Problem with returning a string from a sub - C# Discussion Boards

Problem with returning a string from a sub

23-Aug-07 11:58

Look into the Document property of the WebBrowser control which returns a HTMLDocument[^].

All the controls provided by the .NET framework are free for you to use. You could code from your favorite text editor and use the command line c-sharp compiler and never have to buy a license to anything other than the operating system your using to compile on.

crash89323-Aug-07 9:36

crash893

23-Aug-07 9:36

Hi all

I have a sub that writes to a textbox in the code. I want to change it so it just returns as a string so i can use it over again for other stuff in the program

the current code is this

private void Readlog(string path)<br />
        {<br />
            StreamReader SR;<br />
            string S;<br />
            SR = File.OpenText(path);<br />
            S = SR.ReadLine();<br />
            while (S != null)<br />
            {<br />
                if (S != null)<br />
                {<br />
                   //this is sloppy but i cant have a trailing /r/n so this is the only                <br />
                    //way i can think to get rid of it                    <br />
                   S = S + "\r\n";<br />
                }<br />
                textBox1.AppendText(S);<br />
                S = SR.ReadLine();<br />
            }<br />
            SR.Close();<br />
        }

what i want to do is change it to something like

private string Readlog(string path)<br />
        {<br />
            string temp;<br />
            StreamReader SR;<br />
            string S ;<br />
            SR = File.OpenText(path);<br />
            S = SR.ReadLine();<br />
            temp =s<br />
            while (S != null)<br />
            {<br />
                if (S != null)<br />
                {<br />
                    S = S + "\r\n";<br />
                }<br />
                temp = temp +S;<br />
                S = SR.ReadLine();<br />
            }<br />
            SR.Close();<br />
            return temp;<br />
        }

The problem is that it always returns a null or just one line of text and i know its probably somthing right in front of me but I can't seem to figure out what it is

the idea is that i can use it in something like textbox1.text = readlog(c:\test)

or

<br />
Foreach something in something<br />
{<br />
writelog(merge.txt,readlog(something.filename);<br />
}<br />
<br />

Thanks for pointing me in the right direction

Re: Problem with returning a string from a sub [modified]

ChrisKo23-Aug-07 10:33

Re: Problem with returning a string from a sub

23-Aug-07 10:33

C# is case sensative on variable names, so your use of s and S were a problem. Also having an IF statement to check for null inside your while statement that is calready checking for null makes no sense. But I guess you want to make sure that it's not null.

Here's my cleanup of your code. I also ignored empty strings, but if you want to keep those, then change the while comparison to be while(temp != null)

private string Readlog(string path)
{
	string returnValue = string.Empty;

	using (StreamReader sr = File.OpenText(path))
	{
		string temp = sr.ReadLine();

		while (!string.IsNullOrEmpty(temp))
		{
			returnValue += temp + "\r\n";
			temp = sr.ReadLine();
		}
				
		sr.Close();
	}

	return returnValue;			
}

-- modified at 17:44 Thursday 23rd August, 2007

ChrisKo23-Aug-07 11:43

Re: Problem with returning a string from a sub

23-Aug-07 11:43

BLAH!!!!

I cannot believe I totally missed the string concat inside a loop. Someone please pass me a gun now.

FIXED version

private string Readlog(string path)
{
	StringBuilder sb = new StringBuilder();

	using (StreamReader sr = File.OpenText(path))
	{
		string temp = sr.ReadLine();

		while (!string.IsNullOrEmpty(temp))
		{
			sb.AppendLine(temp);
			temp = sr.ReadLine();
		}
				
		sr.Close();
	}

	return sb.ToString();			
}

crash89323-Aug-07 12:12

crash893

23-Aug-07 12:12

Thanks for all your help

I really appreciate the string.isnullorempty(temp) In are application it doesn't matter because we are joining together .csv files

but if you were to use it for say a text file or something if there was a empty space it would stop at the dump out of the loop.

again I really appreciate it thanks

Re: Problem with returning a string from a sub [modified]

ChrisKo23-Aug-07 12:50

23-Aug-07 12:50

Actually, it doesn't dump out of the loop if there's a space, it just doesn't append it to the output string. The while loop will continue to process until EOF is reached on the file. If you wanted it to stop the loop if an emptry string were to occur, you would need to add a break; statement in there.

-- modified at 19:02 Thursday 23rd August, 2007

BTW, I am zerosity, just had to change the username for the forums as I never did that when I registered way back in time. Big Grin | :-D

Dispose a thread?

verlinden.nick@telenet.be23-Aug-07 9:07

23-Aug-07 9:07

Hi all!

First I would like to say, if it wasn't for the codeproject at all, I would't know C#. My question is the following, i've been trying to figure it out forever!

I have an application, which launches a thread, there is a keyboard hook present in the thread, when the thread receives a keypress, and it matches the criteria, the thread launches another thread and aborts. The problem with this is that the memory that the thread used is not cleaned, is there a way to dispose a thread or something, completely free up all memory it used? because the problem is that after a few keycombinations, there is a huge memory load that is totally worthless, i read somewhere about appdomains, but couldn't get them to work.

Can somebody help?

Kind Regards,
Nick Verlinden

Nick Verlinden
c#-Lover

Judah Gabriel Himango23-Aug-07 13:01

Judah Gabriel Himango

23-Aug-07 13:01

verlinden.nick@telenet.be wrote:
The problem with this is that the memory that the thread used is not cleaned

First of all, are you sure about this? What are you using to measure memory usage? If it's just the Task Manager, chances are you're not looking at the right data. Use a memory profiler, such as the free CLR Profiler or the commercial ANTS profiler.

Now, if you're certain memory keeps building, that means something is keeping your thread alive. Something with a reference to that thread, perhaps? The only way to tell is look at the live objects -- again you'll need a profiler for this -- and see what's still alive that doesn't need to be.

Another possibility is, the .NET garbage collector simply hasn't run and cleaned up the memory used by the thread. You can force a garbage collection just to test this theory: call GC.Collect() to force one.

A final note: it's preferred to use the .NET thread pool instead of creating threads yourself. This way, existing threads are reused instead of being created over an over again. You can use the thread pool using the System.Threading.ThreadPool class.

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Judah Himango

ChrisKo23-Aug-07 13:08

23-Aug-07 13:08

Just to add some more information.

I'm not sure what you're doing with these threads, but if it's executing unmanaged code while you abort the thread, the thread will not abort until the unmanaged code has completed. A ThreadAbortException will be raised during any attempt during an abort.

verlinden.nick@telenet.be24-Aug-07 2:27

24-Aug-07 2:27

Yes, unmanaged code is running, hook to keyboard, but normally, the hooks should be ended before aborting. I tried several programming methods, but this is the only one working for me. I'm talking about a thread launching another thread and killing itself. This is because the threads are on different desktops.

Thanks for the reply,
Kind Regards,
Nick Verlinden

Luc Pattyn23-Aug-07 14:02

Luc Pattyn

23-Aug-07 14:02

Dag Nick,

I have several comments/questions:

1.
It seldom is a good idea to abort a thread; you typically don't know what state it is
in, what resources it may be holding, etc, so you may cause deadlocks and memory
leaks. The preferred way is to have the thread cooperate on its own termination by
regularly checking some flag, or something like that.

2.
I don't see the logic in creating a new thread and aborting another one at the same
time. It you find a way around this, I expect your code will be simpler and not have
the (presumed) memory problem at all.

3.
I am not sure I understand your "when the thread receives a keypress": GUI events
get handled by the GUI thread, normally that is the main or initial thread.
So how can another thread get hold of those KeyPress events ?

In summary, you may have to rework the threading situation; if more help is
wanted I would suggest you provide a more detailed description (+ some code) of your
set-up.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

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verlinden.nick@telenet.be24-Aug-07 2:31

24-Aug-07 2:31

Hi Luc,

Thanks for the reply. To answer a few of your questions, i tried several programming techniques, but this is the only way I can get it done, after a month of trial and error. The means why i program it that way, meaning the thread launching another thread and aborting itself, is becasue the threads run on different desktops. I also need global keyboard hooks, but they should be unhooked before the thread receives an abort.

Kind regards,
Nick verlinden

Luc Pattyn24-Aug-07 2:43

Luc Pattyn

24-Aug-07 2:43

Hi Nick,

we are missing a lot of context here.
seems you have two desktops (meaning two PCs I guess), some threading problems,
and something that starts to work after one month of trial&error, but not quite.

you must explain it all (in a top-down description) if you want anything helpful,
and probably provide several code snippets too.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

verlinden.nick@telenet.be24-Aug-07 9:08

24-Aug-07 9:08

Hi Luc!

I'm trying not to give too much information away Big Grin | :-D

, but i know that i will have too, so here it goes. I have multiple desktops "desktops as in windows desktops, not computers, for example winlogon is also a desktop (winlogon is the desktop where the alt+CTRL+DELETE window is shown)" when the user presses a key on the keyboard, it switches to antoher desktop. But since the keyboard hook is only valid in the desktop where it is being launched, so i have to abort the thread in the previous desktop and launch a new thread in the new desktop, else the user can't switch back to the previous one. if the user switches back to the previous one, the routine repeats. the problem is that the thread that was listening on the previous desktop does not release its used memore, well that's what i think at least. It has unmanaged code for the keyboard hooks.

Is that helpfull?
Kind Regards,
Nick Verlinden

Luc Pattyn24-Aug-07 16:06

Luc Pattyn

24-Aug-07 16:06

Hi Nick,

With so little information I can't help you effectively.

I don't understand how a keyboard hook would imply a thread, a hook lets you attach
your code to some event, the event itself provides the thread, you should not care
about that.

And as I said before I object to aborting a thread.

You probably want to neutralize an existing hook temporarily; you could do that
by having some flags that get tested in the hooked procedure. Or you may choose
to remove the hook (e.g. when a "desktop" deactivates), that would require
an event to call the right system function, no abort involved !

That is all.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

verlinden.nick@telenet.be25-Aug-07 2:04