Re: Ugly error - C# Discussion Boards

30-Jan-06 20:57

Ok here's the error
I am making a chat client. The user has to open a new windows for each client he wants to talk to. So if he clicks the button

if(TO[TOS[this.listBox1.SelectedIndex]].Visible)<br />
			{<br />
				TO[TOS[this.listBox1.SelectedIndex]].Focus();<br />
			}<br />
			else<br />
			{<br />
				TO[TOS[this.listBox1.SelectedIndex]].Show();<br />
			}

I use that and it works. But I also want the program to open a window when it receives data from a client who's window is not opened(just like Yahoo Messenger).

if(TO[num].Visible)<br />
{<br />
   TO[num].Receive(Got.Split(":".ToCharArray(),2)[1]);<br />
}<br />
else<br />
{	<br />
   TO[num].Show();<br />
   TO[num].Receive(Got.Split(":".ToCharArray(),2)[1]);<br />
}

And then i get something like the left-over of a window and the program exits, without pointing out an exceptio at least. Please help. Sigh | :sigh:

-- modified at 2:57 Tuesday 31st January, 2006

Vikram A Punathambekar30-Jan-06 22:03

30-Jan-06 22:03

Did you put a breakpoint and step through the part where it gives you problems?

If you can find out which line breaks your code, it might be easier to fix it.

Cheers,
Vikram.

"When I read in books about a "base class", I figured this was the class that was at the bottom of the inheritence tree. It's the "base", right? Like the base of a pyramid." - Marc Clifton.

i dont mind to be
a stupid,better than being a moron - Adnan Siddiqi.

nc3b30-Jan-06 22:06

30-Jan-06 22:06

Really, I'll try, altough until now I haven't used this method

nc3b30-Jan-06 22:11

30-Jan-06 22:11

Ok, It managed to jam the debugger. I am speechless Frown | :(

Colin Angus Mackay30-Jan-06 22:27

Colin Angus Mackay

30-Jan-06 22:27

nc3b wrote:
It managed to jam the debugger

What do you mean by that? How did it "jam" the debugger?

ColinMackay.net
"Man who stand on hill with mouth open will wait long time for roast duck to drop in." -- Confucius
"If a man empties his purse into his head, no man can take it away from him, for an investment in knowledge pays the best interest." -- Joseph E. O'Donnell

nc3b30-Jan-06 22:29

30-Jan-06 22:29

Simple. I caused it to crash Sigh | :sigh:

Colin Angus Mackay30-Jan-06 22:46

Colin Angus Mackay

30-Jan-06 22:46

How can you expect help when you make vague statements like this. What were the manifestations of the crash? By "jam" it suggests that maybe it hung. You also mentioned you were unused to setting breakpoints. Perhaps you mistook the breakpoint hitting for a hanging application, because that is essentially what it does.

ColinMackay.net
"Man who stand on hill with mouth open will wait long time for roast duck to drop in." -- Confucius
"If a man empties his purse into his head, no man can take it away from him, for an investment in knowledge pays the best interest." -- Joseph E. O'Donnell

nc3b30-Jan-06 22:48

30-Jan-06 22:48

In deed I am unused with breakpoints, but I got that nice old error message, asking me if I want to send the error to microsoft..

Colin Angus Mackay30-Jan-06 22:50

Colin Angus Mackay

30-Jan-06 22:50

Fair enough - but, if you'd said that to start with then we wouldn't have needed this exchange to determine that.

ColinMackay.net
"Man who stand on hill with mouth open will wait long time for roast duck to drop in." -- Confucius
"If a man empties his purse into his head, no man can take it away from him, for an investment in knowledge pays the best interest." -- Joseph E. O'Donnell

Ingo30-Jan-06 22:46

Ingo

30-Jan-06 22:46

Hi!

First I would use a 'try-catch' just like:

try {
-your code-
} catch (Exception expt) {
System.Windows.Forms.MessageBox.Show(expt.ToString());
} // try-catch

The Next Point is that inline-code is easy to programm but hard to debug, so it's no good style to do everytrhing in a single line. So split your code:

string[] strArrayGot = Got.Split(":".ToCharArray(),2);
TO[num].Receive(strArrayGot[1]);

The next thing you have todo is watch your debugger. Then you can find out where the program exists.

I just talk about your variable names. But its hard to read. What the hell is TO and what about TOS? And listBox1 isn't a good name, too. What is handled there? The Number '1'?

Ok, you can programm that way, but it's hard to read and hard to find errors, so you should try to code a little bit more readable.

Hope I didn't dumbfounded you, was just an idea.

Greetings,
Ingo

-- modified at 4:47 Tuesday 31st January, 2006

nc3b30-Jan-06 22:56

30-Jan-06 22:56

Ok, there's no secret about it. TO is an array of forms, TOS is an array of integers. So when I try to open a new form, first i must know which form to try to open. It's part of a dumb mechanism. My problem is with num. I am SURE I am not trying to open the wrong form, but I want to ask you, could the rest of the function that calls TO[num].Show() be the problem? And by the way, my program is full of try-catch but you see, this error doesn't throw any exception, it displays a part of the form it should display and it stops working. Then I get that nice message about sending the report and I wonder if microsoft's coders want to help me solve the problem... Smile | :)

Ingo30-Jan-06 23:08

Ingo

30-Jan-06 23:08

Ok sounds good.

So TO[num] is available and not null?! the string you give to receive(...) is ok?

Then I see the problem, if you thought to check this. The programm should work, but it doesn't. I got a similar error a few weeks ago.
The application crushed while calling a method of an object which was definitivly ok. The solution - sound strange - was to build the project new. I started with an empty projectmap, added empty projects, copied the forms and classes in the directory added each class and compiled again. After that the programm runned whithout any mistake (did I mentioned that I hate .Net? Wink | ;)

) !

Greetings,
Ingo

nc3b30-Jan-06 23:11

30-Jan-06 23:11

The solution to the problem remains illusive... please if anyone can help me... I wonder if the problem is that I am calling TO[num].Show() from
public void OnReceive(IAsyncResult ar), now is have to go...

Ingo30-Jan-06 23:22

Ingo

30-Jan-06 23:22

I don't think so. Why should there be a problem. It's just an event. But you can find out. Don't show the form, start a timer instead, then from the timer-event you can show the form after e.g. 100 ms. If that works, you got the problem, if it doesn't work you know that this isn't the problem.

Greetings,
Ingo

nc3b31-Jan-06 6:52

31-Jan-06 6:52

Ok, I am finally home and I am going to try the timer thing...

nc3b31-Jan-06 7:07

31-Jan-06 7:07

Tried the timer, it simply doesn't trigger. Nothing hasppens. It is incredible. Hmmm | :|

S. Senthil Kumar31-Jan-06 15:50

S. Senthil Kumar

31-Jan-06 15:50

You can't display a form from a threadpool thread (which I think OnReceive is). This[^] article tells you why it's a bad idea to do any UI manipulation from a non UI thread. For your problem, I'd suggest calling Invoke like this

delegate void FormShowDelegate(Form f);

public void OnReceive(IAsyncResult ar)
{
   TO[num].Invoke(new FormShowDelegate(ShowForm), new object[]{TO[num]});
}

private void ShowForm(Form f)
{
   f.Show();
}

This of course, assumes that you populated the TO[num] array from the UI thread..

Regards
Senthil
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nc3b31-Jan-06 21:41

Instantiating a class from a third party DLL and calling methods on it

31-Jan-06 21:41

Thank you verry much. I found out that the function runs in a new thread (or something like that) and to call a function in the main thread I would use invoke a few hours ago. Still, thank you very much, I'm so happy the program works now Big Grin | :-D

Cheers

Vikram A Punathambekar30-Jan-06 20:08

Re: Instantiating a class from a third party DLL and calling methods on it

30-Jan-06 20:08

I'm a bit of a tyro when it comes to .net, so I'm sorry if this question sounds very basic.

I want to create an EXE, which will offer a File Open dialog box. The user has to select a DLL which contains a class that implements a specific interface. I want to be able to create an instance of the class contained in the DLL and call some methods that it exposes, passing certain parameters and receiving return values.

How can I do this? I'd be grateful if anybody can kick me in the right direction. Smile | :)

Cheers,
Vikram.

Kodanda Pani30-Jan-06 20:42

Kodanda Pani

30-Jan-06 20:42

Hi Vikram,

Guess the following link will help you.

http://www.kdkeys.net/forums/785/ShowPost.aspx

Thanks and Regards
Pani

Re: Instantiating a class from a third party DLL and calling methods on it

Vikram A Punathambekar30-Jan-06 21:59

Re: Instantiating a class from a third party DLL and calling methods on it

30-Jan-06 21:59

Thanks, Kodanda Pani.

I don't know VB, but I should be able to decipher it. Smile | :)

Thanks very much. Rose | [Rose]

Cheers,
Vikram.

S. Senthil Kumar31-Jan-06 15:57

S. Senthil Kumar

31-Jan-06 15:57

Reflection is the way to go. You can use Assembly.Load[^] or one of its variations to get an Assembly object, then use the GetExportedTypes[^] method on that Assembly object to retrieve types in that assembly. You can then iterate over the types and use FindInterfaces[^] to check if that type implements the interface you want. Activator.CreateInstance[^] creates instances given the type and you should find it simple from there on.

Remember though, the assembly gets loaded in your AppDomain, so it won't get unloaded till your app (or your AppDomain) shuts down. So if some other process tries to write to that assembly, it will fail.

Regards
Senthil
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Re: Instantiating a class from a third party DLL and calling methods on it

Vikram A Punathambekar31-Jan-06 16:18