressForm.Close();
}

I'd also add that .NET 2 makes this insanely simple using either the BackgroundWorker component, anonymous methods, and delegate inference. If you're stuck on .NET 1.x, you might try looking up an article on this site that created a BackgroundWorker component like the one in .NET 2, but works on .NET 1.x. It will save you the headache of calling control.Invoke/control.BeginInvoke, you won't have to think about apartment states, and it will let you focus on your code rather than thread synchronization issues.

Tech, life, family, faith: Give me a visit.
I'm currently blogging about: Sound The Great Shofar!
The apostle Paul, modernly speaking: Epistles of Paul

Judah Himango

AlexZieg7127-Sep-07 20:50

27-Sep-07 20:50

Thank you very much!!

Luc Pattyn27-Sep-07 9:03

27-Sep-07 9:03

I concur the most likely problem is a cross-thread violation, which can go unnoticed for
a long time when using .NET 1.x; it will cause your app to hang or behave strangely at
any point in time. It would have been catched by .NET >= 2.0 which throws an InvalidOperation
Exception. This is not Vista-specific, but maybe Vista is more likely to make the bug show
itself.

I would suggest you switch to .NET 2.0 to figure it out (this requires all your code
gets recompiled under Visual Studio 2005, so you can no longer use existing .NET 1.x DLLs).
Either temporarily to locate the problem and fix it, or permanently.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

this weeks tips:
- make Visual display line numbers: Tools/Options/TextEditor/...
- show exceptions with ToString() to see all information
- before you ask a question here, search CodeProject, then Google

AlexZieg7127-Sep-07 9:47

27-Sep-07 9:47

Thanks, see my reply to Judah. Do you see a violation in this procedure?

Luc Pattyn27-Sep-07 10:01

27-Sep-07 10:01

Hi,

in practice all Controls should be created by a single STA thread, normally that is
the initial thread. Reason is 1) there is no inherent thread safety in Windows,
and 2) all Controls typically are linked somehow (added to the Controls property
of the main Form, or something similar).

The timer handlers, the SerialPort datareceived handler, and many others run on another
thread and are inappropriate to create Controls , or read or write Control properties,
or call Control methods. There is one exception: the Windows.Forms.Timer, it "ticks"
on the main thread.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

AlexZieg7127-Sep-07 9:49

27-Sep-07 9:49

This sounds good, but another question would be why it worked on other Vista installations...

Luc Pattyn27-Sep-07 10:06

27-Sep-07 10:06

AlexZieg71 wrote:
why it worked on other Vista installations

sorry, this question is irrelevant; a lot of bugs don't show immediately, their negative
impact will only show under certain circumstances, but trust me, as long as your code is
not theoretically sound, they WILL show up in the end.

Under .NET 1.0, .NET 1.1, and all later versions if you turn off the checking:
the cross-thread violations typically hide for a while, then suddenly show up as a slight
GUI malfunction, maybe the main menu remaining blank, or maybe a complete freeze. Activating
another app, then reactiving your app, increases the likelihood the GUI goes wrong.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

AlexZieg7127-Sep-07 10:15

27-Sep-07 10:15

OK, I think you are right... Unsure | :~

That means that I will have to all bigger calculations into worker threads and put the progress bar into the main thread. Glp...

Re: Change Mainform text.

Judah Gabriel Himango27-Sep-07 11:38

Judah Gabriel Himango

27-Sep-07 11:38

Alex, if possible, check out the .NET 2 BackgroundWorker component. It does all the thread-marshaling issues for you, allowing you to focus on your background work and UI updates by themselves.

If you're stuck on .NET 1.x, search this site for BackgroundWorker for .NET 1, there are folks who've implemented the component using .NET 1.x.

Tech, life, family, faith: Give me a visit.
I'm currently blogging about: Sound The Great Shofar!
The apostle Paul, modernly speaking: Epistles of Paul

Judah Himango

Change Mainform text.

projjwal27-Sep-07 7:22

projjwal

27-Sep-07 7:22

Through property window changing form1/mainform text is is very easy. But i want change it at runtime but i can't access form1.text/this.text like property.Pls solve it?

TJoe27-Sep-07 7:27

TJoe

27-Sep-07 7:27

Why can't you access it as a property? You can assign the Text property on the form to change the form's text. From inside the form class you can do:

this.Text = "New Title";

From outside the form class you can do:

form.Text = "New Title";

Take care,
Tom

-----------------------------------------------
Check out my blog at http://tjoe.wordpress.com

Calculate timespan with number?

andredani27-Sep-07 7:15

andredani

27-Sep-07 7:15

If i want to calculate time like this time / pages * 100 = time per 100 pages

for example:

00:05:00 / 5 = 00:00:01 * 100 = 00:01:40

Any suggest

tnx Smile | :)

PIEBALDconsult27-Sep-07 7:25

PIEBALDconsult

27-Sep-07 7:25

Wasn't this answered a few weeks ago?

Dave Kreskowiak27-Sep-07 7:37

Dave Kreskowiak

27-Sep-07 7:37

It was just a week ago this was answered, here[^]. All you have to do is apply a little math.

A guide to posting questions on CodeProject[^]

Dave Kreskowiak
Microsoft MVP
Visual Developer - Visual Basic
2006, 2007

Guffa27-Sep-07 8:00

Guffa

27-Sep-07 8:00

I answered this question in the thread that you created a week ago.

If you keep reposting the same questions without following up on the replies that you actually get, people will stop answering your questions all together.

---
single minded; short sighted; long gone;

Re: GDI draw text question

PIEBALDconsult27-Sep-07 8:09

PIEBALDconsult

27-Sep-07 8:09

... and you don't want to know what we'll do after that. Suspicious | :suss:

GDI draw text question

Jan Roth27-Sep-07 6:52

Jan Roth

27-Sep-07 6:52

Hello!

C# newbie question Confused | :confused:

I have a text (length may vary) which I want to draw to a fixed size graphic. As "standard" I would like to use somthing like font size "arial 16" - but (and now it comes to my problem) if the text is too long to fit into the rectangle, a smaller character size should be used so that the text fits into the rectangle without clipping or ellipsis - even at the risk of having to read a text with fontsize "1" Laugh | :laugh:

Having a limit down to something like fontsize "8", and if the fontsize is smaller than 8 use ellipses would be great, but this would be the coronation Smile | :)

I looked through textrender and drawstring, but could really get an idea how to do it.

Anyone can help??

Thanks!

Jan

il_masacratore27-Sep-07 7:02

il_masacratore

27-Sep-07 7:02

I remember that there was a method that give you the lenght of the string...

Visit my blog at http://dotnetforeveryone.blogspot.com/

Re: GDI draw text question

il_masacratore27-Sep-07 7:05

il_masacratore

27-Sep-07 7:05

The function name was MeasureString... Search for it

Visit my blog at http://dotnetforeveryone.blogspot.com/

Re: GDI draw text question

Luc Pattyn27-Sep-07 7:08

27-Sep-07 7:08

Hi,

Graphics.MeasureString() takes the same parameters as DrawString() except for the starting
point, and returns the size of the text.
You could first measure with some font size, then if too wide, reduce the font size
proportionally; as soon as the font size has been reduced by 50%, you could use the same
height to show two lines of text!

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

Referance Problem

ytubis27-Sep-07 6:29

ytubis

27-Sep-07 6:29

Hi!
I need to activate a function after 5 seconds that the form is running, i created this void fnction in the general class of the project and now i am trying to run it from the TimerHandler function and i get this error:

Error 1 An object reference is required for the nonstatic field, method, or property 'Update_Installer.Form1.Form1_Main()' C:\Documents and Settings\Yossi_Tubis\My Documents\Visual Studio 2005\Projects\Update_Installer\Update_Installer\Update_Installer\Form1.cs 121 13 Update_Installer

this is the TimerFunction:

private static void TimerHandler(Object myObject, EventArgs myEventArgs)
{
Form1_Main();
}

What i am doing wrong?

Thanks Smile | :)

Re: Referance Problem

Vasudevan Deepak Kumar27-Sep-07 6:32

Vasudevan Deepak Kumar

27-Sep-07 6:32

Are you accessing a normal method withing a static one. In that case, you need to have an instance member and then call the normal method using the instance member right?

Vasudevan Deepak Kumar
Personal Homepage
Tech Gossips

Re: Referance Problem

Luc Pattyn27-Sep-07 7:10