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• How to avoid repetition when working with primitive types?

  - by I82Much

  I have the need to perform algorithms on various primitive types; the algorithm is essentially the same with the exception of which type the variables are. So for instance, /** * Determine if <code>value</code> is the bitwise OR of elements of <code>validValues</code> array. * For instance, our valid choices are 0001, 0010, and 1000. * We are given a value of 1001. This is valid because it can be made from * ORing together 0001 and 1000. * On the other hand, if we are given a value of 1111, this is invalid because * you cannot turn on the second bit from left by ORing together those 3 * valid values. */ public static boolean isValid(long value, long[] validValues) { for (long validOption : validValues) { value &= ~validOption; } return value != 0; } public static boolean isValid(int value, int[] validValues) { for (int validOption : validValues) { value &= ~validOption; } return value != 0; } How can I avoid this repetition? I know there's no way to genericize primitive arrays, so my hands seem tied. I have instances of primitive arrays and not boxed arrays of say Number objects, so I do not want to go that route either. I know there are a lot of questions about primitives with respect to arrays, autoboxing, etc., but I haven't seen it formulated in quite this way, and I haven't seen a decisive answer on how to interact with these arrays. I suppose I could do something like: public static<E extends Number> boolean isValid(E value, List<E> numbers) { long theValue = value.longValue(); for (Number validOption : numbers) { theValue &= ~validOption.longValue(); } return theValue != 0; } and then public static boolean isValid(long value, long[] validValues) { return isValid(value, Arrays.asList(ArrayUtils.toObject(validValues))); } public static boolean isValid(int value, int[] validValues) { return isValid(value, Arrays.asList(ArrayUtils.toObject(validValues))); } Is that really much better though? Any thoughts in this matter would be appreciated.

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• Combining FileStream and MemoryStream to avoid disk accesses/paging while receiving gigabytes of data?

  - by w128

  I'm receiving a file as a stream of byte[] data packets (total size isn't known in advance) that I need to store somewhere before processing it immediately after it's been received (I can't do the processing on the fly). Total received file size can vary from as small as 10 KB to over 4 GB. One option for storing the received data is to use a MemoryStream, i.e. a sequence of MemoryStream.Write(bufferReceived, 0, count) calls to store the received packets. This is very simple, but obviously will result in out of memory exception for large files. An alternative option is to use a FileStream, i.e. FileStream.Write(bufferReceived, 0, count). This way, no out of memory exceptions will occur, but what I'm unsure about is bad performance due to disk writes (which I don't want to occur as long as plenty of memory is still available) - I'd like to avoid disk access as much as possible, but I don't know of a way to control this. I did some testing and most of the time, there seems to be little performance difference between say 10 000 consecutive calls of MemoryStream.Write() vs FileStream.Write(), but a lot seems to depend on buffer size and the total amount of data in question (i.e the number of writes). Obviously, MemoryStream size reallocation is also a factor. Does it make sense to use a combination of MemoryStream and FileStream, i.e. write to memory stream by default, but once the total amount of data received is over e.g. 500 MB, write it to FileStream; then, read in chunks from both streams for processing the received data (first process 500 MB from the MemoryStream, dispose it, then read from FileStream)? Another solution is to use a custom memory stream implementation that doesn't require continuous address space for internal array allocation (i.e. a linked list of memory streams); this way, at least on 64-bit environments, out of memory exceptions should no longer be an issue. Con: extra work, more room for mistakes. So how do FileStream vs MemoryStream read/writes behave in terms of disk access and memory caching, i.e. data size/performance balance. I would expect that as long as enough RAM is available, FileStream would internally read/write from memory (cache) anyway, and virtual memory would take care of the rest. But I don't know how often FileStream will explicitly access a disk when being written to. Any help would be appreciated.

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• How to avoid my this facebook app api login page?

  - by user1035140

  I got a problem regrading with my apps which is once I go to my apps, it sure will show me a login page instead of allow page? it always display the login page 1st then only display allow page, I had tried other apps, if I am 1st time user, It sure will appear the allow page only, it did not show me the login page. my question is how to I avoid my login page direct go to allow page? here is my login page picture here is my apps link https://apps.facebook.com/christmas_testing/ here is my facebook php jdk api coding <?php $fbconfig['appid' ] = "XXXXXXXXXXXXX"; $fbconfig['secret'] = "XXXXXXXXXXXXX"; $fbconfig['baseUrl'] = "myserverlink"; $fbconfig['appBaseUrl'] = "http://apps.facebook.com/christmas_testing/"; if (isset($_GET['code'])){ header("Location: " . $fbconfig['appBaseUrl']); exit; } if (isset($_GET['request_ids'])){ //user comes from invitation //track them if you need header("Location: " . $fbconfig['appBaseUrl']); } $user = null; //facebook user uid try{ include_once "facebook.php"; } catch(Exception $o){ echo '<pre>'; print_r($o); echo '</pre>'; } // Create our Application instance. $facebook = new Facebook(array( 'appId' => $fbconfig['appid'], 'secret' => $fbconfig['secret'], 'cookie' => true, )); //Facebook Authentication part $user = $facebook->getUser(); $loginUrl = $facebook->getLoginUrl( array( 'scope' => 'email,publish_stream,user_birthday,user_location,user_work_history,user_about_me,user_hometown' ) ); if ($user) { try { // Proceed knowing you have a logged in user who's authenticated. $user_profile = $facebook->api('/me'); } catch (FacebookApiException $e) { //you should use error_log($e); instead of printing the info on browser d($e); // d is a debug function defined at the end of this file $user = null; } } if (!$user) { echo "<script type='text/javascript'>top.location.href = '$loginUrl';</script>"; exit; } //get user basic description $userInfo = $facebook->api("/$user"); function d($d){ echo '<pre>'; print_r($d); echo '</pre>'; } ?

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• Play! Framework 1.2.4 --- C3P0 settings to avoid Communications link failure do to idle time

  - by HelpMeStackOverflowMyOnlyHope

  I'm trying to customize my C3P0 settings to avoid the error shown at the bottom of this post. It was suggested at this url --- http://make-it-open.blogspot.com/2008/12/sql-error-0-sqlstate-08s01.html --- to adjust the settings as follows: In hibernate.cfg.xml, write <property name="c3p0.min_size">5</property> <property name="c3p0.max_size">20</property> <property name="c3p0.timeout">1800</property> <property name="c3p0.max_statements">50</property> Then create "c3p0.properties" in your root classpath folder and write c3p0.testConnectionOnCheckout=true c3p0.acquireRetryDelay=1000 c3p0.acquireRetryAttempts=1 I've tried to make those adjustments following the direction of the Play! Framework documentation, where they say use "db.pool..." as follows: db.pool.timeout=1800 db.pool.maxSize=15 db.pool.minSize=5 db.pool.initialSize=5 db.pool.acquireRetryAttempts=1 db.pool.preferredTestQuery=SELECT 1 db.pool.testConnectionOnCheckout=true db.pool.acquireRetryDelay=1000 db.pool.maxStatements=50 Are those settings not going to work? Should I be trying to set them in a different way? With those settings I still get the error shown below, that is due to to long of a idle time. Complete Stack Trace of Error: 23:00:44,932 WARN ~ SQL Error: 0, SQLState: 08S01 2012-04-13T23:00:44+00:00 app[web.1]: 23:00:44,932 ERROR ~ Communications link failure 2012-04-13T23:00:44+00:00 app[web.1]: 2012-04-13T23:00:44+00:00 app[web.1]: The last packet successfully received from the server was 274,847 milliseconds ago. The last packet sent successfully to the server was 7 milliseconds ago. 2012-04-13T23:00:44+00:00 app[web.1]: 23:00:44,934 ERROR ~ Why the driver complains here? 2012-04-13T23:00:44+00:00 app[web.1]: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No operations allowed after connection closed.Connection was implicitly closed by the driver. 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.Util.handleNewInstance(Util.java:407) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.Util.getInstance(Util.java:382) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1013) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:987) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:982) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:927) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.ConnectionImpl.throwConnectionClosedException(ConnectionImpl.java:1213) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.ConnectionImpl.getMutex(ConnectionImpl.java:3101) 2012-04-13T23:00:44+00:00 app[web.1]: at com.mysql.jdbc.ConnectionImpl.setAutoCommit(ConnectionImpl.java:4975) 2012-04-13T23:00:44+00:00 app[web.1]: at org.hibernate.jdbc.BorrowedConnectionProxy.invoke(BorrowedConnectionProxy.java:74) 2012-04-13T23:00:44+00:00 app[web.1]: at $Proxy49.setAutoCommit(Unknown Source) 2012-04-13T23:00:44+00:00 app[web.1]: at play.db.jpa.JPAPlugin.closeTx(JPAPlugin.java:368) 2012-04-13T23:00:44+00:00 app[web.1]: at play.db.jpa.JPAPlugin.onInvocationException(JPAPlugin.java:328) 2012-04-13T23:00:44+00:00 app[web.1]: at play.plugins.PluginCollection.onInvocationException(PluginCollection.java:447) 2012-04-13T23:00:44+00:00 app[web.1]: at play.Invoker$Invocation.onException(Invoker.java:240) 2012-04-13T23:00:44+00:00 app[web.1]: at play.jobs.Job.onException(Job.java:124) 2012-04-13T23:00:44+00:00 app[web.1]: at play.jobs.Job.call(Job.java:163) 2012-04-13T23:00:44+00:00 app[web.1]: at play.jobs.Job$1.call(Job.java:66) 2012-04-13T23:00:44+00:00 app[web.1]: at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334) 2012-04-13T23:00:44+00:00 app[web.1]: at java.util.concurrent.FutureTask.run(FutureTask.java:166) 2012-04-13T23:00:44+00:00 app[web.1]: at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$101(ScheduledThreadPoolExecutor.java:165) 2012-04-13T23:00:44+00:00 app[web.1]: at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:266) 2012-04-13T23:00:44+00:00 app[web.1]: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) 2012-04-13T23:00:44+00:00 app[web.1]: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) 2012-04-13T23:00:44+00:00 app[web.1]: at java.lang.Thread.run(Thread.java:636) 2012-04-13T23:00:44+00:00 app[web.1]: Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

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• Survey Data Model - How to avoid EAV and excessive denormalization?

  - by AlexDPC

  Hi everyone, My database skills are mediocre at best and I have to design a data model for survey data. I have spent some thoughts on this and right now I feel that I am stuck between some kind of EAV model and a design involving hundreds of tables, each with hundreds of columns (and thousands of records). There must be a better way to do this and I hope that the wise folks on this forum can help me. I have already searched various forums, but I couldn't really find a solution. If it has already been given elsewhere, please excuse me and provide me with a link so I can read it up. Some assumptions about the data I have to deal with: Each survey consists of 1 to n questionnaires Each questionnaire consists of 100-2,000 questions (please ignore that 2,000 questions really sound like a lot to answer...) Questions can be of various types: multiple-choice, free text, a number (like age, income, percentages, ...) Each survey involves 10-200 countries (These are not the respondents. The respondents are actually people in the countries.) Depending on the type of questionnaire, each questionnaire is answered by 100-20,000 respondents per country. A country can adapt the questionnaires for a survey, i.e. add, remove or edit questions The data for one country is gathered in a separate database in that country. There is no possibility for online integration from the start. The data for all countries has to be integrated later. This means for example, if a country has deleted a question, that data must somehow be derived from what they sent in order to achieve a uniform design across all countries I will have to write the integration and cleaning software, which will need to work with every country's data In the end the data needs to be exported to flat files, one rectangular grid per country and questionnaire. I have already discussed this topic with people from various backgrounds and have not come to a good solution yet. I mainly got two kinds of opinions. The domain experts, who are used to working with flat files (spreadsheet-style) for data processing and analysis vote for a denormalized structure with loads of tables and columns as I described above (1 table per country and questionnaire). This sounds terrible to me, because I learned that wide tables are to be avoided, it will be annoying to determine which columns are actually in a table when working with it, the database will become cluttered with hundreds of tables (or I even need to set up multiple databases, each with a similar yet a bit differetn design), etc. O-O-programmers vote for a strongly "normalized" design, which would effectively lead to a central table containing all the answers from all respondents to all questions. This table would either need to contain a column of type sql_variant type or multiple answer columns with different types to store answers of different types (multiple choice, free text, ..). The former would essentially be a EAV model. I tend to follow Joe Celko here, who strongly discourages its use (he calls it OTLT or "One True Lookup Table"). The latter would imply that each row would contain null cells for the not applicable types by design. Another alternative I could think of would be to create one table per answer type, i.e., one for multiple-choice questions, one for free text questions, etc.. That's not so generic, it would lead to a lot of union joins, I think and I would have to add a table if a new answer type is invented. Sorry for boring you with all this text and thank you for your input! Cheers, Alex PS: I asked the same question here: http://www.eggheadcafe.com/community/aspnet/13/10242616/survey-data-model--how-to-avoid-eav-and-excessive-denormalization.aspx

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• WPF MVVM UserControl Binding "Container", dispose to avoid memory leak.

  - by user178657

  For simplicity. I have a window, with a bindable usercontrol <UserControl Content="{Binding Path = BindingControl, UpdateSourceTrigger=PropertyChanged}"> I have two user controls, ControlA, and ControlB, Both UserControls have their own Datacontext ViewModel, ControlAViewModel and ControlBViewModel. Both ControlAViewModel and ControlBViewModel inh. from a "ViewModelBase" public abstract class ViewModelBase : DependencyObject, INotifyPropertyChanged, IDisposable........ Main window was added to IoC... To set the property of the Bindable UC, i do ComponentRepository.Resolve<MainViewWindow>().Bindingcontrol= new ControlA; ControlA, in its Datacontext, creates a DispatcherTimer, to do "somestuff".. Later on., I need to navigate elsewhere, so the other usercontrol is loaded into the container ComponentRepository.Resolve<MainViewWindow>().Bindingcontrol= new ControlB If i put a break point in the "someStuff" that was in ControlA's datacontext. The DispatcherTimer is still running... i.e. loading a new usercontrol into the bindable Usercontrol on mainwindow does not dispose/close/GC the DispatcherTimer that was created in the DataContext View Model... Ive looked around, and as stated by others, dispose doesnt get called because its not supposed to... :) Not all my usercontrols have DispatcherTimer, just a few that need to do some sort of "read and refresh" updates./. Should i track these DispatcherTimer objects in the ViewModelBase that all Usercontrols inh. and manually stop/dispose them everytime a new usercontrol is loaded? Is there a better way?

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• C#: How to avoid WIA-error when scanning documents with 2400dpi or more?

  - by Stephan_W

  Hello, when we scan a document with a resolution of 2400dpi or higher, we recieve (for example) the following error-message: COMException: Ausnahme von HRESULT: 0x80010100 (RPC_E_SYS_CALL_FAILED) or COMException: Ausnahme von HRESULT: 0x8021006F in one of the following lines img = itm.Transfer(scanFormat.ScanFormat) as WIA.ImageFile; img = ip.Apply(img as WIA.ImageFile); some screenshots for the mentioned errors: http://www.amarant-it.de/TempDownload/WIA_Error01.png or the same path with WIA_Error02.png and WIA_Error03.png for scanning we use the following code: #region Image-Convert-Settings //IP.Filters.Add IP.FilterInfos("Convert").FilterID //IP.Filters(1).Properties("FormatID").Value = wiaFormatJPEG WIA.IImageProcess ip = new WIA.ImageProcessClass(); object convert = "Convert"; WIA.IFilterInfo fi = ip.FilterInfos.get_Item(ref convert); ip.Filters.Add(fi.FilterID, 0); convert = "FormatID"; object formatstring = scanFormat.ScanFormat; WIA.IFilter filter; foreach (WIA.IFilter fTemp in ip.Filters) { filter = fTemp; WIA.IProperty prop = filter.Properties.get_Item(ref convert); prop.set_Value(ref formatstring); } #endregion #region Image-Scan + Convert img = itm.Transfer(scanFormat.ScanFormat) as WIA.ImageFile; img = ip.Apply(img as WIA.ImageFile); img.SaveFile("D:\\scan2." + img.FileExtension); Image image = Image.FromFile("D:\\scan2." + img.FileExtension); ilImages.Images.Add(image.ToString(), image); alImages.Add(image); if (ImageScanned != null) { ImageScanned(image); } #endregion can anyone help us with this problem? thanks

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• How to avoid session sharing provided by IE8 programatically in java/j2ee application ?

  - by Idiot

  Microsoft, in an effort to make Internet Explorer 8 "more stable" and “faster”, have changed the underlying architecture of the browser and introduced a function called "Loosely-Coupled IE" (LCIE) which works on session sharing across TAB and new instances. But session sharing may be fatal when some one is trying to do two different things at a time with the same application, e.g. like someone want to book one forward journey ticket and one return ticket at a time, at that time he will book 2 same tickets what he has not intended to. PROBABLE SOLUTION ON IT While creating new window Instead of creating by clicking on icon or Ctrl+N we should use File - New Session it will not happen. You can make a registry change on the client PC - adding the following. [HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main] “TabProcGrowth" = dword : 00000000 Will disable "Loosely Couple IE8"; IE8 then works as previous versions of IE. But how i will do it programatically ?

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• Is there a way to avoid putting the Perl version number into the "use lib" line for Perl modules in

  - by Kinopiko

  I am trying to install some Perl modules into a non-standard location, let's call it /non/standard/location. In the script which uses the module, it seems to be necessary to specify a long directory path including the version of Perl, like so: #!/usr/local/bin/perl use lib '/non/standard/location/lib/perl5/site_perl/5.8.9/'; use A::B; Is there any use lib or other statement which I can use which is not so long and verbose, and which does not include the actual version of Perl, in order that I don't have to go back and edit this out of the program if the version of Perl is upgraded?

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• How to avoid visual artifacts when hosting WPF user controls within a WinForms MDI app?

  - by jpierson

  When hosting WPF user controls within a WinForms MDI app there is a drawing issue when you have multiple forms that overlap each other that causes very distinct visual artifacts. These artifacts are mostly visible after dragging one child form over another one that also hosts WPF content or by allowing the edges of the child form to be clipped by the main MDI parent when dragging it around. After the drag and drop of the child form is completed the artifacts stay around gernally but I've found that setting focus to a different application's window and then refocusing back on to my application window that it is redrawn and all is good again until the child forms are moved once again. Please see the image below which demonstrates the problem. Since many at Microsoft insist that the WinForms MDI is already a complete solution for MDI even when dealing with WPF I find it hard to believe any of them have ever actually tried creating a mostly WPF app that utilizes WinForms MDI otherwise it would be hard to recommend while keeping a straignt face. I'm hoping to either come up with proof that this solution truly is not acceptable or possibly find a way to overcome this and a few other specific issues.

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• Extend linq-to-sql partial class to avoid writing a property?

  - by Curtis White

  I have a linq-to-sql class. I have a property "Password" for which I want to call the underlying ASP.NET Membership provider. Thus, I do not want this property written out directly but via my own code. I basically want to create a facade/proxy for this property such that I may use the underlying membership provider or a custom stored procedure. I want to accomplish without modifying the LINQ-TO-SQL designer generated code, if at all possible.

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• I'm referencing an WiX extension in a WiX library project -- how do I avoid having to reference this

  - by arathorn

  I'm referencing a WiX extension in a WiX library project. This WiX library project is itself referenced by my main WiX MSI project. Why does the main project have to also reference the WiX extension, even though it doesn't directly need it? I'd like to keep my wixlib's as self-contained as possible, so that other projects that use them don't need to know about their inner workings. I'm using latest stable release of WiX (3.0.x).

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• How do I avoid a repetitive subquery JOIN in SQL?

  - by Karl

  Hi In SQL Server 2008: I have one table, and I want to do something along the following lines: SELECT T1.stuff, T2.morestuff from ( SELECT code, date1, date2 from Table ) as T1 INNER JOIN ( SELECT code, date1, date2 from Table ) as T2 ON T1.code = T2.code and T1.date1 = T2.date2 The two subqueries are exactly identical. Is there any way I can do this without repeating the subquery script? Thanks Karl

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• In Python epoll can I avoid the errno.EWOULDBLOCK, errno.EAGAIN ?

  - by davyzhang

  I wrote a epoll wrapper in python, It works fine but recently I found the performance is not not ideal for large package sending. I look down into the code and found there's actually a LOT of error Traceback (most recent call last): File "/Users/dawn/Documents/workspace/work/dev/server/sandbox/single_point/tcp_epoll.py", line 231, in send_now num_bytes = self.sock.send(self.response) error: [Errno 35] Resource temporarily unavailable and previously silent it as the document said, so my sending function was done this way: def send_now(self): '''send message at once''' st = time.time() times = 0 while self.response != '': try: num_bytes = self.sock.send(self.response) l.info('msg wrote %s %d : %r size %r',self.ip,self.port,self.response[:num_bytes],num_bytes) self.response = self.response[num_bytes:] except socket.error,e: if e[0] in (errno.EWOULDBLOCK,errno.EAGAIN): #here I printed it, but I silent it in normal days #print 'would block, again %r',tb.format_exc() break else: l.warning('%r %r socket error %r',self.ip,self.port,tb.format_exc()) #must break or cause dead loop break except: #other exceptions l.warning('%r %r msg write error %r',self.ip,self.port,tb.format_exc()) break times += 1 et = time.time() I googled it, and says it caused by temporarily network buffer run out So how can I manually and efficiently detect this error instead it goes to exception phase? Because it cause to much time to rasie/handle the exception.

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• AJAX: how to get progress feedback in web apps, and to avoid timeouts on long requests?

  - by David Dombrowsky

  This is a general design question about how to make a web application that will receive a large amount of uploaded data, process it, and return a result, all without the dreaded spinning beach-ball for 5 minutes or a possible HTTP timeout. Here's the requirements: make a web form where you can upload a CSV file containing a list of URLs when the user clicks "submit", the server fetches the file, and checks each URL to see if its alive, and what the title tag of the page is. the result is a downloadable CSV file containing the URL, and the result HTTP code the input CSV can be very large ( 100000 rows), so the fetch process might take 5-30 minutes. My solution so far is to have a spinning javascript loop on the client site, which queries the server every second to determine the overall progress of the job. This seems kludgy to me, and I'm hesitant to accept this as the best solution. I'm using perl, template toolkit, and jquery, but any solution using any web technology would be acceptable.

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• How to avoid OLEDB converting "."s into "#"s in column names?

  - by Andrew Miner

  I'm using the ACE OLEDB driver to read from an Excel 2007 spreadsheet, and I'm finding that any '.' character in column names get converted to a '#' character. For example, if I have the following in a spreadsheet: Name Amt. Due Due Date Andrew 12.50 4/1/2010 Brian 20.00 4/12/2010 Charlie 1000.00 6/30/2010 the name of the second column would be reported as "Amt# Due" when read with the following code: OleDbConnection connection = new OleDbConnection( "Provider=Microsoft.ACE.OLEDB.12.0; Data Source={0}; " + "Extended Properties=\"Excel 12.0 Xml;HDR=YES;FMT=Delimited;IMEX=1\""); OldDbCommand command = new OleDbCommand("SELECT * FROM MyTable", connection); OleDbReader dataReader = command.ExecuteReader(); System.Console.WriteLine(dataReader.GetName(1)); I've read through all the documentation I can find and I haven't found anything which even mentions that this will happen. Has anyone run into this before? Is there a way to fix this behavior?

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• why is a float divided by a larger float yields zero and how to avoid this in c#.net?

  - by Jronny

  I was trying to divide (float)200 / (float)500 but the result is 0.0. Why is this so and how can we have 0.4 as the result? Thanks a lot.

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• In what case does IE8 block Javascript and how to avoid it ?

  - by e-satis

  I got a web site using jQuery, jQuery Tools and some handcrafted JS running performing graphical enhancements. While it's running smooth on FF, Safari and Chrome, IE blocks the script execution : There is nothing particularly more dangerous on this code than, let's say, on Netvibes. Why is even talking about activeX ? I'm using JS. And how can I prevent that ? I don't want my user to click on "I allow this website" to work. It would be like putting a big red absolute DIV reading "Live quick and never come back".

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• How to avoid using duplicate savepoint names in nested transactions in nested stored procs?

  - by Gary McGill

  I have a pattern that I almost always follow, where if I need to wrap up an operation in a transaction, I do this: BEGIN TRANSACTION SAVE TRANSACTION TX -- Stuff IF @error <> 0 ROLLBACK TRANSACTION TX COMMIT TRANSACTION That's served me well enough in the past, but after years of using this pattern (and copy-pasting the above code), I've suddenly discovered a flaw which comes as a complete shock. Quite often, I'll have a stored procedure calling other stored procedures, all of which use this same pattern. What I've discovered (to my cost) is that because I'm using the same savepoint name everywhere, I can get into a situation where my outer transaction is partially committed - precisely the opposite of the atomicity that I'm trying to achieve. I've put together an example that exhibits the problem. This is a single batch (no nested stored procs), and so it looks a little odd in that you probably wouldn't use the same savepoint name twice in the same batch, but my real-world scenario would be too confusing to post. CREATE TABLE Test (test INTEGER NOT NULL) BEGIN TRAN SAVE TRAN TX BEGIN TRAN SAVE TRAN TX INSERT INTO Test(test) VALUES (1) COMMIT TRAN TX BEGIN TRAN SAVE TRAN TX INSERT INTO Test(test) VALUES (2) COMMIT TRAN TX DELETE FROM Test ROLLBACK TRAN TX COMMIT TRAN TX SELECT * FROM Test DROP TABLE Test When I execute this, it lists one record, with value "1". In other words, even though I rolled back my outer transaction, a record was added to the table. What's happening is that the ROLLBACK TRANSACTION TX at the outer level is rolling back as far as the last SAVE TRANSACTION TX at the inner level. Now that I write this all out, I can see the logic behind it: the server is looking back through the log file, treating it as a linear stream of transactions; it doesn't understand the nesting/hierarchy implied by either the nesting of the transactions (or, in my real-world scenario, by the calls to other stored procedures). So, clearly, I need to start using unique savepoint names instead of blindly using "TX" everywhere. But - and this is where I finally get to the point - is there a way to do this in a copy-pastable way so that I can still use the same code everywhere? Can I auto-generate the savepoint name on the fly somehow? Is there a convention or best-practice for doing this sort of thing? It's not exactly hard to come up with a unique name every time you start a transaction (could base it off the SP name, or somesuch), but I do worry that eventually there would be a conflict - and you wouldn't know about it because rather than causing an error it just silently destroys your data... :-(

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• How to avoid "The name 'ConfigurationManager' does not exist in the current context" error?

  - by 5YrsLaterDBA

  I am using VS2008. I have a project connect with a database and the connection string is read from App.config via ConfigurationManager. We are using L2E. Now I added a helper project, AndeDataViewer, to have a simple UI to display data from the database for testing/verification purpose. I don't want to create another set of Entity Data Model in the helper project. I just added all related files as a link in the new helper project. When I compile, I got the following error: Error 15 The name 'ConfigurationManager' does not exist in the current context C:\workspace\SystemSoftware\SystemSoftware\src\systeminfo\RuntimeInfo.cs 24 40 AndeDataViewer I think I may need to add another project setting/config related file's link to the helper project from the main project? There is no App.config file in the new helper project. But it looks I cannot add that file's link to the helper project. Any ideas?

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• For a primary key of an integral type, why is it important to avoid gaps ?

  - by Jacques René Mesrine

  I am generating a surrogate key for a table & due to my hi/lo algorithm, everytime you reboot/restart the machine, gaps may appear. T1: current hi = 10000000 (sequence being dished out .. 1 to 100) Assume that current sequence is 10000050 T2: restart system. T3: System gives out the next_hi as 10000100 (sequence being dished out now ranges from 101 to 200) T4: Next request for a key returns 100001001 From a primary key or indexing internals perspective, why is it important that there be no gaps in the sequences ? I'm asking this for a deeper understanding of mysql specifically. Thanks

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• How to avoid the "divide by zero" error in SQL?

  - by Henrik Staun Poulsen

  I hate this error message: Msg 8134, Level 16, State 1, Line 1 Divide by zero error encountered. What is the best way to write SQL code, so that I will never see this error message again? I mean, I could add a where clause so that my divisor is never zero. Or I could add a case statement, so that there is a special treatment for zero. Is the best way to use a NullIf clause? Is there better way, or how can this be enforced?

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• How to avoid empty implementation in abstract class while implementing an interface?

  - by kannan-engr09

  public interface IMyInterface { int A {get; set; } string S {get; set; } } public abstract class MyAbs : IMyInterface { } public class ConcreteClass : MyAbs { /* Implementation of IMyInterface*/ } Is it possible to omit the empty implementation in an abstract class as above? If so, how? why?

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• How to avoid "source !=null" when using Code Contracts and Linq To Sql?

  - by Florian

  I have the following code using a normal data context which works great: var dc = new myDataContext(); Contract.Assume(dc.Cars!= null); var cars = (from c in dc.Cars where c.Owner = 'Jim' select c).ToList(); However when I convert the filter to an extension method like this: var dc = new myDataContext(); Contract.Assume(dc.Cars!= null); var cars = dc.Cars.WithOwner('Jim'); public static IQueryable<Car> WithOwner(IQueryable<Car> cars, string owner) { Contract.Requires(cars != null); return cars.Where(c => c.Owner = owner); } I get the following warning: warning : CodeContracts: requires unproven: source != null

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• How to avoid a:hover to act on img in CSS?

  - by bodacydo

  Suppose I have the following selector: a { padding: 1em; } a:hover { backgrond-color: #FF0000; } And suppose I have the following HTML code: <a href="http://stackoverflow.com"><img src="so.jpg"></a> What happens is that <img> gets red-background color on mouse hover. Any ideas how to fix it? Thanks, Boda Cydo!

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