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Re: Synchronization via Locks [modified]

Luc Pattyn16-Jan-09 1:53

Luc Pattyn

16-Jan-09 1:53

the_jat wrote:
I think the nutshell author was wrong when he said that the lock protected the variables

Yes, it would be more accurate to say something along the lines: "when the code correctly encloses any statement that accesses (for read or write) a shared variable with a lock, it achieves thread-safety for that variable." So the lock is used to achieve safety, it does not provide it by itself.

So the variable gets protected with a lock, not by a lock.

Smile | :)

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modified on Friday, June 10, 2011 12:22 PM

Re: Synchronization via Locks

CPallini15-Jan-09 22:21

CPallini

15-Jan-09 22:21

the_jat wrote:
static void Go( )

I suppose it is

public static void Go( )

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Re: Synchronization via Locks

the_jat15-Jan-09 22:32

the_jat

15-Jan-09 22:32

CPallini wrote:
I suppose it is...

The author didn't use the "public" keyword, the code posted is correct.

Thanks

Re: Synchronization via Locks

CPallini15-Jan-09 23:25

CPallini

15-Jan-09 23:25

OK, so how may you use it (i.e. How may Go be ever called?)?
Smile | :)

Re: Synchronization via Locks

the_jat15-Jan-09 23:43

the_jat

15-Jan-09 23:43

CPallini wrote:
OK, so how may you use it (i.e. How may Go be ever called?)?

Though the author would know better, but one could also do something like:

public void GoGo()
{
   ........
   ........
   if(....)
    ThreadSafe.Go();// OR Go();
   else
    GoGoGo();
   ........
}

Re: Synchronization via Locks

CPallini16-Jan-09 0:30

CPallini

16-Jan-09 0:30

Hence you must call GoGo() in order to gain access to Go(), thus, provided GoGo() doesn't touch the variables, you've a thread safe method.
Smile | :)

Re: Synchronization via Locks

N a v a n e e t h15-Jan-09 22:44

N a v a n e e t h

15-Jan-09 22:44

the_jat wrote:
but still one thread can(I guess) modify the static variables as the other is executing the if statement

This will not happen as if condition and modifying variable is in the lock. Only one thread will enter into the lock block.

Navaneeth

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Re: Synchronization via Locks

the_jat15-Jan-09 22:51

the_jat

15-Jan-09 22:51

Thanks for the reply, but

N a v a n e e t h wrote:
This will not happen as if condition and modifying variable is in the lock

Did you mean the "modifying variable" or the "statement that modifies the variable"?

Can a lock prevent public static variables of a public class from being modifed by other class running other threads?

Thanks!

Re: Synchronization via Locks

SeMartens15-Jan-09 23:15

SeMartens

15-Jan-09 23:15

The lock itself only prevents the modification of the variable if every statement that modifies the variable is within a lock block, where the lock is using the same lock object.

It's not a bug, it's a feature!

Me in Softwareland.

Re: Synchronization via Locks

SeMartens15-Jan-09 23:24

SeMartens

15-Jan-09 23:24

Just an addition.

Think of a house containing your code. The frontdoor has a doorman, who keeps an eye that only one person is in the house at the same time. Inside the house is a box, containing a number (this is the static variable). If everybody who wants to look into the box, or put sth else in the box is using the front door to enter the house everything is okay. But if the house has a backdoor (the architect/programmer didn't pay attention to this) the doorman doesn't know if there is more than one person in the house. So it is possible that two or more persons get to that box and modify the content.

To avoid this, you could assure that there is no backdoor, or you order another doorman (another lock-construct) for the backdoor.

Hope this associativity makes it a bit clearer.

Regards
Sebastian

P.S.: The doorman doesn't know what is inside the house, he is just protecting the front door.

It's not a bug, it's a feature!

Me in Softwareland.

Re: Synchronization via Locks

the_jat15-Jan-09 23:32

the_jat

15-Jan-09 23:32

Thanks a lot!
I finally got it! Big Grin | :-D

Can I programmatic enumerate running processes?

devvvy15-Jan-09 20:18

devvvy

15-Jan-09 20:18

Can I programmatic enumerate running processes?

Thanks

dev

Re: Can I programmatic enumerate running processes?

J a a n s15-Jan-09 20:36

J a a n s

15-Jan-09 20:36

Yes

*jaans

Re: Can I programmatic enumerate running processes?

SeMartens15-Jan-09 21:08

SeMartens

15-Jan-09 21:08

Nice answer Laugh | :laugh:

Okay, just used google and found this wonderful site

http://msdn.microsoft.com/en-us/library/1f3ys1f9(VS.80).aspx[^].

It's not a bug, it's a feature!

Me in Softwareland.

Re: Can I programmatic enumerate running processes?

devvvy16-Jan-09 4:08

devvvy

16-Jan-09 4:08

thanks mate that's what I was lookin for

dev

Re: Can I programmatic enumerate running processes?

Bharat Jain15-Jan-09 21:13

Bharat Jain

15-Jan-09 21:13

Yes That is possible , you need to use System.Diagnostics Namespace
to use this namespace you should add the following line of code

using System.Diagnostics;

at the top of you application

Then You can use Process.GetProcesses() function to get all the current running process

foreach (Process tempProcess in Process.GetProcesses())
{
    listBox1.Items.Add(tempProcess.ToString());
}

This is a small application where i add list of process to a list box on my form , the name of list box is listBox1 .

Let me know if this was what you want .

-Regards
Bharat Jain
bharat.jain.nagpur@gmail.com

TCP/IP programming in web

kiran_kumar53815-Jan-09 20:11

kiran_kumar538

15-Jan-09 20:11

Hello all,
here i am facing some problem in implementing tcp/ip in my web space.
The application is like this.
In the web space, server program has to be executed which listens for the tcp clients. Once we connect to the corresponding server ip and port number from client, server has to accept the client and display the messages sent from the client.
Now the problem is
though i connect from the client by specifying approproiate server ip and port number, server is unable to accept it.
The code i have used in the server program is as follows.

Int32 port = pno;
IPAddress localAddr = IPAddress.Parse("<server ip>");
server = new TcpListener(localAddr, port);
// Start listening for client requests.
server.Start();
// Enter the listening loop.
while (true)
{					
	client = server.AcceptTcpClient();//execution is getting struck here.
}

Plese let me know if i am doing any thing wrong here.
I can provide any other information if required.
PS: the same thing in working in LAN

Thanks in advance.

Re: TCP/IP programming in web

SeMartens16-Jan-09 3:37

SeMartens

16-Jan-09 3:37

Hi,

how does you know that the "server is unable to accept" the request? Do you receive an error message? If yes, please provide more information about this.

If it is working within the LAN, maybe it is a firewall problem? Maybe the server is not accepting requests on the port specified.

Regards
Sebastian

It's not a bug, it's a feature!

Check out my CodeProject article Permission-by-aspect.

Me in Softwareland.

Adding list of File names from Folder to a Dropdownlist in C#

Vimalsoft(Pty) Ltd15-Jan-09 20:08

Vimalsoft(Pty) Ltd

15-Jan-09 20:08

Good Morning guys,

I will need your help on this. i have Backups on a Folder on my C drive on this Path with a .BAK file extension and i want to restore them.

"C:\DATABASE\"

Now i want to go to the Folder and look for all the File names and Display them in the DropDownlist. Am doing this for a ASP.NET Page. i thought it would post it here , because its C# type of question.

Thank you

Vuyiswa Maseko,

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C#/VB.NET/ASP.NET/SQL7/2000/2005/2008
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Re: Adding list of File names from Folder to a Dropdownlist in C#

Guffa15-Jan-09 20:21

Guffa

15-Jan-09 20:21

This should do it:

Directory.GetFiles(@"c:\database").ToList().ForEach(n => TheDrowDown.Items.Add(Path.GetFileName(n));

Despite everything, the person most likely to be fooling you next is yourself.

Re: Adding list of File names from Folder to a Dropdownlist in C#

Vimalsoft(Pty) Ltd15-Jan-09 20:36

Vimalsoft(Pty) Ltd

15-Jan-09 20:36

hi Guffa

i have not done IO before. So what is the name space ? Does this code supposed to be on one line ? If so i get Errors.

The "Tolist()" is not recognised,

The Foreach not working

.ForEach(n => cmbrestore.Items.Add(Path.GetFileName(n)); <br />

Thanks

Re: Adding list of File names from Folder to a Dropdownlist in C#

Guffa15-Jan-09 20:53

Guffa

15-Jan-09 20:53

Vuyiswa Maseko wrote:
i have not done IO before. So what is the name space ?

System.IO.

Vuyiswa Maseko wrote:
Does this code supposed to be on one line ?

Yes. However, C# is not a line based language, so you can write it in several lines if you like.

Vuyiswa Maseko wrote:
The "Tolist()" is not recognised,

The Foreach not working

You need framework 3.5 for those. If you don't have that you have to loop through the names some other way.

Despite everything, the person most likely to be fooling you next is yourself.

Re: Adding list of File names from Folder to a Dropdownlist in C#

Vimalsoft(Pty) Ltd15-Jan-09 21:00

Vimalsoft(Pty) Ltd

15-Jan-09 21:00

hi Guffa

Thanks , i Found a Solution

DirectoryInfo dir = new DirectoryInfo(@"C:\DATABASES\");

FileInfo[] files = dir.GetFiles();

foreach (FileInfo file in files)
{
    cmbrestore.Items.Add(Convert.ToString(file));
}

Thank you

Re: Adding list of File names from Folder to a Dropdownlist in C#

Giorgi Dalakishvili15-Jan-09 22:18

Giorgi Dalakishvili

15-Jan-09 22:18

You don't need framework 3.5 for ForEach, I guess it's just lambda statement that causes error. anonymous method will work.

Giorgi Dalakishvili

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Re: Adding list of File names from Folder to a Dropdownlist in C#

Guffa16-Jan-09 1:20

Guffa

16-Jan-09 1:20

Giorgi Dalakishvili wrote:
You don't need framework 3.5 for ForEach

That's right, but you need 3.5 for the ToList method.

Despite everything, the person most likely to be fooling you next is yourself.

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