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  • DisplayObject snapshot in flex 3

    - by simplemagik
    i'm creating a visual editor in flex and need to let users export thier projects into Image format. But i have one problem: size of the canvas is fixed and when user add element which is out of these sizes some scroll bars added. And user continue working on the project. but when he want to take snapshot of the canvas he just get the visible part ot the canvas with scrollbars. how to get image of the fullsize canvas? The only solution i found is to check the positions and sizes of canvas child objects and rezise it to fit them. then take snap and resize back. But it hmmmm... too complicated i think. Is there some "easy methods"? <?xml version="1.0" encoding="utf-8"?> <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="vertical"> <mx:Script> <![CDATA[ import mx.graphics.ImageSnapshot; private function SnapshotButtonHandler():void { var snapshot:ImageSnapshot = ImageSnapshot.captureImage(AppCanvas); var file:FileReference = new FileReference(); file.save(snapshot.data, "canvas.png"); } ]]> </mx:Script> <mx:Canvas id="AppCanvas" width="800" height="300" backgroundColor="0xFFFFFF"> <mx:Box x="750" y="100" width="100" height="100" backgroundColor="0xCCCCCC" /> </mx:Canvas> <mx:Button id="SnapshotButton" label="take snapshot" click="SnapshotButtonHandler()" /> </mx:Application>

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  • Using AJAX to get a specific DOM Element (using Javascript, not jQuery)

    - by Matt Frost
    How do you use AJAX (in plain JavaScript, NOT jQuery) to get a page (same domain) and display just a specific DOM Element? (Such as the DOM element marked with the id of "bodyContent"). I'm working with MediaWiki 1.18, so my methods have to be a little less conventional (I know that a version of jQuery can be enabled for MediaWiki, but I don't have access to do that so I need to look at other options). I apologize if the code is messy, but there's a reason I need to build it this way. I'm mostly interested in seeing what can be done with the Javascript. Here's the HTML code: <div class="mediaWiki-AJAX"><a href="http://www.domain.com/whatever"></a></div> Here's the Javascript I have so far: var AJAXs = document.getElementsByClassName('mediaWiki-AJAX'); if (AJAXs.length > 0) { for (var i = AJAXs.length - 1; i >= 0; i--) { var URL = AJAXs[i].getElementsByTagName('a')[0].href; xmlhttp = new XMLHttpRequest(); xmlhttp.onreadystatechange = function() { if (xmlhttp.readyState == 4 && xmlhttp.status == 200) { AJAXs[i].innerHTML = xmlhttp.responseText; } } xmlhttp.open('GET',URL,true); xmlhttp.send(); } }

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  • Validation L2S question

    - by user158020
    This may be a bit winded because I am new to wpf. I have created a partial class for an entity in my L2S class that is primarily used for validation. It implements the onchanging and onvalidate methods. I am trying to use the MVVM pattern, and in a window/view I have set the datacontext in the xaml: <Window.DataContext> <vm:StartViewModel /> </Window.DataContext> when a user leaves a required field in the view blank, the onchanging event of the partial class is fired when I close the form, not when I save the data. So, if a user leaves the textbox blank, the old value is retained and the onchaging method is fired, but I have no idea how to alert the user of the resulting error. here is my onchanging code in the partial class: partial void Ondocument_titleChanging(string value) { if (value.Length == 0) throw new Exception("Document title is required."); if (value.Length > 256) throw new Exception("Document title cannot be longer than 256 characters."); } throwing an exception doesn't notify the user of the error. it just allows the form to close and rejects the changes to the textbox. hope this makes sense... edit: this example was taken from Scott Guthries article here: http://aspalliance.com/1427_LINQ_to_SQL_Part_5__Binding_UI_using_the_ASPLinqDataSource_Control.5

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  • Powerpoint displays a "can't start the application" error when an Excel Chart object is embedded in

    - by A9S6
    This is a very common problem when Excel Worksheet or Chart is embedded into Word or Powerpoint. I am seeing this problem in both Word and Powerpoint and the reason it seems is the COM addin attached to Excel. The COM addin is written in C# (.NET). See the attached images for error dialogs. I debugged the addin and found a very strange behavior. The OnConnection(...), OnDisConnection(...) etc methods in the COM addin works fine until I add an event handler to the code. i.e. handle the Worksheet_SheetChange, SelectionChange or any similar event available in Excel. As soon as I add even a single event handler (though my code has several), Word and Powerpoint start complaining and do not Activate the embedded object. On some of the posts on the internet, people have been asked to remove the anti-virus addins for office (none in my case) so this makes me believe that the problem is somewhat related to COM addins which are loaded when the host app activates the object. Does anyone have any idea of whats happening here?

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  • Images in Applet not showing in web page

    - by Leanne C
    I am trying to display a JPEG image and a moving dot on a Java applet which I am using on a web based application. However, when I run the applet it works fine, but when I display the applet from the JSP page, I get the moving dot but not the JPEG image. Is there a specific folder where the JPEG needs to be? These are the 2 methods i use for drawing the picture and the moving dot on the screen. public class mapplet extends Applet implements Runnable { int x_pos = 10; int y_pos = 100; int radius = 20; Image img, img2; Graphics gr; URL base; MediaTracker m; @Override public void init() { mt = new MediaTracker(this); try { //getDocumentbase gets the applet path. base = getCodeBase(); img = getImage(base, "picture.jpg"); m.addImage(img, 1); m.waitForAll(); } catch (InterruptedException ex) { Logger.getLogger(movement.class.getName()).log(Level.SEVERE, null, ex); } public void paint (Graphics g) { g.drawImage(img, 0, 0, this); // set color g.setColor (Color.red); // paint a filled colored circle g.fillOval (x_pos - radius, y_pos - radius, 2 * radius, 2 * radius); } The code one below is the call from the jsp page <applet archive="mapplet.jar" code="myapplets/mapplet.class" width=350 height=200> </applet> The jar file and the picture are in the same folder as the jsp page, and there is also a folder containing the contents of the class and image of the applet in the web section of the application. The applet loads fine however the picture doesn't display. I think it's not the code but the location of the picture that is causing a problem. Thanks

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  • Write a program which works out which is the lowest priced computer in an ArrayList of computer obje

    - by Eoin
    Hello everybody! I am trying to study some java and cannot get my head around this question! Any help would be really appreciated and would help me in further studies! Thank you so much in advance! Eoin from Dublin, Ireland. ArrayList of Objects Write a program which works out which is the lowest priced computer in an ArrayList of computer objects. You should have two classes, one called ComputerTest, and the other called Computer. In the ComputerTest class you should: Have a main method which declares an ArrayList of type Computer called computerList, each element of which represents a computer. Initialise the first three entries of the ArrayList Call a static method which prints out the lowest price computer, called lowestPrice The parameter of this method is (i) an ArrayList of type Computer i.e. ArrayList data Sample output: The lowest priced computer is the Cheapo400 at 399 euro. The Computer class should have: Private instance variables: manufacturer, model, price and quality. Quality is a rating from 1 to 10. public get and set methods to retrieve and set/change the value of the four instance variables a default constructor a constructor that takes four parameters

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  • Three20 TTSectionedDataSource row height

    - by Ward
    Hey there, I'm using Three20 to create a table with several textfields for user registration. I've found two possible methods using Three20. The first uses the TTSectionedDataSource's tableDidLoadModel method to manually add UI components and the second adds custom items that contains pre formatted UI components. The second option seems way more complex and I'm having a difficult time accessing the individual fields. So if one field is a textfield for the username, I need to access the field to submit the username and it doesn't seem like there's an easy answer. The first option gives me a lot of flexibility, but I can't figure out how to set the individual row heights. One row may have a label above a text field, another may have an image, etc. Is there a method that can be used in TTSectionedDataSource that will allow me to set the height for each row? Thus far, I'm using method one and creating UIViews to hold a label field and a text field. I've tried changing the frame of the uiview before it is added to the items array, but it has no affect. Any ideas?

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  • Cannot implicity convert type void to System.Threading.Tasks.Task<bool>

    - by sagesky36
    I have a WCF Service that contains the following method. All the methods in the service are asynchrounous and compile just fine. public async Task<Boolean> ValidateRegistrationAsync(String strUserName) { try { using (YeagerTechEntities DbContext = new YeagerTechEntities()) { DbContext.Configuration.ProxyCreationEnabled = false; DbContext.Database.Connection.Open(); var reg = await DbContext.aspnet_Users.FirstOrDefaultAsync(f => f.UserName == strUserName); if (reg != null) return true; else return false; } } catch (Exception) { throw; } } My client application was set to access the WCF service with the check box for the "Allow generation of asynchronous operations" and it generated the proxy just fine. I am receiving the above subject error when trying to call this WCF service method from my client with the following code. Mind you, I know what the error message means, but this is my first time trying to call an asynchronous task in a WCF service from a client. Task<Boolean> blnMbrShip = db.ValidateRegistrationAsync(FormsAuthentication.Decrypt(cn.Value).Name); What do I need to do to properly call the method so the design time compile error disappears? Thanks so much in advance...

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  • accessing widgets inside a GWT element

    - by flyingcrab
    I want to access the text elements inside this textbox in GWT from the main method (where I call it like this) DialogBox aBox = newCandidatePop.buildNewElecPopup(); aBox.center(); aBox.getWidget(); MiscUiTools.newCandidateHandler(aBox.firstName, aBox.surName); in newCandidateHandler i want to attach a click handler to the two text boxes However, the above doesnt quite work - I cant get access to the aBox.firstName elements because they are static methods -- I am wondering what is best practice, how would you code something like this up? static TextBox firstName = new TextBox(); static TextBox surName = new TextBox(); static DialogBox box; // public newCandidatePop() { // box = buildNewElecPopup(); // } static public DialogBox buildNewElecPopup() { DialogBox box = new DialogBox(); box.setAutoHideEnabled(true); box.setText("Add a New Candidate"); box.setAnimationEnabled(true); box.setGlassEnabled(true); Grid dialogGrid = new Grid(2, 3); dialogGrid.setPixelSize(250 , 125); dialogGrid.setCellPadding(10); dialogGrid.setWidget(0, 0, new HTML("<strong>First Name</strong>")); dialogGrid.setWidget(0, 1, firstName); dialogGrid.setWidget(1, 0, new HTML("<strong>Surname</strong>")); dialogGrid.setWidget(1, 1, surName); box.add(dialogGrid); return box; }

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  • How do you save and retrieve a Key/IV pair securely?

    - by Shawn Steward
    I'm using VB.Net's RijndaelManaged (RM) to encrypt files, using the RM.GenerateKey and RM.GenerateIV methods to generate the Key and IV and encrypting the file using the CryptoStream class. I'm planning on saving this Key and IV to a file and want to make sure I'm doing it the right way. I am combining the IV+Key, and encrypting that with my RSA Public key and writing it out to a file. Then, to decrypt I use the RSA Private key on this file to get the IV+Key, split them up and set RM.Key and RM.IV to these values and run the decryptor. Is this the best method to accomplish this, or is there a preferred method for saving the IV & Key? Also, what's the best way to construct and deconstruct the byte array? I used the .Concat method to join them together and that seems to work well but I can't seem to find something as easy to deconstruct it. I played with the .Take method that takes the first x # of bytes and it works for the first part but can't find anything that gets the rest of it.

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  • How should I progressively enhance this content with JavaScript?

    - by Sean Dunwoody
    The background to this problem is that I'm doing a computing project which involves Some drop down boxes for input, and a text input where the user can input a date. I've used YUI to enhance the form, so the calendar input uses the YUI calendar widget and the drop down list is converted into a horizontal list of inputs where the user only has to click once to select any input as opposed to two clicks with the drop down box (hope that makes sense, not sure how to explain it clearly) The problem is, that in the design section of my project I stated that I would follow the progressive enhancement principles. I am struggling however to ensure that users without JavaScript are able to view the drop down box / text input on said page. This is not because I do not necessarily know how, but the two methods I've tried seem unsatisfactory. Method 1 - I tried using YUI to hide the text box and drop down list, this seemed like the ideal solution however there was quite a noticeable lag when loading the page (especially for the first time), the text box and drop down list where visibile for at least a second. I included the script for this just before the end of the body tag, is there any way that I can run it onload with YUI? Would that help? Method 2 - Use the noscript tag . . . however I am loathed to do this as while it would be a simple solution, I have read various bad things about the noscript tag. Is there a way of making mehtod one work? Or is there a better way of doing this that I am yet to encounter?

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  • Resolve php endless recursion issue

    - by Matt
    Hey all, I'm currently running into an endless recursion situation. I'm implementing a message service that calls various object methods.. it's quite similar to observer pattern.. Here's whats going on: Dispatcher.php class Dispatcher { ... public function message($name, $method) { // Find the object based on the name $object = $this->findObjectByName($name); // Slight psuedocode.. for ease of example if($this->not_initialized($object)) $object = new $object(); // This is where it locks up. } return $object->$method(); ... } class A { function __construct() { $Dispatcher->message("B", "getName"); } public function getName() { return "Class A"; } } class B { function __construct() { // Assume $Dispatcher is the classes $Dispatcher->message("A", "getName"); } public function getName() { return "Class B"; } } It locks up when neither object is initialized. It just goes back and forth from message each other and no one can be initialized. I'm looking for some kind of queue implementation that will make messages wait for each other.. One where the return values still get set. I'm looking to have as little boilerplate code in class A and class B as possible Any help would be immensely helpful.. Thanks! Matt Mueller

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  • Decoupling the view, presentation and ASP.NET Web Forms

    - by John Leidegren
    I have an ASP.NET Web Forms page which the presenter needs to populate with controls. This interaction is somewhat sensitive to the page-life cycle and I was wondering if there's a trick to it, that I don't know about. I wanna be practical about the whole thing but not compromise testability. Currently I have this: public interface ISomeContract { void InstantiateIn(System.Web.UI.Control container); } This contract has a dependency on System.Web.UI.Control and I need that to be able to do things with the ASP.NET Web Forms programming model. But neither the view nor the presenter may have knowledge about ASP.NET server controls. How do I get around this? How can I work with the ASP.NET Web Forms programming model in my concrete views without taking a System.Web.UI.Control dependency in my contract assemblies? To clarify things a bit, this type of interface is all about UI composition (using MEF). It's known through-out the framework but it's really only called from within the concrete view. The concrete view is still the only thing that knows about ASP.NET Web Forms. However those public methods that say InstantiateIn(System.Web.UI.Control) exists in my contract assemblies and that implies a dependency on ASP.NET Web Forms. I've been thinking about some double dispatch mechanism or even visitor pattern to try and work around this.

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  • Dynamic Control loading at wrong time?

    - by Telos
    This one is a little... odd. Basically I have a form I'm building using ASP.NET Dynamic Data, which is going to utilize several custom field templates. I've just added another field to the FormView, with it's own custom template, and the form is loading that control twice for no apparent reason. Worse yet, the first time it loads the template, the Row is not ready yet and I get the error message: {"Databinding methods such as Eval(), XPath(), and Bind() can only be used in the context of a databound control."} I'm accessing the Row variable in a LinqDataSource OnSelected event in order to get the child object... Now for the wierd part: If I reorder the fields a little, the one causing the problem no longer gets loaded twice. Any thoughts? EDIT: I've noticed that Page_Load gets called on the first load (when Row throws an exception if you try to use it) but does NOT get called the second time around. If that helps any... Right now managing it by just catching and ignoring the exception, but still a little worried that things will break if I don't find the real cause. EDIT 2: I've traced the problem to using FindControl recursively to find other controls on the page. Apparently FindControl can cause the page lifecycle events (at least up to page_load) to fire... and this occurs before that page "should" be loading so it's dynamic data "stuff" isn't ready yet.

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  • Prevent comment form re-submission

    - by Rob
    I'm got a comment form for an article and i'd to prevent re-submission. I notice that Worpdress handles this very well (going back doesn't cause the browser to request a form re-submission), but I can't figure out how they do it, even though our methods are very similar. My Script User visits mydomain.com/article/1/article_title.html Fills in a form which posts to mydomain.com/addnewcomment/1.html I then do a 302 redirect back to mydomain.com/article/1/article_title.html Now if I press back from this position it doesn't request a redirect. However, if I go to another page e.g. mydomain.com/tag/1/my_tag.html and press back it does resubmit the form. Obviously I want to prevent this. What Wordpress does User visits mydomain.com/?p=1 Fills in a form which posts to mydomain.com/wp-comments-post.php This then does a 302 redirect back to mydomain.com/?p=1 Pressing back or visiting another page and pressing back doesn't cause a re-submission. I've had a look through the WP code but I can't see how they manage this. Obviously it's something i'd like to achieve. Does anyone have any thoughts on where I may be going wrong? (I'm only using Wordpress as an example to prove that it's possible, obviously i'm not trying to exactly duplicate WP, that would be pointless)

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  • How does the PHP IteratorIterator class work?

    - by WilliamMartin
    Try as I might I cannot get my head around what the IteratorIterator class actually does. I understand that classes can implement Traversable so the engine knows it can loop using foreach and I realise that IteratorIterator is supposed to convert anything that is Traversable into an Iterator but I cannot for the life of me understand how. Take for example, the PDOStatement class; how would the standard Iterator methods (next, key, rewind, etc) be implemented to allow iteration over a PDOStatement? Sorry if my question is unclear, I am just struggling to grasp the exact reason for this class and the documentation on it is scant. Thanks, Will Update: Going through the phpt files, I found one test which uses IteratorIterator: <?php $root = simplexml_load_string('<?xml version="1.0"?> <root> <child>Hello</child> <child>World</child> </root> '); foreach (new IteratorIterator($root->child) as $child) { echo $child."\n"; } ?> The expected output is: Hello World I don't really follow how the IteratorIterator construct takes $root-child as an argument and how it manages to iterate over the child elements.

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  • Which software for intranet CMS - Django or Joomla?

    - by zalun
    In my company we are thinking of moving from wiki style intranet to a more bespoke CMS solution. Natural choice would be Joomla, but we have a specific architecture. There is a few hundred people who will use the system. System should be self explainable (easier than wiki). We use a lot of tools web, applications and integrated within 3rd party software. The superior element which is a glue for all of them is API. In example for the intranet tools we do use Django, but it's used without ORM, kind of limited to templates and url - every application has an adequate methods within our API. We do not use the Django admin interface, because it is hardly dependent on ORM. Because of that Joomla may be hard to integrate. Every employee should be able to edit most of the pages, authentication and privileges have to be managed by our API. How hard is it to plug Joomla to use a different authentication process? (extension only - no hacks) If one knows Django better than Joomla, should Django be used?

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  • C# DynamicMethod prelink

    - by soywiz
    I'm the author of a psp emulator made in C#. I'm generating lots of "DynamicMethod" using ILGenerator. I'm converting assembly code into an AST, and then generating IL code and building that DynamicMethod. I'm doing this in another thread, so I can generate new methods while the program is executing others so it can run smoothly. My problem is that the native code generation is lazy, so the machine code is generated when the function is called, not when the IL is generated. So it generates in the program executing thread, native code generation is prettly slow as it is the asm-ast-il step. I have tried the Marshal.Prelink method that it is suposed to generate the machine code before executing the function. It does work on Mono, but it doesn't work on MS .NET. Marshal.Prelink(MethodInfo); Is there a way of prelinking a DynamicMethod on MS .NET? I thought adding a boolean parameter to the function that if set, exits the function immediately so no code is actually executed. I could "prelink" that way, but I think that's a nasty solution I want to avoid. Any idea?

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  • Java iteration reading & parsing

    - by Patrick Lorio
    I have a log file that I am reading to a string public static String Read (String path) throws IOException { StringBuilder sb = new StringBuilder(); InputStream in = new BufferedInputStream(new FileInputStream(path)); int r; while ((r = in.read()) != -1) { sb.append(r); } return sb.toString(); } Then I have a parser that iterates over the entire string once void Parse () { String con = Read("log.txt"); for (int i = 0; i < con.length; i++) { /* parsing action */ } } This is hugely a waste of cpu cycles. I loop over all the content in Read. Then I loop over all the content in Parse. I could just place the /* parsing action */ under the while loop in the Read method, which would be find but I don't want to copy the same code all over the place. How can I parse the file in one iteration over the contents and still have separate methods for parsing and reading? In C# I understand there is some sort of yield return thing, but I'm locked with Java. What are my options in Java?

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  • Awkward looking uses of Contract.ValueAtReturn()

    - by devoured elysium
    I am designing a method that will add an element to an internal list. The structure of the class is something along the lines of: class MyCustomerDatabase { private IList<Customer> _customers = new List<Customer>(); public int NumberOfCustomers { get { return _customers; } } public void AddCustomer(Customer customer) { _customers.Add(customer); } } Now, I was thinking of adding a Contract.Ensures() about the size of the _customers growing by 1 with this call. The problem is that I end up with some weird looking code: public void AddCustomer(Customer customer) { int numberOfCustomersAtReturn; Contract.Ensures(Contract.ValueAtReturn<int>(out numberOfCustomersAtReturn) == Contract.OldValue<int>(NumberOfCustomers) + 1); _customers.Add(customer); numberOfCustomersAtReturn = NumberOfCustomers; } The main problem is that properties are in fact methods, so you can't just reference them direcly when using Contract.ValueAtReturn() as its only parameter accepts variables as out. The situation gets even odder if I want to achieve the same but this time with a method that should return a value: public int MyReturningMethod() { ... return abc(); //abc will add by one the number of customers in list } //gets converted to public int MyReturningMethod() { int numberOfCustomersAtReturn; Contract.Ensures(Contract.ValueAtReturn<int>(out numberOfCustomersAtReturn) == Contract.OldValue<int>(NumberOfCustomers) + 1); int returnValue = abc(); numberOfCustomersAtReturn = NumberOfCustomers; return returnValue; } This seems pretty clumsy :( Code Contracts should aim to get things clearer and this seems right the opposite. Am I doing something wrong? Thanks

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  • How can I diff against a revision of a single file using only the default Git GUI tools?

    - by Rich
    I want to view the history of a single file, and then compare a single revision from that history against the current version. On the command line, this is easy: Run: git log -- <filename> Locate the version you want to compare, Run: git diff <commitid> -- <filename> But how can this be done using only the default Git gui tools, git gui and gitk? I know of two methods using gitk, but they're both horribly clunky: Either: Select the New View option from the View menu, Type in the full path to your file into the box labelled Enter files and directories to include, one per line, Locate the version you want to compare by looking at the highlighted items in the top pane, and click on it to select it, Right-click on the current version and select Diff selected - this, Or: Select Tree in the bottom right-hand pane, Locate the file you want to look at, right-click on it, and select Highlight this only, Locate the version you want to compare by looking at the highlighted items in the top pane, and click on it to select it, Right-click on the current version and select Diff selected - this, Click on the file in the bottom right-hand pane to jump to it in the diff output, or scroll manually. Is a better method than this?

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  • Globalize/Localize Excel Reports Using Spreadsheet

    - by mga911
    My company has new customers in Brazil and we realized that our excel reports are not working when our Brazilian customers tried to open the reports in their Brazilian versions of excel. For excel output we use spreadsheet gear in our vb.net web application. Our excel worksheets are fairly simple. Mostly outputted text/numbers/dates, a couple of formulas (sum, if) and formatting on the currency and dates. I've tried several methods to get my excel reports to work: First I left the excel workbook in the "en-US" culture and tried simply chaging the number format for Brazil to: _-[$R$-416] * #.##0,00_-;-[$R$-416] * #.##0,00_-;_-[$R$-416] * "-"??_-;_-@_- And this formatted the regular cells but the formulas still failed to show a value. Instead they showed a 0 value. Next I tried changing the workbook to the "pt-BR" culture and that also forced me to translate the formula names (Sum - Soma, If - Se) but they still wouldn't should a value and instead showed a #Name/#Nome error. Interestingly enough the formulas would work if I edited the cell and hit enter. The formula wouldn't change but it would some how fix that cell. I need to be able to out excel reports that can format dates/currencies and apply simple formulas (IF, Sum) for other excel cultures. Anyone have any advice?

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  • What are the responsibilities of the data layer?

    - by alimac83
    I'm working on a project where I had to add a data layer to my application. I've always thought that the data layer is purely responsible for CRUD functions ie. shouldn't really contain any logic but should simply retrieve data for the business layer to manipulate. However I'm a little confused with my project because I'm not sure whether I've structured my app correctly for this scenario. Basically I'm trying to retrieve a list of products from the database that fall within a certain pricing threshold. At the moment I have a function in my data layer that basically returns all products where price min threshold and price < max threshold. But it got me thinking that maybe this is incorrect. Should the data layer simply return a list of ALL products and then the business logic do the filtering? I'm pretty confused over whether the data layer should simply provide methods that allow the business layer to get raw data or whether it should be responsible for getting filtered data too? If anyone has an article or something explaining this in detail it'd be very helpful. Thanks

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  • When to choose which machine learning classifier?

    - by LM
    Suppose I'm working on some classification problem. (Fraud detection and comment spam are two problems I'm working on right now, but I'm curious about any classification task in general.) How do I know which classifier I should use? (Decision tree, SVM, Bayesian, logistic regression, etc.) In which cases is one of them the "natural" first choice, and what are the principles for choosing that one? Examples of the type of answers I'm looking for (from Manning et al.'s "Introduction to Information Retrieval book": http://nlp.stanford.edu/IR-book/html/htmledition/choosing-what-kind-of-classifier-to-use-1.html): a. If your data is labeled, but you only have a limited amount, you should use a classifier with high bias (for example, Naive Bayes). [I'm guessing this is because a higher-bias classifier will have lower variance, which is good because of the small amount of data.] b. If you have a ton of data, then the classifier doesn't really matter so much, so you should probably just choose a classifier with good scalability. What are other guidelines? Even answers like "if you'll have to explain your model to some upper management person, then maybe you should use a decision tree, since the decision rules are fairly transparent" are good. I care less about implementation/library issues, though. Also, for a somewhat separate question, besides standard Bayesian classifiers, are there 'standard state-of-the-art' methods for comment spam detection (as opposed to email spam)? [Not sure if stackoverflow is the best place to ask this question, since it's more machine learning than actual programming -- if not, any suggestions for where else?]

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  • Dynamic expression tree how to

    - by Savvas Sopiadis
    Hello everybody! Implemented a generic repository with several Methods. One of those is this: public IEnumerable<T> Find(Expression<Func<T, bool>> where) { return _objectSet.Where(where); } Given to be it is easy to call this like this: Expression<Func<Culture, bool>> whereClause = c => c.CultureId > 4 ; return cultureRepository.Find(whereClause).AsQueryable(); But now i see (realize) that this kind of quering is "limiting only to one criteria". What i would like to do is this: in the above example c is of type Culture. Culture has several properties like CultureId, Name, Displayname,... How would i express the following: CultureId 4 and Name.contains('de') and in another execution Name.contains('us') and Displayname.contains('ca') and .... Those queries should be created dynamically. I had a look in Expression trees (as i thought this to be a solution to my problem - btw i never used them before) but i cannot find anything which points to my requirement. How can this be costructed? Thanks in advance

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