C# Discussion Boards - CodeProject

Judah Gabriel Himango29-Mar-06 11:19

29-Mar-06 11:19

Well, upon initial glance it all seems ok...what line of code is it crashing on? You should first find out where the null reference exception is occurring; what's most likely occurring is that some object is being accessed by multiple threads. One of the threads sets the object to null, then another thread tries to use that object after the fact, causing the error. But it's difficult to debug it unless you know where the error is occurring.

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Judah Himango

Re: Help! Asynchronous Executions

swanmynova30-Mar-06 5:18

swanmynova

30-Mar-06 5:18

Hi Judah,

Thank you very much for your reply. As I mentioned in my original message, the line of code that caused the reference exception is one of the many EndInvoke statements (not always the same one, but one of them randomly). Like I said before, the application works most of the time. So, this leads me to think that there is no programming error. But sporadically it crashed on one of the EndInvoke statements as indicated by the Exception Management. So this bug is really incomprehensible to me.

Thanks again,

SL

Re: Help! Asynchronous Executions

Judah Gabriel Himango30-Mar-06 6:30

Judah Gabriel Himango

30-Mar-06 6:30

When you're executing asynchronous code, EndInvoke will re-throw any unhandled errors that occurred somewhere in your asynchronous code blocks (the code that gets executed on background threads). This is by design.

What I would do is put some try/catch around the code that gets executed on a background thread. Log it somehow by outputting to the console, a file, anything that lets you track it down when it happens. Then when it happens, make sure you log the stack trace, the error message, and any other error information that will help you solve it. Also, in your asynchronous code, validate all the data you're dealing with. If you're using an object that is shared among the other threads, make no assumptions about it! Check if such resources are null or in an invalid state before using them.

Re: Help! Asynchronous Executions

swanmynova30-Mar-06 7:54

swanmynova

30-Mar-06 7:54

Thank you, I will dig in further.

FLOPS

Mridang Agarwalla29-Mar-06 5:58

Mridang Agarwalla

29-Mar-06 5:58

Has anyone seen a program that will tell you the FLOPS of a processor in C#?

Flags problem

Mridang Agarwalla29-Mar-06 5:53

Mridang Agarwalla

29-Mar-06 5:53

I'm having a slight problem with flags. I downloaded a small class from CP called Task Scheduler. It contains an enum called DaysOfTheWeek. This enumeration contains all the seven days of the week. This enumeration has the Flag option set to on and as i read somewhere, multiple flags can be passed at once by using the pipe operator (|). Now the class contains a function which takes the enumeration DaysOfTheWeek as a parameter. When I have to call the function, I can easily do so by writing

TestFunction(DaysOfTheWeek.Monday)

That was easy. Now, I have seven check boxes on my form called chkSunday, chkMonday....chkSaturday. Now, I have to call the function by passing the flags which in turn depend on the check boxes that are selected. For example, if the user has selected chkMonday and chkSunday, I would call the function like this

TestFunction(DaysOfTheWeek.Monday | DaysOfTheWeek.Sunday)

This is where the the problem lies. i can't possibly write a set of if else statements that take into account all the possible combinations of checkboxes being selected and appropriately calling the function. How do I do this?

I thought of this but it doesnt work:

<br />
TaskScheduler.DaysOfTheWeek enmDays;<br />
if (chkSunday.Checked == true)<br />
	enmDays = enmDays | DaysOfTheWeek.Sunday;<br />
if (chkMonday.Checked == true)<br />
	enmDays = enmDays | DaysOfTheWeek.Monday;<br />
if (chkTuesday.Checked == true)<br />
	enmDays = enmDays | DaysOfTheWeek.Tuesday;<br />
if (chkWednesday.Checked == true)<br />
	enmDays = enmDays | DaysOfTheWeek.Wednesday;<br />
if (chkThursday.Checked == true)<br />
	enmDays = enmDays | DaysOfTheWeek.Thursday;<br />
if (chkFriday.Checked == true)<br />
	enmDays = enmDays | DaysOfTheWeek.Friday;<br />
if (chkSaturday.Checked == true)<br />
	enmDays = enmDays | DaysOfTheWeek.Saturday;<br />
TestFunction(enmDays);<br />

Re: Flags problem

Guffa29-Mar-06 6:52

Guffa

29-Mar-06 6:52

Standard question #1:
What do you mean by "not working"?

Mridang Agarwal wrote:
i can't possibly write a set of if else statements that take into account all the possible combinations of checkboxes being selected and appropriately calling the function.

Yes, you can. It's only 128 combinations. I can very well understand if you don't want to do it, but it's clearly possible to do. Wink | ;)

---
b { font-weight: normal; }

Re: Flags problem

Ravi Bhavnani29-Mar-06 7:39

Ravi Bhavnani

29-Mar-06 7:39

Why not just use a loop? Confused | :confused:

// Create checkbox collection (do this once)
ArrayList checkBoxes = new ArrayList();
chkSunday.Tag = DaysOfTheWeek.Sunday;
checkBoxes.Add (chkSunday);
...
chkSunday.Tag = DaysOfTheWeek.Saturday;
checkBoxes.Add (chkSaturday);
 
// Get the selected days
DaysOfTheWeek selectedDays = DaysOfTheWeek.None; // 0 or -1
for (int nDay=0; (nDay < checkBoxes.Count); nDay++) {
  CheckBox cb = checkBoxes[nDay] as CheckBox;
  if (cb.Checked) {
    if (selectedDays == DaysOfTheWeek.None)
       selectedDays = (DaysOfTheWeek) cb.Tag;
    else
       selectedDays |= (DaysOfTheWeek) cb.Tag;
  }
}

/ravi

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Re: Flags problem

Mridang Agarwalla29-Mar-06 15:17

Mridang Agarwalla

29-Mar-06 15:17

There isn't a DaysOfTheWeek.None. What do I do now?

Re: Flags problem

Ravi Bhavnani29-Mar-06 16:12

Ravi Bhavnani

29-Mar-06 16:12

Make up your own enum (eg: MyDayOfTheWeek) or use a set of days of the week, where the empty set implies "no day selected".

/ravi

My new year's resolution: 2048 x 1536
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Re: Flags problem

darkelv29-Mar-06 16:10

darkelv

29-Mar-06 16:10

bool checkMonday = true;
bool checkTuesday = true;
bool checkWednesday = true;
bool checkThursday = false;
bool checkFriday = false;
bool checkSaturday = false;
bool checkSunday = true;

DaysOfTheWeek day=(DaysOfTheWeek)0x00;
day |= (DaysOfTheWeek)((checkMonday ? 0x01 : 0x00) << Convert.ToInt32(DaysOfTheWeek.Monday));
day |= (DaysOfTheWeek)((checkTuesday ? 0x01 : 0x00) << Convert.ToInt32(DaysOfTheWeek.Tuesday));
day |= (DaysOfTheWeek)((checkWednesday ? 0x01 : 0x00) << Convert.ToInt32(DaysOfTheWeek.Wednesday));
day |= (DaysOfTheWeek)((checkThursday ? 0x01 : 0x00) << Convert.ToInt32(DaysOfTheWeek.Thursday));
day |= (DaysOfTheWeek)((checkFriday ? 0x01 : 0x00) << Convert.ToInt32(DaysOfTheWeek.Friday));
day |= (DaysOfTheWeek)((checkSaturday ? 0x01 : 0x00) << Convert.ToInt32(DaysOfTheWeek.Saturday));
day |= (DaysOfTheWeek)((checkSunday ? 0x01 : 0x00) << Convert.ToInt32(DaysOfTheWeek.Sunday));
TestFunction(day);

-- modified at 22:12 Wednesday 29th March, 2006

canny edge detection

preci29-Mar-06 5:41

preci

29-Mar-06 5:41

hi!
I'm doing a project in image processing. I have implemented sobel edge detection.But the edge is not thin.
I tried to implement canny edge detection. But I don't understand how to do non maximum suppression.If anyone has canny edge detection implemented please please share it.

any edge tracking algorithm for thinning the edges will be helpful.

signing off is preci

Re: canny edge detection

Ravi Bhavnani29-Mar-06 8:16

Ravi Bhavnani

29-Mar-06 8:16

Are any of these links useful?

• Canny edge detector[^]
• Canny edge detection tutorial[^]

/ravi

My new year's resolution: 2048 x 1536
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Re: canny edge detection

preci29-Mar-06 21:08

preci

29-Mar-06 21:08

Thankyou Ravi.
I have already been to the links the you have specified.I have also implemented canny edge detection in vb.net but the results are not good, meaning the edges are not thin (preferably a single line of pixels).
Is there some way to do that? Non maximum suppression is not very helpful. If you know how to track the edges please help.It's urgent.

signing off is preci

Re: canny edge detection

Ravi Bhavnani30-Mar-06 2:10

Ravi Bhavnani

30-Mar-06 2:10

Sorry, my knowledge of image processing resembles the null set. Frown | :(

That being said, have you seen the Rothwell[^] method? Any better than Sobel and canny?

/ravi

My new year's resolution: 2048 x 1536
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Re: Thank you Ravi

preci30-Mar-06 3:30

preci

30-Mar-06 3:30

Hi again!
I have worked around the problem.I added some new conditions and some new ideas and the results were good.But I still work to do.I greatly appreciate your help. Thank you
again!! Smile | :)

signing off is preci

Get computer name

superdragon29-Mar-06 5:20

superdragon

29-Mar-06 5:20

I want to get computer name, but i dont know how to do.
help me!
Thanks a lot

superdragon

Re: Get computer name

superdragon29-Mar-06 5:50

superdragon

29-Mar-06 5:50

I have found it, i used SystemInformation.ComputerName to get computername

superdragon

checking whether checkedlistbox .items[i] is selected?

superdragon29-Mar-06 4:52

superdragon

29-Mar-06 4:52

i have chekedlistbox, it has some items in it,when it runs, after checking some items, i want to indecate which items is checked, but i dont know what properties to indicate that.

please help me to solve it.
Thanks for helpings.

superdragon

Re: checking whether checkedlistbox .items[i] is selected?

superdragon29-Mar-06 5:30

superdragon

29-Mar-06 5:30

i have found it. Thanks everyone!

superdragon

Program runs different on other computers

TofuBug2429-Mar-06 4:48

TofuBug24

29-Mar-06 4:48

I'm not even sure how to ask this but i've got a problem that has me stumped and i'm hoping someone can shed some light on it.

I've got a winform application written in c# 2.0 that has most of it's content and controls wired to a remote sql server 2000 database. now there is one specific control tha is acting weird on another computer it's a standard NumericUpDown Control when the form it belongs to is shown it's min and max value as well as it's current value are set based on criteria from the main form. now i've run the program on windows xp, xp 64 and server 2003 enterprise on my computer and it works fine in all of them. but when i took it to the computer it was supposed to be run on after the install ran it installed the .net framework and registered everything with caspol. Now once the program is run and everything else works fine but when the form with the numericupdown control is loaded the numericupdown control has some arbitrary negative number passed to it like -17 or -16 and i have no clue why it would do that on one xp pro machine and not on another.

Anyway i hope someone can at least point me in the right direction

Thanks

Ryan

PocketPC + playsound

hung_ngole29-Mar-06 3:47

hung_ngole

29-Mar-06 3:47

Hi, I have a problem as follow:
I'm developing a application on PocketPC using C#, I have a file .wav on PC, but I don't know how to add this file to my application ( so that this file is deployed to PocketPC with my application).
Can you help me?
Thanks,
Hung.

Hung

Retrieve shortcut(.lnk) target location

boshesh29-Mar-06 3:30

boshesh

29-Mar-06 3:30

Dear all,
I am trying to get the target location data a shortcut file on a desktop. I managed to get to the desktop using Environment.GetEnvironmentVariables() and can retrieve the shortcut file but can not find the way to retrieve the target location. Could anyone please help? Thank you!

Re: Retrieve shortcut(.lnk) target location

Robin Panther29-Mar-06 7:44

Robin Panther

29-Mar-06 7:44

If you use Shell interface function CreateShortcut with name of existing link as argument - created WshShortcut object will be filled with shortcut information.
sample:
IWshShell ws = new IWshRuntimeLibrary.WshShell();
string shortcutFile = System.Environment.GetFolderPath(System.Environment.SpecialFolder.Desktop) + "\\" + "ToDo.txt.lnk";
IWshShortcut sc = (IWshShortcut)ws.CreateShortcut(shortcutFile);

after that sc.TargetPath will contain link target. Of course, if you have ToDo.txt shortcut on your desktop Smile | :)

.
Don't forget to add reference to %system32%\\wshom.ocx and add "using IWshRuntimeLibrary;"

Hope that helps.

____________________________________________
Robin Panther http://www.robinland.com

Re: Retrieve shortcut(.lnk) target location

boshesh29-Mar-06 21:19

boshesh

29-Mar-06 21:19

Thank you very much for your reply.
The shortcut files already exist on the desktop so I just need to read? the file property
to get the target location. I have looked at IWshShortcut before and only found how to create a shortcut file.
Unless ws.CreateShortcut(shortcut) works for existing shortcut files too?

Thank you !

-- modified at 3:25 Thursday 30th March, 2006

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