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  • ADO/SQL Server: What is the error code for "timeout expired"?

    - by Ian Boyd
    i'm trying to trap a "timeout expired" error from ADO. When a timeout happens, ADO returns: Number: 0x80040E31 (DB_E_ABORTLIMITREACHED in oledberr.h) SQLState: HYT00 NativeError: 0 The NativeError of zero makes sense, since the timeout is not a function of the database engine (i.e. SQL Server), but of ADO's internal timeout mechanism. The Number (i.e. the COM hresult) looks useful, but the definition of DB_E_ABORTLIMITREACHED in oledberr.h says: Execution stopped because a resource limit was reached. No results were returned. This error could apply to things besides "timeout expired" (some potentially server-side), such as a governor that limits: CPU usage I/O reads/writes network bandwidth and stops a query. The final useful piece is SQLState, which is a database-independent error code system. Unfortunately the only reference for SQLState error codes i can find have no mention of HYT00. What to do? What do do? Note: i can't trust 0x80040E31 (DB_E_ABORTLIMITREACHED) to mean "timeout expired", anymore than i could trust 0x80004005 (E_UNSPECIFIED_ERROR) to mean "Transaction was deadlocked on lock resources with another process and has been chosen as the deadlock victim". My pseudo-question becomes: does anyone have documentation on what the SQLState "HYT000" means? And my real question still remains: How can i specifically trap an ADO timeout expired exception thrown by ADO? Gotta love the questions where the developer is trying to "do the right thing", but nobody knows how to do the right thing. Also gotta love how googling for DB_E_ABORTLIMITREACHED and this question is #9, with MSDN nowhere to be found. Update 3 From the OLEdb ICommand.Execute reference: DB_E_ABORTLIMITREACHED Execution has been aborted because a resource limit has been reached. For example, a query timed out. No results have been returned. "For example", meaning not an exhaustive list.

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  • Creating a service (SERVICE_ACCEPT_SESSIONCHANGE)

    - by Ron
    Hi there, I am trying to create a service following the example documented in the link below: http://msdn.microsoft.com/en-us/library/bb540475(v=VS.85).aspx What I am interested in is to be able to catch user "lock" and "unlock" workstation events. Using the code on from the example provided, I modified the following: Line 15: Original: VOID WINAPI SvcCtrlHandler( DWORD ); Modified: DWORD WINAPI SvcCtrlHandler( DWORD, DWORD, LPVOID, LPVOID ); Line 141: Original: gSvcStatusHandle = RegisterServiceCtrlHandler( SVCNAME, SvcCtrlHandler); Modified: gSvcStatusHandle = RegisterServiceCtrlHandlerEx( SVCNAME, SvcCtrlHandler, NULL); Line 244: Original: SvcStatus.dwControlsAccepted = SERVICE_ACCEPT_STOP; Modified: gSvcStatus.dwControlsAccepted = SERVICE_ACCEPT_STOP|SERVICE_ACCEPT_SESSIONCHANGE; Line 266: Original: VOID WINAPI SvcCtrlHandler( DWORD dwCtrl ) { // Handle the requested control code. switch(dwCtrl) { case SERVICE_CONTROL_STOP: ReportSvcStatus(SERVICE_STOP_PENDING, NO_ERROR, 0); // Signal the service to stop. SetEvent(ghSvcStopEvent); ReportSvcStatus(gSvcStatus.dwCurrentState, NO_ERROR, 0); return; case SERVICE_CONTROL_INTERROGATE: break; default: break; } }` Modified: DWORD WINAPI SvcCtrlHandler( DWORD dwControl, DWORD dwEventType, LPVOID lpEventData, LPVOID lpContext ) { DWORD dwErrorCode = NO_ERROR; switch(dwControl) { case SERVICE_CONTROL_STOP: ReportSvcStatus(SERVICE_STOP_PENDING, NO_ERROR, 0); // Signal the service to stop. SetEvent(ghSvcStopEvent); ReportSvcStatus(gSvcStatus.dwCurrentState, NO_ERROR, 0); break; case SERVICE_CONTROL_INTERROGATE: break; case SERVICE_CONTROL_SESSIONCHANGE: ReportSvcStatus(gSvcStatus.dwCurrentState, NO_ERROR, 0); break; default: break; } return dwErrorCode; } With the changes above, my service compiled and install fine. But when I try to start my service on my Windows 2000 machine, it does not start properly (it will be stuck on the "starting" status) Can anyone please advise? Thank you in advance, Ron

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  • Calling QAxWidget method outside of the GUI thread

    - by user304361
    I'm beginning to wonder if this is impossible, but I thought I'd ask in case there's a clever way to get around the problems I'm having. I have a Qt application that uses an ActiveX control. The control is held by a QAxWidget, and the QAxWidget itself is contained within another QWidget (I needed to add additional signals/slots to the widget, and I couldn't just subclass QAxWidget because the class doesn't permit that). When I need to interact with the ActiveX control, I call a method of the QWidget, which in turn calls the dynamicCall method of the QAxWidget in order to invoke the appropriate method of the ActiveX control. All of that is working fine. However, one method of the ActiveX control takes several seconds to return. When I call this method, my entire GUI locks up for a few seconds until the method returns. This is undesirable. I'd like the ActiveX control to go off and do its processing by itself and come back to me when it's done without locking up the Qt GUI. I've tried a few things without success: Creating a new QThread and calling QAxWidget::dynamicCall from the new thread Connecting a signal to the appropriate slot method of the QAxWidget and calling the method using signals/slots instead of using dynamicCall Calling QAxWidget::dynamicCall using QtConcurrent::run Nothing seems to affect the behavior. No matter how or where I use dynamicCall (or trigger the appropriate slot of the QAxWidget), the GUI locks until the ActiveX control completes its operation. Is there any way to detach this ActiveX processing from the Qt GUI thread so that the GUI doesn't lock up while the ActiveX control is running a method? Is there something clever I can do with QAxBase or QAxObject to get my desired results?

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  • Is it possible to unstick a remote IIS ASP server after an exception hangs the session?

    - by user89691
    I have been coding an app in classic ASP that accesses 2 Access databases. I had a page I was working on throw an exception, which is normal during development and causes no lasting problems. This time however, after the exception any attempt to open either of the databases would freeze the session with an infinite script timeout. If I delete the session cookie I an able to access ASP pages again until I try to open the database again. The database that was open when the exception was thrown is left open. There is a LDB lock file and I can't rename or delete either the LDB or MDB file, though I can download the MDB file with FTP. The 2nd access database is not open but any attempt to read this also hangs the session. Accessing HTML pages is fine. The site is hosted with Hostway and they are not interested ("Coding problem = Your problem" even though it leaves my site dead in the water, I suspect until the next reboot, whenever that might be). Here is the dump from the relevant ASP page that threw the exception: Active Server Pages error 'ASP 0115' Unexpected error /translatestats.asp A trappable error (C0000005) occurred in an external object. The script cannot continue running. Active Server Pages error 'ASP 0240' Script Engine Exception /translatestats.asp A ScriptEngine threw exception 'C0000005' in 'IActiveScript::Close()' from 'CActiveScriptEngine::FinalRelease()'. Is there any way I can unstick the site / force close the database remotely ?

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  • How to TDD Asynchronous Events?

    - by Padu Merloti
    The fundamental question is how do I create a unit test that needs to call a method, wait for an event to happen on the tested class and then call another method (the one that we actually want to test)? Here's the scenario if you have time to read further: I'm developing an application that has to control a piece of hardware. In order to avoid dependency from hardware availability, when I create my object I specify that we are running in test mode. When that happens, the class that is being tested creates the appropriate driver hierarchy (in this case a thin mock layer of hardware drivers). Imagine that the class in question is an Elevator and I want to test the method that gives me the floor number that the elevator is. Here is how my fictitious test looks like right now: [TestMethod] public void TestGetCurrentFloor() { var elevator = new Elevator(Elevator.Environment.Offline); elevator.ElevatorArrivedOnFloor += TestElevatorArrived; elevator.GoToFloor(5); //Here's where I'm getting lost... I could block //until TestElevatorArrived gives me a signal, but //I'm not sure it's the best way int floor = elevator.GetCurrentFloor(); Assert.AreEqual(floor, 5); } Edit: Thanks for all the answers. This is how I ended up implementing it: [TestMethod] public void TestGetCurrentFloor() { var elevator = new Elevator(Elevator.Environment.Offline); elevator.ElevatorArrivedOnFloor += (s, e) => { Monitor.Pulse(this); }; lock (this) { elevator.GoToFloor(5); if (!Monitor.Wait(this, Timeout)) Assert.Fail("Elevator did not reach destination in time"); int floor = elevator.GetCurrentFloor(); Assert.AreEqual(floor, 5); } }

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  • Cannot edit values of DataGridView bound to a BindingList

    - by m_oLogin
    Hello community, I have trouble editing a databound bindinglist. Let me illustrate it with the following: Say I have the Person class: public Class Person{ private string m_firstname; private string m_lastname; public string FirstName{get;set;} public string LastName{get;set;} public Person{ ... } } I then have a containing class called Population: public class Population{ private BindingList<Person> m_lstPerson = new BindingList<Person>(); private string m_countryName; public BindingList<Person> ListPerson{get; set;} public string CountryName { get; set; } } I then have on one form a first datagridview with DataSource = m_lstPopulation (BindingList). The binding works like a charm when working with the Population objects. When I double click, it opens up a dialog form showing the object details. One tab in the details holds a datagridview bound to that population's ListPerson. The second datagridview displays fine. However, I cannot edit or add cells in this datagridview. None of the columns is set to read-only. In fact, both datagridview have just about the same parameters. What am I missing? It seems that a lock has been placed on the Population object so that its inner fields cannot be edited... Please advise. Thanks.

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  • Why is this SocketException not caught by a generic catch routine?

    - by Tarnschaf
    Our company provides a network component (DLL) for a GUI application. It uses a Timer that checks for disconnections. If it wants to reconnect, it calls: internal void timClock_TimerCallback(object state) { lock (someLock) { // ... try { DoConnect(); } catch (Exception e) { // Log e.Message omitted // Raise event with e as parameter ErrorEvent(this, new ErrorEventArgs(e)); DoDisconnect(); } // ... } } So the problem is, inside of the DoConnect() routine a SocketException is thrown (and not caught). I would assume, that the catch (Exception e) should catch ALL exceptions but somehow the SocketException was not caught and shows up to the GUI application. protected void DoConnect() { // client = new TcpClient(); client.NoDelay = true; // In the following call the SocketException is thrown client.Connect(endPoint.Address.ToString(), endPoint.Port); // ... (login stuff) } The doc confirmed that SocketException extends Exception. The stacktrace that showed up is: TcpClient.Connect() -> DoConnect() -> timClock_TimerCallback So the exception is not thrown outside the try/catch block. Any ideas why it doesn't work?

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  • Thread-safe initialization of function-local static const objects

    - by sbi
    This question made me question a practice I had been following for years. For thread-safe initialization of function-local static const objects I protect the actual construction of the object, but not the initialization of the function-local reference referring to it. Something like this: namspace { const some_type& create_const_thingy() { lock my_lock(some_mutex); static const some_type the_const_thingy; return the_const_thingy; } } void use_const_thingy() { static const some_type& the_const_thingy = create_const_thingy(); // use the_const_thingy } The idea is that locking takes time, and if the reference is overwritten by several threads, it won't matter. I'd be interested if this is safe enough in practice? safe according to The Rules? (I know, the current standard doesn't even know what "concurrency" is, but what about trampling over an already initialized reference? And do other standards, like POSIX, have something to say that's relevant to this?) For the inquiring minds: Many such function-local static const objects I used are maps which are initialized from const arrays upon first use and used for lookup. For example, I have a few XML parsers where tag name strings are mapped to enum values, so I could later switch over the tags enum values.

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  • How much should the AppDelegate do?

    - by Rudiger
    I'm designing quite a large App and on startup it will create sessions with a few different servers. As they are creating a session which is used across all parts of the app its something I thought would be best in App Delegate. But the problem is I need the session progress to be represented on the screen. I plan to have a UIToolBar at the bottom of the main menu which I don't want to cover with the progress bar but cover the UIView above it.So the way I see it I could do it a few different ways. 1) Have the App Delegate establish the sessions and report the progress to the main menu class so it can represent it in the progress bar (will I have any issues doing this if the sessions are created in a separate thread?), 2) have the App delegate display the main menu (UIView with a bunch of buttons and UIToolBar) and have it track and display the progress (I have never displayed anything in the App Delegate but assume you can do this but its not recommended) or 3) have the App Delegate just push the main menu and have the mainMenu class create the sessions and display the progress bar. 4) I think the other way to do it is to create the sessions in a delegate class and have the delegate set to mainMenu rather than self (AppDelegate), although I've never used anything other then self so not sure if this will work or if I will be able to close the thread (through calling super maybe?) as its running in the AppDelegate rather than the delegate of the class. As I've kinda said before the sessions are being created in a class in a separate thread so it wont lock the UI and I think the best way is the first but am I going to have issues having it running in a separate thread, reporting back to the app delegate and then sending that message to the mainMenu view? I hope that all makes sense, let me know if you need any further clarification. Any information is appreciated Cheers,

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  • Correct way to generate order numbers in SQL Server

    - by Anton Gogolev
    This question certainly applies to a much broader scope, but here it is. I have a basic ecommerce app, where users can, naturally enough, place orders. Said orders need to have a unique number, which I'm trying to generate right now. Each order is Vendor-specific. Basically, I have an OrderNumberInfo (VendorID, OrderNumber) table. Now whenever a customer places an order I need to increment OrderNumber for a particuar Vendor and return that value. Naturally, I don't want other processes to interfere with me, so I need to exclusively lock this row somehow: begin tranaction declare @n int select @n = OrderNumber from OrderNumberInfo where VendorID = @vendorID update OrderNumberInfo set OrderNumber = @n + 1 where OrderNumber = @n and VendorID = @vendorID commit transaction Now, I've read about select ... with (updlock rowlock), pessimistic locking, etc., but just cannot fit all this in a coherent picture: How do these hints play with SQL Server 2008s' snapshot isolation? Do they perform row-level, page-level or even table-level locks? How does this tolerate multiple users trying to generate numbers for a single Vendor? What isolation levels are appropriate here? And generally - what is the way to do such things?

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  • BackgroundWorker might be causing my application to hang

    - by alexD
    I have a Form that uses a BackgroundWorker to execute a series of tests. I use the ProgressChanged event to send messages to the main thread, which then does all of the updates on the UI. I've combed through my code to make sure I'm not doing anything to the UI in the background worker. There are no while loops in my code and the BackgroundWorker has a finite execution time (measured in seconds or minutes). However, for some reason when I lock my computer, often times the application will be hung when I log back in. The thing is, the BackgroundWorker isn't even running when this happens. The reason I believe it is related to the BackgroundWorker though is because the form only hangs when the BackgroundWorker has been executed since the application was loaded (it only runs when given a certain user input). I pass this thread a List of TreeNodes from a TreeView in my UI through the RunWorkerAsync method, but I only read those nodes in the worker thread..any modifications I make to them is done in the UI thread through the progressChanged event. I do use Thread.Sleep in my worker thread to execute tests at timed intervals (which involves sending messages over a TCP socket, which was not created in the worker thread). I am completely perplexed as to why my application might be hanging. I'm sure I'm doing something 'illegal' somewhere, I just don't know what.

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  • Is it possible to store pointers in shared memory without using offsets?

    - by Joseph Garvin
    When using shared memory, each process may mmap the shared region into a different area of their address space. This means that when storing pointers within the shared region, you need to store them as offsets of the start of the shared region. Unfortunately, this complicates use of atomic instructions (e.g. if you're trying to write a lock free algorithm). For example, say you have a bunch of reference counted nodes in shared memory, created by a single writer. The writer periodically atomically updates a pointer 'p' to point to a valid node with positive reference count. Readers want to atomically write to 'p' because it points to the beginning of a node (a struct) whose first element is a reference count. Since p always points to a valid node, incrementing the ref count is safe, and makes it safe to dereference 'p' and access other members. However, this all only works when everything is in the same address space. If the nodes and the 'p' pointer are stored in shared memory, then clients suffer a race condition: x = read p y = x + offset Increment refcount at y During step 2, p may change and x may no longer point to a valid node. The only workaround I can think of is somehow forcing all processes to agree on where to map the shared memory, so that real pointers rather than offsets can be stored in the mmap'd region. Is there any way to do that? I see MAP_FIXED in the mmap documentation, but I don't know how I could pick an address that would be safe.

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  • C++ Returning Multiple Items

    - by Travis Parks
    I am designing a class in C++ that extracts URLs from an HTML page. I am using Boost's Regex library to do the heavy lifting for me. I started designing a class and realized that I didn't want to tie down how the URLs are stored. One option would be to accept a std::vector<Url> by reference and just call push_back on it. I'd like to avoid forcing consumers of my class to use std::vector. So, I created a member template that took a destination iterator. It looks like this: template <typename TForwardIterator, typename TOutputIterator> TOutputIterator UrlExtractor::get_urls( TForwardIterator begin, TForwardIterator end, TOutputIterator dest); I feel like I am overcomplicating things. I like to write fairly generic code in C++, and I struggle to lock down my interfaces. But then I get into these predicaments where I am trying to templatize everything. At this point, someone reading the code doesn't realize that TForwardIterator is iterating over a std::string. In my particular situation, I am wondering if being this generic is a good thing. At what point do you start making code more explicit? Is there a standard approach to getting values out of a function generically?

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  • Compile subversion on CentOs

    - by peter
    I have downloaded, compiled and installed so far: apr-1.3.9 apr-util-1.3.9 sqlite-3.6.23 zlib-1.2.4 libtool-2.2.6b Now after downloading subversion-1.6.9, the config works fine but compiling it will end with the following error: cd subversion/svn && /bin/sh /root/subversion-1.6.9/libtool --tag=CC --silent --mode=link gcc -g -O2 -g -O2 -pthread -rpath /usr/local/lib -o svn add-cmd.o blame-cmd.o cat-cmd.o changelist-cmd.o checkout-cmd.o cleanup-cmd.o commit-cmd.o conflict-callbacks.o copy-cmd.o delete-cmd.o diff-cmd.o export-cmd.o help-cmd.o import-cmd.o info-cmd.o list-cmd.o lock-cmd.o log-cmd.o main.o merge-cmd.o mergeinfo-cmd.o mkdir-cmd.o move-cmd.o notify.o propdel-cmd.o propedit-cmd.o propget-cmd.o proplist-cmd.o props.o propset-cmd.o resolve-cmd.o resolved-cmd.o revert-cmd.o status-cmd.o status.o switch-cmd.o tree-conflicts.o unlock-cmd.o update-cmd.o util.o ../../subversion/libsvn_client/libsvn_client-1.la ../../subversion/libsvn_wc/libsvn_wc-1.la ../../subversion/libsvn_ra/libsvn_ra-1.la ../../subversion/libsvn_delta/libsvn_delta-1.la ../../subversion/libsvn_diff/libsvn_diff-1.la ../../subversion/libsvn_subr/libsvn_subr-1.la /usr/local/apr/lib/libaprutil-1.la -lexpat /usr/local/apr/lib/libapr-1.la -lrt -lcrypt -lpthread -ldl /usr/bin/ld: cannot find -lexpat collect2: ld returned 1 exit status make: * [subversion/svn/svn] Error 1 The file at /usr/local/apr/lib/libapr-1.la exists and seems to be OK (from permission perspective What could be the problem here? Thanks Peter

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  • Can Core Data be used for objects with variable schemas?

    - by glenc
    I'm implementing a new iPhone app and am relatively new to Cocoa development overall. I am at the stage of choosing how the persistence layer of this app will work, and it looks like I'm basically choosing between Core Data and sqlite3. The persisted models in this app are intended to have a schema that is loaded at runtime (from some kind of defn file, probably XML). By which I mean, this app is intended to have objects that are user-definable to some extent, e.g. the Customer type (which has certain built-in fields like "name" and "email") can be modified to have extra fields based on the user's specific needs (e.g. a user might want to add a "favourite fruit" field to their Customer type). Having said that, will Core Data work for an app with a non-baked-in data model like this? I've just started playing around with the Core Data object designer thing in XCode and it seems like this thing wants to work with objects that have fixed fields that are compiled in. I'm definitely trying to take the path of least resistance here, and I can see the benefits of using an Apple-supplied data framework, but don't want to start down that path if it's going to lock me into a data model that's defined at compile time.

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  • Android app after update: crashes on Motorola Cliq with weird stacktrace

    - by sandis
    So after updating my app on the market I am getting reports from motorola cliq-users that my app crashes on start. The stacktrace is below, and is not very helpful since it does not go trough my app! Unfortunately I have no access to a motorola cliq-phone by myself, and I have changed too many things in this update to know what is causing the trouble. Have anyone of you guys run into the same problem? I would very much appreciate help with this problem! 05-26 11:44:06.521 I/PacketReader( 116): Got the features element 05-26 11:44:06.941 W/WindowManager( 86): No window to dispatch pointer action 0 05-26 11:44:07.381 W/WindowManager( 86): No window to dispatch pointer action 1 05-26 11:44:07.691 W/ActivityManager( 86): Launch timeout has expired, giving up wake lock! 05-26 11:44:07.931 W/ActivityManager( 86): Activity idle timeout for HistoryRecord{43714db8 {my.package/my.package.Main}} 05-26 11:44:08.531 E/AndroidRuntime( 565): Uncaught handler: thread main exiting due to uncaught exception 05-26 11:44:08.541 E/AndroidRuntime( 565): java.lang.RuntimeException: Unable to start activity ComponentInfo{my.packageC/my.package.Main}: java.lang.NullPointerException 05-26 11:44:08.541 E/AndroidRuntime( 565): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2297) 05-26 11:44:08.541 E/AndroidRuntime( 565): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2313) 05-26 11:44:08.541 E/AndroidRuntime( 565): at android.app.ActivityThread.access$2000(ActivityThread.java:115) 05-26 11:44:08.541 E/AndroidRuntime( 565): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1721) 05-26 11:44:08.541 E/AndroidRuntime( 565): at android.os.Handler.dispatchMessage(Handler.java:99) 05-26 11:44:08.541 E/AndroidRuntime( 565): at android.os.Looper.loop(Looper.java:123) 05-26 11:44:08.541 E/AndroidRuntime( 565): at android.app.ActivityThread.main(ActivityThread.java:3977) 05-26 11:44:08.541 E/AndroidRuntime( 565): at java.lang.reflect.Method.invokeNative(Native Method) 05-26 11:44:08.541 E/AndroidRuntime( 565): at java.lang.reflect.Method.invoke(Method.java:521) 05-26 11:44:08.541 E/AndroidRuntime( 565): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:782) 05-26 11:44:08.541 E/AndroidRuntime( 565): at com.android.internal.os.ZygoteI

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  • Core Data: Deleting causes 'NSObjectInaccessibleException' from NSOperation with a reference to a deleted object

    - by Bryan Irace
    My application has NSOperation subclasses that fetch and operate on managed objects. My application also periodically purges rows from the database, which can result in the following race condition: An background operation fetches a bunch of objects (from a thread-specific context). It will iterate over these objects and do something with their properties. A bunch of rows are deleted in the main managed object context. The background operation accesses a property on an object that was deleted from the main context. This results in an 'NSObjectInaccessibleException', reason: 'CoreData could not fulfill a fault' Ideally, the objects that are fetched by the NSOperation can be operated on even if one is deleted in the main context. The best way I can think to achieve this is either to: Call [request setReturnsObjectsAsFaults:NO] to ensure that Core Data won't try to fulfill a fault for an object that no longer exists in the main context. The problem here is I may need to access the object's relationships, which (to my understanding) will still be faulted. Iterate through the managed objects up front and copy the properties I will need into separate non-managed objects. The problem here is that (I think) I will need to synchronize/lock this part, in case an object is deleted in the main context before I can finish copying. Am I missing something obvious? It doesn't seem like what I'm trying to accomplish is too out of the ordinary. Thanks for your help.

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  • Mutex example / tutorial ?

    - by Nav
    I've noticed that asking questions for the sake of creating a reference list etc. is encouraged in SO. This is one such question, so that anyone Googling for a mutex tutorial will find a good one here. I'm new to multithreading, and was trying to understand how mutexes work. Did a lot of Googling and this is the only decent tutorial I found, but it still left some doubts of how it works because I created my own program and the locking didn't work. One absolutely non-intuitive syntax of the mutex is pthread_mutex_lock( &mutex1 );, where it looks like the mutex is being locked, when what I really want to lock is some other variable. Does this syntax mean that locking a mutex locks a region of code until the mutex is unlocked? Then how do threads know that the region is locked? And isn't such a phenomenon supposed to be called critical section? In short, could you please help with the simplest possible mutex example program and the simplest possible explanation on the logic of how it works? I'm sure this will help plenty of other newbies.

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  • Passing variables from a thread to another form using C#

    - by kirstom14
    Hi, I am trying to pass 2 variables from a thread, in the MainForm, to another form, but when doing so an error occurs. private void TrackingThread( ) { float targetX = 0; float targetY = 0; while ( true ) { camera1Acquired.WaitOne( ); camera2Acquired.WaitOne( ); lock ( this ) { // stop the thread if it was signaled if ( ( x1 == -1 ) && ( y1 == -1 ) && ( x2 == -1 ) && ( y2 == -1 ) ) { break; } // get middle point targetX = ( x1 + x2 ) / 2; targetY = ( y1 + y2 ) / 2; } if (directionForm != null) { directionForm.RunMotors(targetX, targetY); } } } In the form, directionForm, I am simply displaying the variables targetX and targetY. The code for the directionForm.RunMotors() is the following: public void RunMotors(float x, float y) { label1.Text = "X-ordinate " + x.ToString(); label2.Text = "Y-ordinate " + y.ToString(); } The error happen when I am trying to display the two variables: "InvalidOperationException was unhandled Cross-threading operation not valid: Control label1 accessed from a thread other than . the thread it was created on" What shall I do??? Thanks in advance

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  • WPF: Editable ComboBox; how to make search/auto-fill functionality case sensitive?

    - by unforgiven3
    Say I have a ComboBox, like so: <ComboBox IsEditable="True" Height="30"> <ComboBoxItem>robot</ComboBoxItem> <ComboBoxItem>Robot</ComboBoxItem> </ComboBox> If a user comes along and starts by typing a lower-case 'r' into that ComboBox when it is empty, the ComboBox predictably auto-fills itself with the word 'robot'. Great. Now the same user comes along and starts typing an upper-case 'R' into that ComboBox when it is again empty. Unpredictable, the ComboBox auto-fills itself with the lower-case word 'robot'. Not great. I desperately want it to auto-fill itself with 'Robot', but WPF does not seem to want to smile down upon me. No matter what you do (CAPS lock, shift+key), the ComboBox will always auto-fill with the lower case 'robot', provided that the lower case 'robot' precedes the upper case 'Robot' in the ComboBox's items collection. Is there any way to prevent this? This behavior is maddening and makes for an absolutely abysmal user experience.

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  • Threading Practice with Polling.

    - by Stacey
    I have a C# application that has to constantly read from a program; sometimes there is a chance it will not find what it needs, which will throw an exception. This is a limitation of the program it has to read from. This frequently causes the program to lock up as it tries to poll. So I solved it by spawning the 'polling' off into a separate thread. However watching the debugger, the thread is created and destroyed each time. I am uncertain if this is typical or not; but my question is, is this good practice, or am I using the threading for the wrong purpose? ProgramReader { static Thread oThread; public static void Read( Program program ) { // check to see if the program exists if ( false ) oThread = new ThreadStart(program.Poll); if(oThread != null || !oThread.IsAlive ) oThread.Start(); } } This is my general pseudocode. It runs every 10 seconds or so. Is this a huge hit to performance? The operation it performs is relatively small and lightweight; just repetitive.

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  • Webbrowser locks first Excel Instance

    - by figus
    VB.NET 2008 - WinForms Hi Everyone! I've been looking for an answer to my problem but I only find more questions related to my problem... The thing is that I'm using a AxWebBrowser control in VB.NET 2008 to open a excel file in a WindowsForm, it opens succesfully and everything... but the problem is this: If I had a Excel File Open before opening another Excel File in my WebBrowser Control, the window that contains the file that was already open gets locked... (I can't give focus to that Excel window... If I click on it, the focus returns to my application) I tried creating a new excel instance with CreateObject("Excel.Application") just before loading the file, but the WebBrowser locks the first Excel Instance... Is there a way to lock it to the last instance??? I use the WebBrowser1.Navigate(Url) method to load the file... where Url is a String like C:\myExcelFile.xlsm WebBrowser1.Document.Application.UserControl is also True, but it get's locked. Any Suggestion?? Thanks in Advance!!!

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  • What is the right pattern for a async data fetching method in .net async/await

    - by s093294
    Given a class with a method GetData. A few other clients call GetData, and instead of it fetching data each time, i would like to create a pattern where the first call starts the task to get the data, and the rest of the calls wait for the task to complete. private Task<string> _data; private async Task<string> _getdata() { return "my random data from the net"; //get_data_from_net() } public string GetData() { if(_data==null) _data=_getdata(); _data.wait(); //are there not a problem here. cant wait a task that is already completed ? if(_data.status != rantocompletion) _data.wait() is not any better, it might complete between the check and the _data.wait? return _data.Result; } How would i do the pattern correctly? (Solution) private static object _servertime_lock = new object(); private static Task<string> _servertime; private static async Task<string> servertime() { try { var thetvdb = new HttpClient(); thetvdb.Timeout = TimeSpan.FromSeconds(5); // var st = await thetvdb.GetStreamAsync("http://www.thetvdb.com/api/Updates.php?type=none"); var response = await thetvdb.GetAsync("http://www.thetvdb.com/api/Updates.php?type=none"); response.EnsureSuccessStatusCode(); Stream stream = await response.Content.ReadAsStreamAsync(); XDocument xdoc = XDocument.Load(stream); return xdoc.Descendants("Time").First().Value; } catch { return null; } } public static async Task<string> GetServerTime() { lock (_servertime_lock) { if (_servertime == null) _servertime = servertime(); } var time = await _servertime; if (time == null) _servertime = null; return time; }

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  • git-svn cannot create a branch to follow SVN branching

    - by Serhiy Yakovyn
    Hello everybody, I'm struggling with the following issue. When I continue fetching revisions from SVN with git svn fetch I'm getting the following error (removed https to be able to post question): *Found possible branch point: somecompany.com/product/trunk = somecompany.com/product/branches/deep/branches/product-001, 72666 Found branch parent: (refs/remotes/deep/branches/product-001) b685b7b92813885fdf 6b8e2663daf884bf504b14 Following parent with do_switch Successfully followed parent error: 'refs/remotes/deep' exists; cannot create 'refs/remotes/deep/branches/product-001' fatal: Cannot lock the ref 'refs/remotes/deep/branches/product-001'. update-ref -m r72667 refs/remotes/deep/branches/product-001 df51920e8f0a53f26507 c2679eb6a9dbad91e0d6: command returned error: 128* This happened because I was fetching revisions using the default filter for SVN branches: [svn-remote "svn"] url = https://somecompany.com/someproduct fetch = trunk:refs/remotes/trunk branches = branches/*:refs/remotes/* tags = tags/*:refs/remotes/tags/* Now, I have the line below added, but it's too late: branches = branches/deep/branches/*:refs/remotes/deep/branches/* I have tried to fix this by using git reset to remove all the commits. Actually I can see from the error message that git is trying right thing, but cannot because of the branch remotes/deep being existing. I have tried to search for 2 possible solutions: 1. Remove that branch (remotes/deep), but as it is tracked by git as a remote, I was not able to find any solution for that. 2. Remove the whole history related to that branch. No success too :( Does anybody know how to deal with my issue? Thank you in advance, Serhiy Y

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  • "database already closed" is shown using a custom cursor adapter

    - by kiduxa
    I'm using a cursor with a custom adapter that extends SimpleCursorAdapter: public class ListWordAdapter extends SimpleCursorAdapter { private LayoutInflater inflater; private Cursor mCursor; private int mLayout; private String[] from; private int[] to; public ListWordAdapter(Context context, int layout, Cursor c, String[] from, int[] to, int flags) { super(context, layout, c, from, to, flags); this.mCursor = c; this.inflater = LayoutInflater.from(context); this.mLayout = layout; this.from = from; this.to = to; } private static class ViewHolder { //public ImageView img; public TextView name; public TextView type; public TextView translate; } @Override public View getView(int position, View convertView, ViewGroup parent) { if (mCursor.moveToPosition(position)) { ViewHolder holder; if (convertView == null) { convertView = inflater.inflate(mLayout, null); holder = new ViewHolder(); // holder.img = (ImageView) convertView.findViewById(R.id.img_row); holder.name = (TextView) convertView.findViewById(to[0]); holder.type = (TextView) convertView.findViewById(to[1]); holder.translate = (TextView) convertView.findViewById(to[2]); convertView.setTag(holder); } else { holder = (ViewHolder) convertView.getTag(); } holder.name.setText(mCursor.getString(mCursor.getColumnIndex(from[0]))); holder.type.setText(mCursor.getString(mCursor.getColumnIndex(from[1]))); holder.translate.setText(mCursor.getString(mCursor.getColumnIndex(from[2]))); // holder.img.setImageResource(img_resource); } return convertView; } } And in the main activity I call it as: adapter = new ListWordAdapter(getSherlockActivity(), R.layout.row_list_words, mCursorWords, from, to, 0); When a modification in the list is made, I call this method: public void onWordSaved() { WordDAO wordsDao = new WordSqliteDAO(); Cursor mCursorWords = wordsDao.list(getSherlockActivity()); adapter.changeCursor(mCursorWords); } The thing here is that this produces me this exception: 10-29 11:14:33.810: E/AndroidRuntime(18659): java.lang.IllegalStateException: database /data/data/com.example.palabrasdeldia/databases/palabrasDelDia (conn# 0) already closed Complete stack trace: 10-29 11:14:33.810: E/AndroidRuntime(18659): FATAL EXCEPTION: main 10-29 11:14:33.810: E/AndroidRuntime(18659): java.lang.IllegalStateException: database /data/data/com.example.palabrasdeldia/databases/palabrasDelDia (conn# 0) already closed 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.database.sqlite.SQLiteDatabase.verifyDbIsOpen(SQLiteDatabase.java:2123) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.database.sqlite.SQLiteDatabase.lock(SQLiteDatabase.java:398) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.database.sqlite.SQLiteDatabase.lock(SQLiteDatabase.java:390) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.database.sqlite.SQLiteQuery.fillWindow(SQLiteQuery.java:74) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.database.sqlite.SQLiteCursor.fillWindow(SQLiteCursor.java:311) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.database.sqlite.SQLiteCursor.onMove(SQLiteCursor.java:283) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.database.AbstractCursor.moveToPosition(AbstractCursor.java:173) 10-29 11:14:33.810: E/AndroidRuntime(18659): at com.example.palabrasdeldia.adapters.ListWordAdapter.getView(ListWordAdapter.java:42) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.widget.AbsListView.obtainView(AbsListView.java:2128) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.widget.ListView.makeAndAddView(ListView.java:1817) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.widget.ListView.fillSpecific(ListView.java:1361) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.widget.ListView.layoutChildren(ListView.java:1646) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.widget.AbsListView.onLayout(AbsListView.java:1979) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.view.View.layout(View.java:9593) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.view.ViewGroup.layout(ViewGroup.java:3877) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1542) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.widget.LinearLayout.layoutHorizontal(LinearLayout.java:1527) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.widget.LinearLayout.onLayout(LinearLayout.java:1316) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.view.View.layout(View.java:9593) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.view.ViewGroup.layout(ViewGroup.java:3877) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.widget.FrameLayout.onLayout(FrameLayout.java:400) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.view.View.layout(View.java:9593) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.view.ViewGroup.layout(ViewGroup.java:3877) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.support.v4.view.ViewPager.onLayout(ViewPager.java:1589) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.view.View.layout(View.java:9593) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.view.ViewGroup.layout(ViewGroup.java:3877) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.widget.FrameLayout.onLayout(FrameLayout.java:400) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.view.View.layout(View.java:9593) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.view.ViewGroup.layout(ViewGroup.java:3877) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1542) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1403) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.widget.LinearLayout.onLayout(LinearLayout.java:1314) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.view.View.layout(View.java:9593) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.view.ViewGroup.layout(ViewGroup.java:3877) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.widget.FrameLayout.onLayout(FrameLayout.java:400) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.view.View.layout(View.java:9593) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.view.ViewGroup.layout(ViewGroup.java:3877) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1542) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1403) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.widget.LinearLayout.onLayout(LinearLayout.java:1314) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.view.View.layout(View.java:9593) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.view.ViewGroup.layout(ViewGroup.java:3877) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.widget.FrameLayout.onLayout(FrameLayout.java:400) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.view.View.layout(View.java:9593) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.view.ViewGroup.layout(ViewGroup.java:3877) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.widget.FrameLayout.onLayout(FrameLayout.java:400) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.view.View.layout(View.java:9593) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.view.ViewGroup.layout(ViewGroup.java:3877) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.view.ViewRoot.performTraversals(ViewRoot.java:1253) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.view.ViewRoot.handleMessage(ViewRoot.java:2017) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.os.Handler.dispatchMessage(Handler.java:99) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.os.Looper.loop(Looper.java:132) 10-29 11:14:33.810: E/AndroidRuntime(18659): at android.app.ActivityThread.main(ActivityThread.java:4028) 10-29 11:14:33.810: E/AndroidRuntime(18659): at java.lang.reflect.Method.invokeNative(Native Method) 10-29 11:14:33.810: E/AndroidRuntime(18659): at java.lang.reflect.Method.invoke(Method.java:491) 10-29 11:14:33.810: E/AndroidRuntime(18659): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:844) 10-29 11:14:33.810: E/AndroidRuntime(18659): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:602) 10-29 11:14:33.810: E/AndroidRuntime(18659): at dalvik.system.NativeStart.main(Native Method) If I use SimpleCursorAdapter directly instead of ListWordAdapter, it works fine. What's wrong with my custom adapter implementation? The line in bold in the stack trace corresponds with: if (mCursor.moveToPosition(position)) inside getView method. EDIT: I have created a custom class to manage DB operations as open and close: public class ConexionBD { private Context context; private SQLiteDatabase database; private DataBaseHelper dbHelper; public ConexionBD(Context context) { this.context = context; } public ConexionBD open() throws SQLException { this.dbHelper = DataBaseHelper.getInstance(context); this.database = dbHelper.getWritableDatabase(); database.execSQL("PRAGMA foreign_keys=ON"); return this; } public void close() { if (database.isOpen() && database != null) { dbHelper.close(); } } /*Getters y setters*/ public SQLiteDatabase getDatabase() { return database; } public void setDatabase(SQLiteDatabase database) { this.database = database; } } And this is my DataBaseHelper: public class DataBaseHelper extends SQLiteOpenHelper { private static final String DATABASE_NAME = "myDb"; private static final int DATABASE_VERSION = 1; private static DataBaseHelper sInstance = null; public static DataBaseHelper getInstance(Context context) { // Use the application context, which will ensure that you // don't accidentally leak an Activity's context. // See this article for more information: http://bit.ly/6LRzfx if (sInstance == null) { sInstance = new DataBaseHelper(context.getApplicationContext()); } return sInstance; } @Override public void onCreate(SQLiteDatabase database) { ... } .... And this is an example of how I manage a query: public Cursor list(Context context) { ConexionBD conexion = new ConexionBD(context); Cursor mCursor = null; try{ conexion.open(); mCursor = conexion.getDatabase().query(DataBaseHelper.TABLE_WORD , null , null, null, null, null, Word.NAME); if (mCursor != null) { mCursor.moveToFirst(); } }finally{ conexion.close(); } return mCursor; } For every connection to the DB I open it and close it.

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