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• c#: Design advice. Using DataTable or List<MyObject> for a generic rule checker

  - by Andrew White

  Hi, I have about 100,000 lines of generic data. Columns/Properties of this data are user definable and are of the usual data types (string, int, double, date). There will be about 50 columns/properties. I have 2 needs: To be able to calculate new columns/properties using an expression e.g. Column3 = Column1 * Column2. Ultimately I would like to be able to use external data using a callback, e.g. Column3 = Column1 * GetTemperature The expression is relatively simple, maths operations, sum, count & IF are the only necessary functions. To be able to filter/group the data and perform aggregations e.g. Sum(Data.Column1) Where(Data.Column2 == "blah") As far as I can see I have two options: 1. Using a DataTable. = Point 1 above is achieved by using DataColumn.Expression = Point 2 above is acheived by using DataTable.DefaultView.RowFilter & C# code 2. Using a List of generic Objects each with a Dictionary< string, object to store the values. = Point 1 could be achieved by something like NCalc = Point 2 is achieved using LINQ DataTable: Pros: DataColumn.Expression is inbuilt Cons: RowFilter & coding c# is not as "nice" as LINQ, DataColumn.Expression does not support callbacks(?) = workaround could be to get & replace external value when creating the calculated column GenericList: Pros: LINQ syntax, NCalc supports callbacks Cons: Implementing NCalc/generic calc engine Based on the above I would think a GenericList approach would win, but something I have not factored in is the performance which for some reason I think would be better with a datatable. Does anyone have a gut feeling / experience with LINQ vs. DataTable performance? How about NCalc? As I said there are about 100,000 rows of data, with 50 columns, of which maybe 20 are calculated. In total about 50 rules will be run against the data, so in total there will be 5 million row/object scans. Would really appreciate any insights. Thx. ps. Of course using a database + SQL & Views etc. would be the easiest solution, but for various reasons can't be implemented.

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• Memory efficient int-int dict in Python

  - by Bolo

  Hi, I need a memory efficient int-int dict in Python that would support the following operations in O(log n) time: d[k] = v # replace if present v = d[k] # None or a negative number if not present I need to hold ~250M pairs, so it really has to be tight. Do you happen to know a suitable implementation (Python 2.7)? EDIT Removed impossible requirement and other nonsense. Thanks, Craig and Kylotan! To rephrase. Here's a trivial int-int dictionary with 1M pairs: >>> import random, sys >>> from guppy import hpy >>> h = hpy() >>> h.setrelheap() >>> d = {} >>> for _ in xrange(1000000): ... d[random.randint(0, sys.maxint)] = random.randint(0, sys.maxint) ... >>> h.heap() Partition of a set of 1999530 objects. Total size = 49161112 bytes. Index Count % Size % Cumulative % Kind (class / dict of class) 0 1 0 25165960 51 25165960 51 dict (no owner) 1 1999521 100 23994252 49 49160212 100 int On average, a pair of integers uses 49 bytes. Here's an array of 2M integers: >>> import array, random, sys >>> from guppy import hpy >>> h = hpy() >>> h.setrelheap() >>> a = array.array('i') >>> for _ in xrange(2000000): ... a.append(random.randint(0, sys.maxint)) ... >>> h.heap() Partition of a set of 14 objects. Total size = 8001108 bytes. Index Count % Size % Cumulative % Kind (class / dict of class) 0 1 7 8000028 100 8000028 100 array.array On average, a pair of integers uses 8 bytes. I accept that 8 bytes/pair in a dictionary is rather hard to achieve in general. Rephrased question: is there a memory-efficient implementation of int-int dictionary that uses considerably less than 49 bytes/pair?

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• Ruby on Rails check box not updating on form submission

  - by user284194

  I have an entries controller that allows users to add contact information the website. The user-submitted information isn't visible to users until the administrator checks a check box and submits the form. So basically my problem is that if I check the check box as an administrator while initially creating an entry (entries#new) the entry will be publicly visible as expected, but if a non-admin user creates an entry (the normal user view doesn't include the 'live' check box, only the admin one does) then that entry is stuck in limbo because the entries#edit view for some reason doesn't update the boolean check box value when logged in as an admin. entries#new view: <% form_for(@entry) do |f| %> <%= f.error_messages %> Name<br /> <%= f.text_field :name %> Mailing Address<br /> <%= f.text_field :address %> #... <%- if current_user -%> <%= f.label :live %><br /> <%= f.check_box :live %> <%- end -%> <%= f.submit 'Create' %> <% end %> entries#edit (only accessible by admin) view: <% form_for(@entry) do |f| %> <%= f.error_messages %> <%= f.label :name %><br /> <%= f.text_field :name %> Mailing Address<br /> <%= f.text_field :address %> <%= f.label :live %><br /> <%= f.check_box :live %> <%= f.submit 'Update' %> <% end %> Any ideas as to why an administrator can't update the :live check box from the edit view? I would greatly appreciate any suggestions. I'm new to rails. I can post more code if it's needed. Thanks for reading my question.

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• Complex SQL query with group by and two rows in one

  - by Ricket

  Okay, I need help. I'm usually pretty good at SQL queries but this one baffles me. By the way, this is not a homework assignment, it's a real situation in an Access database and I've written the requirements below myself. Here is my table layout. It's in Access 2007 if that matters; I'm writing the query using SQL. Id (primary key) PersonID (foreign key) EventDate NumberOfCredits SuperCredits (boolean) There are events that people go to. They can earn normal credits, or super credits, or both at one event. The SuperCredits column is true if the row represents a number of super credits earned at the event, or false if it represents normal credits. So for example, if there is an event which person 174 attends, and they earn 3 normal credits and 1 super credit at the event, the following two rows would be added to the table: ID PersonID EventDate NumberOfCredits SuperCredits 1 174 1/1/2010 3 false 2 174 1/1/2010 1 true It is also possible that the person could have done two separate things at the event, so there might be more than two columns for one event, and it might look like this: ID PersonID EventDate NumberOfCredits SuperCredits 1 174 1/1/2010 1 false 2 174 1/1/2010 2 false 3 174 1/1/2010 1 true Now we want to print out a report. Here will be the columns of the report: PersonID LastEventDate NumberOfNormalCredits NumberOfSuperCredits The report will have one row per person. The row will show the latest event that the person attended, and the normal and super credits that the person earned at that event. What I am asking of you is to write, or help me write, the SQL query to SELECT the data and GROUP BY and SUM() and whatnot. Or, let me know if this is for some reason not possible, and how to organize my data to make it possible. This is extremely confusing and I understand if you do not take the time to puzzle through it. I've tried to simplify it as much as possible, but definitely ask any questions if you give it a shot and need clarification. I'll be trying to figure it out but I'm having a real hard time with it, this is grouping beyond my experience...

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• Writing to a comet stream using tomcat 6.0

  - by user301247

  Hey I'm new to java servlets and I am trying to write one that uses comet so that I can create a long polling Ajax request. I can successfully start the stream and perform operations but I can't write anything out. Here is my code: public class CometTestServlet extends HttpServlet implements CometProcessor { /** * */ private static final long serialVersionUID = 1070949541963627977L; private MessageSender messageSender = null; protected ArrayList<HttpServletResponse> connections = new ArrayList<HttpServletResponse>(); public void event(CometEvent cometEvent) throws IOException, ServletException { HttpServletRequest request = cometEvent.getHttpServletRequest(); HttpServletResponse response = cometEvent.getHttpServletResponse(); //final PrintWriter out = response.getWriter(); if (cometEvent.getEventType() == CometEvent.EventType.BEGIN) { PrintWriter writer = response.getWriter(); writer.println("<!doctype html public \"-//w3c//dtd html 4.0 transitional//en\">"); writer.println("<head><title>JSP Chat</title></head><body bgcolor=\"#FFFFFF\">"); writer.println("</body></html>"); writer.flush(); cometEvent.setTimeout(10 * 1000); //cometEvent.close(); } else if (cometEvent.getEventType() == CometEvent.EventType.ERROR) { log("Error for session: " + request.getSession(true).getId()); synchronized(connections) { connections.remove(response); } cometEvent.close(); } else if (cometEvent.getEventType() == CometEvent.EventType.END) { log("End for session: " + request.getSession(true).getId()); synchronized(connections) { connections.remove(response); } PrintWriter writer = response.getWriter(); writer.println("</body></html>"); cometEvent.close(); } else if (cometEvent.getEventType() == CometEvent.EventType.READ) { //handleReadEvent(cometEvent); InputStream is = request.getInputStream(); byte[] buf = new byte[512]; do { int n = is.read(buf); //can throw an IOException if (n > 0) { log("Read " + n + " bytes: " + new String(buf, 0, n) + " for session: " + request.getSession(true).getId()); } else if (n < 0) { //error(cometEvent, request, response); return; } } while (is.available() > 0); } } Any help would be appreciated.

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• Why won't this Jquery run on IE?

  - by Charles Marsh

  Hello All, I have this Jquery code (function($){ $.expr[':'].linkingToImage = function(elem, index, match){ // This will return true if the specified attribute contains a valid link to an image: return !! ($(elem).attr(match[3]) && $(elem).attr(match[3]).match(/\.(gif|jpe?g|png|bmp)$/i)); }; $.fn.imgPreview = function(userDefinedSettings){ var s = $.extend({ /* DEFAULTS */ // CSS to be applied to image: imgCSS: {}, // Distance between cursor and preview: distanceFromCursor: {top:2, left:2}, // Boolean, whether or not to preload images: preloadImages: true, // Callback: run when link is hovered: container is shown: onShow: function(){}, // Callback: container is hidden: onHide: function(){}, // Callback: Run when image within container has loaded: onLoad: function(){}, // ID to give to container (for CSS styling): containerID: 'imgPreviewContainer', // Class to be given to container while image is loading: containerLoadingClass: 'loading', // Prefix (if using thumbnails), e.g. 'thumb_' thumbPrefix: '', // Where to retrieve the image from: srcAttr: 'rel' }, userDefinedSettings), $container = $('<div/>').attr('id', s.containerID) .append('<img/>').hide() .css('position','absolute') .appendTo('body'), $img = $('img', $container).css(s.imgCSS), // Get all valid elements (linking to images / ATTR with image link): $collection = this.filter(':linkingToImage(' + s.srcAttr + ')'); // Re-usable means to add prefix (from setting): function addPrefix(src) { return src.replace(/(\/?)([^\/]+)$/,'$1' + s.thumbPrefix + '$2'); } if (s.preloadImages) { (function(i){ var tempIMG = new Image(), callee = arguments.callee; tempIMG.src = addPrefix($($collection[i]).attr(s.srcAttr)); tempIMG.onload = function(){ $collection[i + 1] && callee(i + 1); }; })(0); } $collection .mousemove(function(e){ $container.css({ top: e.pageY + s.distanceFromCursor.top + 'px', left: e.pageX + s.distanceFromCursor.left + 'px' }); }) .hover(function(){ var link = this; $container .addClass(s.containerLoadingClass) .show(); $img .load(function(){ $container.removeClass(s.containerLoadingClass); $img.show(); s.onLoad.call($img[0], link); }) .attr( 'src' , addPrefix($(link).attr(s.srcAttr)) ); s.onShow.call($container[0], link); }, function(){ $container.hide(); $img.unbind('load').attr('src','').hide(); s.onHide.call($container[0], this); }); // Return full selection, not $collection! return this; }; })(jQuery); It works perfectly in all browsers apart from IE, which it does nothing, no errors, no clues? I have a funny feeling IE doesn't support attr? Can anyone offer any advice?

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• ArithmeticException thrown during BigDecimal.divide

  - by polygenelubricants

  I thought java.math.BigDecimal is supposed to be The Answer™ to the need of performing infinite precision arithmetic with decimal numbers. Consider the following snippet: import java.math.BigDecimal; //... final BigDecimal one = BigDecimal.ONE; final BigDecimal three = BigDecimal.valueOf(3); final BigDecimal third = one.divide(three); assert third.multiply(three).equals(one); // this should pass, right? I expect the assert to pass, but in fact the execution doesn't even get there: one.divide(three) causes ArithmeticException to be thrown! Exception in thread "main" java.lang.ArithmeticException: Non-terminating decimal expansion; no exact representable decimal result. at java.math.BigDecimal.divide It turns out that this behavior is explicitly documented in the API: In the case of divide, the exact quotient could have an infinitely long decimal expansion; for example, 1 divided by 3. If the quotient has a non-terminating decimal expansion and the operation is specified to return an exact result, an ArithmeticException is thrown. Otherwise, the exact result of the division is returned, as done for other operations. Browsing around the API further, one finds that in fact there are various overloads of divide that performs inexact division, i.e.: final BigDecimal third = one.divide(three, 33, RoundingMode.DOWN); System.out.println(three.multiply(third)); // prints "0.999999999999999999999999999999999" Of course, the obvious question now is "What's the point???". I thought BigDecimal is the solution when we need exact arithmetic, e.g. for financial calculations. If we can't even divide exactly, then how useful can this be? Does it actually serve a general purpose, or is it only useful in a very niche application where you fortunately just don't need to divide at all? If this is not the right answer, what CAN we use for exact division in financial calculation? (I mean, I don't have a finance major, but they still use division, right???).

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• Unselecting RadioButtons in Java Swing

  - by Thomas

  When displaying a group of JRadioButtons, initially none of them is selected (unless you programmatically enforce that). I would like to be able to put buttons back into that state even after the user already selected one, i.e., none of the buttons should be selected. However, using the usual suspects doesn't deliver the required effect: calling 'setSelected(false)' on each button doesn't work. Interestingly, it does work when the buttons are not put into a ButtonGroup - unfortunately, the latter is required for JRadioButtons to be mutually exclusive. Also, using the setSelected(ButtonModel, boolean) - method of javax.swing.ButtonGroup doesn't do what I want. I've put together a small program to demonstrate the effect: two radio buttons and a JButton. Clicking the JButton should unselect the radio buttons so that the window looks exactly as it does when it first pops up. import java.awt.Container; import java.awt.GridLayout; import java.awt.event.*; import javax.swing.*; /** * This class creates two radio buttons and a JButton. Initially, none * of the radio buttons is selected. Clicking on the JButton should * always return the radio buttons into that initial state, i.e., * should disable both radio buttons. */ public class RadioTest implements ActionListener { /* create two radio buttons and a group */ private JRadioButton button1 = new JRadioButton("button1"); private JRadioButton button2 = new JRadioButton("button2"); private ButtonGroup group = new ButtonGroup(); /* clicking this button should unselect both button1 and button2 */ private JButton unselectRadio = new JButton("Unselect radio buttons."); /* In the constructor, set up the group and event listening */ public RadioTest() { /* put the radio buttons in a group so they become mutually * exclusive -- without this, unselecting actually works! */ group.add(button1); group.add(button2); /* listen to clicks on 'unselectRadio' button */ unselectRadio.addActionListener(this); } /* called when 'unselectRadio' is clicked */ public void actionPerformed(ActionEvent e) { /* variant1: disable both buttons directly. * ...doesn't work */ button1.setSelected(false); button2.setSelected(false); /* variant2: disable the selection via the button group. * ...doesn't work either */ group.setSelected(group.getSelection(), false); } /* Test: create a JFrame which displays the two radio buttons and * the unselect-button */ public static void main(String[] args) { JFrame frame = new JFrame(); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); RadioTest test = new RadioTest(); Container contentPane = frame.getContentPane(); contentPane.setLayout(new GridLayout(3,1)); contentPane.add(test.button1); contentPane.add(test.button2); contentPane.add(test.unselectRadio); frame.setSize(400, 400); frame.setVisible(true); } } Any ideas anyone? Thanks!

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• The Math of a Jump in a 2D game.

  - by ONi

  I have been all around with this question and I can't find the correct answer! So, behold, the description of my question: I'm working in J2ME, I have my gameloop that do the following: public void run() { Graphics g = this.getGraphics(); while (running) { long diff = System.currentTimeMillis() - lastLoop; lastLoop = System.currentTimeMillis(); input(); this.level.doLogic(); render(g, diff); try { Thread.sleep(10); } catch (InterruptedException e) { stop(e); } } } so it's just a basic gameloop, the doLogic() function calls for all the logic functions of the characters in the scene and render(g, diff) calls the animateChar function of every character on scene, following this, the animChar function in the Character class sets up everything in the screen as this: protected void animChar(long diff) { this.checkGravity(); this.move((int) ((diff * this.dx) / 1000), (int) ((diff * this.dy) / 1000)); if (this.acumFrame > this.framerate) { this.nextFrame(); this.acumFrame = 0; } else { this.acumFrame += diff; } } This ensures me that everything must to move according to the time that the machine takes to go from cycle to cycle (remember it's a phone, not a gaming rig). I'm sure it's not the most efficient way to achieve this behavior so I'm totally open for criticism of my programming skills in the comments, but here my problem: When I make I character jump, what I do is that I put his dy to a negative value, say -200 and I set the boolean jumping to true, that makes the character go up, and then I have this function called checkGravity() that ensure that everything that goes up has to go down, checkGravity also checks for the character being over platforms so I will strip it down a little for the sake of your time: public void checkGravity() { if (this.jumping) { this.jumpSpeed += 10; if (this.jumpSpeed > 0) { this.jumping = false; this.falling = true; } this.dy = this.jumpSpeed; } if (this.falling) { this.jumpSpeed += 10; if (this.jumpSpeed > 200) this.jumpSpeed = 200; this.dy = this.jumpSpeed; if (this.collidesWithPlatform()) { this.falling = false; this.standing = true; this.jumping = false; this.jumpSpeed = 0; this.dy = this.jumpSpeed; } } } So, the problem is, that this function updates the dy regardless of the diff, making the characters fly like Superman in slow machines, and I have no idea how to implement the diff factor so that when a character is jumping, his speed decrement in a proportional way to the game speed. Can anyone help me fix this issue? or give me pointers on how to make a 2D Jump in J2ME the right way. Thank you very much for your time.

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• Display an Image using C# in Web Application

  - by Josh

  Hello again, I have a Web Application that I built a C# class in that generates a Report. This report takes nearly 40 seconds to generate because it searches hundreds of folders for certain files. So I was hoping there was a way to display a "Loading.." icon as this report is generating. I have a gif stored in my Images folder that would be perfect. The research that I've done at this point mostly talks about picturebox's and image controls that can hold the image but I was hoping there was just a way of displaying the image above the report while its being created. The Web Application is from a Web ADF Geocortex website and again I created a C# class that generates this report. Below is some code that may help. /// <summary> /// Generates HTML for the current report using the data in /// the given table. /// </summary> /// <param name="reportLayers">The layers to include in the report.</param> /// <returns> public override string GenerateReportHtml(List<ReportLayer> reportLayers) { StringBuilder htmlString = new StringBuilder(); StringWriter stringWriter = new StringWriter(htmlString); HtmlTextWriter writer = new HtmlTextWriter(stringWriter); string holdAPI = ""; List<string> exclusions = GetExcludedFields(); foreach (ReportLayer layer in reportLayers) { string[] strFiles = null; Boolean val = false; if (layer.Layer.Name == "Bottom Hole Location (OP)") writer.RenderBeginTag(HtmlTextWriterTag.P); // <p> writer.RenderBeginTag(HtmlTextWriterTag.Strong); // <strong> writer.Write(layer.Layer.Name); writer.RenderEndTag(); // end </strong> writer.RenderEndTag(); // end </p> writer.WriteBreak(); // <br /> foreach (ReportFeature feature in layer.ReportFeatures) { // each feature will be in a table writer.RenderBeginTag(HtmlTextWriterTag.Table); // <table> foreach (ReportField field in feature.ReportFields) { string fieldName = field.Alias; if (!exclusions.Contains(fieldName)) {

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• java timer on current instance

  - by hspim

  import java.util.Scanner; import java.util.Timer; import java.util.TimerTask; public class Boggle { Board board; Player player; Timer timer; boolean active; static Scanner in = new Scanner(System.in); public Boggle() { board = new Board(4); timer = new Timer(); } public void newGame() { System.out.println("Please enter your name: "); String line = in.nextLine(); player = new Player(line); active = true; board.shuffle(); System.out.println(board); timer.schedule(new timesUP(), 20000); while(active) { String temp = in.nextLine(); player.addGuess(temp); } } public void endGame() { active = false; int score = Scoring.calculate(player, board); System.out.println(score); } class timesUP extends TimerTask { public void run() { endGame(); } } public static void main(String[] args) { Boggle boggle = new Boggle(); boggle.newGame(); } } I have the above class which should perform a loop for a given length of time and afterwards invoke an instance method. Essentially I need the loop in newGame() to run for a minute or so before endGame() is invoked on the current instance. However, using the Timer class I'm not sure how I would invoke the method I need on the current instance since I can't pass any parameters to the timertasks run method? Is there an easy way to do this or am I going about this the wrong way? (note: this is a console project only, no GUI) ========== code edited I've changed the code to the above following the recommendations, and it works almost as I expect however the thread still doesnt seem to end properly. I was the while loop would die and control would eventually come back to the main method. Any ideas?

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• Exception: attempt to acquire a reference on a close SQLiteClosable

  - by CommonsWare

  I posted this back in May on the [android-developers] Google Group. I never heard back and was not able to reproduce the problem until one of my students did last week. I figured I'd post it here and see if it rang any bells for anyone. In one of my code samples, I have the following method: static Cursor getAll(SQLiteDatabase db, String orderBy) { return(db.rawQuery("SELECT * FROM restaurants "+orderBy, null)); } When I run it, sporadically, I get this: 05-01 14:45:05.849: ERROR/AndroidRuntime(1145): java.lang.IllegalStateException: attempt to acquire a reference on a close SQLiteClosable 05-01 14:45:05.849: ERROR/AndroidRuntime(1145): at android.database.sqlite.SQLiteClosable.acquireReference(SQLiteClosable.java:31) 05-01 14:45:05.849: ERROR/AndroidRuntime(1145): at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:56) 05-01 14:45:05.849: ERROR/AndroidRuntime(1145): at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:49) 05-01 14:45:05.849: ERROR/AndroidRuntime(1145): at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:49) 05-01 14:45:05.849: ERROR/AndroidRuntime(1145): at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1118) 05-01 14:45:05.849: ERROR/AndroidRuntime(1145): at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1092) 05-01 14:45:05.849: ERROR/AndroidRuntime(1145): at apt.tutorial.Restaurant.getAll(Restaurant.java:14) This makes no sense to me. The database is definitely open. The SQLiteClosable is the SQLiteQuery created by SQLiteQueryDriver, and I see no evidence that there is an object pool or something going on here that might explain how a "new" SQLiteClosable is already closed. The fact that it is sporadic (meaning the same UI operations sometimes trigger the exception, but not always) suggests some sort of pool, race condition, or something...but I'm not sure where. Thoughts? Thanks! UPDATE: The code in question is from the LunchList tutorials out of my Android Programming Tutorials book. It's a bit spread out and not terribly suitable for posting directly in SO. You can download the code for that book from the above link if you want to take a look at it. I do not recall exactly which edition of the tutorial the student was working on at the time, though it was in the Tutorial 12-Tutorial 16 range. I was mostly hoping to run across somebody who had tripped over this problem before and had a likely culprit. I'm fairly certain my database is open. Thanks again!

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• Can't get InputStream read to block...

  - by mark dufresne

  I would like the input stream read to block instead of reading end of stream (-1). Is there a way to configure the stream to do this? Here's my Servlet code: PrintWriter out = response.getWriter(); BufferedReader in = request.getReader(); try { String line; int loop = 0; while (loop < 20) { line = in.readLine(); lgr.log(Level.INFO, line); out.println("<" + loop + "html>"); Thread.sleep(1000); loop++; // } } catch (InterruptedException ex) { lgr.log(Level.SEVERE, null, ex); } finally { out.close(); } Here's my Midlet code: private HttpConnection conn; InputStream is; OutputStream os; private boolean exit = false; public void run() { String url = "http://localhost:8080/WebApplication2/NewServlet"; try { conn = (HttpConnection) Connector.open(url); is = conn.openInputStream(); os = conn.openOutputStream(); StringBuffer sb = new StringBuffer(); int c; while (!exit) { os.write("<html>\n".getBytes()); while ((c = is.read()) != -1) { sb.append((char) c); } System.out.println(sb.toString()); sb.delete(0, sb.length() - 1); try { Thread.sleep(1000); } catch (InterruptedException ex) { ex.printStackTrace(); } } os.close(); is.close(); conn.close(); } catch (IOException ex) { ex.printStackTrace(); } } I've tried InputStream.read, but it doesn't block either, it returns -1 as well. I'm trying to keep the I/O streams on either side alive. I want the servlet to wait for input, process the input, then send back a response. In the code above it should do this 20 times. thanks for any help

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• Blackberry ListField Text Wrapping - only two lines.

  - by Diego Tori

  Within my ListField, I want to be able to take any given long String, and just be able to wrap the first line within the width of the screen, and just take the remaining string and display it below and ellipsis the rest. Right now, this is what I'm using to detect wrapping within my draw paint call: int totalWidth = 0; int charWidth = 0; int lastIndex = 0; int spaceIndex = 0; int lineIndex = 0; String firstLine = ""; String secondLine = ""; boolean isSecondLine = false; for (int i = 0; i < longString.length(); i++){ charWidth = Font.getDefault().getAdvance(String.valueOf(longString.charAt(i))); //System.out.println("char width: " + charWidth); if(longString.charAt(i) == ' ') spaceIndex = i; if((charWidth + totalWidth) > (this.getWidth()-32)){ //g.drawText(longString.substring(lastIndex, spaceIndex), xpos, y +_padding, DrawStyle.LEFT, w - xpos); lineIndex++; System.out.println("current lines to draw: " + lineIndex); /*if (lineIndex = 2){ int idx = i; System.out.println("first line " + longString.substring(lastIndex, spaceIndex)); System.out.println("second line " + longString.substring(spaceIndex+1, longString.length())); }*/ //firstLine = longString.substring(lastIndex, spaceIndex); firstLine = longString.substring(0, spaceIndex); //System.out.println("first new line: " +firstLine); //isSecondLine=true; //xpos = 0; //y += Font.getDefault().getHeight(); i = spaceIndex + 1; lastIndex = i; System.out.println("Rest of string: " + longString.substring(lastIndex, longString.length())); charWidth = 0; totalWidth = 0; } totalWidth += charWidth; System.out.println("total width: " + totalWidth); //g.drawText(longString.substring(lastIndex, i+1), xpos, y + (_padding*3)+4, DrawStyle.ELLIPSIS, w - xpos); //secondLine = longString.substring(lastIndex, i+1); secondLine = longString.substring(lastIndex, longString.length()); //isSecondLine = true; } Now this does a great job of actually wrapping any given string (assuming the y values were properly offsetted and it only drew the text after the string width exceeded the screen width, as well as the remaining string afterwards), however, every time I try to get the first two lines, it always ends up returning the last two lines of the string if it goes beyond two lines. Is there a better way to do this sort of thing, since I am fresh out of ideas?

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• Scrolling RelativeLayout- white border over part of the content

  - by Tanis.7x

  I have a fairly simply Fragment that adds a handful of colored ImageViews to a RelativeLayout. There are more images than can fit on screen, so I implemented some custom scrolling. However, When I scroll around, I see that there is an approximately 90dp white border overlapping part of the content right where the edges of the screen are before I scroll. It is obvious that the ImageViews are still being created and drawn properly, but they are being covered up. How do I get rid of this? I have tried: Changing both the RelativeLayout and FrameLayout to WRAP_CONTENT, FILL_PARENT, MATCH_PARENT, and a few combinations of those. Setting the padding and margins of both layouts to 0dp. Example: Fragment: public class MyFrag extends Fragment implements OnTouchListener { int currentX; int currentY; RelativeLayout container; final int[] colors = {Color.BLACK, Color.RED, Color.BLUE}; @Override public View onCreateView(LayoutInflater inflater, ViewGroup fragContainer, Bundle savedInstanceState) { return inflater.inflate(R.layout.fragment_myfrag, null); } @Override public void onActivityCreated(Bundle savedInstanceState) { super.onActivityCreated(savedInstanceState); container = (RelativeLayout) getView().findViewById(R.id.container); container.setOnTouchListener(this); // Temp- Add a bunch of images to test scrolling for(int i=0; i<1500; i+=100) { for (int j=0; j<1500; j+=100) { int color = colors[(i+j)%3]; ImageView image = new ImageView(getActivity()); image.setScaleType(ImageView.ScaleType.CENTER); image.setBackgroundColor(color); LayoutParams lp = new RelativeLayout.LayoutParams(100, 100); lp.setMargins(i, j, 0, 0); image.setLayoutParams(lp); container.addView(image); } } } @Override public boolean onTouch(View v, MotionEvent event) { switch (event.getAction()) { case MotionEvent.ACTION_DOWN: { currentX = (int) event.getRawX(); currentY = (int) event.getRawY(); break; } case MotionEvent.ACTION_MOVE: { int x2 = (int) event.getRawX(); int y2 = (int) event.getRawY(); container.scrollBy(currentX - x2 , currentY - y2); currentX = x2; currentY = y2; break; } case MotionEvent.ACTION_UP: { break; } } return true; } } XML: <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="fill_parent" android:layout_height="fill_parent" tools:context=".FloorPlanFrag"> <RelativeLayout android:id="@+id/container" android:layout_width="fill_parent" android:layout_height="fill_parent" /> </FrameLayout>

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• XML Schema for a .NET type that inherits and implements

  - by John Ruiz

  Hi, Please consider the following three .NET types: I have an interface, an abstract class, and a concrete class. My question is how to write the XML Schema to include the properties from the interface and from the abstract class. public interface IStartable { bool RequiresKey { get; set; } void Start(object key); } public abstract class Vehicle { uint WheelCount { get; set; } } public class Car : Vehicle, IStartable { public bool RequiresKey { get; set; } public string Make { get; set; } publilc string Model { get; set; } public Car() {} public void Start(object key) { // start car with key } } I don't know how to complete this schema: <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="cars" xmlns="cars" xmlns:c="cars"> <!-- How do I get car to have vehicle's wheelcount AND IStartable's RequiresKey? --> <xs:element name="Car" type="c:Car" /> <xs:complexType name="Car"> <xs:complexContent> <xs:extension base="c:Vehicle"> <xs:group ref=c:CarGroup" /> </xs:extension> </xs:complexContent> </xs:complexType> <xs:group name="CarGroup"> <xs:sequence> <xs:element name="Make" type="xs:token" /> <xs:element name="Model" type="xs:token" /> </xs:sequence> </xs:group> <xs:complexType name="Vehicle"> <xs:sequence> <xs:element name="WheelCount" type="xs:unsignedInt" /> </xs:sequence> </xs:complexType> <xs:complexType name="IStartable"> <xs:sequence> <xs:element name="RequiresKey" type="xs:boolean" /> </xs:sequence> </xs:complexType> </xs:schema>

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• How to maxmise the largest contiguous block of memory in the Large Object Heap

  - by Unsliced

  The situation is that I am making a WCF call to a remote server which is returns an XML document as a string. Most of the time this return value is a few K, sometimes a few dozen K, very occasionally a few hundred K, but very rarely it could be several megabytes (first problem is that there is no way for me to know). It's these rare occasions that are causing grief. I get a stack trace that starts: System.OutOfMemoryException: Exception of type 'System.OutOfMemoryException' was thrown. at System.Xml.BufferBuilder.AddBuffer() at System.Xml.BufferBuilder.AppendHelper(Char* pSource, Int32 count) at System.Xml.BufferBuilder.Append(Char[] value, Int32 start, Int32 count) at System.Xml.XmlTextReaderImpl.ParseText() at System.Xml.XmlTextReaderImpl.ParseElementContent() at System.Xml.XmlTextReaderImpl.Read() at System.Xml.XmlTextReader.Read() at System.Xml.XmlReader.ReadElementString() at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationReaderMDRQuery.Read2_getMarketDataResponse() at Microsoft.Xml.Serialization.GeneratedAssembly.ArrayOfObjectSerializer2.Deserialize(XmlSerializationReader reader) at System.Xml.Serialization.XmlSerializer.Deserialize(XmlReader xmlReader, String encodingStyle, XmlDeserializationEvents events) at System.Xml.Serialization.XmlSerializer.Deserialize(XmlReader xmlReader, String encodingStyle) at System.Web.Services.Protocols.SoapHttpClientProtocol.ReadResponse(SoapClientMessage message, WebResponse response, Stream responseStream, Boolean asyncCall) at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters) I've read around and it is because the Large Object Heap is just getting too fragmented, so even preceding the call with a quick check to StringBuilder.EnsureCapacity just causes the OutOfMemoryException to be thrown earlier (and because I'm guessing at what's needed, it might not actually need that much so my check is causing more problems than it is solving). Some opinions are that there's not much I can do about it. Some of the questions I've asked myself: Use less memory - have you checked for leaks? Yes. The memory usage goes up and down, but there's no fundamental growth that guarantees this to happen. Some of the times it fails, it succeeded at that stage previously. Transfer smaller amounts Not an option, this is a third party web service over which I have no control (or at least it would take a long time to resolve, in the meantime I still have a problem) Can you do something to the LOH to make it less likely to fail? ... now this is most fruitful course. It's a 32-bit process (it has to be for various political, technical and boring reasons) but there's normally hundreds of meg free (multiples of the largest amount for which we've seen failures). Can we monitor the LOH? Using perfmon I can track the size of the heaps, but I don't think there's a way to monitor the largest available contiguous block of memory. Question is: any advice or suggestions for things to try?

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• How do I display a jquery dialog box before the entire page is loaded?

  - by obarshay

  On my site a number of operations can take a long time to complete. When I know a page will take a while to load, I would like to display a progress indicator while the page is loading. Ideally I would like to say something along the lines of: $("#dialog").show("progress.php"); and have that overlay on top of the page that is being loaded (disappearing after the operation is completed). Coding the progress bar and displaying progress is not an issue, the issue is getting a progress indicator to pop up WHILE the page is being loaded. I have been trying to use JQuery's dialogs for this but they only appear after the page is already loaded. This has to be a common problem but I am not familiar enough with JavaScript to know the best way to do this. Here's simple example to illustrate the problem. The code below fails to display the dialog box before the 20 second pause is up. I have tried in Chrome and Firefox. In fact I don't even see the "Please Wait..." text. Here's the code I am using: <html> <head> <link type="text/css" href="http://jqueryui.com/latest/themes/base/ui.all.css" rel="stylesheet" /> <script type="text/javascript" src="http://jqueryui.com/latest/jquery-1.3.2.js"></script> <script type="text/javascript" src="http://jqueryui.com/latest/ui/ui.core.js"></script> <script type="text/javascript" src="http://jqueryui.com/latest/ui/ui.dialog.js"></script> </head> <body> <div id="please-wait">My Dialog</div> <script type="text/javascript"> $("#please-wait").dialog(); </script> <?php flush(); echo "Waiting..."; sleep(20); ?> </body> </html>

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• Android: roatating images in a loop.

  - by user573736

  Hello, I am trying with no success to modify the code example from: http://www.inter-fuser.com/2009/08/android-animations-3d-flip.html so it will rotate the images in a loop, when clicking on the image once. (second click should pause). I tried using Handler and threading but cannot update the view since only the main thread can update UI. Exception I get from the code below: android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views. [in 'image1.startAnimation(rotation);' ('applyRotation(0, 90);' from the main thread)] package com.example.flip3d; import android.app.Activity; import android.os.Bundle; import android.view.View; import android.view.animation.AccelerateInterpolator; import android.widget.ImageView; public class Flip3d extends Activity { private ImageView image1; private ImageView image2; private boolean isFirstImage = true; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); image1 = (ImageView) findViewById(R.id.image01); image2 = (ImageView) findViewById(R.id.image02); image2.setVisibility(View.GONE); image1.setOnClickListener(new View.OnClickListener() { public void onClick(View view) { if (isFirstImage) { applyRotation(0, 90); isFirstImage = !isFirstImage; } else { applyRotation(0, -90); isFirstImage = !isFirstImage; } } }); } private void applyRotation(float start, float end) { // Find the center of image final float centerX = image1.getWidth() / 2.0f; final float centerY = image1.getHeight() / 2.0f; // Create a new 3D rotation with the supplied parameter // The animation listener is used to trigger the next animation final Flip3dAnimation rotation = new Flip3dAnimation(start, end, centerX, centerY); rotation.setDuration(500); rotation.setFillAfter(true); rotation.setInterpolator(new AccelerateInterpolator()); rotation.setAnimationListener(new DisplayNextView(isFirstImage, image1, image2)); if (isFirstImage) { image1.startAnimation(rotation); } else { image2.startAnimation(rotation); } } } How can I manage to update the UI and control the rotation within onClick listener? Thank you, Oakist

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• C# Select clause returns system exception instead of relevant object

  - by Kashif

  I am trying to use the select clause to pick out an object which matches a specified name field from a database query as follows: objectQuery = from obj in objectList where obj.Equals(objectName) select obj; In the results view of my query, I get: base {System.SystemException} = {"Boolean Equals(System.Object)"} Where I should be expecting something like a Car, Make, or Model Would someone please explain what I am doing wrong here? The method in question can be seen here: // this function searches the database's table for a single object that matches the 'Name' property with 'objectName' public static T Read<T>(string objectName) where T : IEquatable<T> { using (ISession session = NHibernateHelper.OpenSession()) { IQueryable<T> objectList = session.Query<T>(); // pull (query) all the objects from the table in the database int count = objectList.Count(); // return the number of objects in the table // alternative: int count = makeList.Count<T>(); IQueryable<T> objectQuery = null; // create a reference for our queryable list of objects T foundObject = default(T); // create an object reference for our found object if (count > 0) { // give me all objects that have a name that matches 'objectName' and store them in 'objectQuery' objectQuery = from obj in objectList where obj.Equals(objectName) select obj; // make sure that 'objectQuery' has only one object in it try { foundObject = (T)objectQuery.Single(); } catch { return default(T); } // output some information to the console (output screen) Console.WriteLine("Read Make: " + foundObject.ToString()); } // pass the reference of the found object on to whoever asked for it return foundObject; } } Note that I am using the interface "IQuatable<T>" in my method descriptor. An example of the classes I am trying to pull from the database is: public class Make: IEquatable<Make> { public virtual int Id { get; set; } public virtual string Name { get; set; } public virtual IList<Model> Models { get; set; } public Make() { // this public no-argument constructor is required for NHibernate } public Make(string makeName) { this.Name = makeName; } public override string ToString() { return Name; } // Implementation of IEquatable<T> interface public virtual bool Equals(Make make) { if (this.Id == make.Id) { return true; } else { return false; } } // Implementation of IEquatable<T> interface public virtual bool Equals(String name) { if (this.Name.Equals(name)) { return true; } else { return false; } } } And the interface is described simply as: public interface IEquatable<T> { bool Equals(T obj); }

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• How can I make this client as a multithread client?

  - by Johanna

  Hi, I have read a lot about multithread client but for this one,I can not make it multithread! would you please help me? public class MainClient implements Runnable{ private static InformationClass info = new InformationClass(); private static Socket c; private static String text; public static String getText() { return text; } public static void setText(String text) { MainClient.text = text; } private static PrintWriter os; private static BufferedReader is; static boolean closed = false; /** * @param args the command line arguments */ public static void main(String[] args) { MainFrame farme = new MainFrame(); farme.setVisible(true); try { c = new Socket("localhost", 5050); os = new PrintWriter(c.getOutputStream(), true); is = new BufferedReader(new InputStreamReader(c.getInputStream())); } catch (UnknownHostException ex) { Logger.getLogger(MainClient.class.getName()).log(Level.SEVERE, null, ex); } catch (IOException ex) { Logger.getLogger(MainClient.class.getName()).log(Level.SEVERE, null, ex); } } public static void active() { String teXt = MainClient.getText(); System.out.println(teXt); os.println(teXt); try { String line = is.readLine(); System.out.println("Text received: " + line); os.flush(); is.close(); is.close(); c.close(); } catch (IOException ex) { Logger.getLogger(MainClient.class.getName()).log(Level.SEVERE, null, ex); } } } also active method will be called when the client write something on the text area and then clicks on the send button. 2) also i have a question that: in the other class I have this action performed for my send button,does it mean that client is multithread?? private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) { new Thread(new Runnable() { @Override public void run() { // This gets run in a background thread String text = jTextArea1.getText(); jTextArea2.append(client.getCurrentName() + " : " + text + "\n"); MainClient.setText(client.getCurrentName() + " : " + text + "\n"); clear(); MainClient.active(); } }).start(); } Last EDIT: this is my active method: public static void active() { String teXt = MainClient.getText(); os.println(teXt); String line = is.readLine(); System.out.println("Text received: " + line); os.flush(); is.close(); is.close(); c.close(); }

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• Overwhelmed by design patterns... where to begin?

  - by Pete

  I am writing a simple prototype code to demonstrate & profile I/O schemes (HDF4, HDF5, HDF5 using parallel IO, NetCDF, etc.) for a physics code. Since focus is on IO, the rest of the program is very simple: class Grid { public: floatArray x,y,z; }; class MyModel { public: MyModel(const int &nip1, const int &njp1, const int &nkp1, const int &numProcs); Grid grid; map<string, floatArray> plasmaVariables; }; Where floatArray is a simple class that lets me define arbitrary dimensioned arrays and do mathematical operations on them (i.e. x+y is point-wise addition). Of course, I could use better encapsulation (write accessors/setters, etc.), but that's not the concept I'm struggling with. For the I/O routines, I am envisioning applying simple inheritance: Abstract I/O class defines read & write functions to fill in the "myModel" object HDF4 derived class HDF5 HDF5 using parallel IO NetCDF etc... The code should read data in any of these formats, then write out to any of these formats. In the past, I would add an AbstractIO member to myModel and create/destroy this object depending on which I/O scheme I want. In this way, I could do something like: myModelObj.ioObj->read('input.hdf') myModelObj.ioObj->write('output.hdf') I have a bit of OOP experience but very little on the Design Patterns front, so I recently acquired the Gang of Four book "Design Patterns: Elements of Reusable Object-Oriented Software". OOP designers: Which pattern(s) would you recommend I use to integrate I/O with the myModel object? I am interested in answering this for two reasons: To learn more about design patterns in general Apply what I learn to help refactor an large old crufty/legacy physics code to be more human-readable & extensible. I am leaning towards applying the Decerator pattern to myModel, so I can attach the I/O responsibilities dynamically to myModel (i.e. whether to use HDF4, HDF5, etc.). However, I don't feel very confident that this is the best pattern to apply. Reading the Gang of Four book cover-to-cover before I start coding feels like a good way to develop an unhealthy caffeine addiction. What patterns do you recommend?

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• translating specifications into query predicates

  - by Jeroen

  I'm trying to find a nice and elegant way to query database content based on DDD "specifications". In domain driven design, a specification is used to check if some object, also known as the candidate, is compliant to a (domain specific) requirement. For example, the specification 'IsTaskDone' goes like: class IsTaskDone extends Specification<Task> { boolean isSatisfiedBy(Task candidate) { return candidate.isDone(); } } The above specification can be used for many purposes, e.g. it can be used to validate if a task has been completed, or to filter all completed tasks from a collection. However, I want to re-use this, nice, domain related specification to query on the database. Of course, the easiest solution would be to retrieve all entities of our desired type from the database, and filter that list in-memory by looping and removing non-matching entities. But clearly that would not be optimal for performance, especially when the entity count in our db increases. Proposal So my idea is to create a 'ConversionManager' that translates my specification into a persistence technique specific criteria, think of the JPA predicate class. The services looks as follows: public interface JpaSpecificationConversionManager { <T> Predicate getPredicateFor(Specification<T> specification, Root<T> root, CriteriaQuery<?> cq, CriteriaBuilder cb); JpaSpecificationConversionManager registerConverter(JpaSpecificationConverter<?, ?> converter); } By using our manager, the users can register their own conversion logic, isolating the domain related specification from persistence specific logic. To minimize the configuration of our manager, I want to use annotations on my converter classes, allowing the manager to automatically register those converters. JPA repository implementations could then use my manager, via dependency injection, to offer a find by specification method. Providing a find by specification should drastically reduce the number of methods on our repository interface. In theory, this all sounds decent, but I feel like I'm missing something critical. What do you guys think of my proposal, does it comply to the DDD way of thinking? Or is there already a framework that does something identical to what I just described?

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• ASP.NET MVC CRUD PartialView Popup Issue

  - by Smiley Face

  I am creating an MVC website which makes use of Partial Views on Popups to handle all my CRUD transactions. Please note that my application can already handle these CRUD operations perfectly (LINQ-To-Entity). However, I have a problem with my popup forms. Below is the code from my _Add.cshtml: @model MyStore.Models.MyModels.ProductsModel @{ Layout = null; } @using (Ajax.BeginForm("_Add", "Products", new AjaxOptions { InsertionMode = InsertionMode.Replace, HttpMethod = "POST", OnSuccess = "addSuccess" }, new { @id = "addForm" })) { @Html.ValidationSummary(true) <div id="add-message" class="error invisible"></div> <fieldset> <legend>Products</legend> @Html.HiddenFor(m => Model.ProductCode) <div class="editor-label"> @Html.LabelFor(model => model.ProductName) </div> <div class="editor-field"> @Html.EditorFor(model => model.ProductName) @Html.ValidationMessageFor(model => model.ProductName) </div> <div class="editor-label"> @Html.LabelFor(model => model.Price) </div> <div class="editor-field"> @Html.TextBoxFor(model => model.Price) @Html.ValidationMessageFor(model => model.Price) </div> </fieldset> } Below is the code from my Controller: [HttpGet] public ActionResult _Add(string productCode) { ProductsModel model = newProductsModel(); model.ProductCode = ProductCode ; return PartialView(model); } [HttpPost] public JsonResult _Add(ProductsModel model) { if (ModelState.IsValid) { ProductsManager prod = new ProductsManager(); Products pa = new Products(); pa.ProductCode = model.ProductCode; pa.ProductName = model.ProductName; pa.Price = model.Price; prod.AddProduct(pa); return Json(HelperClass.SuccessResponse(pa), JsonRequestBehavior.AllowGet); } else { return Json(HelperClass.ErrorResponse("Please review your form"), JsonRequestBehavior.DenyGet); } } Please note that the _Add.cshtml is a partial view which is being rendered through a Popup.js which I found on the internet. It is rendered through this code: @Html.ActionLink("[Add Product]", "_Add", new { ProductCode = @ViewData["ProductCode"] }, new { @class = "editLink" }) This works okay. I mean it adds product to my database. But my problem is upon clicking the Proceed button, I get this pop-up download dialog from the page: Can somebody please help me with this? I have a hunch it's because of the HttpMethod i'm using (POST, PUT, GET, DELETE) but i'm not really sure which one is right to use or if it really is the problem in the first place. Any help would be greatly appreciated! PS. Sorry for the long post.

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• Using pointers, references, handles to generic datatypes, as generic and flexible as possible

  - by Patrick

  In my application I have lots of different data types, e.g. Car, Bicycle, Person, ... (they're actually other data types, but this is just for the example). Since I also have quite some 'generic' code in my application, and the application was originally written in C, pointers to Car, Bicycle, Person, ... are often passed as void-pointers to these generic modules, together with an identification of the type, like this: Car myCar; ShowNiceDialog ((void *)&myCar, DATATYPE_CAR); The 'ShowNiceDialog' method now uses meta-information (functions that map DATATYPE_CAR to interfaces to get the actual data out of Car) to get information of the car, based on the given data type. That way, the generic logic only has to be written once, and not every time again for every new data type. Of course, in C++ you could make this much easier by using a common root class, like this class RootClass { public: string getName() const = 0; }; class Car : public RootClass { ... }; void ShowNiceDialog (RootClass *root); The problem is that in some cases, we don't want to store the data type in a class, but in a totally different format to save memory. In some cases we have hundreds of millions of instances that we need to manage in the application, and we don't want to make a full class for every instance. Suppose we have a data type with 2 characteristics: A quantity (double, 8 bytes) A boolean (1 byte) Although we only need 9 bytes to store this information, putting it in a class means that we need at least 16 bytes (because of the padding), and with the v-pointer we possibly even need 24 bytes. For hundreds of millions of instances, every byte counts (I have a 64-bit variant of the application and in some cases it needs 6 GB of memory). The void-pointer approach has the advantage that we can almost encode anything in a void-pointer and decide how to use it if we want information from it (use it as a real pointer, as an index, ...), but at the cost of type-safety. Templated solutions don't help since the generic logic forms quite a big part of the application, and we don't want to templatize all this. Additionally, the data model can be extended at run time, which also means that templates won't help. Are there better (and type-safer) ways to handle this than a void-pointer? Any references to frameworks, whitepapers, research material regarding this?

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