Re: Some issue with thread synchronization & events - C# Discussion Boards

General Questions using Attach Process [modified]

19-Nov-07 6:33

I'm not sure why the message is not displayed. But why are you using an else if?

If the user is an admin it will pass through the first if. If it gets to the else part then we already know they're not an admin, there should be no need to check again.

My current favourite word is: PIE!

Good ol' pie, it's been a while.

Re: login page problem

rocky81119-Nov-07 6:34

rocky811

19-Nov-07 6:34

ya its fine !!! but just like i want to display a text message .. when u enter wrong details !!!

Khoramdin19-Nov-07 6:18

Khoramdin

19-Nov-07 6:18

Hello everyone,

I am working on a BHO and created a Class Library. I am using the Attach Process (Tools -> Attach Process...) to attach my Class Library Assembly(MyProject.dll and Interop.SHDocVw.dll) to the running process.

My question is, using Windows Module (Debug -> Windows -> Modules) should I be able to see the two mentioned dll files also loaded? I think I should but would like to know your opinion on this. If this is not the right way to check what file has been attached then how can I check to see what has been attached to the running process? I ask since when I use the mentioned approach I don't see any of the mentioned DLL file loaded which leaves me with the question: "What has been attached/loaded then?!!!"

I don't have to register the BHO if I am using Attach Process approach to attach the Assembly. Do I have to? I don't think I should since I am attaching it manually but I was told by someone that I should but I am not 100% sure on that. What do you think?

Thank you very much for all your help.

Khoramdin

-- modified at 12:41 Monday 19th November, 2007

Some issue with thread synchronization & events

Karma Komae19-Nov-07 5:44

Karma Komae

19-Nov-07 5:44

Hello,

Well, i'm messing with C# for one month now (sort of new to me), and i've studied a bit how thread works in .NET 2.0, but i'm facing an annoying problem i can't fix ! Here it is :

Let's assume i've got the main thread in my windows Form, and two others i'm trying to manage within this Form. A big point of interest to me is to know for sure a thread has ended, so it seems kinda easy at first. Thing is, there are some stuff that i can't make it work, so i'm here to ask for your help Big Grin | :-D

!

The main thread is rather big with some processing, and handles the two others.

One of the others is a small one, looping to wait for data input. It looks like this :

public void dataReadThread(){
    try{
        while(true){
            if(eventAbortRead.WaitOne(5,false))break;
            dataReceived = receiveData();
            if(dataReceived)eventProceedNext.Set();
        }
    }
    catch (...) {}
    eventReadThreadHasExited.Set();
}

So it's supposed to allways try to read data, and send an event when it get a response. If the thread is asked to abort, the break statement leaves the while and then fires the event eventReadThreadHasExited.

Well, thing is that works without any issues because the function receiveData is quite simple.

Now the processing thread is rather similar in it's architecture, but a bit more complex !

private void processInstructionThread(){
    while(!stop){
        if(eventAbortProcess.WaitOne(5,false))break;
        stop = processLine();  //return true when the whole processing is done
        if(FLAG_WaitAnswer){
            WaitHandle[] wh = new WaitHandle[2] {eventProceedNext, eventAbortProcess}; //To avoid being blocked
            if(WaitHandle.WaitAny(wh) == 1) //i.e. abort
                break;
        }
        //do some work
    }
    eventProcessThreadHasExited();
}

So there's no huge difference between these two threads, except the processLine function is really complex and does a lot of processing.

Now on the main thread, my thread are started and processing, and everything goes fine ... until i try to abort the threads ...

To do so, it seems quite easy, but to me it's not (maybe my code is totally wrong, but looked rather suitable to me). Here is what i'm trying to do and where i get the issues on the main thread :

protected override void OnClose(EventArgs e){
    this.eventAbortRead.Set();
    if( ! eventReadThreadHasFinished.WaitOne(5000, false) ){
         //display some error message
    }
    this.eventAbortProcess.Set();
    if( ! eventProcessThreadHasFinished.WaitOne(5000, false) ){
         //display some error message
    }
    //Has to be sure both threads ended before processing the remaining code
}

The thing is that for some unknow reason, it sometimes works and sometimes doesn't. Most of the time the read abortion is doing fine, but the Process abortion is impossible ! It looks like doing a WaitOne() in the main thread pauses or interrupts the other threads at some time !

I've also tried to code the waiting with FLAGs (with a while(!FLAG) Thread.Sleep(0); ) and it seems to do the same error Frown | :-(

.

I've also tried to code these thread using backgroundWorker but no success Frown | :-(

Well, seems a bit weird to me, and i think i miss something enomous, but can't figure out what !

So if any of you has any idea, i'd be glad to test it !

Best Regards,

Mamat,

Re: Some issue with thread synchronization & events

Judah Gabriel Himango19-Nov-07 9:31

Judah Gabriel Himango

19-Nov-07 9:31

I'd say your approach is wrong. Constantly polling threads to see if they're done, aborting threads, using lots of synchronization events; these kind of things raise flags to me.

Let's step back for a moment. Ignoring possible implementation details, what are trying to accomplish?

Tech, life, family, faith: Give me a visit.
I'm currently blogging about: The Lord Is So Good
The apostle Paul, modernly speaking: Epistles of Paul

Judah Himango

Re: Some issue with thread synchronization & events

Karma Komae19-Nov-07 21:56

Karma Komae

19-Nov-07 21:56

Hello, and thank you for your reply !

Well, this is what i thought, but i don't know how to do that another way Frown | :-(

I'm writing an interactive application, with a RichTextBox containing a script to process and get the answer to these lines. It has to handle debug features such as run, step by step, breakpoints, halt, and so on.

The thing is, i've got a main thread (my windows form), and i have to do two things :

1/ Have a background thread to listen to data input, that may come at anytime (i.e. even when the script is not processing, but have the possibility to disable it in order to process some specific commands)

2/ Have another thread to process the script lines, one by one or the whole script depending on the debug button pressed.

To me, i don't see another way to do that. Considering the reading thread for example, it has to loop for data input, unless i tell it to stop/pause. So i thought it was the right way to implement this feature.

Now after reading from you, i guess it's not right to start/stop constantly the threads, because for the step by step for example, i run the process thread just for one line and then i cut it off before the user asks for another interaction. I've also thought at using the events to pause the threads but it wasn't doing what i expected (maybe i've done some mistake on that implementation, i tried it in a hurry). But the thing is that i need to know when a thread is running, then have the ability to tell it to stop/pause and be sure it has done processing before performing the remaining operations.

As i have two loops (one for each thread), i can't find out another way that polling at each loop if they're asked to stop/pause.

I hope it's more clear for you now, and i also hope you can give me hand to find out how to implement that correctly !

Best Regards,

Mamat,

DataBound DataGridView Relational DB Problem

shirazamod19-Nov-07 5:03

shirazamod

19-Nov-07 5:03

I've got a databound datagrid from SQL Server Express '05 and one of the columns is the foreign key to another table. Right now this column just displays a number (the ID) but I want it to display the name associated with that ID.

I'm sure that this is possible as I've seen it done with databound comboboxes.

Re: DataBound DataGridView Relational DB Problem

pmarfleet19-Nov-07 9:04

pmarfleet

19-Nov-07 9:04

Change the query for your datagrid to JOIN to the table that contains the names for IDs. Include the 'name' field in your query output and bind your grid column to this field instead of the ID field itself.

Paul Marfleet

"No, his mind is not for rent
To any God or government"
Tom Sawyer - Rush

Re: DataBound DataGridView Relational DB Problem

shirazamod19-Nov-07 9:45

shirazamod

19-Nov-07 9:45

Paul you beauty! Thank you so much, you just made my ~~week~~ year!

Re: DataBound DataGridView Relational DB Problem

pmarfleet19-Nov-07 9:50

pmarfleet

19-Nov-07 9:50

No problem. Happy to help Smile | :)

Paul Marfleet

"No, his mind is not for rent
To any God or government"
Tom Sawyer - Rush

Enumerators and locks.

jmhamm19-Nov-07 4:40

jmhamm

19-Nov-07 4:40

Does anyone know how to best lock access to the object during enumeration? Eg, is it a bad/good idea to use a Monitor.Enter in the constructor and a Monitor.Exit in the dispose function? I know, I could put a lock around, but I really need this to happen automatically.

Cheers.

Re: Enumerators and locks.

Bekjong19-Nov-07 5:00

Bekjong

19-Nov-07 5:00

Check out this [e-book]. It has some really nice examples on (automatic) locking and when (not) to use it in chapter 2. You might want to look at the Mutex class.

Standards are great! Everybody should have one!

Re: Enumerators and locks.

jmhamm19-Nov-07 5:08

jmhamm

19-Nov-07 5:08

Will do, thanks!

Re: Enumerators and locks.

Daniel Grunwald19-Nov-07 11:42

Daniel Grunwald

19-Nov-07 11:42

When you compile this code:

IEnumerable<string> Test() {
  lock (someObj) {
    yield return "a";
    yield return "b";
  }
}

Then the C# compiler creates an enumerator class that calls Monitor.Enter on the first MoveNext call; and calls Monitor.Exit in the third MoveNext call, or in the Dispose method if Dispose is called between after the first MoveNext call and before the third.
foreach will automatically dispose the enumerator, but I've seen people write code like

IEnumerable<MyType> myCollection = ...;
if (e.GetEnumerator.MoveNext()) { // if the collection is not empty

So yes, using Monitor.Exit in the Dispose function is the way locking is meant to happen in enumerators, but make sure that your team is aware of the fact that enumerators must be disposed!

FindControl on Fields on an aspx screen.

imnotso#19-Nov-07 4:33

19-Nov-07 4:33

I am trying to find every control on my page with "txt" in the id, they are all my textboxes. The following bit of code is working fine and duly goes into the inner condition for some of the textboxes on the screen. But not all.....will this only work on textboxes that are visible at runtime as I have some sent to txtBox.visible = false at startup.

foreach (Control c in Page.FindControl("MyPage").Controls)
{
if (c.ID != "" && c.ID != null && c.ID.ToString().IndexOf("txt") > -1)
{
TextBox txtClearBox =new TextBox();
txtClearBox.ID = c.ID;
txtClearBox.Text = "";
}
}

Any advice on clearing all my textboxes would be great.

Thanks in Advance

Anthony Mushrow19-Nov-07 4:42

19-Nov-07 4:42

Instead of checking that the name isn't null, and that it contains "txt"
Can you not use Control.GetType() and see if it is a textbox?

And... are you making a new textbox everytime you want to clear it? Why not just set the text to ""?

My current favourite word is: PIE!

Good ol' pie, it's been a while.

imnotso#19-Nov-07 4:58

19-Nov-07 4:58

No, not a new textbox, just want to clear the existing textboxes when event 'A' or 'B' happens. There are a few and obviously I could say txtBoxA = "";txtBoxB = "" etc, there are about 20.

I'm gonna try Control.GetType now, I'll let you know, thanks for the quick response Undefeated.

Harvey

martin_hughes19-Nov-07 5:27

martin_hughes

19-Nov-07 5:27

this should do it (untested).

foreach (Control c in Page.FindControl("MyPage").Controls)
{
   if (c is TextBox)
   {
      c.Text = String.Empty;

   }
}

"On one of my cards it said I had to find temperatures lower than -8. The numbers I uncovered were -6 and -7 so I thought I had won, and so did the woman in the shop. But when she scanned the card the machine said I hadn't.

"I phoned Camelot and they fobbed me off with some story that -6 is higher - not lower - than -8 but I'm not having it."
-Tina Farrell, a 23 year old thicky from Levenshulme, Manchester.

imnotso#19-Nov-07 5:36

19-Nov-07 5:36

thanks guys, I've got to that point, that works great. However the code does not find any of the textboxes if they are in an asp:panel

<asp:label id="lblRaisedBy">Raised By
<asp:dropdownlist ="ddlraisername"="">
<asp:textbox id="txtOrganisation">

<asp:panel id="pnlRaiser" runat="Server" visible="True">

<asp:label id="lblOrg" runat="server" width="7em" cssclass="NonMandatoryLabel" visible="true">Organisation
<asp:textbox id="txtRaiserName">

txtOrganisation is found whereas txtRaiserName isn't. Why is the panel causing a problem?

Anthony Mushrow19-Nov-07 5:42

19-Nov-07 5:42

Because the textbox is a control on the panel, not the form, so you'd have to do this:

foreach(Control c in Page.FindControl("MyPage").Controls) {

    if(c is TextBox)
        c.Text = "";

    if(c is Panel)
        foreach(Control d in c) {
            if(c is TextBox)
                c.Text = "";
        }
}

And loop through each control in the panel

My current favourite word is: PIE!

Good ol' pie, it's been a while.

imnotso#19-Nov-07 5:55

19-Nov-07 5:55

It seems the foreach inside each other doesn't work..

foreach statement cannot operate on variables of type 'System.Web.UI.Control' because 'System.Web.UI.Control' does not contain a definition for 'GetEnumerator', or it is inaccessible

Is that right?

Anthony Mushrow19-Nov-07 6:08

19-Nov-07 6:08

Oops, made a slight error it should be:

foreach(Control d in c.Controls) {<br />
...

And it then should of course be:

if(d is textbox)
...
not if(c is textbox) Roll eyes | :rolleyes:

foreach(Control c in Page.FindControl("MyPage").Controls) {
    if(c is TextBox)
        c.Text = "";
    if(c is Panel)
        foreach(Control d in c.Controls) {
            if(d is TextBox)
                d.Text = "";
        }
}

My current favourite word is: PIE!

Good ol' pie, it's been a while.

imnotso#19-Nov-07 6:13