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  • Windows.Forms.Timer instance and UI threads

    - by David Rutten
    I have a custom control whose primary purpose is to draw data. I want to add a ScheduleUpdate(int milliSeconds) method to the control which will force an update X milliseconds from now. Since this is all GUI land, I should be using a Windows.Forms.Timer, but how does this timer instance know which thread it belongs to? What if ScheduleUpdate() is called from a non-UI thread? Should I construct the timer in the Control constructor? Or perhaps the Load event? Or is it safe to postpone construction until I'm inside ScheduleUpdate()? I know there are some very similar questions about this already, but I don't have a Timer component on my control, I'm constructing it on a when-it's-needed basis.

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  • How do I destruct data associated with an object after the object no longer exists?

    - by Phineas
    I'm creating a class (say, C) that associates data (say, D) with an object (say, O). When O is destructed, O will notify C that it soon will no longer exist :( ... Later, when C feels it is the right time, C will let go of what belonged to O, namely D. If D can be any type of object, what's the best way for C to be able to execute "delete D;"? And what if D is an array of objects? My solution is to have D derive from a base class that C has knowledge of. When the time comes, C calls delete on a pointer to the base class. I've also considered storing void pointers and calling delete, but I found out that's undefined behavior and doesn't call D's destructor. I considered that templates could be a novel solution, but I couldn't work that idea out. Here's what I have so far for C, minus some details: // This class is C in the above description. There may be many instances of C. class Context { public: // D will inherit from this class class Data { public: virtual ~Data() {} }; Context(); ~Context(); // Associates an owner (O) with its data (D) void add(const void* owner, Data* data); // O calls this when he knows its the end (O's destructor). // All instances of C are now aware that O is gone and its time to get rid // of all associated instances of D. static void purge (const void* owner); // This is called periodically in the application. It checks whether // O has called purge, and calls "delete D;" void refresh(); // Side note: sometimes O needs access to D Data *get (const void *owner); private: // Used for mapping owners (O) to data (D) std::map _data; }; // Here's an example of O class Mesh { public: ~Mesh() { Context::purge(this); } void init(Context& c) const { Data* data = new Data; // GL initialization here c.add(this, new Data); } void render(Context& c) const { Data* data = c.get(this); } private: // And here's an example of D struct Data : public Context::Data { ~Data() { glDeleteBuffers(1, &vbo); glDeleteTextures(1, &texture); } GLint vbo; GLint texture; }; }; P.S. If you're familiar with computer graphics and VR, I'm creating a class that separates an object's per-context data (e.g. OpenGL VBO IDs) from its per-application data (e.g. an array of vertices) and frees the per-context data at the appropriate time (when the matching rendering context is current).

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  • How does this method give me a -61 Error?

    - by prestonmarshall
    This is in an application I am using called Mirth, but it appears to be coming from inside an Apache Commons library from a method that checks if something is indeed Base64 encoded or not. All of the docs say the only return is true or false, so how am I getting -61? -61 org.apache.commons.codec.binary.Base64.isBase64(Base64.java:137) org.apache.commons.codec.binary.Base64.discardNonBase64(Base64.java:478) org.apache.commons.codec.binary.Base64.decodeBase64(Base64.java:374) org.apache.commons.codec.binary.Base64.decode(Base64.java:220) com.webreach.mirth.plugins.pdfviewer.PDFViewer.viewAttachments(PDFViewer.java:51) com.webreach.mirth.client.ui.browsers.message.MessageBrowser$16.doInBackground(MessageBrowser.java:1429) com.webreach.mirth.client.ui.browsers.message.MessageBrowser$16.doInBackground(MessageBrowser.java:1426) org.jdesktop.swingworker.SwingWorker$1.call(SwingWorker.java:276) java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303) java.util.concurrent.FutureTask.run(FutureTask.java:138) org.jdesktop.swingworker.SwingWorker.run(SwingWorker.java:315) java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) java.lang.Thread.run(Thread.java:637)

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  • Ruby Rack: startup and teardown operations (Tokyo Cabinet connection)

    - by clint.tseng
    I have built a pretty simple REST service in Sinatra, on Rack. It's backed by 3 Tokyo Cabinet/Table datastores, which have connections that need to be opened and closed. I have two model classes written in straight Ruby that currently simply connect, get or put what they need, and then disconnect. Obviously, this isn't going to work long-term. I also have some Rack middleware like Warden that rely on these model classes. What's the best way to manage opening and closing the connections? Rack doesn't provide startup/shutdown hooks as I'm aware. I thought about inserting a piece of middleware that provides reference to the TC/TT object in env, but then I'd have to pipe that through Sinatra to the models, which doesn't seem efficient either; and that would only get be a per-request connection to TC. I'd imagine that per-server-instance-lifecycle would be a more appropriate lifespan. Thanks!

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  • Algorithm for finding symmetries of a tree

    - by Paxinum
    I have n sectors, enumerated 0 to n-1 counterclockwise. The boundaries between these sectors are infinite branches (n of them). The sectors live in the complex plane, and for n even, sector 0 and n/2 are bisected by the real axis, and the sectors are evenly spaced. These branches meet at certain points, called junctions. Each junction is adjacent to a subset of the sectors (at least 3 of them). Specifying the junctions, (in pre-fix order, lets say, starting from junction adjacent to sector 0 and 1), and the distance between the junctions, uniquely describes the tree. Now, given such a representation, how can I see if it is symmetric wrt the real axis? For example, n=6, the tree (0,1,5)(1,2,4,5)(2,3,4) have three junctions on the real line, so it is symmetric wrt the real axis. If the distances between (015) and (1245) is equal to distance from (1245) to (234), this is also symmetric wrt the imaginary axis. The tree (0,1,5)(1,2,5)(2,4,5)(2,3,4) have 4 junctions, and this is never symmetric wrt either imaginary or real axis, but it has 180 degrees rotation symmetry if the distance between the first two and the last two junctions in the representation are equal. Edit: This is actually for my research. I have posted the question at mathoverflow as well, but my days in competition programming tells me that this is more like an IOI task. Code in mathematica would be excellent, but java, python, or any other language readable by a human suffices. Here are some examples (pretend the double edges are single and we have a tree) http://www2.math.su.se/~per/files.php?file=contr_ex_1.pdf http://www2.math.su.se/~per/files.php?file=contr_ex_2.pdf http://www2.math.su.se/~per/files.php?file=contr_ex_5.pdf Example 1 is described as (0,1,4)(1,2,4)(2,3,4)(0,4,5) with distances (2,1,3). Example 2 is described as (0,1,4)(1,2,4)(2,3,4)(0,4,5) with distances (2,1,1). Example 5 is described as (0,1,4,5)(1,2,3,4) with distances (2). So, given the description/representation, I want to find some algorithm to decide if it is symmetric wrt real, imaginary, and rotation 180 degrees. The last example have 180 degree symmetry. (These symmetries corresponds to special kinds of potential in the Schroedinger equation, which has nice properties in quantum mechanics.)

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  • How to generate GIR files from the Vala compiler?

    - by celil
    I am trying to create python bindings to a vala library using pygi with gobject introspection. However, I am having trouble generating the GIR files (that I am planning to compile to typelib files subsequently). According to the documentation valac should support generating GIR files. Compiling the following helloworld.vala public struct Point { public double x; public double y; } public class Person { public int age = 32; public Person(int age) { this.age = age; } } public int main() { var p = Point() { x=0.0, y=0.1 }; stdout.printf("%f %f\n", p.x, p.y); var per = new Person(22); stdout.printf("%d\n", per.age); return 0; } with the command valac helloworld.vala --gir=Hello-1.0.gir doesn't create the Hello-1.0.gir file as one would expect. How can I generate the gir file?

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  • Is SynchronizationContext.Post() threadsafe?

    - by cyclotis04
    This is a pretty basic question, and I imagine that it is, but I can't find any definitive answer. Is SynchronizationContext.Post() threadsafe? I have a member variable which holds the main thread's context, and _context.Post() is being called from multiple threads. I imagine that Post() could be called simultaneously on the object. Should I do something like lock (_contextLock) _context.Post(myDelegate, myEventArgs); or is that unnecessary? Edit: MSDN states that "Any instance members are not guaranteed to be thread safe." Should I keep my lock(), then?

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  • Would watching a file for changes or redundantly querying that file be more efficient?

    - by badpanda
    I am wondering whether watching a file/directory for changes using the FileSystemWatcher class is extremely memory intensive. I am developing a desktop application in C# that will be running behind the scenes continuously on low-performance computers, and I need some way of checking to see if various files have changed. I can think of a few solutions: Watch the directories using FileSystemWatcher. Run a timed thread on an interval that goes through and manually checks this. Check manually every time the actionhandler thread runs (the program will occasionally do something, on an action). Any suggestions? Thanks! badPanda

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  • launching java test bycommand line

    - by lamisse
    I created runner.bat to launch one java test it contains : path to java,classpath org.junit.runner.JUnitCore package.class when I launch it : FAILURES Tests run: 1, Failures: 1 Exception in thread "Thread-0" java.lang.IllegalStateException: Shutdown in progress at java.lang.ApplicationShutdownHooks.add(Unknown Source) at java.lang.Runtime.addShutdownHook(Unknown Source) at com.sun.imageio.stream.StreamCloser$2.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at com.sun.imageio.stream.StreamCloser.addToQueue(Unknown Source) at javax.imageio.stream.FileCacheImageInputStream.<init>(Unknown Source) at com.sun.imageio.spi.InputStreamImageInputStreamSpi.createInputStreamInstance(Unknown Source) at javax.imageio.ImageIO.createImageInputStream(Unknown Source) at javax.imageio.ImageIO.read(Unknown Source) at com.polyspace.util.guicomponent.CompositePanel.setBufferedImage(Unknown Source) at com.polyspace.util.guicomponent.CompositePanel.<init>(Unknown Source)

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  • Issue with RegConnectRegistry connecting to 64 bit machines

    - by RA
    I'm seeing a weird thing when connecting to the performance registry on 64 bit editions of Windows. The whole program stalls and callstacks becomes unreadable. After a long timeout, the connection attempts aborts and everything goes back to normal. The only solution is to make sure that only one thread at the time queries the remote registry, unless the remote machine is a 32 bit Windows XP, 2003, 2000 , then you can use as many threads as you like. Have anyone a technical explanation why this might be happening ? I've spent 2-3 days searching the web without coming up with anything. Here is a test program, run it first with one thread (connecting to a 64 bit Windows), then remove the comment in tmain and run it with 4 threads. Running it with one thread works as expected, running with 4, returns ERROR_BUSY (dwRet == 170) after stalling for a while. Remember to set a remote machine correctly in RegConnectRegistry before running the program. #define TOTALBYTES 8192 #define BYTEINCREMENT 4096 void PerfmonThread(void *pData) { DWORD BufferSize = TOTALBYTES; DWORD cbData; DWORD dwRet; PPERF_DATA_BLOCK PerfData = (PPERF_DATA_BLOCK) malloc( BufferSize ); cbData = BufferSize; printf("\nRetrieving the data..."); HKEY hKey; DWORD dwAccessRet = RegConnectRegistry(L"REMOTE_MACHINE",HKEY_PERFORMANCE_DATA,&hKey); dwRet = RegQueryValueEx( hKey,L"global",NULL,NULL,(LPBYTE) PerfData, &cbData ); while( dwRet == ERROR_MORE_DATA ) { // Get a buffer that is big enough. BufferSize += BYTEINCREMENT; PerfData = (PPERF_DATA_BLOCK) realloc( PerfData, BufferSize ); cbData = BufferSize; printf("."); dwRet = RegQueryValueEx( hKey,L"global",NULL,NULL,(LPBYTE) PerfData,&cbData ); } if( dwRet == ERROR_SUCCESS ) printf("\n\nFinal buffer size is %d\n", BufferSize); else printf("\nRegQueryValueEx failed (%d)\n", dwRet); RegCloseKey(hKey); } int _tmain(int argc, _TCHAR* argv[]) { _beginthread(PerfmonThread,0,NULL); /* _beginthread(PerfmonThread,0,NULL); _beginthread(PerfmonThread,0,NULL); _beginthread(PerfmonThread,0,NULL); */ while(1) { Sleep(2000); } }

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  • Programmer Health - how to avoid going blind and sick!

    - by stefanyko
    Hi All! this is my very first time here! so nice to meet you guys! ;-) When i was starting with this job, ( when i have chosed of doing this for the rest of my life) i have thinked also, one day, before or after, i would become blind or at least sick by drinking 5 or more coffee per day and of course by sitting down on my pc for hours!!! ;-\ From many years now, i'm asking myself how my eyes can stay in front o the monitor for so many hours per day!? well now i'm to a point of no return!!! i feel my eyes each day more tired, and my productivity is waning, but i can't change work now and i don't want do this!!!! what i need to do for prevent this to become a more serious problem for me and for my eyes!? any suggestion will be really appreciated!!! Thanks!

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  • synchronized block in JSP tag class

    - by Sudhakar
    Hi, I am trying to find answer for the following ,for the past couple of days ,but couldnt find comprehensive answer Problem Statement I have a custom JSP tag class which handles a web form submission ,captures data and write it to same file in the filesystem. As all web applications,this can be triggeredsimultaneosly ,and i fear that multiple threads would be in action handling each of the submission (we all know thats how Servlet works.) CODE synchronized (this){ final String reportFileName = "testReport.csv"; File reportDir = new File( rootCsDirectory, "reports" ); if(!reportDir.isDirectory())reportDir.mkdir(); File reportFile = new File (reportDir, reportFileName); logReport(reportFile,reportContent.toString()); } ISSUE: - A File object can be opened by one thread for writing and at same time another thread might try to access and fail and throw an exception So i thought of synchronizing (on the object ) should solve the issue , but read some where that jsp engine would have pool of jsp tag objects, so i am afraid that synchronized (this) wont work and it should be changed to synchronized (this.getClass())

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  • Using device variable by multiple threads on CUDA

    - by ashagi
    I am playing around with cuda. At the moment I have a problem. I am testing a large array for particular responses, and when I get the response, I have to copy the data onto another array. For example, my test array of 5 elements looks like this: [ ][ ][v1][ ][ ][v2] Result must look like this: [v1][v2] The problem is how do I calculate the address of the second array to store the result? All elements of the first array are checked in parallel. I am thinking to declare a device variable int addr = 0. Every time I find a response, I will increment the addr. But I am not sure about that because it means that addr may be accessed by multiple threads at the same time. Will that cause problems? Or will the thread wait until another thread finishes using that variable?

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  • Building a subquery with ARel in Rails3

    - by Christopher
    I am trying to build this query in ARel: SELECT FLOOR(AVG(num)) FROM ( SELECT COUNT(attendees.id) AS num, meetings.club_id FROM `meetings` INNER JOIN `attendees` ON `attendees`.`meeting_id` = `meetings`.`id` WHERE (`meetings`.club_id = 1) GROUP BY meetings.id) tmp GROUP BY tmp.club_id It returns the average number of attendees per meeting, per club. (a club has many meetings and a meeting has many attendees) So far I have (declared in class Club < ActiveRecord::Base): num_attendees = meetings.select("COUNT(attendees.id) AS num").joins(:attendees).group('meetings.id') Arel::Table.new('tmp', self.class.arel_engine).from(num_attendees).project('FLOOR(AVG(num))').group('tmp.club_id').to_sql but, I am getting the error: undefined method `visit_ActiveRecord_Relation' for #<Arel::Visitors::MySQL:0x9b42180> The documentation for generating non trivial ARel queries is a bit hard to come by. I have been using http://rdoc.info/github/rails/arel/master/frames Am I approaching this incorrectly? Or am I a few methods away from a solution?

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  • What happens to an ActiveX control (COleControl) after the call to OnDestroy() ?

    - by richj
    I have an ActiveX control written in C++ that runs in Internet Explorer 8. Most of the time (approx 90%) when the tab or browser containing the control is closed, there is an access violation like this: The thread 'Win32 Thread' (0x1bf0) has exited with code 0 (0x0). Unhandled exception at 0x77b3b9fd in iexplore.exe: 0xC0000005: Access violation reading location 0x65007408. The access violation occurs after the call to OnDestroy() but before the call to the control's destructor. The debug output says: No symbols are loaded for any call stack frame. The source code cannot be displayed. None of my code is present in the stacktrace, although perhaps the heap was corrupted at some earlier point during execution. What lifecycle events does an ActiveX control receive between the call to OnDestroy() and the control's destructor?

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  • How to free virtual memory ?

    - by Mehdi Amrollahi
    I have a crawler application (with C#) that downloads pages from web . The application take more virtual memory , even i dispose every object and even use GC.Collect() . This , have 10 thread and each thread has a socket that downloads pages . I use dispose method and even use GC.Collect() in my application , but in 3 hour my application take 500 MB on virtual memory (500 MB on private bytes in Process explorer) . Then my system will be hang and i should restart my pc . Is there any way that i use to free vitual memory ? Thanks .

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  • Mock Assertions on objects inside Parallel ForEach's???

    - by jacko
    Any idea how we can assert a mock object was called when it is being accessed inside Parallel.ForEach via a closure? I assume that because each invocation is on a different thread that Rhino Mocks loses track of the object? Pseudocode: var someStub = MockRepository.GenerateStub() Parallel.Foreach(collectionOfInts, anInt => someStub.DoSomething(anInt)) someStub.AssertWasCalled(s => s.DoSomething, Repeat.Five.Times) This test will return an expectation violation, expecting the stub to be called 5 times but being actually called 0 times. Any ideas how we can tell the lambdas to keep track of the thread-local stub object?

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  • two threads acting on the same runnable

    - by Eslam
    Given: public class Thread1 { int x = 0; public class Runner implements Runnable { public void run() { int current = 0; for (int i = 0; i < 4; i++) { current = x; System.out.print(current + " "); x = current + 2; } } } public void go() { Runnable r1 = new Runner(); new Thread(r1).start(); new Thread(r1).start(); } public static void main(String[] args) { new Thread1().go(); } } Which two are possible results? (Choose two) A. 0, 2, 4, 4, 6, 8, 10, 6, B. 0, 2, 4, 6, 8, 10, 2, 4, C. 0, 2, 4, 6, 8, 10, 12, 14, D. 0, 0, 2, 2, 4, 4, 6, 6, 8, 8, 10, 10, 12, 12, 14, 14, E. 0, 2, 4, 6, 8, 10, 12, 14, 0, 2, 4, 6, 8, 10, 12, 14, i chosed A,B but i'm not certain is those is the true or not.

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  • log4j performance

    - by Bob
    Hi, I'm developing a web app, and I'd like to log some information to help me improve and observe the app. (I'm using Tomcat6) First I thought I would use StringBuilders, append the logs to them and a task would persist them into the database like every 2 minutes. Because I was worried about the out-of-the-box logging system's performance. Then I made some test. Especially with log4j. Here is my code: Main.java public static void main(String[] args) { Thread[] threads = new Thread[LoggerThread.threadsNumber]; for(int i = 0; i < LoggerThread.threadsNumber; ++i){ threads[i] = new Thread(new LoggerThread("name - " + i)); } LoggerThread.startTimestamp = System.currentTimeMillis(); for(int i = 0; i < LoggerThread.threadsNumber; ++i){ threads[i].start(); } LoggerThread.java public class LoggerThread implements Runnable{ public static int threadsNumber = 10; public static long startTimestamp; private static int counter = 0; private String name; public LoggerThread(String name) { this.name = name; } private Logger log = Logger.getLogger(this.getClass()); @Override public void run() { for(int i=0; i<10000; ++i){ log.info(name + ": " + i); if(i == 9999){ int c = increaseCounter(); if(c == threadsNumber){ System.out.println("Elapsed time: " + (System.currentTimeMillis() - startTimestamp)); } } } } private synchronized int increaseCounter(){ return ++counter; } } } log4j.properties log4j.logger.main.LoggerThread=debug, f log4j.appender.f=org.apache.log4j.RollingFileAppender log4j.appender.f.layout=org.apache.log4j.PatternLayout log4j.appender.f.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n log4j.appender.f.File=c:/logs/logging.log log4j.appender.f.MaxFileSize=15000KB log4j.appender.f.MaxBackupIndex=50 I think this is a very common configuration for log4j. First I used log4j 1.2.14 then I realized there was a newer version, so I switched to 1.2.16 Here are the figures (all in millisec) LoggerThread.threadsNumber = 10 1.2.14: 4235, 4267, 4328, 4282 1.2.16: 2780, 2781, 2797, 2781 LoggerThread.threadsNumber = 100 1.2.14: 41312, 41014, 42251 1.2.16: 25606, 25729, 25922 I think this is very fast. Don't forget that: in every cycle the run method not just log into the file, it has to concatenate strings (name + ": " + i), and check an if test (i == 9999). When threadsNumber is 10, there are 100.000 loggings and if tests and concatenations. When it is 100, there are 1.000.000 loggings and if tests and concatenations. (I've read somewhere JVM uses StringBuilder's append for concatenation, not simple concatenation). Did I missed something? Am I doing something wrong? Did I forget any factor that could decrease the performance? If these figures are correct I think, I don't have to worry about log4j's performance even if I heavily log, do I?

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  • Java multi-threading - what is the best way to monitor the activity of a number of threads?

    - by MalcomTucker
    I have a number of threads that are performing a long runing task. These threads themselves have child threads that do further subdivisions of work. What is the best way for me to track the following: How many total threads my process has created What the state of each thread currently is What part of my process each thread has currently got to I want to do it in as efficient a way as possible and once threads finish, I don't want any references to them hanging around becasuse I need to be freeing up memory as early as possible. Any advice?

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  • nginx-tornado-django request timeout

    - by Xie
    We are using nginx-tornado-django to provide web services. That is, no web page frontend. The nginx server serves as a load-balancer. The server has 8 cores, so we launched 8 tornado-django processes on every server. Memcached is also deployed to gain better performance. The requests per day is about 1 million per server. We use MySQL as backend DB. The code is tested and correct. Our profiling shows that normally every request are processed within 100ms. The problem is, we find that about 10 percent of the requests suffers from time-out issue. Many requests didn't even reach tornado. I really don't have much experience on tuning of nginx/tornado/MySQL. Right now I don't have a clue on what is going wrong. Any advise is appreiciated.

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  • Php fetch rows from multiple MySQL tables

    - by Jon McIntosh
    Right now I am fetching all of the rows from one of my tables: query = "SELECT * FROM thread WHERE threadid = 2 ORDER BY threadid DESC"; $result = mysql_query($query); $num_rows = mysql_num_rows($result); if((!is_bool($result) || $result) && $num_rows) { while($row = mysql_fetch_array($result)) { $thread = $row['title']; $threadID = $row['threadid']; $poster = $row['postusername']; } What I want to do is go to another table on my database: "post_display", and get the row 'text' where the threadid = 2.

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  • Unhandled exceptions in BackgroundWorker

    - by edg
    My WinForms app uses a number of BackgroundWorker objects to retrieve information from a database. I'm using BackgroundWorker because it allows the UI to remain unblocked during long-running database queries and it simplifies the threading model for me. I'm getting occasional DatabaseExceptions in some of these background threads, and I have witnessed at least one of these exceptions in a worker thread while debugging. I'm fairly confident these exceptions are timeouts which I suppose its reasonable to expect from time to time. My question is about what happens when an unhandled exception occurs in one of these background worker threads. I don't think I can catch an exception in another thread, but can I expect my WorkerCompleted method to be executed? Is there any property or method of the BackgroundWorker I can interrogate for exceptions?

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