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  • Working with fields which can mutate or be new instances altogether

    - by dotnetdev
    Structs are usually used for immutable data, eg a phone number, which does not mutate, but instead you get a new one (eg the number 000 becoming 0001 would mean two seperate numbers). However, pieces of information like Name, a string, can either mutate (company abc changing its name to abcdef, or being given a new name like def). For fields like this, I assume they should reside in the mutable class and not an immutable structure? My way of structuring code is to have an immutable concept, like Address (any change is a new address completely), in a struct and then reference it from a class like Customer, since Customer always has an address. So I would put CompanyName, or Employer, in the class as it is mutable. But a name can either mutate and so be the same 1 instance, or a new name setup and while the company still owning the first name too. Would the correct pattern for assigning a new instance (eg a new company name but the old name still owned by the company) be?: string name = ""; string newName = new string(); newName = "new"; name = newName; And a mutation just the standard assignment pattern? Thanks

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  • JQuery: how to use "delegate" instead of "live"?

    - by JacobD
    I've read countless articles how using the JQuery delegate is much more efficient than using the "live" event. As such, I'm having trouble converting my existing Live code to using Delegate. $("#tabs li:eq(0)").live('click',function(){ //...code }); $('#A > div.listing, #B > div.listing, #C > div.listing').live('mouseover',function(){ // ...code }); When I replace the previous code with what I assume is more efficient delegate code, my page doesn't load. $("#tabs li:eq(0)").delegate('click',function(){ //...code }); $('#A > div.listing, #B > div.listing, #C > div.listing').delegate('mouseover',function(){ // ...code }); Any idea why my delegate code doesn't work? Also, any suggestions on how to make this more efficient? UPDATE: The think part of the problem is that, both "#tabs" and "#A, #B, #C" are't present on the web page at page load. Those attributes are dynamically inserted onto the page with an AJAX call. As such, does that mean I have to use live over delegate?

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  • Codeigniter/mySQL question. Checking if several inserts are possible before actual insertion.

    - by Ethan
    Hey SO, So I'm trying to perform a couple inserts at once that are kind of co-dependent on each other. Let's say I'm doing a dog rating website. Anyone can add a dog to my database, but in doing so they also need to add a preliminary rating of the dog. Other people can then rate the dog afterwards. The dogs to ratings is a many to one relationship: a dog has many ratings. This means for my preliminary add, since I have the person both rate and add the dog, I need to take the rating, and set a foreign key to the dog's primary key. As far as I know, this means I have to actually add the dog, then check what that new addition's primary key is, and then put that in my rating before insertion. Now suppose something were to go wrong with the rating's insert, be it a string that's too long, or something that I've overlooked somehow. If the rating's failed, the dog has already been inserted, but the rating has not. In this case, I'd like the dog to not have been added in the first place. Does this mean I have to write code that says "if the rating fails, do a remove for the dog," or is there a way to predict what the key will be for the dog should everything go as planned. Is there a way to say "hold that spot," and then if everything works, add it? Any help would be greatly appreciated. Thanks!!

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  • Is the C++ compiler optimizer allowed to break my destructor ability to be called multiple times?

    - by sharptooth
    We once had an interview with a very experienced C++ developer who couldn't answer the following question: is it necessary to call the base class destructor from the derived class destructor in C++? Obviously the answer is no, C++ will call the base class destructor automagically anyway. But what if we attempt to do the call? As I see it the result will depend on whether the base class destructor can be called twice without invoking erroneous behavior. For example in this case: class BaseSafe { public: ~BaseSafe() { } private: int data; }; class DerivedSafe { public: ~DerivedSafe() { BaseSafe::~BaseSafe(); } }; everything will be fine - the BaseSafe destructor can be called twice safely and the program will run allright. But in this case: class BaseUnsafe { public: BaseUnsafe() { buffer = new char[100]; } ~BaseUnsafe () { delete[] buffer; } private: char* buffer; }; class DerivedUnsafe { public: ~DerivedUnsafe () { BaseUnsafe::~BaseUnsafe(); } }; the explicic call will run fine, but then the implicit (automagic) call to the destructor will trigger double-delete and undefined behavior. Looks like it is easy to avoid the UB in the second case. Just set buffer to null pointer after delete[]. But will this help? I mean the destructor is expected to only be run once on a fully constructed object, so the optimizer could decide that setting buffer to null pointer makes no sense and eliminate that code exposing the program to double-delete. Is the compiler allowed to do that?

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  • C++ polymorphism, function calls

    - by moai
    Okay, I'm pretty inexperienced as a programmer, let alone in C++, so bear with me here. What I wanted to do was to have a container class hold a parent class pointer and then use polymorphism to store a child class object. The thing is that I want to call one of the child class's functions through the parent class pointer. Here's a sort of example of what I mean in code: class SuperClass { public: int x; } class SubClass : public SuperClass { public: void function1() { x += 1; } } class Container { public: SuperClass * alpha; Container(SuperClass& beta) { alpha = beta; } } int main() { Container cont = new Container(new SubClass); } (I'm not sure that's right, I'm still really shaky on pointers. I hope it gets the point across, at least.) So, I'm not entirely sure whether I can do this or not. I have a sneaking suspicion the answer is no, but I want to be sure. If someone has another way to accomplish this sort of thing, I'd be glad to hear it.

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  • How can I build a generic dataset-handling Perl library?

    - by Pep.
    Hello, I want to build a generic Perl module for handling and analysing biomedical character separated datasets and which can, most certain, be used on any kind of datasets that contain a mixture of categorical (A,B,C,..) and continuous (1.2,3,881..) and identifier (XXX1,XXX2...). The plan is to have people initialize the module and then use some arguments to point to the data file(s), the place were the analysis reports should be placed and the structure of the data. By structure of data I mean which variable is in which place and its name/type. And this is where I need some enlightenment. I am baffled how to do this in a clean way. Obviously, having people create a simple schema file, be it XML or some other format would be the cleanest but maybe not all people enjoy doing something like this. The solutions I can think of are: Create a configuration file in XML or similar and with a prespecified format. Pass the information during initialization of the module. Use the first row of the data as headers and try to guess types (ouch) Surely there must be a "canonical" way of doing this that is also usable and efficient. Thanks p.

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  • "No keyboard for id 0"?

    - by Mellon
    I am new in Android app. development, now I have encountered a strange problem with the Menu button. Here is the thing: I have two activities, "ActivityOne" and "ActivityTwo", where "ActivityTwo" is the child Activity of "ActivityOne". In both activity, I have defined the menu button options like following: @Override public boolean onCreateOptionsMenu(Menu menu) { super.onCreateOptionsMenu(menu); MenuItem insertMenuItem = menu.add(0, INSERT_ID, 0, R.string.menu_insert); insertMenuItem.setIcon(R.drawable.ic_menu_add); MenuItem settingMenuItem = menu.add(0, SETTING_ID, 0, R.string.menu_setting); settingMenuItem.setIcon(R.drawable.ic_menu_settings); MenuItem aboutMenuItem = menu.add(0, ABOUT_ID, 0, R.string.menu_about); aboutMenuItem.setIcon(R.drawable.ic_menu_about); logPrinter.println("creating menu options..."); return true; } @Override public boolean onMenuItemSelected(int featureId, MenuItem item) { switch(item.getItemId()) { case INSERT_ID: doInsert(); return true; case SETTING_ID: return true; case ABOUT_ID: showAbout(); return true; } return super.onMenuItemSelected(featureId, item); } In "ActivityOne", when I click the physical Menu button, there is no menu options pop up from screen bottom, when I checked the LogCat console, there are two warning messages, which are "No keyboard for id 0" and "Using default keyMap:/system/usr/keychars/qwerty.kcm.bin" . BUT, in "ActivityTwo", the menu button works fine, it shows me those menu options I defined. Why the menu button does not work in "ActivityOne" ?? What does the warning msg mean???

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  • How to extend a jquery ui widget ? (1.7)

    - by Jide
    I would like to create a custom version of the sortable widget. I have been searching for documentation, but could not find something really accurate. The best information I found was : http://jqueryui.pbworks.com/Widget-factory. I tried : $.widget("ui.customsortable", $.extend($.ui.sortable, { _init: function() { $.widget.prototype._init.apply(this, arguments); } })); But $.widget.prototype._init is not the function I want to call I guess since it is the $.widget prototype. Then, I tried something I read here and there : var _init = $.ui.sortable.prototype._init; $.widget("ui.customsortable", $.extend($.ui.sortable, { _init: function() { _init.apply(this, arguments); }, })); But : I can't believe I have to store all methods I want to override like this, it is so ugly. It throws an error ("this.refresh is not a function"), which means the refresh method does not exist. Does that mean I would have to recreate all methods I want to override ? What's the point of extending in that case ? Am I missing something here ? Thanks for your help !

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  • SIMPLE PHP MVC Framework [closed]

    - by Allen
    I need a simple and basic MVC example to get me started. I don't want to use any of the available packaged frameworks. I am in need of a simple example of a simple PHP MVC framework that would allow, at most, the basic creation of a simple multi-page site. I am asking for a simple example because I learn best from simple real world examples. Big popular frameworks (such as code igniter) are to much for me to even try to understand and any other "simple" example I have found are not well explained or seem a little sketchy in general. I should add that most examples of simple MVC frameworks I see use mod_rewrite (for URL routing) or some other Apache-only method. I run PHP on IIS. I need to be able to understand a basic MVC framework, so that I could develop my own that would allow me to easily extend functionality with classes. I am at the point where I understand basic design patterns and MVC pretty well. I understand them in theory, but when it comes down to actually building a real world, simple, well designed MVC framework in PHP, I'm stuck. Edit: I just want to note that I am looking for a simple example that an experienced programmer could whip up in under an hour. I mean simple as in bare bones simple. I don't want to use any huge frameworks, I am trying to roll my own. I need a decent SIMPLE example to get me going.

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  • What's the meaning of the angle brackets on LINQ methods in Intellisense? (Contains<>, Count<>, Dis

    - by user312758
    They usually involve generics. But some methods with generics don't have them, and not all extension methods have them. They've just "been there" since day one, we've all seen them; but I realized I still don't know what they mean, and I can't find the answer anywhere. Now it's really bugging me. Google just turns up results that are about XML, etc. Is this officially documented anywhere? Thanks. EDIT: Well that's just great. Since I just created an account to make my first Stack Overflow post, to get an answer for this burning question; I'm not allowed to post my pretty Intellisense picture, or create a new tag "angle-brackets". I love Stack Overflow, but... what a welcome! Maybe my problem is that they aren't actually called "angle brackets"... ?? Anyway, I guess if you really want to see my beautiful screenshot you could manually go to: http://www.freeimagehosting.net/uploads/6a6c2f3268.png Bump me up please so I can include it in the post, thanks. ;)

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  • Is there "good" PRNG generating values without hidden state?

    - by actual
    I need some good pseudo random number generator that can be computed like a pure function from its previous output without any state hiding. Under "good" I mean: I must be able to parametrize generator in such way that running it for 2^n iterations with any parameters should cover all or almost all values between 0 and 2^n - 1, where n is the number of bits in output value. Combined generator output of n + p bits must cover all or almost all values between 0 and 2^(n + p) - 1 if I run it for 2^n iterations for every possible combination of its parameters, where p is the number of bits in parameters. For example, LCG can be computed like a pure function and it can meet first condition, but it can not meet second one. Say, we have 32-bit generator, m = 2^32 and it is constant, our p = 64 (two 32-bit parameters a and c), n + p = 96, so we must peek data by three ints from output to meet second condition. Unfortunately, condition can not be meet because of strictly alternating sequence of odd and even ints in output. To overcome this, hidden state must be introduced, but that makes function not pure and breaks first condition (period become much longer). Am I wanting too much?

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  • Can redirection of screen output to file change the result of a C++ code?

    - by Biga
    I am having this very weird behaviour with a C++ code: It gives me different results when running with and without redirecting the screen output to a file (reproducible in cygwin and linux). I mean, if I get the same executable and run it like ./run or run it like ./run >out.log, I get different results! I use std::cout to output to screen, all lines ending with endl; I use ifstream for the input file; I use ofstream for output, all lines ending with endl. I am using g++ 4. Any idea what is going on? UPDATE: I have hard-coded the input data, so 'ifstream' is not used, and problem persists. UPDATE 2: That's getting interesting. I have probed three variables that are computed initially, and that's what I get when using with and without redirecting the output to file redirected to file: 0 -0.02 0 direct to screen: 0 -0.02 1.04083e-17 So there's a round-off difference in the code variables with and without redirecting the output! Now, why redirecting would interefere with an internal computation of the code? UPDATE 3: If I redirect to /dev/null, I get the sam behaviour as outputing direct to screen, instead of redirecting to file.

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  • What are possible/good ways to prototype iPhone applications?

    - by Ted Johnson
    This is intentionally left broad. If you wanted to show users what iPhone/mobile applications could to for them. The more interactive the better, but it must be quick to build as you can't code up every idea. Let us assume real-time games are out of scope. Throw out ideas or state which approach would be best. Here are some of my ideas, what are yours? Hack a app that loads mostly web or image content, but has hyperlinks to get around in. This would mean static data. Build screens which look great but can only be navigated in a story board type fashion. Load the web version or equivalent on the iPhone and say: now image the buttons and navigation is better. A paper based prototype. Flash or video walk through running on the phone. String existing iPhone apps and web pages together with minimal glue just to convey the idea. Can anyone share prototyping methods for other mobile devices? Ex: The palm prototype was just a block of wood and note pad that was carried around.

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  • C# & SQL Server Authentication

    - by Peter
    Hello, I'm currently developing a C# app with an SQL Server DB back-end. I'm approaching the point of deployment and hitting a problem. The applicaiton will be deployed within an active directory network. As far as SQL authentication goes, I understand that I have 2 options - Windows Authenticaiton or Server Authenticaiton. If I use Server Authentication, I'm concerned that the username and password for the account will be stored in plain text in the app.config file, and therefore leave the database vulnerable. Using Windows Authenticaiton will avoid this issue, however it would mean giving every member of staff within our organisation read/write access to the database in order to run the app correctly. Whilst this is ok, it also means that they can easily connect to the database themselves via other means and directly alter the data outside of the app. I'm guessing there is someting really obvious I'm missing here, but I've been googling all evening to no avail. Any advice/guidance would be much appreciated! Peter Addition - my project is Windows Form based not ASP.NET - is encrypting the app.config file still the right answer? If it is, does anyone have any examples that are not ASP.NET based?

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  • Being pressured to GOTO the dark-side

    - by Dan McG
    We have a situation at work where developers working on a legacy (core) system are being pressured into using GOTO statements when adding new features into existing code that is already infected with spagetti code. Now, I understand there may be arguments for using 'just one little GOTO' instead of spending the time on refactoring to a more maintainable solution. The issue is, this isolated 'just one little GOTO' isn't so isolated. At least once every week or so there is a new 'one little GOTO' to add. This codebase is already a horror to work with due to code dating back to or before 1984 being riddled with GOTOs that would make many Pastafarians believe it was inspired by the Flying Spagetti Monster itself. Unfortunately the language this is written in doesn't have any ready made refactoring tools, so it makes it harder to push the 'Refactor to increase productivity later' because short-term wins are the only wins paid attention to here... Has anyone else experienced this issue whereby everybody agrees that we cannot be adding new GOTOs to jump 2000 lines to a random section, but continually have Anaylsts insist on doing it just this one time and having management approve it? tldr; How can one go about addressing the issue of developers being pressured (forced) to continually add GOTO statements (by add, I mean add to jump to random sections many lines away) because it 'gets that feature in quicker'? I'm beginning to fear we may loses valuable developers to the raptors over this...

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  • Java NullPointerException In the constructor's class

    - by AndreaF
    I have made a Java class where I have defined a constructor and some methods but I get a NullPointer Exception, and I don't know how I could fix It. public class Job { String idJob; int time; int timeRun; Job j1; List<Job> startBeforeStart; List<Job> restricted; Job(String idJob, int time){ this.idJob=idJob; this.time=time; } public boolean isRestricted() { return restricted.size() != 0; } public void startsBeforeStartOf(Job job){ startBeforeStart.add(job); job.restricted.add(this); } public void startsAfterStartOf(Job job){ job.startsBeforeStartOf(this); } public void checkRestrictions(){ if (!isRestricted()){ System.out.println("+\n"); } else{ Iterator<Job> itR = restricted.iterator(); while(itR.hasNext()){ Job j1 = itR.next(); if(time>timeRun){ System.out.println("-\n"); time--; } else { restricted.remove(j1); } } } } @Override public boolean equals(Object obj) { return obj instanceof Job && ((Job) obj).idJob.equals(idJob); } public void run() { timeRun++; } } PS Looking in a forum a user says that to fix the error I should make an ArrayList inside the constructor (without modify the received parameters that should remain String id and int time), but I haven't understand what He mean.

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  • Can piping of screen to file change the result of a C++ code?

    - by Biga
    I am having this very weird behaviour with a C++ code: It gives me different results when running with and without piping the screen to a file (reproducible in cygwin and linux). I mean, if I get the same executable and run it like './run' or run it like './run out.log', I get different results! I use std::cout to output to screen, all lines ending with endl; I use ifstream for the input file; I use ofstream for output, all lines ending with endl. I am using g++ 4. Any idea what is going on? UPDATE: I have hard-coded the input data, so 'ifstream' is not used, and problem persists. UPDATE 2: That's getting interesting. I have output three variables that are computed initially, and that's what I get with and without piping direct to screen: 0 -0.02 0 piped: 0 -0.02 1.04083e-17 So there's a round-off difference with and without piping the output! Now, why piping would interefere with an internal computation of the code?

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  • How to pass checkbox array to Java from jsp

    - by eddy
    Hi, I'd like to know if there's any way to send data to the server for the selected rows using the checkboxes I've put on those rows? I mean , how can I send only the data of those selected rows to the server? Here's the html code I use: <table> <thead> <tr class="tableheader"> <td width="10%"></td> <td width="30%">Vehicle</td> <td width="40%">Driver</td> <td width="10%">Mileage</td> </tr> </thead> <tbody> <c:forEach items="${list}" var="item"> <tr> <td align="center"> <input type="checkbox" name="selectedItems" value="c:out value="${item.numberPlate}"/>"/> </td> <td align="left"><c:out value="${item.numberPlate}"/></td> <td align="left"><c:out value="${item.driver.fullName}" /></td> <td align="left"><input type="text" name="mileage" value="" /></td> </tr> </c:forEach> </tbody> </table> I really hope you can give some guidance on this. Thanks in beforehand.

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  • Does the pointer to free() have to point to beginning of the memory block, or can it point to the interior?

    - by Lambert
    The question is in the title... I searched but couldn't find anything. Edit: I don't really see any need to explain this, but because people think that what I'm saying makes no sense (and that I'm asking the wrong questions), here's the problem: Since people seem to be very interested in the "root" cause of all the problem rather than the actual question asked (since that apparently helps things get solved better, let's see if it does), here's the problem: I'm trying to make a D runtime library based on NTDLL.dll, so that I can use that library for subsystems other than the Win32 subsystem. So that forces me to only link with NTDLL.dll. Yes, I'm aware that the functions are "undocumented" and could change at any time (even though I'd bet a hundred dollars that wcstombs will still do the same exact thing 20 years from now, if it still exists). Yes, I know people (especially Microsoft) don't like developers linking to that library, and that I'll probably get criticized for the right here. And yes, those two points above mean that programs like chkdsk and defragmenters that run before the Win32 subsystem aren't even supposed to be created in the first place, because it's literally impossible to link with anything like kernel32.dll or msvcrt.dll and still have NT-native executables, so we developers should just pretend that those stages are meant to be forever out of our reaches. But no, I doubt that anyone here would like me to paste a few thousand lines of code and help me look through them and try to figure out why memory allocations that aren't failing are being rejected by the source code I'm modifying. So that's why I asked about a different problem than the "root" cause, even though that's supposedly known to be the best practice by the community. If things still don't make sense, feel free to post comments below! :)

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  • Custom UIButton Memory Management in dealloc

    - by ddawber
    I am hoping to clarify the processes going on here. I have created a subclass of UIButton whose init method looks like this: - (id)initWithTitle:(NSString *)title frame:(CGRect)btnFrame { self = [UIButton buttonWithType:UIButtonTypeCustom]; [self setTitle:title forState:UIControlStateNormal]; self.frame = btnFrame; return self; } In my view controller I am creating one of these buttons and adding it as a subview: myButton = [[CustomButton alloc] initWithTitle:@"Title" frame:someFrame]; [self.view addSubview:myButton]; In the view controller's dealloc method I log the retain count of my button: - (void)dealloc { NSLog(@"RC: %d", [myButton retainCount]); //RC = 2 [super dealloc]; NSLog(@"RC: %d", [myButton retainCount]); //RC = 1 } The way I understand it, myButton is not actually retained, even though I invoked it using alloc, because in my subclass I created an autorelease button (using buttonWithType:). In dealloc, does this mean that, when dealloc is called the superview releases the button and its retain count goes down to 1? The button has not yet been autoreleased? Or do I need to get that retain count down to zero after calling [super dealloc]? Cheers.

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  • Mixing menuItem.setIntent with onOptionsItemSelected doesn't work

    - by superjos
    While extending a sample Android activity that fires some other activities from its menu, I came to have some menu items handled within onOptionsItemSelected, and some menu items (that just fired intents) handled by calling setIntent within onCreateOptionsMenu. Basically something like: @Override public boolean onCreateOptionsMenu(Menu menu) { super.onCreateOptionsMenu(menu); menu.add(0, MENU_ID_1, Menu.NONE, R.string.menu_text_1); menu.add(0, MENU_ID_2, Menu.NONE, R.string.menu_text_2); menu.add(0, MENU_ID_3, Menu.NONE, R.string.menu_text_3). setIntent(new Intent(this, MyActivity_3.class)); return true; } @Override public boolean onOptionsItemSelected(MenuItem item) { super.onOptionsItemSelected(item); switch (item.getItemId()) { case (MENU_ID_1): // Process menu command 1 ... return true; case (MENU_ID_2): // Process menu command 2 ... // E.g. also fire Intent for MyActivity_2 return true; default: return false; } } Apparently, in this situation the Intent set on MENU_ID_3 is never fired, or anyway the related activity is never started. Android javadoc at some point goes like <<[if you set an intent on a menu item] and nothing else handles the item, then the default behavior will be to [start the activity with the intent]. What does it actually mean "and nothing else handles the item"? Is it enough to return false from onOptionsItemSelected? I also tried not to call super.onOptionsItemSelected(item) at the beginning and only invoke it in the default switch case, but I had same results. Does anyone have any suggestion? Does Android allow to mix the two type of handling? Thanks for your time everyone.

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  • java gui image problem : doesn't display in the background

    - by thegamer
    Hello, i have a query about why is my image not being displayed in my background of my program. I mean i did all the steps necessary and still it would'nt be displayed. The code runs perfectly but without having the image displayed. The directory is written in the good location of the image. I am using java with gui. If anyone could help me solve my problem, i would appreciate :) here is the code below: import java.awt.*; import java.awt.event.*; import javax.swing.*; public class hehe extends JPanel{ public hehe(){ setOpaque(false); setLayout(new FlowLayout()); } public static void main (String args[]){ JFrame win = new JFrame("yooooo"); // it is automaticcally hidden JPanel mainPanel = new JPanel(new BorderLayout()); win.add(mainPanel); JLabel titleLabel = new JLabel("title boss"); titleLabel.setFont(new Font("Arial",Font.BOLD,18)); titleLabel.setForeground(Color.blue); mainPanel.add(titleLabel,BorderLayout.NORTH); win.setSize(382,269); // the dimensions of the image win.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); win.setVisible(true); } public void paint(Graphics g) { Image a = Toolkit.getDefaultToolkit().getImage("C:\\Users\\andrea\\Desktop\\Gui\\car"); // car is the name of the image file and is in JPEG g.drawImage(a,0,0,getSize().width,getSize().height,this); super.paint(g); } }

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  • C#: Using one Data Table in order to fill 2 different comboboxes?

    - by odiseh
    Hi all. I have 2 comboboxes on a form (form1) called combobox1 and combobox2. Each comboboxes should be filled with data stored in 2 different tables in Sql server 2005: table1 and table2 I mean: combobox1 -- table1 combobox2 -- table2 I fill data table with proper data and then bind the comboboxes to it separately. My problem is: after filling 2 combos, both of them have equal data got from table2. This is my code: DataTable tb1 = new DataTable(); //Filling tb1 with data got from table1 combobox1.Items.Clear(); combobox1.DataSource = tb1; combobox1.DisplayMember = "Name"; combobox1.ValueMember = "ID"; combobox1.SelectedIndex = -1; //filling tb1 with data got from table2 combobox2.Items.Clear(); combobox2.DataSource = tb1; combobox2.DisplayMember = "Name"; combobox2.ValueMember = "ID"; combobox2.SelectedIndex = -1; What's wrong? It seems that if I get 2 different data tables (tb1 and tb2) , every thing will be all right. Any suggestions please. Thank you

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  • different thread accessing MemoryStream

    - by Wayne
    There's a bit of code which writes data to a MemoryStream object directly into it's data buffer by calling GetBuffer(). It also uses and updates the Position and SetLength() properties appropriately. This code works purposes 99.9999% of the time. Literally. Only every so many 100,000's of iterations it will barf. The specific problem is that the memory.Position property suddenly returns zero instead of the appropriate value. However, code was added that checks for the 0 and throws an exception which include log of the MemoryStream properties like Position and Length in a separate method. Those return the correct value. Further addition shows that when this rare condition occurs, the memory.Position only has zero inside this particular method. Okay. Obviously, this must be a threading issue. But this code is well locked. However, the nature of this software is that it's organized by "tasks" with a scheduler and so any one of several actual O/S thread may run this code at any give time--but never more than one at a time. So it's my guess that ordinarily it so happens that the same thread keeps getting used for this method and then on a rare occasion a different thread get used. Then due to compiler optimizations, the different thread never gets the correct value. It gets a "stale" value. Ordinarily in a situation like this I would apply a "volatile" keyword to the variable in question. But that (those) variables are inside the MemoryStream object. Does anyone have any other idea? Or does this mean we have to implement our own MemoryStream object? (Just like we end up having to do with practically every collection in .NET?) It's a shame to have such an awesome platform as .NET and have virtually the entire system useless as-is for seriously parallelized applications. If I'm wrong or you have other ideas, please advise. Sincerely, Wayne

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  • Best method to search hierarchical data

    - by WDuffy
    I'm looking at building a facility which allows querying for data with hierarchical filtering. I have a few ideas how I'm going to go about it but was wondering if there are any recommendations or suggestions that might be more efficient. As an example imagine that a user is searching for a job. The job areas would be as follows. 1: Scotland 2: --- West Central 3: ------ Glasgow 4: ------ Etc 5: --- North East 6: ------ Ayrshire 7: ------ Etc A user can search specific (i.e. Glasgow) or in a larger area (i.e. Scotland). The two approaches I am considering are: keep a note of children in the database for each record (i.e. cat 1 would have 2, 3, 4 in its children field) and query against that record with a SELECT * FROM Jobs WHERE Category IN Areas.childrenField. Use a recursive function to find all results who have a relation to the selected area. The problems I see from both are: Holding this data in the db will mean having to keep track of all changes to structure. Recursion is slow and inefficent. Any ideas, suggestion or recommendations on the best approach? I'm using C# ASP.NET with MSSQL 2005 DB.

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