.NET Threading Question

[Arun Kumar]

What is wrong with this code. All i am trying to test is 3 progressbar and
one button. On buttonclick i create 3 threads and each thread calls a method
which in turn updates the progressbar and it works. I would to know if this
can be used.
Thanks
private void button1_Click(o bject sender, System.EventArg s e)

{

ThreadStart job = new ThreadStart(one method);

Thread thread = new Thread(job);

thread.Start();

ThreadStart job1 = new ThreadStart(sec ondmethod);

Thread thread1 = new Thread(job1);

thread1.Start() ;

ThreadStart job2 = new ThreadStart(thi rdmethod);

Thread thread2 = new Thread(job2);

thread2.Start() ;

}

public void onemethod()

{

for (int i=0;i<100;i++)

{

progressBar1.Va lue = i;

Thread.Sleep(10 0);

}

}

public void secondmethod()

{

for (int i=0;i<100;i++)

{

progressBar2.Va lue = i;

Thread.Sleep(10 0);

}

}

public void thirdmethod()

{

for (int i=0;i<100;i++)

{

progressBar3.Va lue = i;

Thread.Sleep(10 0);

}

}

[DotNet Coder]

Hi Arun,

The code should work fine, although it violates best practices by
interacting directly with the UI from threads other than the main
thread. Other than that though, it *looks* like it should run just fine.

~d

Arun Kumar wrote:

What is wrong with this code. All i am trying to test is 3 progressbar and
one button. On buttonclick i create 3 threads and each thread calls a method
which in turn updates the progressbar and it works. I would to know if this
can be used.
Thanks
private void button1_Click(o bject sender, System.EventArg s e)

{

ThreadStart job = new ThreadStart(one method);

Thread thread = new Thread(job);

thread.Start();

ThreadStart job1 = new ThreadStart(sec ondmethod);

Thread thread1 = new Thread(job1);

thread1.Start() ;

ThreadStart job2 = new ThreadStart(thi rdmethod);

Thread thread2 = new Thread(job2);

thread2.Start() ;

}

public void onemethod()

{

for (int i=0;i<100;i++)

{

progressBar1.Va lue = i;

Thread.Sleep(10 0);

}

}

public void secondmethod()

{

for (int i=0;i<100;i++)

{

progressBar2.Va lue = i;

Thread.Sleep(10 0);

}

}

public void thirdmethod()

{

for (int i=0;i<100;i++)

{

progressBar3.Va lue = i;

Thread.Sleep(10 0);

}

}

[Arun Kumar]

DotNet Coder,

I agree, its not the best practices but my point is, if you use threads and
use it carefully it shouldn't be a problem.
Check this link
http://www.yoda.arachsys.com/csharp/...winforms.shtml

let me know you comments.

Arun
"DotNet Coder" <d0*********@ya hoo.dot.com> wrote in message
news:%2******** ********@TK2MSF TNGP12.phx.gbl. ..

Hi Arun,

The code should work fine, although it violates best practices by
interacting directly with the UI from threads other than the main thread.
Other than that though, it *looks* like it should run just fine.

~d

Arun Kumar wrote:

What is wrong with this code. All i am trying to test is 3 progressbar
and one button. On buttonclick i create 3 threads and each thread calls a
method which in turn updates the progressbar and it works. I would to
know if this can be used.
Thanks
private void button1_Click(o bject sender, System.EventArg s e)

{

ThreadStart job = new ThreadStart(one method);

Thread thread = new Thread(job);

thread.Start();

ThreadStart job1 = new ThreadStart(sec ondmethod);

Thread thread1 = new Thread(job1);

thread1.Start() ;

ThreadStart job2 = new ThreadStart(thi rdmethod);

Thread thread2 = new Thread(job2);

thread2.Start() ;

}

public void onemethod()

{

for (int i=0;i<100;i++)

{

progressBar1.Va lue = i;

Thread.Sleep(10 0);

}

}

public void secondmethod()

{

for (int i=0;i<100;i++)

{

progressBar2.Va lue = i;

Thread.Sleep(10 0);

}

}

public void thirdmethod()

{

for (int i=0;i<100;i++)

{

progressBar3.Va lue = i;

Thread.Sleep(10 0);

}

}

[DotNet Coder]

Completely wrong... if you use threads and use it carefully, it will
still be a problem. As that article states, "Never invoke any method or
property on a control created on another thread other than Invoke,
BeginInvoke, EndInvoke or CreateGraphics, and InvokeRequired. ".

This is not just a golden rule, it is a fact of winforms programming.
When you start messing with objects created in other threads, you start
running into all sorts of problems, like race conditions, deadlocks, etc.

Also, as the author stated, you may get away with it for awhile, but
eventually, your application will start displaying some pretty strange
behaviors and debugging could become a horrible process, especially if
it is threading errors that are killing the app.

HTH,
~d

Arun Kumar wrote:

DotNet Coder,

I agree, its not the best practices but my point is, if you use threads and
use it carefully it shouldn't be a problem.
Check this link
http://www.yoda.arachsys.com/csharp/...winforms.shtml

let me know you comments.

Arun
"DotNet Coder" <d0*********@ya hoo.dot.com> wrote in message
news:%2******** ********@TK2MSF TNGP12.phx.gbl. ..

Hi Arun,

The code should work fine, although it violates best practices by
interacting directly with the UI from threads other than the main thread.
Other than that though, it *looks* like it should run just fine.

~d

Arun Kumar wrote:

What is wrong with this code. All i am trying to test is 3 progressbar
and one button. On buttonclick i create 3 threads and each thread calls a
method which in turn updates the progressbar and it works. I would to
know if this can be used.
Thanks
private void button1_Click(o bject sender, System.EventArg s e)

{

ThreadStar t job = new ThreadStart(one method);

Thread thread = new Thread(job);

thread.Start ();

ThreadStar t job1 = new ThreadStart(sec ondmethod);

Thread thread1 = new Thread(job1);

thread1.Star t();

ThreadStar t job2 = new ThreadStart(thi rdmethod);

Thread thread2 = new Thread(job2);

thread2.Star t();

}

public void onemethod()

{

for (int i=0;i<100;i++)

{

progressBar1 .Value = i;

Thread.Sleep (100);

}

}

public void secondmethod()

{

for (int i=0;i<100;i++)

{

progressBar2 .Value = i;

Thread.Sleep (100);

}

}

public void thirdmethod()

{

for (int i=0;i<100;i++)

{

progressBar3 .Value = i;

Thread.Sleep (100);

}

}

[Willy Denoyette [MVP]]

"Arun Kumar" <ar****@hotmail .com> wrote in message
news:OG******** ******@TK2MSFTN GP12.phx.gbl...

DotNet Coder,

I agree, its not the best practices but my point is, if you use threads
and use it carefully it shouldn't be a problem.
Check this link
http://www.yoda.arachsys.com/csharp/...winforms.shtml

let me know you comments.

Arun

There is nothing "carefully" with this, it may work in this simple sample
and it may work a million times but sooner or later it will break, it's
simply wrong to touch the UI element (a window handle) from a thread other
than the thread that owns the handle.

Willy.

[Jon Skeet [C# MVP]]

Arun Kumar <ar****@hotmail .com> wrote:

I agree, its not the best practices but my point is, if you use threads and
use it carefully it shouldn't be a problem.
Not true.
Check this link
http://www.yoda.arachsys.com/csharp/...winforms.shtml

Which part of:

<quote>
Never invoke any method or property on a control created on another
thread other than Invoke, BeginInvoke, EndInvoke or CreateGraphics, and
InvokeRequired.
</quote>

gives you the impression that it shouldn't be a problem?

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Arun Kumar]

Alright,
Let me go back a step and tell you what i did in Win32 and I know it may not
be true in "WinForms"( As Microsoft keeps changing things)
I am a Delphi Developer, in Delphi, I got a Mainform with a statusbar and a
Thread which creates database.
I use Synchronize() to update the main form which i believe is correct.

I want to do the same in .Net and after playing around with things and
reading the article. (Correct me if i m wrong here)
1. Creating the Thread from Mainform
2. If the Thread calls a method which updates the mainform, is this wrong?

I dont want to write complex code just update the mainform.
Very simple
Mainform -> Creates Thread -> does some background database stuff, while
doing that it should update the mainform telling the user hey I am still
working on it wait till i complete it and also give them an indication where
its at.
This is what i am looking for and started playing with Threads. If its were
to be Delphi its a "piece of Cake" and I can do it with few lines.
But, I thought .Net is going to make coding lot easier I guess not.
<Article>" class itself, setting it in one thread, retrieving and processing
it in the other (updating the display in the UI thread, for example).
"<Article> Create a Thread to do stuff and create another Thread to update
UI what is going on here???

Anyway there is no point in hitting the wall

Arun


"DotNet Coder" <d0*********@ya hoo.dot.com> wrote in message
news:ey******** ******@TK2MSFTN GP14.phx.gbl...

Completely wrong... if you use threads and use it carefully, it will still
be a problem. As that article states, "Never invoke any method or property
on a control created on another thread other than Invoke, BeginInvoke,
EndInvoke or CreateGraphics, and InvokeRequired. ".

This is not just a golden rule, it is a fact of winforms programming. When
you start messing with objects created in other threads, you start running
into all sorts of problems, like race conditions, deadlocks, etc.

Also, as the author stated, you may get away with it for awhile, but
eventually, your application will start displaying some pretty strange
behaviors and debugging could become a horrible process, especially if it
is threading errors that are killing the app.

HTH,
~d

Arun Kumar wrote:

DotNet Coder,

I agree, its not the best practices but my point is, if you use threads
and use it carefully it shouldn't be a problem.
Check this link
http://www.yoda.arachsys.com/csharp/...winforms.shtml

let me know you comments.

Arun
"DotNet Coder" <d0*********@ya hoo.dot.com> wrote in message
news:%2******** ********@TK2MSF TNGP12.phx.gbl. ..

Hi Arun,

The code should work fine, although it violates best practices by
interactin g directly with the UI from threads other than the main thread.
Other than that though, it *looks* like it should run just fine.

~d

Arun Kumar wrote:

What is wrong with this code. All i am trying to test is 3 progressbar
and one button. On buttonclick i create 3 threads and each thread calls
a method which in turn updates the progressbar and it works. I would to
know if this can be used.
Thanks
private void button1_Click(o bject sender, System.EventArg s e)

{

ThreadSta rt job = new ThreadStart(one method);

Thread thread = new Thread(job);

thread.Star t();

ThreadSta rt job1 = new ThreadStart(sec ondmethod);

Thread thread1 = new Thread(job1);

thread1.Sta rt();

ThreadSta rt job2 = new ThreadStart(thi rdmethod);

Thread thread2 = new Thread(job2);

thread2.Sta rt();

}

public void onemethod()

{

for (int i=0;i<100;i++)

{

progressBar 1.Value = i;

Thread.Slee p(100);

}

}

public void secondmethod()

{

for (int i=0;i<100;i++)

{

progressBar 2.Value = i;

Thread.Slee p(100);

}

}

public void thirdmethod()

{

for (int i=0;i<100;i++)

{

progressBar 3.Value = i;

Thread.Slee p(100);

}

}

[DotNet Coder]

Hey Jon? Didn't you write an article on this very subject? I seem to
remember you mentioning an article sometime last year.

~d

Jon Skeet [C# MVP] wrote:

Arun Kumar <ar****@hotmail .com> wrote:

I agree, its not the best practices but my point is, if you use threads and
use it carefully it shouldn't be a problem.

Not true.

Check this link
http://www.yoda.arachsys.com/csharp/...winforms.shtml

Which part of:

<quote>
Never invoke any method or property on a control created on another
thread other than Invoke, BeginInvoke, EndInvoke or CreateGraphics, and
InvokeRequired.
</quote>

gives you the impression that it shouldn't be a problem?

[Arun Kumar]

"Willy Denoyette [MVP]" <wi************ *@telenet.be> wrote in message
news:%2******** ********@TK2MSF TNGP09.phx.gbl. ..

"Arun Kumar" <ar****@hotmail .com> wrote in message
news:OG******** ******@TK2MSFTN GP12.phx.gbl...

DotNet Coder,

I agree, its not the best practices but my point is, if you use threads
and use it carefully it shouldn't be a problem.
Check this link
http://www.yoda.arachsys.com/csharp/...winforms.shtml

let me know you comments.

Arun

There is nothing "carefully" with this, it may work in this simple sample
and it may work a million times but sooner or later it will break, it's
simply wrong to touch the UI element (a window handle) from a thread other
than the thread that owns the handle.

Willy.

Thanks for your response.

Yes. I know that. there is nothing called "carefully" . I have worked on
Threads alot in Win32 and I know what will have happen." simply wrong to touch the UI element (a window handle) from a thread
other than the thread that owns the handle."

True. its a sample, yes I am trying out things what i can and what i cannot
do in .Net and what are the limitations and I strong believe there is
nothing wrong in doing that and putting my words out here and get the best
out it.

Arun

[Jon Skeet [C# MVP]]

Arun Kumar <ar****@hotmail .com> wrote:

Let me go back a step and tell you what i did in Win32 and I know it may not
be true in "WinForms"( As Microsoft keeps changing things)
I am a Delphi Developer, in Delphi, I got a Mainform with a statusbar and a
Thread which creates database.
I use Synchronize() to update the main form which i believe is correct.
I'm afraid I don't know what Synchronize() does in Delphi. The "don't
change the UI from a non-UI thread" is a general Win32 rule though.
I want to do the same in .Net and after playing around with things and
reading the article. (Correct me if i m wrong here)
1. Creating the Thread from Mainform
2. If the Thread calls a method which updates the mainform, is this wrong?
Yes.
I dont want to write complex code just update the mainform.
Very simple
Mainform -> Creates Thread -> does some background database stuff, while
doing that it should update the mainform telling the user hey I am still
working on it wait till i complete it and also give them an indication where
its at.
Sure - so use Invoke or BeginInvoke, and you should be fine. There's a
pretty full example in the article.
This is what i am looking for and started playing with Threads. If its were
to be Delphi its a "piece of Cake" and I can do it with few lines.
But, I thought .Net is going to make coding lot easier I guess not.
<Article>" class itself, setting it in one thread, retrieving and processing
it in the other (updating the display in the UI thread, for example).
"<Article> Create a Thread to do stuff and create another Thread to update
UI what is going on here???
You don't create another thread to update the UI - you tell the
existing UI thread to update the UI.
Anyway there is no point in hitting the wall

There's every point in learning how to do it properly though. I suggest
you read the article again, preferably starting at the first page of it
(rather than just the windows forms page) and taking it a bit at a
time. Threading is fundamentally pretty tricky, but it's very useful
too.

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too