BackgroundWorker - C# Discussion Boards

Session Problem. Pls Help

27-Oct-06 23:20

If your program crashes you won't be able to use it to dump its own memory now, would you? Big Grin | :-D

Anyway, if you implement exception catching well in your program, it shouldn't crash or hang -specially in a managed environment like .Net where you can't screw up with pointers-, it's unhandled exceptions that makes your program crash, and windows Xp or later provides an automatic memory dump for your application. Most user won't know how to extract the data from the report and send it to you, but if Hex dump is one of your favourite languages you can simulate the scenario and read it as you please -not convenient as you can see-.

pranu_13 wrote:
Can i use ADPlus for this, if so how to implement it??????

Read this[^].

Regards

subrata.jana27-Oct-06 21:44

subrata.jana

27-Oct-06 21:44

Hi
I have 2 page 1)Master 2)Pop-Up(window.open). Now i open 2 of this master page. From 1 of them i open this popup which is part of same session and copy the url and past it in other opened master page which has different session. Now if i press Go the the current session is being modified by the popup-ups session.

Why is it so ?? Why session variable become null. I have checked google and taken all possible measure still no luck.

Pls help me.

Thanks in advance.

Re: Session Problem. Pls Help

Guffa28-Oct-06 1:34

Guffa

28-Oct-06 1:34

Please don't cross post.

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How to open a file in c# winform?

ecscheng27-Oct-06 21:00

ecscheng

27-Oct-06 21:00

Hi all,
How can I open a file (e.g pdf) with its default program (e.g acrobat reader) in C#?
Thx

Ed

Re: How to open a file in c# winform?

Stefan Troschuetz27-Oct-06 21:31

Stefan Troschuetz

27-Oct-06 21:31

Process.Start(filePath);

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning." - Rick Cook

www.troschuetz.de

BackgroundWorker

freshonlineMax27-Oct-06 19:46

27-Oct-06 19:46

Hello
I wrote a multithreading program in vs2003 that don't work in vs2005.
Now I want to write multithreading code with backgroundworker.
But all samples in the web confusing me and i can't understand them!
Please help me to write a simple program to do this :
1-Button 2-TextBox 3-ListBox
By pressing Button, ListBox should fill as equal as TextBox's number.

Button1_Click()
{
  for (int i=0;i<convert.toint16(TextBox1.text);i++)
  {
    ListBox1.items.add("Item #" + i.tostring());
  }
}

But i want to do this with BackgroundWorker, So i'll have ability to create second set of this controls on my form to work parallely.
Just give me a simple code for first section.
Tank You

Nader Elshehabi27-Oct-06 20:41

27-Oct-06 20:41

IMO background worker is quite useless if you already know how to do multithreading yourself. You did it in 2003 you can do it in 2005.

freshonlineMax wrote:
don't work in vs2005.

Define "don't work"? What error do you get, and what code do you use?

About your issue if you want to manipulate a control from another thread simple use Control.Invoke() method. ie. Put the above code in a method, and call it from the other thread using Invoke().

Regards

Re: BackgroundWorker [modified]

Robert Rohde28-Oct-06 3:37

Robert Rohde

28-Oct-06 3:37

Hi,

accessing controls from another thread can result in weird errors. You could use Invoke but I think in this case that doesn't make sense. I suppose this operation takes a while. To shorten this time make sure that ListBox.Sorted is set to false. Second first create a array with all your elements and then use AddRange. That should improve your performance to an extend where threading is hopefully not required anymore.

Robert

freshonlineMax28-Oct-06 7:57

28-Oct-06 7:57

Dear robert Rohde
Thanks for advice, but filling ListBox is not my problem. I wanted it, just for an example of BackgroundWorker. Please if you have easy example about BackgroundWorker help me about this. I really want to know it's functionality.

Regards

-- modified at 14:03 Saturday 28th October, 2006

Robert Rohde28-Oct-06 19:46

Robert Rohde

28-Oct-06 19:46

Hi,

as said you should find an example where no GUI manipulation is involved. You could make some heavy operations in the thread. Make a Form with a ListBox, two Buttons, a BackgroundWorker and a Progressbar and add the following code:

private void button1_Click(object sender, EventArgs e)
{
    listBox1.Items.Clear();
    progressBar1.Value = 0;
    progressBar1.ForeColor = Color.Green;
    backgroundWorker1.RunWorkerAsync();
}

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
    CalcPrimes(10000000, 10005000, e);
}

private void CalcPrimes(int start, int end, DoWorkEventArgs e)
{
    for (int i = start; i <= end; i++)
    {
        if (backgroundWorker1.CancellationPending)
            return;

        bool isPrime = false;
        if (i % 2 == 1)
        {
            isPrime = true;
            for (int j = 3; j < i / 2; j++)
            {
                if (i % j == 0)
                {
                    isPrime = false;
                    break;
                }
            }
        }
        int p = 100 * (i - start) / (end - start);

        backgroundWorker1.ReportProgress(p, isPrime ? i : 0);
    }
}

private void button2_Click(object sender, EventArgs e)
{
    progressBar1.ForeColor = Color.Red;
    backgroundWorker1.CancelAsync();
}

private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
    int primeNumber = (int)e.UserState;
    progressBar1.Value = e.ProgressPercentage;
    if (primeNumber > 0)
        listBox1.Items.Insert(0, primeNumber);
}

This should be a typical scenario for the BackgroundWorker. Don't forget to bind all eventhandlers.

Robert

freshonlineMax28-Oct-06 20:09

28-Oct-06 20:09

Hi Dear Robert
I got error for below line in "CalcPrimes()" :
backgroundWorker1.ReportProgress(p, isPrime ? i : 0);
error says that : "This BackgroundWorker states that it doesn't report progress. Modify WorkerReportsProgress to state that it does report progress."

Anyway, So thanks to spending your time for solving problems.

Regards

Robert Rohde28-Oct-06 21:46

Robert Rohde

28-Oct-06 21:46

Hi,

there are two properties on the BackgroundWorker you need to set to true. I think they are call SupportsCancelation and ReportsProgress or something similar.

Robert

freshonlineMax29-Oct-06 18:49

reentrant call to the SetCurrentCellAddressCore function.

29-Oct-06 18:49

Hello professor Robert
Program was solved successfully.
I found my problem and as you said i should set backgroundworker properties to "True".
Thank you;)

Nadia Monalisa27-Oct-06 18:53

Nadia Monalisa

27-Oct-06 18:53

Hello,
In my Win Form, I have We browser control and sometimes I am getting error like following
:
" Operation is not valid because it results in a reentrant call to the SetCurrentCellAddressCore
function. "

Can you please give me an idea why I am getting this error ?

Thanks
Emran

Re: reentrant call to the SetCurrentCellAddressCore function.

Nader Elshehabi27-Oct-06 20:47

Re: reentrant call to the SetCurrentCellAddressCore function.

27-Oct-06 20:47

Hello

In what line of code do you get this error? And you said "sometimes"? What about "othertimes"? What do you do exactly to get the error -ie. under what conditions-?

PS.

Take a look at this link[^]. Specially the first hit.

Regards

Nadia Monalisa29-Oct-06 6:41

Nadia Monalisa

29-Oct-06 6:41

Hi Nader,
Thanks for your information. Actually this error is coming magically sometimes.... not all the times... and I have no idea from which part of the code is throwing this error. I thought may be this error is some thing common to DataGridView, now it looks like, My guess is wrong. I will do some more research on it.

Thanks again
emran

how to get holding key down to repeat an action

bradsnobar27-Oct-06 14:07

Re: how to get holding key down to repeat an action

27-Oct-06 14:07

I want to be able to hold the down arrow key to continue to scroll on a custom control that I've written.

How do I check for a key being held down? Is there a property or something to let a keydown event repeat itself?

sam#27-Oct-06 18:21

sam#

27-Oct-06 18:21

implement keyDown event in your control and write your code there.
and where ever you are ebedding your control.create a explict handle for keyDown event for this control and link it with keyDown event which you have created in your control

sameer

Re: how to get holding key down to repeat an action

bradsnobar27-Oct-06 21:15

Re: how to get holding key down to repeat an action

27-Oct-06 21:15

sorry, that's not correct in this case.

Nader Elshehabi27-Oct-06 20:56

Re: how to get holding key down to repeat an action

27-Oct-06 20:56

Holding the key down and repeat rate is windows related. For example some users might disable this feature in their windows. Your control has nothing to do with it. All you have to do is handle the KeyDown event and implement scrolling for each stroke. When the user holds the arrow key down your program should receive multiple strokes, not just the first.

Regards

bradsnobar27-Oct-06 21:15

Re: how to get holding key down to repeat an action

27-Oct-06 21:15

sorry, that's not correct in this case.

Nader Elshehabi27-Oct-06 21:31

27-Oct-06 21:31

Why is that? I just made a small test:

1- Make any control that accepts focus
2- Make a ListBox for example
3- Handle the KeyDown event in the first control and in that handler call ListBox.Items.Add() for example and see if it will be repeated or not.

Regards

Found the answer

bradsnobar27-Oct-06 21:20