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• How is jQuery so fast?

  - by ClarkeyBoy

  Hey, I have a rather large application which, on the admin frontend, takes a few seconds to load a page because of all the pageviews that it has to load into objects before displaying anything. Its a bit complex to explain how the system works, but a few of my other questions explains the system in great detail. The main difference between what they say and the current system is that the customer frontend no longer loads all the pageviews into objects when a customer first views the page - it simply adds the pageview to the database and creates an object in an unsynchronised list... to put it simply, when a customer views a page it no longer loads all the pageviews into objects; but the admin frontend still does. I have been working on some admin tools on the customer frontend recently, so if an administrator clicks the description of an item in the catalogue then the right hand column will display statistics and available actions for the selected item. To do this the page which gets loaded (through $('action-container').load(bla bla bla);) into the right hand column has to loop through ALL the pageviews - this ultimately means that ALL the pageviews are loaded into objects if they haven't been already. For some reason this loads really REALLY fast. The difference in speed is only like a second on my dev site, but the live site has thousands of pageviews so the difference is quite big... So my question is: why is it that the admin frontend loads so slowly while using $(bla).load(bla); is so fast? I mean whatever method jQuery uses, can't browsers use this method too and load pages super-fast? Obviously not as someone would've done that by now - but I am interested to know just why the difference is so big... is it just my system or is there a major difference in speed between the browser getting a page and jQuery getting a page? Do other people experience the same kind of differences? Thanks in advance, Regards, Richard

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• Time to start returning IQueryable<T> instead of IList<T> to my Web UI / Web API Layer?

  - by JohnnyO

  I've got a multi-layer application that starts with the repository pattern for all data access and it returns IQueryable to the Services layer. The Services layer, which includes all of the business logic, returns IList to the Controllers (note: I'm using ASP.NET MVC for the UI layer). The benefit of returning IQueryable in the data access layer is that it allows my repositories to be extremely simple and the database queries to be deferred. However, I'm triggering the database queries in my services layer so that my unit tests is more reliable and I don't give flexibility to the Controllers to reshape my queries. However, I've recently encountered several situations where deferring the execution of queries down to the Controllers would have been significantly more performant because the Controllers had to do some projections on the data that was UI specific. Additionally, with the emergence of things like oData, I was starting to wonder if end points (e.g. web UI or web apis) should be working directly with IQueryable. What are your thoughts? Is it time to start returning IQueryable from the services layer to the UI layer? Or stick with IList? This thread here: http://stackoverflow.com/questions/718624/to-return-iqueryablet-or-not-return-iqueryablet seems to vouch for returning IList to the UI layers, but I was wondering if things are changing because of new emerging technologies and techniques.

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• Flex 4 vs JavaScript Options (Cappuccino, JQuery, etc.)

  - by user320681

  Rehashing an older post: http://stackoverflow.com/questions/1570070/jquery-vs-flex-choosing-a-platform-for-saas We are preparing to develop an application that is exceptionally dynamic and interactive. It's particularly heavy on the graphics side. We are 85% convinced that Adobe Flash built atop Flex is the right path to take, however Cappuccino is quite nice and seems as though it may be able to nearly fit the bill. The only pause we have right now is portability for the iPhone. With the lack of blessings from Apple we will most certainly have to create a 2nd interface for the iPhone for the site, however... Having two interfaces may not be bad as it will likely have to be custom anyway to take advantage of the differences that it affords. Any further thoughts or reevaluations of points enumerated in the noted article? Further, Flex 4 adds a lot of strength to the position mentioned previously regarding UI development. Fx4 is very nice vs Fx3 and shaves 90% from the development time when coupled with Flash Catalyst, which is not really always fully appropriate, but with some round trip tricks it seems as though it can cut through things rather well... Please do advise and many thanks.

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• Identifying and Resolving Oracle ITL Deadlock

  - by Allan

  I have an Oracle DB package that is routinely causing what I believe is an ITL (Interested Transaction List) deadlock. The relevant portion of a trace file is below. Deadlock graph: ---------Blocker(s)-------- ---------Waiter(s)--------- Resource Name process session holds waits process session holds waits TM-0000cb52-00000000 22 131 S 23 143 SS TM-0000ceec-00000000 23 143 SX 32 138 SX SSX TM-0000cb52-00000000 30 138 SX 22 131 S session 131: DID 0001-0016-00000D1C session 143: DID 0001-0017-000055D5 session 143: DID 0001-0017-000055D5 session 138: DID 0001-001E-000067A0 session 138: DID 0001-001E-000067A0 session 131: DID 0001-0016-00000D1C Rows waited on: Session 143: no row Session 138: no row Session 131: no row There are no bit-map indexes on this table, so that's not the cause. As far as I can tell, the lack of "Rows waited on" plus the "S" in the Waiter waits column likely indicates that this is an ITL deadlock. Also, the table is written to quite often (roughly 8 insert or updates concurrently, as often as 240 times a minute), so and ITL deadlock seems like a strong possibility. I've increased the INITRANS parameter of the table and it's indexes to 100 and increased the PCT_FREE on the table from 10 to 20 (then rebuilt the indexes), but the deadlocks are still occurring. The deadlock seems to happen most often during an update, but that could just be a coincidence, as I've only traced it a couple of times. My questions are two-fold: 1) Is this actually an ITL deadlock? 2) If it is an ITL deadlock, what else can be done to avoid it?

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• How do I log from inside my web application in Tomcat 6.

  - by Carlos

  How do I log from within my web application deployed on Tomcat 6? Where should I expect the logging output to go (internal tomcat log files, or will another logfile be generated)? I see a ton of documentation but am having a hard time finding a direct answer to the above questions. Where should I expect the logging to show up (currently it is log4j is not generating a log file and it is not showing up in my console). I am trying to follow http://www.laliluna.de/articles/log4j-tutorial.html . ### direct log messages to stdout ### log4j.appender.stdout=org.apache.log4j.ConsoleAppender log4j.appender.stdout.Target=System.out log4j.appender.stdout.layout=org.apache.log4j.PatternLayout log4j.appender.stdout.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n ### file appender log4j.appender.file=org.apache.log4j.RollingFileAppender log4j.appender.file.maxFileSize=100KB log4j.appender.file.maxBackupIndex=5 log4j.appender.file.File=test.log log4j.appender.file.threshold=info log4j.appender.file.layout=org.apache.log4j.PatternLayout log4j.appender.file.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n log4j.rootLogger=debug, stdout In my application I define a log object: private static org.apache.log4j.Logger log = Logger.getLogger(MyClass.class); log.error("LOGGING!"); Thanks for the help.

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• How can I effectively test against the Windows API?

  - by Billy ONeal

  I'm still having issues justifying TDD to myself. As I have mentioned in other questions, 90% of the code I write does absolutely nothing but Call some Windows API functions and Print out the data returned from said functions. The time spent coming up with the fake data that the code needs to process under TDD is incredible -- I literally spend 5 times as much time coming up with the example data as I would spend just writing application code. Part of this problem is that often I'm programming against APIs with which I have little experience, which forces me to write small applications that show me how the real API behaves so that I can write effective fakes/mocks on top of that API. Writing implementation first is the opposite of TDD, but in this case it is unavoidable: I do not know how the real API behaves, so how on earth am I going to be able to create a fake implementation of the API without playing with it? I have read several books on the subject, including Kent Beck's Test Driven Development, By Example, and Michael Feathers' Working Effectively with Legacy Code, which seem to be gospel for TDD fanatics. Feathers' book comes close in the way it describes breaking out dependencies, but even then, the examples provided have one thing in common: The program under test obtains input from other parts of the program under test. My programs do not follow that pattern. Instead, the only input to the program itself is the system upon which it runs. How can one effectively employ TDD on such a project?

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• how to create wizard forms in ruby on rails

  - by Branden Silva

  I'm trying to understand the best options for pulling off a wizard form in ruby on rails. Ideally I'd like to have it so the application signup has a back and next button that allows the user to submit data in steps. So in step 1 they could fill out contact info. Once they are done they could click next and be on step 2 to fill out payment info, etc. If they make a mistake, they can click back and correct it. Some steps will be required, while others will not, but you do have to make it to the last step to submit the data to the database to sign up. They then need the ability to go back and fill out the past steps in the same fashion after completion. (example: perhaps if they clicked on a profile link they could recomplete the steps in the same fashion because they didn't want to complete all the steps right away. Maybe by being given a skip button before they completed the steps to sign up?). I also need validation to happen on what steps have been completed preventing them from moving onto the next step until corrected or completed. Option 1) I've noticed that ajax has been recommended as an option in other questions on stackoverflow. The only problem I have with it is that the user would not be able to sign up if javascript was disabled. Ideally I'd like to have it be native to ruby on rails but I'm willing to work with whatever is necessary to get it to work.

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• C# file write permission issue under "Program Files" folder

  - by George2

  Hello everyone, I am using inno setup to make a installation package for my application, and my application is written by C# + .Net 2.0 + VSTS 2008. Inno setup = http://www.jrsoftware.org/isinfo.php and I install my application under Program Files/Foo folder (Foo is my application name). My application is targeting to Windows Vista. The issue I found is my program cannot write to the folder Program Files/Foo. And I need the permission of write to this folder in order to save some configuration files. The strange thing I notice is the folder Program Files/Foo is marked as readonly and I have checked all folders under Program Files are marked with read only, such as Office. My questions are, Why all folders are marked as read only under Program Files? It means we should not write to individual application folders under Program Files? If not, where should we write information to disk like user last selected configuration information of an individual application? If we could write to individual application folders under Program Files, what is the solution? I do not want my application to Run As administrator to solve this issue, and if there are solution to write to this folder, I want to require minimal permission if possible. thanks in advance, George

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• Call long running operation in WSS feature OnActivated Event

  - by dirq

  More specifically - How do I reference SPContext in Web Service with [SoapDocumentMethod(OneWay=true)]? We are creating a feature that needs to run a job when a site is created. The job takes about 4 minutes to complete. So, we made a web service that we can call when the feature is activated. This works but we want it to run asynchronously now. We've found the SoapDocumentMethod's OneWay property and that would work awesomely but the SPContext is now NULL. We have our web services in the _vti_bin virtual directory so it's available in each Windows Sharepoint Services site. I was using the SPContext.Current.Web to get the site and perform the long running operation. I wanted to just fire and forget about it by returning a soap response right away and letting the process run. How can I get the current SPContext? I used to be able to do this in my web service: SPWeb mySite = SPContext.Current.Web; Can I get the same context when I have the [SoapDocumentMethod(OneWay=true)] attribute applied to my web service? Or must I recreate the SPWeb from the url? This is similar to this thread: http://stackoverflow.com/questions/340192/webservice-oneway-and-new-spsitemyurl Update: I've tried these two ways but they didn't work: SPWeb targetSite = SPControl.GetContextWeb(this.Context); SPWeb targetSite2 = SPContext.GetContext(this.Context).Web;

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• C# using consts in static classes

  - by NickLarsen

  I was plugging away on an open source project this past weekend when I ran into a bit of code that confused me to look up the usage in the C# specification. The code in questions is as follows: internal static class SomeStaticClass { private const int CommonlyUsedValue = 42; internal static string UseCommonlyUsedValue(...) { // some code value = CommonlyUsedValue + ...; return value.ToString(); } } I was caught off guard because this appears to be a non static field being used by a static function which some how compiled just fine in a static class! The specification states (§10.4): A constant-declaration may include a set of attributes (§17), a new modifier (§10.3.4), and a valid combination of the four access modifiers (§10.3.5). The attributes and modifiers apply to all of the members declared by the constant-declaration. Even though constants are considered static members, a constant-declaration neither requires nor allows a static modifier. It is an error for the same modifier to appear multiple times in a constant declaration. So now it makes a little more sense because constants are considered static members, but the rest of the sentence is a bit surprising to me. Why is it that a constant-declaration neither requires nor allows a static modifier? Admittedly I did not know the spec well enough for this to immediately make sense in the first place, but why was the decision made to not force constants to use the static modifier if they are considered constants? Looking at the last sentence in that paragraph, I cannot figure out if it is regarding the previous statement directly and there is some implicit static modifier on constants to begin with, or if it stands on its own as another rule for constants. Can anyone help me clear this up?

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• Correlating traditional Windows joystick axes with HID

  - by Wade Williams

  I'm a bit confused on the description of joystick axes and I'm hoping that someone has a link or document which could help clear my confusion. I'm not a Windows guy, so trying to port some traditional Windows gameport code has me a bit confused. We all know about the common first three axes: X Y Z My understanding was that in the gameport-style interface the three other axes are: R U V However, looking in my IOHIDUsageTables (OS X), I see: kHIDUsage_GD_X = 0x30, /* Dynamic Value */ kHIDUsage_GD_Y = 0x31, /* Dynamic Value */ kHIDUsage_GD_Z = 0x32, /* Dynamic Value */ kHIDUsage_GD_Rx = 0x33, /* Dynamic Value */ kHIDUsage_GD_Ry = 0x34, /* Dynamic Value */ kHIDUsage_GD_Rz = 0x35, /* Dynamic Value */ kHIDUsage_GD_Vx = 0x40, /* Dynamic Value */ kHIDUsage_GD_Vy = 0x41, /* Dynamic Value */ kHIDUsage_GD_Vz = 0x42, /* Dynamic Value */ kHIDUsage_GD_Vbrx = 0x43, /* Dynamic Value */ kHIDUsage_GD_Vbry = 0x44, /* Dynamic Value */ kHIDUsage_GD_Vbrz = 0x45, /* Dynamic Value */ kHIDUsage_GD_Vno = 0x46, /* Dynamic Value */ This has me a bit confused due to the three R axis (though that does not appear to be uncommon) and the lack of a U axis. Two questions: 1) Can anyone confirm to what axis the traditional U axis would be? I saw one document describe it as "the axis for rudder pedals" leading me to believe it would be Rz. 2) Can anyone describe in more detail the typical usages of the V and Vbr axes? I understand the descriptions are "vector" and "relative vector,' respectively, but I'm having difficult visualizing what that means in terms of a physical device. All enlightenment and documentation pointers welcome.

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• MonoRail: Testing, Route Extensions, Folder Structures

  - by Kezzer

  I've got a few questions related to the use of MonoRail Testing Does everyone tend to use NUnit for their testing? I haven't worked enough with testing to know if this is a good testing framework to use. I'm just looking to get more into testing my applications a lot more than before and wanted to know if there's any general guidelines. Are you supposed to copy the controller over to a test area and just rename it with test in the name and re-run it? How do you ensure your test project and main project coincide with one another? Is it just a case of copying everything over again or are there tools available to do it for you? Route Extensions MonoRail tends to use <action>.rails, can you omit the .rails part if you configure your routing correctly? Why does this seem to be the standard? Folder Structures I haven't found anywhere which really points out your standard folder structure. Sure, you have Controllers, Models, and Views. But your Models folder should contain your data access objects as well. I've seen some have something like -> Models -> DaoClasses -> Entities But what about custom structures used to get data out of views? And if you're using NHibernate, where's a good place to stick the mappings? I know it's entirely dependent on the developer, but I haven't really seen any standard approach. Cheers

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• Routing audio from GSM module to a Bluetooth HandsFree device

  - by Shaihi

  I have a system with the following setup: I use: Windows CE 6 R3 Microsoft's Bluetooth stack including all profiles Motorola H500 The Audio Gateway service is up and running (checked through services list in cmd) GSM Module is functional - I am able to set outgoing calls and to answer calls. Bluetooth is functional - the A2DP profile plays music to Motorola headphones (can't remember the model right now) I want to hold a conversation using a headset device. I have included all Bluetooth components in the catalog. I pair the device using the Control Panel applet. When I press the button on the Motorla device to answer a call I get a print by the Audio Gateway: BTAGSVC: ConnectionEvent. BTAGSVC: SCOListenThread_Int - Connection Event. BTAGSVC: ConnectionEvent. BTAGSVC: SCOListenThread_Int - Connection Event. BTAGSVC: ConnectionEvent. BTAGSVC: A Bluetooth peer device has connected to the Audio Gateway. BTAGSVC: Could not open registry key for BT Addr: 2. BTAGSVC: The peer device was not accepted since the user has never confirmed it as a device to be used. So my questions are as follows: What do I need to do to pair the device with the Audio Gateway? Once my device is paired, do I need to set anything else up? (except for the GSM module of course)

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• evaluation of a java thread dump

  - by raticulin

  I got a thread dump of one of my processes. It has a bunch of these threads. I guess they are keeping a bunch of memory so I am getting OOM. "Thread-8264" prio=6 tid=0x4c94ac00 nid=0xf3c runnable [0x4fe7f000] java.lang.Thread.State: RUNNABLE at java.util.zip.Inflater.inflateBytes(Native Method) at java.util.zip.Inflater.inflate(Inflater.java:223) - locked <0x0c9bc640 (a java.util.zip.Inflater) at org.apache.commons.compress.archivers.zip.ZipArchiveInputStream.read(ZipArchiveInputStream.java:235) at com.my.ZipExtractorCommonsCompress.extract(ZipExtractorCommonsCompress.java:48) at com.my.CustomThreadedExtractorWrapper$ExtractionThread.run(CustomThreadedExtractorWrapper.java:151) Locked ownable synchronizers: - None "Thread-8241" prio=6 tid=0x4c94a400 nid=0xb8c runnable [0x4faef000] java.lang.Thread.State: RUNNABLE at java.util.zip.Inflater.inflateBytes(Native Method) at java.util.zip.Inflater.inflate(Inflater.java:223) - locked <0x0c36b808 (a java.util.zip.Inflater) at org.apache.commons.compress.archivers.zip.ZipArchiveInputStream.read(ZipArchiveInputStream.java:235) at com.my.ZipExtractorCommonsCompress.extract(ZipExtractorCommonsCompress.java:48) at com.my.CustomThreadedExtractorWrapper$ExtractionThread.run(CustomThreadedExtractorWrapper.java:151) Locked ownable synchronizers: - None I am trying to find out how it arrived to this situation. CustomThreadedExtractorWrapper is a wrapper class that fires a thread to do some work (ExtractionThread, which uses ZipExtractorCommonsCompress to extract zip contents from a compressed stream). If the task is taking too long, ExtractionThread.interrupt(); is called to cancel the operation. I can see in my logs that the cancellation happened 25 times. And I see 21 of these threads in my dump. My questions: What is the status of these threads? Alive and running? Blocked somehow? They did not die with .interrupt() apparently? Is there a sure way to really kill a thread? What does really mean 'locked ' in the stack trace? Line 223 in Inflater.java is: public synchronized int inflate(byte[] b, int off, int len) { ... //return is line 223 return inflateBytes(b, off, len); }

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• ffmpeg(libavcodec). memory leaks in avcodec_encode_video

  - by gavlig

  I'm trying to transcode a video with help of libavcodec. On transcoding big video files(hour or more) i get huge memory leaks in avcodec_encode_video. I have tried to debug it, but with different video files different functions produce leaks, i have got a little bit confused about that :). [Here] (http://stackoverflow.com/questions/4201481/ffmpeg-with-qt-memory-leak) is the same issue that i have, but i have no idea how did that person solve it. QtFFmpegwrapper seems to do the same i do(or i missed something). my method is lower. I took care about aFrame and aPacket outside with av_free and av_free_packet. int Videocut::encode( AVStream *anOutputStream, AVFrame *aFrame, AVPacket *aPacket ) { AVCodecContext *outputCodec = anOutputStream->codec; if (!anOutputStream || !aFrame || !aPacket) { return 1; /* NOTREACHED */ } uint8_t * buffer = (uint8_t *)malloc( sizeof(uint8_t) * _DefaultEncodeBufferSize ); if (NULL == buffer) { return 2; /* NOTREACHED */ } int packetSize = avcodec_encode_video( outputCodec, buffer, _DefaultEncodeBufferSize, aFrame ); if (packetSize < 0) { free(buffer); return 1; /* NOTREACHED */ } aPacket->data = buffer; aPacket->size = packetSize; return 0; }

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• how can I add a custom non-DataTable column to my DataView, in a winforms ADO.net application?

  - by Greg

  Hi, How could I (/is it possible) to add a custom column to my DataView, and in this column display the result of a specific calculation. That is, I currently have a dataGridView which has a binding to a DataView, based on the DataTable from my database. I'd like to add an additional column to the dataGridView to display a number which is calculated by looking at this current row plus it's children row. In other words the info for the column isn't just derivable from the row data itself. Specific questions might be: a) where to add the column itself? to the DataView I assume? b) which method / event to trigger the re-calculation of the value of this custom column from ( / how do I control this) Thanks PS. I've also noted if I use the following code/approach I get a infinite loop... // Custom Items DataColumn dc = new DataColumn("OverallSize", typeof(long)); DT_Webfiles.Columns.Add(dc); DT_Webfiles.RowChanged += new DataRowChangeEventHandler(DT_Row_Changed); private static void DT_Row_Changed(object sender, DataRowChangeEventArgs e) { e.Row["OverallSize"] = e.Row["OverallSize"] ?? 0; e.Row["OverallSize"] = (long)e.Row["OverallSize"] + 1; } What other approach could avoid this looping. i.e. currently I'm saying update the value of the custom column when the row changes, however after then changing the row it triggers antoher 'row has changed' event...

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• Using Gdata Calendar API for PHP App to create a calender system with event ownership

  - by linuxlover101

  Hello, I'm working on a PHP app, and I'm trying to find the best way to set up a calendar system. First let me describe the intended function of the system: The application has multiple users who can login simultaneously. Each user should be able to add their own events and display them on their "profile." Also, on another page, the events should be able to be shown all together (from all users) and from each individual users exclusively. Since Google Calendar has a nice calendar-looking interface, I thought I would work with the GData APIs. Originally, I thought this would make things easier. But then it seems that if I want to represent event ownership, either each user would have to have a google account or somehow they all would each have to have a separate calendar. Thus, the application would have to create the calendar (if it does not exist) and be able to edit only their calendar. Two questions: Can I somehow use the GData APIs to accomplish my goal? (Mainly event ownership.) Should I just create my own calendar like application? Thanks!

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• How to perform two-way data binding of controls in a user control inside a FormView

  - by Sandor Drieënhuizen

  I'm trying to perform two-way data binding on the controls in my user control, which is hosted inside a FormView template. FormView: <asp:ObjectDataSource runat="server" ID="ObjectDataSource" TypeName="WebApplication1.Data" SelectMethod="GetItem" UpdateMethod="UpdateItem"> </asp:ObjectDataSource> <asp:FormView runat="server" ID="FormView" DataSourceID="ObjectDataSource"> <ItemTemplate> <uc:WebUserControl1 runat="server"></uc:WebUserControl1> </ItemTemplate> <EditItemTemplate> <uc:WebUserControl1 runat="server"></uc:WebUserControl1> </EditItemTemplate> </asp:FormView> User control: <%@ Control Language="C#" ... %> <asp:TextBox runat="server" ID="TitleTextBox" Text='<%# Bind("Title") %>'> </asp:TextBox> The binding works fine when the FormView is in View mode but when I switch to Edit mode, upon calling UpdateItem on the FormView, the bindings are lost. I know this because the FormView tries to call an update method on the ObjectDataSource that does not have an argument called 'Title'. I tried to solve this by implementing IBindableTemplate to load the controls that are inside my user control, directly into the templates (just like I had entered them declaratively like in the code above). However, when calling UpdateItem in edit mode, the container that gets passed into the ExtractValues method of the template, does not contain the TextBox anymore. It did in view mode! I have found some questions on SO that relate to this problem but they are rather dated and they don't provide any answers that helped me solve this problem. How do you think I could solve this problem? It seems to be such a simple requirement but apparently it's more like opening a can of worms...

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• UTF-8 BOM signature in PHP files

  - by skidding

  I was writing some commented PHP classes and I stumbled upon a problem. My name (for the @author tag) ends up with a ? (which is a UTF-8 character, ...and a strange name, I know). Even though I save the file as UTF-8, some friends reported that they see that character totally messed up (È™). This problem goes away by adding the BOM signature. But that thing troubles me a bit, since I don't know that much about it, except from what I saw on Wikipedia and on some other similar questions here on SO. I know that it adds some things at the beginning of the file, and from what I understood it's not that bad, but I'm concerned because the only problematic scenarios I read about involved PHP files. And since I'm writing PHP classes to share them, being 100% compatible is more important than having my name in the comments. But I'm trying to understand the implications, should I use it without worrying? or are there cases when it might cause damage? When? Thanks!

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• Java: How do you really force a GC using JVMTI's ForceGargabeCollection?

  - by WizardOfOdds

  I'm not looking for the usual "you can only hint the GC in Java using System.gc()" answers, this is not at all what this question is about. My questions is not subjective and is based on a reality: GC can be forced in Java for a fact. A lot of programs that we use daily do it: IntelliJ IDEA, NetBeans, VisualVM. They all can force GC to happen. How is it done? I take it they're all using JVMTI and more specifically the ForceGarbabeCollection (notice the "Force") but how can I try it for myself? http://java.sun.com/javase/6/docs/platform/jvmti/jvmti.html#ForceGarbageCollection Also note that this question is not about "why" I'd want to do this: the "why" may be "curiosity" or "we're writing a program similar to VisualVM", etc. The question is really "how do you force a GC using JVMTI's ForceGarbageCollection"? Does the JVM needs to be launched with any special parameters? Is any JNI required? If so, what code exactly? Does it only work on Sun VMs? Any complete and compilable example would be most welcome.

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• Help a C# developer understand: What is a monad?

  - by Charlie Flowers

  There is a lot of talk about monads these days. I have read a few articles / blog posts, but I can't go far enough with their examples to fully grasp the concept. The reason is that monads are a functional language concept, and thus the examples are in languages I haven't worked with (since I haven't used a functional language in depth). I can't grasp the syntax deeply enough to follow the articles fully ... but I can tell there's something worth understanding there. However, I know C# pretty well, including lambda expressions and other functional features. I know C# only has a subset of functional features, and so maybe monads can't be expressed in C#. However, surely it is possible to convey the concept? At least I hope so. Maybe you can present a C# example as a foundation, and then describe what a C# developer would wish he could do from there but can't because the language lacks functional programming features. This would be fantastic, because it would convey the intent and benefits of monads. So here's my question: What is the best explanation you can give of monads to a C# 3 developer? Thanks! (EDIT: By the way, I know there are at least 3 "what is a monad" questions already on SO. However, I face the same problem with them ... so this question is needed imo, because of the C#-developer focus. Thanks.)

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• Alternative native api for Process.Start

  - by Akash Kava

  Ok this is not duplicate of "http://stackoverflow.com/questions/2065592/alternative-to-process-start" because my question is something different here. I need to run a process and wait till execution of process and get the output of console. There is way to set RedirectStandardOutput and RedirectStandardError to true, however this does not function well on some machines, (where .NET SDK is not installed), only .NET runtime is installed, now it works on some machines and doesnt work on some machines so we dont know where is the problem. I have following code, ProcessStartInfo info = new ProcessStartInfo("myapp.exe", cmd); info.CreateNoWindow = true; info.UseShellExecute = false; info.RedirectStandardError = true; info.RedirectStandardOutput = true; Process p = Process.Start(info); p.WaitForExit(); Trace.WriteLine(p.StandardOutput.ReadToEnd()); Trace.WriteLine(p.StandardError.ReadToEnd()); On some machines, this will hang forever on p.WaitForExit(), and one some machine it works correctly, the behaviour is so random and there is no clue. Now if I can get a real good workaround for this using pinvoke, I will be very happy.

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• Variant datatype library for C

  - by Joey Adams

  Is there a decent open-source C library for storing and manipulating dynamically-typed variables (a.k.a. variants)? I'm primarily interested in atomic values (int8, int16, int32, uint, strings, blobs, etc.), while JSON-style arrays and objects as well as custom objects would also be nice. A major case where such a library would be useful is in working with SQL databases. The most obvious feature of such a library would be a single type for all supported values, e.g.: struct Variant { enum Type type; union { int8_t int8_; int16_t int16_; // ... }; }; Other features might include converting Variant objects to/from C structures (using a binding table), converting values to/from strings, and integration with an existing database library such as SQLite. Note: I do not believe this is question is a duplicate of http://stackoverflow.com/questions/649649/any-library-for-generic-datatypes-in-c , which refers to "queues, trees, maps, lists". What I'm talking about focuses more on making working with SQL databases roughly as smooth as working with them in interpreted languages.

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• PostgreSQL: Auto-partition a table

  - by Adam Matan

  Hi, I have a huge database which holds pairs of numbers (A,B), each ranging from 0 to 10,000 and stored as floats. e.g., (1, 9984.4), (2143.44, 124.243), (0.55, 0), ... Since the PostgreSQL table which stores these pairs grew quite large, I have decided to partition it into inheriting sub-tables. I intend to create 100 such tables, each storing a range of 1000x1000. The problem is that these numbers tend to come in large chunks of nearby numbers. It means that in the future, some tables will be nearly empty and some will hold a very large portion of the database. Unfortunately, the distribution of future pairs is yet unknown. I am looking for a way to automatically repartition my table. That means that if a certain subtable holds more than a specific number of pairs, it will be automatically partitioned into four sub-sub tables, and so on. My questions are: Is recursive partitioning and inheritance possible in PostgreSQL 8.3? Will indexes and query plans understand it? What's the best way to split a subtable once it grew too large? I should point out that this isn't a live database, so a downtime of few hours every week is totally acceptable. Thanks in advance, Adam

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• Prefuse: Reloading of XML files

  - by John

  Hello all, I am a new to the prefuse visualization toolkit and have a couple of general questions. For my purpose, I would like to perform an initial visualization using prefuse (graphview / graphml). Once rendered, upon a user click of a node, I would like to completely reload a new xml file for a new visualization. I want to do this in order to allow me to "pre-package" graphs for display. For example. If I search for Ted. I would like to have an xml file relating to Ted load and render a display. Now in the display I see that Ted has nodes associated called Bill and Joe. When I click Joe, I would like to clear the display and load an xml file associated with Joe. And so on. I have looked into loading one very large xml file containing all node and node relationship info and allowing prefuse to handle this using the hops from one level to another. However, eventually I am sure that system performance issues will arise due to the size of data. Thanks in advance for any help, John

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