C# Discussion Boards - CodeProject

George Nistor30-Jul-12 5:45

30-Jul-12 5:45

Hi
I use System.Io.Ports and the serial interface to receive data in a Terminal like application. From the .Net driver I have a
DataReceivedHandler where I receive call with each small part of information sent on the serial.

the problem: I have seen sometime some "garbage info", data from previous read. I suspect the call come realy fast and it happens sometime to get old data.

intention:
I want to change my current implementation in this DataReceivedHandler to write in a circular list. This list I intend to be a vector where I put struct having 2 fiels:
- a State bit or boolean flag
- and the information

When I write I just check the state bit (which is similar to a lock), and if it is still false I write the info and increase the indexWrite.

and now the question:
Whould be safe this implementation without using lock{ circularList } when I receive very fast calls to the DataReceivedHandler?

george

Re: Circular list as vector, lock needed?

OriginalGriff30-Jul-12 6:07

OriginalGriff

30-Jul-12 6:07

Probably not - IIRC none of the .NET Collections are intrinsically thread safe, and they should all be locked.

Either use the .NET Queue[^] with a lock or homebrew a safe version. If you are just using a single in-feed and a single out-feed, you don't need to use locking if you write it correctly.

One way is to use an array, with two indexes - input and output. If insert only affects the input, and remove only affects the output, the only time they need to both be checked is for a full/empty test, which shouldn't need a lock - it would if you used more than one input source, or more than one remover.

Ideological Purity is no substitute for being able to stick your thumb down a pipe to stop the water

Re: Circular list as vector, lock needed?

dybs30-Jul-12 8:07

dybs

30-Jul-12 8:07

OriginalGriff wrote:
IIRC none of the .NET Collections are intrinsically thread safe

Actually, .NET 4 introduced the System.Collections.Concurrent namespace[^], which includes a ConcurrentQueue.

However, IIRC there's the potential for a delayed garbage collection - the queue keeps a reference to the object even after it's dequeued until it's been overwritten in the queue's buffer. This becomes more of an issue with a large-capacity queue. Our workaround was to use the Mono implementation of the ConcurrentQueue instead (it doesn't have this problem).

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Re: Circular list as vector, lock needed?

OriginalGriff30-Jul-12 8:12

OriginalGriff

30-Jul-12 8:12

Didn't know that - have a five!

Ideological Purity is no substitute for being able to stick your thumb down a pipe to stop the water

Re: Circular list as vector, lock needed? [Modified]

Wes Aday30-Jul-12 8:51

Wes Aday

30-Jul-12 8:51

OriginalGriff wrote:
thread safe

New in .NET 4, http://msdn.microsoft.com/en-us/library/dd997305.aspx[^]

[Edit]
Never mind. OP already posted that.

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Re: Circular list as vector, lock needed?

George Nistor30-Jul-12 21:43

George Nistor

30-Jul-12 21:43

yes this was my intention to have to indexes one for read, one for write,
and because it is in a Handlerfunction it should be executed very fast so I will use a vector - as the circular list (or Buffer).

I will try this solution first, after the other with the Thread safe collections.

thx

Re: Circular list as vector, lock needed?

George Nistor30-Jul-12 23:48

George Nistor

30-Jul-12 23:48

probably I need some kind of lightweight lock, bacause the call to the Handler can come realy fast and mess up with my array index, which is already done in ConcurrentQueue<t> Class.
Even if I use a state bit on every element the index could be messed up by another call just before it is used.

I have been wondering how it is implemented.
Would be possible this class: ConcurrentQueue<t> Class to e implemented using just Interlock class
witout any SpinWait or while loops?

modified 31-Jul-12 6:46am.

sutapa das29-Jul-12 20:30

sutapa das

29-Jul-12 20:30

how to create monthly calendar in c#?

Re: c#

Abhinav S29-Jul-12 20:46

Abhinav S

29-Jul-12 20:46

Kindly don't repost.

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how to create monthly calander in c#?

sutapa das29-Jul-12 20:27

sutapa das

29-Jul-12 20:27

plz give me appropiate answer.

Re: how to create monthly calander in c#?

Midnight Ahri29-Jul-12 20:40

Midnight Ahri

29-Jul-12 20:40

sutapa das wrote:
plz give me appropiate answer.

I'm not sure but maybe this link can help you. Smile | :)

How to create your monthly calendar.
Moreover, you don't have to post the same question to get your answer faster.
It won't work here.

Re: how to create monthly calander in c#?

Richard MacCutchan29-Jul-12 21:54

Richard MacCutchan

29-Jul-12 21:54

Why not just use one of these[^], or one of these[^].

One of these days I'm going to think of a really clever signature.

Re: how to create monthly calander in c#?

Dave Kreskowiak30-Jul-12 2:19

Dave Kreskowiak

30-Jul-12 2:19

Well, how "appropriate" the answer is depends entirely on what the hell you mean by "create monthly calender".

That could mean anything! Are you trying to come up with a control that lets you input a date, a data range over months, something to display an entire month, storing data based on some month requirement, ... ??? WHAT?

A guide to posting questions on CodeProject[^]

Dave Kreskowiak

Application Level Key Shortcut

Jassim Rahma29-Jul-12 11:54

Jassim Rahma

29-Jul-12 11:54

Hi,

Is it possible to make a shortcut in application level not control level so no matter where the focus is or which form is active, shortcut will be invoked?

Re: Application Level Key Shortcut

Richard Andrew x6429-Jul-12 12:19

Richard Andrew x64

29-Jul-12 12:19

You can use the PreviewKeyDown event to see what key is pressed at the Form level.

The difficult we do right away...
...the impossible takes slightly longer.

Re: Application Level Key Shortcut

Trak4Net29-Jul-12 20:30

Trak4Net

29-Jul-12 20:30

As a side note to your answer you also need to set the KeyPreview property to true for the form.

Re: Application Level Key Shortcut

BobJanova29-Jul-12 23:23

BobJanova

29-Jul-12 23:23

Shortcuts generally work whichever control on a form has focus, unless the control explicitly steals that character (i.e. text boxes with Ctrl+C/X/Z/V). I think you need to put a shortcut handler on every form, though, if you want app-wide ones.

Re: Application Level Key Shortcut

Andrei Straut30-Jul-12 0:59

Andrei Straut

30-Jul-12 0:59

Yes, it is, but you will have to go on treacherous ground to do so (needs some unmanaged code). Take a look at keyboard hooks, more specifically RegisterHotKey and UnregisterHotKey, both from user32.dll.

Google it further, there are a lot of threads detailing how this can be achieved, for instance here[^], or here[^]

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Re: Application Level Key Shortcut

Shameel30-Jul-12 2:47

Shameel

30-Jul-12 2:47

If your application has an MDI form, you can create a menu item with the intended code and assign a shortcut to it. It would work "universally" in your entire application.

Difference Between BeginGetResponse and GetResponse

baranils29-Jul-12 9:48

baranils

29-Jul-12 9:48

Hello

Does anyone have already experienced the BeginGetResponse illutrated in the Microsoft example ?

http://msdn.microsoft.com/en-us/library/system.net.httpwebrequest.begingetresponse.aspx[^]

My need will be to make an hrttprequest in asynchronous mode. To not let the user wait for a response that can be processed in backround.
First I was thinking to use a BackroundWorker, then I see that begingetresponse example
But it react exacly as the BeginResponse : when I step over it wait a few seconds to get the response.
So maybe I misunderstand something but I don't see any advantage of this method ??

Thank for your help

Re: Difference Between BeginGetResponse and GetResponse

Richard Andrew x6429-Jul-12 11:17

Richard Andrew x64

29-Jul-12 11:17

When you run it, is it timing out? Or is it receiving a response?

The difficult we do right away...
...the impossible takes slightly longer.

Re: Difference Between BeginGetResponse and GetResponse

Trak4Net29-Jul-12 12:01

Trak4Net

29-Jul-12 12:01

BeginGetResponse will execute the method in the AsyncCallBack asynchronously. If you do like in the MSDN example then it will wait for that asynchronous operation to finish
this is the code that will cause it to wait and also implements a timeout method so if the asynchronous operation takes to long it will end the asynchronous operation.

// this line implements the timeout, if there is a timeout, the callback fires and the request becomes aborted
      ThreadPool.RegisterWaitForSingleObject (result.AsyncWaitHandle, new WaitOrTimerCallback(TimeoutCallback), myHttpWebRequest, DefaultTimeout, true);

      // The response came in the allowed time. The work processing will happen in the
      // callback function.
      allDone.WaitOne();

Re: Difference Between BeginGetResponse and GetResponse

baranils29-Jul-12 19:02

baranils

29-Jul-12 19:02

Thank for the answer

But it seems that the BeginGetResponse itself takes long to come back

// Start the asynchronous request.
IAsyncResult result=
(IAsyncResult) myHttpWebRequest.BeginGetResponse(new AsyncCallback(RespCallback),myRequestState);

I test it a few times yesterday
But today I try again and now it return immediately !
Even if I cut the network connexion !

I probably miss something ! Confused | :confused:

Some told me that I have to wrap this code example in a dedicated thread !
But if so I dond see the advantage of using the BeginGetResponse

Re: Difference Between BeginGetResponse and GetResponse

Trak4Net29-Jul-12 20:28

Trak4Net

29-Jul-12 20:28

I'm thinking you must have missed something initially, BeginGetResponse should return immedialtely.
The only reason I would see to run that in a dedicated thread is if you want to worry about a timeout or want to ensure the asynchronous method completes like the example, as the method will block waiting for the ManualResetEvent to be set. Using the ManualResetEvent is for situations where you can't process the next step until that process has completed.

Re: Difference Between BeginGetResponse and GetResponse

baranils29-Jul-12 20:38

baranils

29-Jul-12 20:38

Thank you Trak4Net

Ok ... maybe I was too tired yesterday
I will try again tonight

But indeed I'm expecting that BeginGetResponse return immediately whatever the connexion state !

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.