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• Where do I start ?

  - by Panthe

  Brief History: Just graduated high school, learned a bit of python and C++, have no friends with any helpful computer knowledge at all. Out of anyone i met in my school years I was probably the biggest nerd, but no one really knew. I consider my self to have a vast amount of knowledge on computers and tech then the average person. built/fixed tons of computers, and ability to troubleshoot pretty much any problem I came across. Now that high school is over, Ive really been thinking about my career. Loving, living computers for the past 15 years of my life I decided to take my ability's and try to learn computer programming, why I didn't start earlier I don't know, seems to be big mistake on my part... Doing some research I concluded that Python was the first programming language I should learn, since it was high level and easier to understand then C++ and Java. I also knew that to become good at what I did I needed to know more then just 2 or 3 languages, which didn't seem like a big problem considering once I learned the way Python worked, mainly syntax changed, and the rest would come naturally. I watched a couple of youtube videos, downloaded some book pdf's and snooped around from some tutorials here and there to get the hang of what to do. A two solid weeks had passed of trying to understand the syntax, create small programs that used the basic functions and understanding how it worked, I think i have got the hang of it. It breaks down into what ive been dealing with all this time (although i kinda knew) is that, input,output, loops, functions and other things derived from 0's and 1's storing data and recalling it, ect. (A VERY BASIC IDEA). Ive been able to create small programs, Hangman, file storing, temperature conversion, Caeser Cipher decode/encoding, Fibonacci Sequence and more, which i can create and understand how each work. Being 2 weeks into this, I have learned alot. Nothing at all compared to what i should be learning in the years to come if i get a grip on what I'm doing. While doing these programs I wont stop untill I've done doing a practice problem on a book, which embarresing enough will take me a couple hour depending on the complexity of it. I absolutly will not put aside the challenge until its complete, WHICH CAN BE EXTREMELY DRAINING, ive tried most problems without cheating and reached success, which makes me feel extremely proud of my self after completing something after much trial and error. After all this I have met the demon, alogrithm's which seem to be key to effiecent code. I cant seem to rap my head around some of the computer codes people put out there using numbers, and sometimes even basic functions, I have been able to understand them after a while but i know there are alot more complex things to come, considering my self smart, functions that require complex codes, actually hurt my brain. NOTHING EVER IN LIFE HURT MY BRAIN....... not even math classes in highschool, trying to understand some of the stuff people put out there makes me feel like i have a mental disadvantage lol... i still walk forward though, crossing my fingers that the understanding will come with time. Sorry if is this is long i just wish someone takes all these things into consideration when answering my question. even through all these downsides im still pushing through and continuing to try and get good at this, i know reading these tutorials wont make me any good unless i can become creative and make my own, understand other peoples programs, so this leads me to the simple question i could have asked in the beginning..... WHERE IN THE WORLD DO I START ? Ive been trying to find out how to understand some of the open source projects, how i can work with experianced coders to learn from them and help them, but i dont think thats even possible by the way how far people's knowledge is compared to me, i have no freinds who i can learn from, can someone help me and guide me into the right direction.. i have a huge motivation to get good at coding, anything information would be extremely helpful

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• Detecting Acceleration in a car (iPhone Accelerometer)

  - by TheGazzardian

  Hello, I am working on an iPhone app where we are trying to calculate the acceleration of a moving car. Similar apps have accomplished this (Dynolicious), but the difference is that this app is designed to be used during general city driving, not on a drag strip. This leads us to one big concern that Dynolicious was luckily able to avoid: hills. Yes, hills. There are two important stages to this: calibration, and actual driving. Our initial run was simple and suffered the consequences. During the calibration stage, I took the average force on the phone, and during running, I just subtracted the average force from the current force to get the current acceleration this frame. The problem with this is that the typical car receives much more force than just the forward force - everything from turning to potholes was causing the values to go out of sync with what was really happening. The next run was to add the condition that the iPhone must be oriented in such a way that the screen was facing toward the back of the car. Using this method, I attempted to follow only force on the z-axis, but this obviously lead to problems unless the iPhone was oriented directly upright, because of gravity. Some trigonometry later, and I had managed to work gravity out of the equation, so that the car was actually being read very, very well by the iPhone. Until I hit a slope. As soon as the angle of the car changed, suddenly I was receiving accelerations and decelerations that didn't make sense, and we were once again going out of sync. Talking with someone a lot smarter than me at math lead to a solution that I have been trying to implement for longer than I would like to admit. It's steps are as follows: 1) During calibration, measure gravity as a vector instead of a size. Store that vector. 2) When the car initially moves forward, take the vector of motion and subtract gravity. Use this as the forward momentum. (Ignore, for now, the user cases where this will be difficult and let's concentrate on the math :) 3) From the forward vector and the gravity vector, construct a plane. 4) Whenever a force is received, project it onto said plane to get rid of sideways force/etc. 5) Then, use that force, the known magnitude of gravity, and the known direction of forward motion to essentially solve a triangle to get the forward vector. The problem that is causing the most difficulty in this new system is not step 5, which I have gotten to the point where all the numbers look as they should. The difficult part is actually the detection of the forward vector. I am selecting vectors whose magnitude exceeds gravity, and from there, averaging them and subtracting gravity. (I am doing some error checking to make sure that I am not using a force just because the iPhone accelerometer was off by a bit, which happens more frequently than I would like). But if I plot these vectors that I am using, they actually vary by an angle of about 20-30 degrees, which can lead to some strong inaccuracies. The end result is that the app is even more inaccurate now than before. So basically - all you math and iPhone brains out there - any glaring errors? Any potentially better solutions? Any experience that could be useful at all? Award: offering a bounty of $250 to the first answer that leads to a solution.

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• Java Applet Deployment, ClassNotFoundException (primary class)

  - by Matt

  This is driving me up the wall. I have checked and rechecked spelling and paths. I have tried just about every combination of paths, including relative, absolute, and full http paths. I continue to get the following error when trying to load a Java applet: java.lang.ClassNotFoundException: AppletClient.class at sun.plugin2.applet.Applet2ClassLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at sun.plugin2.applet.Plugin2ClassLoader.loadCode(Unknown Source) at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source) at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source) at java.lang.Thread.run(Unknown Source) Exception: java.lang.ClassNotFoundException: AppletClient.class The HTML used to load the applet: <applet width="100" height="100" archive="applet/myapplet.jar, applet/applet_dependency.jar" code="AppletClient.class"> <param value="blahblah" name="username"> <param value="false" name="codebase_lookup"> </applet> The applet is in a relative directory, "applet", from the path of the current page. I have unzipped the jar file and can see AppletClient.class. Also, in the source of the project, it is spelled that way (casing and all). I have tried with/without the parameters. I have changed the names of the archive jars in the applet include tag just to see if I get a different error for bad file names (same error). I have manually done GETs on the jars to make sure the server is responding to the requests (it is). I have tried with and without the codebase tag, with all different varieties of paths (start getting bad "magic number" errors on those). I know that this error sometimes pops up when a dependency fails to load, so it can be misleading, but all dependencies are present, accounted for, and are fetchable via manual GETs. Between each and every attempt I always clear my cache in FireFox. These problems are reproduced in IE8 and Chrome as well. Per my Java Console from the browser, I am running Java Plug-in 1.6.0_20. This is from the same machine that I develop the applet on, which runs fine via Eclipse. Finally, I kicked on Fiddler2, and I don't see a single request for the jar files anywhere The host site is running from my Visual Studio debugger, so it's running on localhost. But I see the requests for all the other resources on Fiddler. Just... no Jars. ANYWHERE. I clear the log, cleared my browser cache, and did a ctrl-R refresh. And still, not a single Jar request on the Fiddler log. I even did a delayed write (with JS) of the applet tag after the page loaded, once all the Fiddler activity slowed down. The element gets written to the document (and I can see the 100x100 Java error window), but not a single request shows up on Fiddler. Any suggestions, before I go crawl into the corner and cry myself to sleep? EDIT: From the Java console, if I hit "l" (el) to "dump classloader list", I see something that looks like this: Live entry: key=http://localhost:55446/BaseWebSite/,http://localhost:55446/BaseWebSite/applet/myappliet.jar, http://localhost:55446/BaseWebSite/applet/applet_dependency.jar, refCount=1, threadGroup=sun.plugin2.applet.Applet2ThreadGroup[name=http://localhost:55446/BaseWebSite/-threadGroup,maxpri=4]

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• UI not updated while using ProgressMonitorInputStream in Swing to monitor compressed file decompress

  - by Bozhidar Batsov

  I'm working on swing application that relies on an embedded H2 database. Because I don't want to bundle the database with the app(the db is frequently updated and I want new users of the app to start with a recent copy), I've implemented a solution which downloads a compressed copy of the db the first time the application is started and extracts it. Since the extraction process might be slow I've added a ProgressMonitorInputStream to show to progress of the extraction process - unfortunately when the extraction starts, the progress dialog shows up but it's not updated at all. It seems like to events are getting through to the event dispatch thread. Here is the method: public static String extractDbFromArchive(String pathToArchive) { if (SwingUtilities.isEventDispatchThread()) { System.out.println("Invoking on event dispatch thread"); } // Get the current path, where the database will be extracted String currentPath = System.getProperty("user.home") + File.separator + ".spellbook" + File.separator; LOGGER.info("Current path: " + currentPath); try { //Open the archive FileInputStream archiveFileStream = new FileInputStream(pathToArchive); // Read two bytes from the stream before it used by CBZip2InputStream for (int i = 0; i < 2; i++) { archiveFileStream.read(); } // Open the gzip file and open the output file CBZip2InputStream bz2 = new CBZip2InputStream(new ProgressMonitorInputStream( null, "Decompressing " + pathToArchive, archiveFileStream)); FileOutputStream out = new FileOutputStream(ARCHIVED_DB_NAME); LOGGER.info("Decompressing the tar file..."); // Transfer bytes from the compressed file to the output file byte[] buffer = new byte[1024]; int len; while ((len = bz2.read(buffer)) > 0) { out.write(buffer, 0, len); } // Close the file and stream bz2.close(); out.close(); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException ex) { ex.printStackTrace(); } try { TarInputStream tarInputStream = null; TarEntry tarEntry; tarInputStream = new TarInputStream(new ProgressMonitorInputStream( null, "Extracting " + ARCHIVED_DB_NAME, new FileInputStream(ARCHIVED_DB_NAME))); tarEntry = tarInputStream.getNextEntry(); byte[] buf1 = new byte[1024]; LOGGER.info("Extracting tar file"); while (tarEntry != null) { //For each entry to be extracted String entryName = currentPath + tarEntry.getName(); entryName = entryName.replace('/', File.separatorChar); entryName = entryName.replace('\\', File.separatorChar); LOGGER.info("Extracting entry: " + entryName); FileOutputStream fileOutputStream; File newFile = new File(entryName); if (tarEntry.isDirectory()) { if (!newFile.mkdirs()) { break; } tarEntry = tarInputStream.getNextEntry(); continue; } fileOutputStream = new FileOutputStream(entryName); int n; while ((n = tarInputStream.read(buf1, 0, 1024)) > -1) { fileOutputStream.write(buf1, 0, n); } fileOutputStream.close(); tarEntry = tarInputStream.getNextEntry(); } tarInputStream.close(); } catch (Exception e) { } currentPath += "db" + File.separator + DB_FILE_NAME; if (!currentPath.isEmpty()) { LOGGER.info("DB placed in : " + currentPath); } return currentPath; } This method gets invoked on the event dispatch thread (SwingUtilities.isEventDispatchThread() returns true) so the UI components should be updated. I haven't implemented this as an SwingWorker since I need to wait for the extraction anyways before I can proceed with the initialization of the program. This method get invoked before the main JFrame of the application is visible. I don't won't a solution based on SwingWorker + property changed listeners - I think that the ProgressMonitorInputStream is exactly what I need, but I guess I'm not doing something right. I'm using Sun JDK 1.6.18. Any help would be greatly appreciated.

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• Why are transactions not rolling back when using SpringJUnit4ClassRunner/MySQL/Spring/Hibernate

  - by Trevor

  I am doing unit testing and I expect that all data committed to the MySQL database will be rolled back... but this isn't the case. The data is being committed, even though my log was showing that the rollback was happening. I've been wrestling with this for a couple days so my setup has changed quite a bit, here's my current setup. LoginDAOTest.java: @RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration(locations={"file:web/WEB-INF/applicationContext-test.xml", "file:web/WEB-INF/dispatcher-servlet-test.xml"}) @TransactionConfiguration(transactionManager = "transactionManager", defaultRollback = true) public class UserServiceTest { private UserService userService; @Test public void should_return_true_when_user_is_logged_in () throws Exception { String[] usernames = {"a","b","c","d"}; for (String username : usernames) { userService.logUserIn(username); assertThat(userService.isUserLoggedIn(username), is(equalTo(true))); } } ApplicationContext-Text.xml: <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p" xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.5.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd"> <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close"> <property name="driverClassName" value="com.mysql.jdbc.Driver"/> <property name="url" value="jdbc:mysql://localhost:3306/test"/> <property name="username" value="root"/> <property name="password" value="Ecosim07"/> </bean> <tx:annotation-driven transaction-manager="transactionManager"/> <bean id="userService" class="Service.UserService"> <property name="userDAO" ref="userDAO"/> </bean> <bean id="userDAO" class="DAO.UserDAO"> <property name="hibernateTemplate" ref="hibernateTemplate"/> </bean> <bean id="sessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean"> <property name="dataSource" ref="dataSource"/> <property name="mappingResources"> <list> <value>/himapping/User.hbm.xml</value> <value>/himapping/setup.hbm.xml</value> <value>/himapping/UserHistory.hbm.xml</value> </list> </property> <property name="hibernateProperties"> <props> <prop key="hibernate.dialect">org.hibernate.dialect.SQLServerDialect</prop> <prop key="hibernate.show_sql">true</prop> </props> </property> </bean> <bean id="transactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager" p:sessionFactory-ref="sessionFactory"/> <bean id="hibernateTemplate" class="org.springframework.orm.hibernate3.HibernateTemplate"> <property name="sessionFactory"> <ref bean="sessionFactory"/> </property> </bean> </beans> I have been reading about the issue, and I've already checked to ensure that the MySQL database tables are setup to use InnoDB. Also I have been able to successfully implement rolling back of transactions outside of my testing suite. So this must be some sort of incorrect setup on my part. Any help would be greatly appreciated :)

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• surfaceDestroyed called out of turn

  - by Avasulthiris

  I'm currently developing on minimum sdk version 3 (Android 1.5 - cupcake) and I'm having a strange unexplained issue that I have not been able to solve on my own. It is now becoming a rather urgent issue as I've already missed 1 deadline... I'm writing a high-level library to make long term android development easier and quicker. The one specific module has to capture images for a application... I've gotten everything right so far over the last couple months, except this one little thing and I don't know what to do any more: When I use the Camera object and implement a SurfaceHolder.Callback, the methods surfaceCreated() and surfaceChanged() are called one after the other. Then when the activity finishes, surfaceDestroyed() is called. This is how it should be, but when I stick the exact same code in my library (plain Java library that references the Android API - not in an activity), surfaceDestroyed() is called directly after created and changed. As a result - the camera object is closed before I can use it and the application force closes. What a pain. I can't do anything! This method call is controlled by the device.. Why does the surface close for no reason? Even when I post it to run on the activity thread through my own invokeAndWait(Runnable) method, like I do for many other things. I have 5 different working examples of different ways and implementations of capturing images in android but I still get the same issue when I plug it into my library. I don't understand what the difference is. The code is pretty much the same - and I post all the related code to the UI thread so its not a thread handling issue or anything like that. I've rewritten it about 20 times in different ways - same issue every time.. The only other way to approach it that I know of is creating a new Camera and setting it to the VideoView. The android source (c++ native code) however provides no Camera constructor, only an open() method which automatically forwards the camera's state to 'prepared' but I can only set the camera to the VideoView from the 'initialized' state. Pretty silly, I know, but there is no way around it unless I modify the Android library source code haha. not an option! The API does not allow for this method - you are expected to use it like my first example. So essentially - i just need to understand exactly why surfaceDestroyed() is called out of turn and if there is anything I can do to avoid it closing? If i can just understand the exact logic behind it and how it works! The documentation isn't much help! Secondly, if someone knows of any alternative ways to do it, as my second example, but hopefully one which the API actually allows for? haha Thanks guys. I would post code, but its fairly complicated, a couple thousand lines for this specific class and it would probably take a couple days to explain with all the threading and event listeners and what not. I just need help with this 1 single thing. Please let me know if you have any questions.

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• Mouseover triggered on absolute positioned div

  - by Tauren

  Objective Have a small magnifying glass icon that appears in the top right corner of a table cell when the table cell is hovered over. Mousing over the magnifying glass icon and clicking it will open a dialog window to show detailed information about the item in that particular table cell. I want to reuse the same icon for hundreds of table cells without recreating it each time. Partial Solution Have a single <span> that is absolutely positioned and hidden. When a _previewable table cell is hovered, the <span> is moved to the correct location and shown. This <span> is also moved in the DOM to be a child of the _previewable table cell. This enables a click handler attached to the <span> to find the _previewable parent, and get information from it's jquery data() object that is used to populate the contents of the dialog. Here is a very simplified version of my HTML: <body> <span id="options"> <a class="ui-state-default ui-corner-all"> <span class="ui-icon ui-icon-search"></span> Preview </a> </span> <table> <tr> <td class="_previewable"> <img scr="user_1.png"/> <span>Bob Smith</span> </td> </tr> </table> </body> And this CSS: #options { position: absolute; display: none; } With this jQuery code: var $options = $('#options'); $options.click(function() { $item = $(this).parents("._previewable"); // Show popup based on data in $item.data("id"); Layout.renderPopup($item.data("id"),$item.data("popup")); }); $('._previewable').live('mouseover mouseout',function(event) { if (event.type == 'mouseover') { var $target = $(this); var $parent = $target.offsetParent()[0]; var left = $parent.scrollLeft + $target.position().left + $target.outerWidth() - $options.outerWidth() + 1; var top = $parent.scrollTop + $target.position().top + 2; $options.appendTo($target); $options.css({ "left": left + "px", "top": top + "px" }).show(); } else { // On mouseout, $options continues to be a child of $(this) $options.hide(); } }); Problem This solution works perfectly until the contents of my table are reloaded or changed via AJAX. Because the <span> was moved from the <body> to be a child of the cell, it gets thrown out and replaced during the AJAX call. So my first thought is to move the <span> back to the body on mouseout of the table cell, like this: else { // On mouseout, $options is moved back to be a child of body $options.appendTo("body"); $options.hide(); } However, with this, the <span> disappears as soon as it is mouseover. The mouseout event seems to be called on _previewable when the mouse moves into the <span>, even though the <span> is a child of _previewable and fully displayed within the boundaries of the _previewable table cell. At this point, I've only tested this in Chrome. Questions Why would mouseout be called on _previewable, when the mouse is still within the boundaries of _previewable? Is it because the <span> is absolutely positioned? How can I make this work, without recreating the <span> and it's click handler on each AJAX table referesh?

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• Change ListView background - strage behaviour

  - by Beasly

  Hi again, I have a problem with changing the background of a view in a ListView. What I need: Change the background image of a row onClick() What actually happens: The background gets changed (selected) after pressing e.g. the first entry. But after scrolling down the 8th entry is selected too. Scroll back to the top the first isn't selected anymore. The second entry is selected now. Continue scrolling and it continues jumping... What i'm dong in the Code: I have channels, and onClick() I toggle an attribute of channel boolean selected and then I change the background. I'm doing this only onClick() thats why I don't get why it's actuelly happening on other entries too. One thing I notices is: It seems to be only the "drawing"-part because the item which get selected "by it self" has still the selected value on false I think it seems to have something to do with the reuse of the views in the custom ListAdapters getView(...) Code of onClick() in ListActivity: @Override protected ViewHolder createHolder(View v) { // createHolder will be called only as long, as the ListView is not // filled TextView title = (TextView) v .findViewById(R.id.tv_title_channel_list_adapter); TextView content = (TextView) v .findViewById(R.id.tv_content_channel_list_adapter); ImageView icon = (ImageView) v .findViewById(R.id.icon_channel_list_adapter); if (title == null || content == null || icon == null) { Log.e("ERROR on findViewById", "Couldn't find Title, Content or Icon"); } ViewHolder mvh = new MyViewHolder(title, content, icon); // We make the views become clickable // so, it is not necessary to use the android:clickable attribute in // XML v.setOnClickListener(new ChannelListAdapter.OnClickListener(mvh) { public void onClick(View v, ViewHolder viewHolder) { // we toggle the enabled state and also switch the the // background MyViewHolder mvh = (MyViewHolder) viewHolder; Channel ch = (Channel) mvh.data; ch.setSelected(!ch.getSelected()); // toggle if (ch.getSelected()) { v.setBackgroundResource(R.drawable.row_blue_selected); } else { v.setBackgroundResource(R.drawable.row_blue); } // TESTING Log.d("onClick() Channel", "onClick() Channel: " + ch.getTitle() + " selected: " + ch.getSelected()); } }); return mvh; } Code of getView(...): @Override public View getView(int position, View view, ViewGroup parent) { ViewHolder holder; // When view is not null, we can reuse it directly, there is no need // to reinflate it. // We only inflate a new View when the view supplied by ListView is // null. if (view == null) { view = mInflater.inflate(mViewId, null); // call own implementation holder = createHolder(view); // TEST // we set the holder as tag view.setTag(holder); } else { // get holder back...much faster than inflate holder = (ViewHolder) view.getTag(); } // we must update the object's reference holder.data = getItem(position); // call the own implementation bindHolder(holder); return view; } I really would appreciate any idea how to solve this! :) If more information is needed please tell me. Thanks in advance!

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• Entity Framework RC1 DbContext query issue

  - by Steve

  I'm trying to implement the repository pattern using entity framework code first rc 1. The problem I am running into is with creating the DbContext. I have an ioc container resolving the IRepository and it has a contextprovider which just news up a new DbContext with a connection string in a windsor.config file. With linq2sql this part was no problem but EF seems to be choking. I'll describe the problem below with an example. I've pulled out the code to simplify things a bit so that is why you don't see any repository pattern stuff here. just sorta what is happening without all the extra code and classes. using (var context = new PlssContext()) { var x = context.Set<User>(); var y = x.Where(u => u.UserName == LogOnModel.UserName).FirstOrDefault(); } using (var context2 = new DbContext(@"Data Source=.\SQLEXPRESS;Initial Catalog=PLSS.Models.PlssContext;Integrated Security=True;MultipleActiveResultSets=True")) { var x = context2.Set<User>(); var y = x.Where(u => u.UserName == LogOnModel.UserName).FirstOrDefault(); } PlssContext is where I am creating my DbContext class. The repository pattern doesn't know anything about PlssContext. The best I thought I could do was create a DbContext with the connection string to the sqlexpress database and query the data that way. The connection string in the var context2 was grabbed from the context after newing up the PlssContext object. So they are pointing at the same sqlexpress database. The first query works. The second query fails miserably with this error: The model backing the 'DbContext' context has changed since the database was created. Either manually delete/update the database, or call Database.SetInitializer with an IDatabaseInitializer instance. For example, the DropCreateDatabaseIfModelChanges strategy will automatically delete and recreate the database, and optionally seed it with new data. on this line var y = x.Where(u => u.UserName == LogOnModel.UserName).FirstOrDefault(); Here is my DbContext namespace PLSS.Models { public class PlssContext : DbContext { public DbSet<User> Users { get; set; } public DbSet<Corner> Corners { get; set; } public DbSet<Lookup_County> Lookup_County { get; set; } public DbSet<Lookup_Accuracy> Lookup_Accuracy { get; set; } public DbSet<Lookup_MonumentStatus> Lookup_MonumentStatus { get; set; } public DbSet<Lookup_CoordinateSystem> Lookup_CoordinateSystem { get; set; } public class Initializer : DropCreateDatabaseAlways<PlssContext> { protected override void Seed(PlssContext context) { I've tried all of the Initializer strategies with the same errors. I don't think the database is changing. If I remove the modelBuilder.Conventions.Remove<IncludeMetadataConvention>(); Then the error returns is The entity type User is not part of the model for the current context. Which sort of makes sense. But how do you bring this all together?

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• Source code versioning with comments (organizational practice) - leave or remove?

  - by ADTC

  Before you start admonishing me with "DON'T DO IT," "BAD PRACTICE!" and "Learn to use proper source code control", please hear me out first. I am fully aware that the practice of commenting out old code and leaving it there forever is very bad and I hate such practice myself. But here's the situation I'm in. A few months ago I joined a company as software developer. I had worked in the company for few months as an intern, about a year before joining recently. Our company uses source code version control (CVS) but not properly. Here's what happened both in my internship and my current permanent position. Each time I was assigned to work on a project (legacy, about 8-10 years old). Instead of creating a CVS account and letting me check out code and check in changes, a senior colleague exported the code from CVS, zipped it up and passed it to me. While this colleague checks in all changes in bulk every few weeks, our usual practice is to do fine-grained versioning in the actual source code itself (each file increments in versions independent from the rest). Whenever a change is made to a file, old code is commented out, new code entered below it, and this whole section is marked with a version number. Finally a note about the changes is placed at the top of the file in a section called Modification History. Finally the changed files are placed in a shared folder, ready and waiting for the bulk check-in. /* * Copyright notice blah blah * Some details about file (project name, file name etc) * Modification History: * Date Version Modified By Description * 2012-10-15 1.0 Joey Initial creation * 2012-10-22 1.1 Chandler Replaced old code with new code */ code .... //v1.1 start //old code new code //v1.1 end code .... Now the problem is this. In the project I'm working on, I needed to copy some new source code files from another project (new in the sense that they didn't exist in destination project before). These files have a lot of historical commented out code and comment-based versioning including usually long or very long Modification History section. Since the files are new to this project I decided to clean them up and remove unnecessary code including historical code, and start fresh at version 1.0. (I still have to continue the practice of comment-based versioning despite hating it. And don't ask why not start at version 0.1...) I have done similar something during my internship and no one said anything. My supervisor has seen the work a few times and didn't say I shouldn't do such clean-up (if at all it was noticed). But a same-level colleague saw this and said it's not recommended as it may cause downtime in the future and increase maintenance costs. An example is when changes are made in another project on the original files and these changes need to be propagated to this project. With code files drastically different, it could cause confusion to an employee doing the propagation. It makes sense to me, and is a valid point. I couldn't find any reason to do my clean-up other than the inconvenience of a ridiculously messy code. So, long story short: Given the practice in our company, should I not do such clean-up when copying new files from project to project? Is it better to make changes on the (copy of) original code with full history in comments? Or what justification can I give for doing the clean-up? PS to mods: Hope you allow this question some time even if for any reason you determine it to be unfit in SO. I apologize in advance if anything is inappropriate including tags.

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• Recommended integration mechanism for bi-directional, authenticated, encrypted connection in C clien

  - by rcampbell

  Let me first give an example. Imagine you have a single server running a JVM application. This server keeps a collection of N equations, once for each client: Client #1: 2x Client #2: 1 + y Client #3: z/4 This server includes an HTTP interface so that random visitors can type https://www.acme.com/client/3 int their browsers and see the latest evaluated result of z/4. The tricky part is that either the client or the server may change the variable value at any time, informing the other party immediately. More specifically, Client #3 - a C app - can initially tell the server that z = 20. An hour later that same client informs the server that z = 23. Likewise the server can later inform the client that z = 28. As caf pointed out in the comments, there can be a race condition when values are changed by the client and server simultaneously. The solution would be for both client and server to send the operation performed in their message, which would need to be executed by the other party. To keep things simple, let's limit the operations to (commutative) addition, allowing us to disregard message ordering. For example, the client seeds the server with z = 20: server:z=20, client:z=20 server sends {+3} message (so z=23 locally) & client sends {-2} message (so z=18 locally) at the exact same time server receives {-2} message at some point, adds to his local copy so z=21 client receives {+3} message at some point, adds to his local copy so z=21 As long as all messages are eventually evaluated by both parties, the correct answer will eventually be given to the users of the client and server since we limited ourselves to commutative operations (addition of 3 and -2). This does mean that both client and server can be returning incorrect answers in the time it takes for messages to be exchanged and processed. While undesirable, I believe this is unavoidable. Some possible implementations of this idea include: Open an encrypted, always on TCP socket connection for communication Pros: no additional infrastructure needed, client and server know immediately if there is a problem (disconnect) with the other party, fairly straightforward (except the the encryption), native support from both JVM and C platforms Cons: pretty low-level so you end up writing a lot yourself (protocol, delivery verification, retry-on-failure logic), probably have a lot of firewall headaches during client app installation Asynchronous messaging (ex: ActiveMQ) Pros: transactional, both C & Java integration, free up the client and server apps from needing retry logic or delivery verification, pretty straightforward encryption, easy extensibility via message filters/routers/etc Cons: need additional infrastructure (message server) which must never fail, Database or file system as asynchronous integration point Same pros/cons as above but messier RESTful Web Service Pros: simple, possible reuse of the server's existing REST API, SSL figures out the encryption problem for you (maybe use RSA key a la GitHub for authentication?) Cons: Client now needs to run a C HTTP REST server w/SSL, client and server need retry logic. Axis2 has both a Java and C version, but you may be limited to SOAP. What other techniques should I be evaluating? What real world experiences have you had with these mechanisms? Which do you recommend for this problem and why?

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• When to draw/layout child controls in UserControl

  - by Ted Elliott

  I have a list-type UserControl (like a ListBox). The items inside the control are another complex UserControl containing a few other controls (ComboBox, TextBox, etc). I'm wondering what the preferred or best method would be to override to draw/layout the child controls. I basically want to trigger this method any time the list changes. I originally had a RedrawItems method that I just called whenever I needed to redraw which added or removed Controls from the Controls collection. But it was getting triggered too early in the lifecycle of the code from some of the designer code. Now I've switched to overriding OnLayout and doing my stuff there. I call PerformLayout when I want to trigger a redraw, such as when the DataSource property changes or when it fires a changed event. Is OnLayout the best place for this? Here is the code: [ComplexBindingProperties("DataSource")] public partial class CustomList : UserControl { private object _dataSource; private CustomListItem _newRow; public CustomList() { InitializeComponent(); } protected override void OnCreateControl() { base.OnCreateControl(); _newRow = new CustomListItem(); Controls.Add(_newRow); } public object DataSource { get { return _dataSource; } set { bool register = _dataSource != value; if (_dataSource != null && _dataSource != value) { UnregisterDataSource(_dataSource); } _dataSource = value; if (_dataSource != null) RegisterDataSource(_dataSource); PerformLayout(); } } public CustomListItem ItemTemplate { get { return _newRow; } } protected override void OnLayout(LayoutEventArgs e) { base.OnLayout(e); int ctrlCount = this.Controls.AsEnumerable().OfType<CustomListItem>().Count(); ctrlCount--; // subtract 1 for the add row var ds = this.DataSource as System.Collections.IList; int itemCount = ds == null? 0 : ds.Count; int maxCount = Math.Max(ctrlCount,itemCount); if (maxCount == 0) return; this.SuspendLayout(); // temporarily remove the template Controls.RemoveAt(Controls.Count-1); for (int i = 0; i < maxCount; i++) { CustomListItem item; if (i >= itemCount) { Controls.RemoveAt(i); } else { if (i >= ctrlCount) { item = ItemTemplate.Copy(); this.Controls.Add(item); item.Location = new Point(0, item.Height * i); item.TabIndex = i + 1; item.ViewMode = true; } else { item = (CustomListItem) Controls[i]; } item.Data = ds[i]; } } this.Controls.Add(ItemTemplate); ItemTemplate.Location = new Point(0, ItemTemplate.Height * maxCount); ItemTemplate.TabIndex = maxCount + 1; this.ResumeLayout(true); } private void RegisterDataSource(object dataSource) { IBindingList ds = dataSource as IBindingList; if (ds != null) { ds.ListChanged += new ListChangedEventHandler(DataSource_ListChanged); } } void DataSource_ListChanged(object sender, ListChangedEventArgs e) { switch (e.ListChangedType) { case ListChangedType.ItemAdded: PerformLayout(); break; case ListChangedType.ItemChanged: break; case ListChangedType.ItemDeleted: PerformLayout(); break; case ListChangedType.ItemMoved: PerformLayout(); break; case ListChangedType.Reset: PerformLayout(); break; default: break; } } private void UnregisterDataSource(object dataSource) { IBindingList ds = dataSource as IBindingList; if (ds != null) { ds.ListChanged -= new ListChangedEventHandler(DataSource_ListChanged); } } }

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• How to bind to the sum of two data bound values in WPF?

  - by Sheridan

  I have designed an analog clock control. It uses the stroke from two ellipses to represent an outer border and an inner border to the clock face. I have exposed properties in the UserControl that allow a user to alter the thickness of these two borders. The Ellipse.StrokeThickness properties are then bound to these UserControl properties. At the moment, I am binding the UserControl property for the outer border thickness to the margins of the inner elements so that they are not hidden when the border size is increased. <Ellipse Name="OuterBorder" Panel.ZIndex="1" StrokeThickness="{Binding OuterBorderThickness, ElementName=This}" Stroke="{StaticResource OuterBorderBrush}" /> <Ellipse Name="InnerBorder" Panel.ZIndex="5" StrokeThickness="{Binding InnerBorderThickness, ElementName=This}" Margin="{Binding OuterBorderThickness, ElementName=This}" Stroke="{StaticResource InnerBorderBrush}"> ... <Ellipse Name="Face" Panel.ZIndex="1" Margin="{Binding OuterBorderThickness, ElementName=This}" Fill="{StaticResource FaceBackgroundBrush}" /> ... The problem is that if the inner border thickness is increased, this does not affect the margins and so the hour ticks and numbers can become partially obscured or hidden. So what I really need is to be able to bind the margin properties of the inner controls to the sum of the inner and outer border thickness values (they are of type double). I have done this successfully using 'DataContext = this;', but am trying to rewrite the control without this as I hear it is not recommended. I also thought about using a converter and passing the second value as the ConverterParameter, but didn't know how to bind to the ConverterParameter. Any tips would be greatly appreciated. EDIT Thanks to Kent's suggestion, I've created a simple MultiConverter to add the input values and return the result. I've hooked the SAME multibinding with converter XAML to both a TextBlock.Text property and the TextBlock.Margin property to test it. <TextBlock> <TextBlock.Text> <MultiBinding Converter="{StaticResource SumConverter}" ConverterParameter="Add"> <Binding Path="OuterBorderThickness" ElementName="This" /> <Binding Path="InnerBorderThickness" ElementName="This" /> </MultiBinding> </TextBlock.Text> <TextBlock.Margin> <MultiBinding Converter="{StaticResource SumConverter}" ConverterParameter="Add"> <Binding Path="OuterBorderThickness" ElementName="This" /> <Binding Path="InnerBorderThickness" ElementName="This" /> </MultiBinding> </TextBlock.Margin> </TextBlock> I can see the correct value displayed in the TexBlock, but the Margin is not set. Any ideas? EDIT Interestingly, the Margin property can be bound to a data property of type double, but this does not seem to apply within a MultiBinding. As advised by Kent, I changed the Converter to return the value as a Thickness object and now it works. Thanks Kent.

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• Trouble with Code First DatabaseGenerated Composite Primary Key

  - by Nick Fleetwood

  This is a tad complicated, and please, I know all the arguments against natural PK's, so we don't need to have that discussion. using VS2012/MVC4/C#/CodeFirst So, the PK is based on the date and a corresponding digit together. So, a few rows created today would be like this: 20131019 1 20131019 2 And one created tomorrow: 20131020 1 This has to be automatically generated using C# or as a trigger or whatever. The user wouldn't input this. I did come up with a solution, but I'm having problems with it, and I'm a little stuck, hence the question. So, I have a model: public class MainOne { //[Key] //public int ID { get; set; } [Key][Column(Order=1)] [DatabaseGenerated(DatabaseGeneratedOption.None)] public string DocketDate { get; set; } [Key][Column(Order=2)] [DatabaseGenerated(DatabaseGeneratedOption.None)] public string DocketNumber { get; set; } [StringLength(3, ErrorMessage = "Corp Code must be three letters")] public string CorpCode { get; set; } [StringLength(4, ErrorMessage = "Corp Code must be four letters")] public string DocketStatus { get; set; } } After I finish the model, I create a new controller and views using VS2012 scaffolding. Then, what I'm doing is debugging to create the database, then adding the following instead of trigger after Code First creates the DB [I don't know if this is correct procedure]: CREATE TRIGGER AutoIncrement_Trigger ON [dbo].[MainOnes] instead OF INSERT AS BEGIN DECLARE @number INT SELECT @number=COUNT(*) FROM [dbo].[MainOnes] WHERE [DocketDate] = CONVERT(DATE, GETDATE()) INSERT INTO [dbo].[MainOnes] (DocketDate,DocketNumber,CorpCode,DocketStatus) SELECT (CONVERT(DATE, GETDATE ())),(@number+1),inserted.CorpCode,inserted.DocketStatus FROM inserted END And when I try to create a record, this is the error I'm getting: The changes to the database were committed successfully, but an error occurred while updating the object context. The ObjectContext might be in an inconsistent state. Inner exception message: The object state cannot be changed. This exception may result from one or more of the primary key properties being set to null. Non-Added objects cannot have null primary key values. See inner exception for details. Now, what's interesting to me, is that after I stop debugging and I start again, everything is perfect. The trigger fired perfectly, so the composite PK is unique and perfect, and the data in other columns is intact. My guess is that EF is confused by the fact that there is seemingly no value for the PK until AFTER an insert command is given. Also, appearing to back this theory, is that when I try to edit on of the rows, in debug, I get the following error: The number of primary key values passed must match number of primary key values defined on the entity. Same error occurs if I try to pull the 'Details' or 'Delete' function. Any solution or ideas on how to pull this off? I'm pretty open to anything, even creating a hidden int PK. But it would seem redundant. EDIT 21OCT13 [HttpPost] public ActionResult Create(MainOne mainone) { if (ModelState.IsValid) { var countId = db.MainOnes.Count(d => d.DocketDate == mainone.DocketNumber); //assuming that the date field already has a value mainone.DocketNumber = countId + 1; //Cannot implicitly convert type int to string db.MainOnes.Add(mainone); db.SaveChanges(); return RedirectToAction("Index"); } return View(mainone); } EDIT 21OCT2013 FINAL CODE SOLUTION For anyone like me, who is constantly searching for clear and complete solutions. if (ModelState.IsValid) { String udate = DateTime.UtcNow.ToString("yyyy-MM-dd"); mainone.DocketDate = udate; var ddate = db.MainOnes.Count(d => d.DocketDate == mainone.DocketDate); //assuming that the date field already has a value mainone.DocketNumber = ddate + 1; db.MainOnes.Add(mainone); db.SaveChanges(); return RedirectToAction("Index"); }

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• How to get Rid of this strange Border on JButton in Windows System look and Feel?

  - by Timo J.

  I have a small Problem with the Layout of my Frame. As You could see in a picture (if i would have my 10 rep ;) ) there is a small Border around my JButtons. I'm already searching long time on this topic and i finally decided to ask for help, i'm just out of ideas. Is this Part of the Windows Theme which shouldn't be changed? It just doesnt fit into my current Layout, as I'm Listing TextBoxes and Comboboxes on Page Axis without any Border. I would be very happy if there is solution for this issue. Thanks in advance! EDIT 1: I do not mean the Focus Border. I like the Highlighting of a focussed Element. What i mean is the Border in the Background Color which causes a small distance of background-colored space beetween a JButton and another Element. (Picture on Personnal Webspace: http://tijamocobs.no-ip.biz/border_jbutton.png) EDIT 2: I'm using the Windows 8 Look and Feel but saw this Problem on Windows 7 Look and Feel, too. short Example import javax.swing.BoxLayout; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.UIManager; import javax.swing.UnsupportedLookAndFeelException; public class TestFrame extends JFrame { public TestFrame(){ setLayout(new BoxLayout(getContentPane(), BoxLayout.PAGE_AXIS)); for (int i = 0; i < 3; i++) { JButton btn = new JButton("."); // not working: // btn.setBorder(null); // btn.setBorder(BorderFactory.createEmptyBorder()); add(btn); } pack(); } public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException, UnsupportedLookAndFeelException { UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); TestFrame tiss = new TestFrame(); tiss.setVisible(true); } } Example Code (long version): import java.awt.BorderLayout; import java.awt.Container; import java.awt.Dimension; import javax.swing.Box; import javax.swing.BoxLayout; import javax.swing.JButton; import javax.swing.JComboBox; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; import javax.swing.UIManager; import javax.swing.UnsupportedLookAndFeelException; public class TestFrame extends JFrame { public TestFrame(){ JPanel muh = new JPanel(); muh.setLayout(new BoxLayout(muh, BoxLayout.PAGE_AXIS)); for (int i = 0; i < 3; i++) { Container c = new JPanel(); c.setLayout(new BoxLayout(c, BoxLayout.LINE_AXIS)); Box bx = Box.createHorizontalBox(); final String[] tmp = {"anything1","anything2"}; JComboBox<String> cmbbx = new JComboBox<String>(tmp); cmbbx.setMinimumSize(new Dimension(80,20)); bx.add(cmbbx); JButton btn = new JButton("."); btn.setMinimumSize(new Dimension(cmbbx.getMinimumSize().height,cmbbx.getMinimumSize().height)); btn.setPreferredSize(new Dimension(30,30)); btn.setMaximumSize(new Dimension(30,30)); bx.add(btn); c.setMaximumSize(new Dimension(Integer.MAX_VALUE,30)); c.add(new JLabel("Just anything")); c.add(bx); muh.add(c); } add(muh,BorderLayout.CENTER); pack(); } public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException, UnsupportedLookAndFeelException { UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); TestFrame tiss = new TestFrame(); tiss.setVisible(true); } }

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• TDD - beginner problems and stumbling blocks

  - by Noufal Ibrahim

  While I've written unit tests for most of the code I've done, I only recently got my hands on a copy of TDD by example by Kent Beck. I have always regretted certain design decisions I made since they prevented the application from being 'testable'. I read through the book and while some of it looks alien, I felt that I could manage it and decided to try it out on my current project which is basically a client/server system where the two pieces communicate via. USB. One on the gadget and the other on the host. The application is in Python. I started off and very soon got entangled in a mess of rewrites and tiny tests which I later figured didn't really test anything. I threw away most of them and and now have a working application for which the tests have all coagulated into just 2. Based on my experiences, I have a few questions which I'd like to ask. I gained some information from http://stackoverflow.com/questions/1146218/new-to-tdd-are-there-sample-applications-with-tests-to-show-how-to-do-tdd but have some specific questions which I'd like answers to/discussion on. Kent Beck uses a list which he adds to and strikes out from to guide the development process. How do you make such a list? I initially had a few items like "server should start up", "server should abort if channel is not available" etc. but they got mixed and finally now, it's just something like "client should be able to connect to server" (which subsumed server startup etc.). How do you handle rewrites? I initially selected a half duplex system based on named pipes so that I could develop the application logic on my own machine and then later add the USB communication part. It them moved to become a socket based thing and then moved from using raw sockets to using the Python SocketServer module. Each time things changed, I found that I had to rewrite considerable parts of the tests which was annoying. I'd figured that the tests would be a somewhat invariable guide during my development. They just felt like more code to handle. I needed a client and a server to communicate through the channel to test either side. I could mock one of the sides to test the other but then the whole channel wouldn't be tested and I worry that I'd miss that. This detracted from the whole red/green/refactor rhythm. Is this just lack of experience or am I doing something wrong? The "Fake it till you make it" left me with a lot of messy code that I later spent a lot of time to refactor and clean up. Is this the way things work? At the end of the session, I now have my client and server running with around 3 or 4 unit tests. It took me around a week to do it. I think I could have done it in a day if I were using the unit tests after code way. I fail to see the gain. I'm looking for comments and advice from people who have implemented large non trivial projects completely (or almost completely) using this methodology. It makes sense to me to follow the way after I have something already running and want to add a new feature but doing it from scratch seems to tiresome and not worth the effort. P.S. : Please let me know if this should be community wiki and I'll mark it like that. Update 0 : All the answers were equally helpful. I picked the one I did because it resonated with my experiences the most. Update 1: Practice Practice Practice!

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• ListBoxFor not populating with selected items

  - by user576838

  I've see this question asked a couple of other times, and I followed this after I tried things on my own with the MS music store demo to no avail, but I still can't get this to work. I've also noticed when I look at my MultiSelectList object in the viewmodel, it has the correct items in the selected items property, but if I expand the results view, it doesn't have any listboxitem with the selected value. What am I missing here? I feel like I'm taking crazy pills! Thanks in advance. model: public class Article { public int ArticleID { get; set; } public DateTime? DatePurchased { get; set; } public DateTime? LastWorn { get; set; } public string ThumbnailImg { get; set; } public string LargeImg { get; set; } public virtual List<Outfit> Outfits { get; set; } public virtual List<Tag> Tags { get; set; } } viewmodel: public class ArticleViewModel { public int ArticleID { get; set; } public List<Tag> Tags { get; set; } public MultiSelectList mslTags { get; set; } public virtual Article Article { get; set; } public ArticleViewModel(int ArticleID) { using (ctContext db = new ctContext()) { this.Article = db.Articles.Find(ArticleID); this.Tags = db.Tags.ToList(); this.mslTags = new MultiSelectList(this.Tags, "TagID", "Name", this.Article.Tags); } } } controller: public ActionResult Index() { ArticleIndexViewModel vm = new ArticleIndexViewModel(db); return View(vm); } view: @model ClosetTracker.ArticleViewModel @using (Html.BeginForm()) { <img id="bigImg" src="@Model.Article.ThumbnailImg" alt="img" /> @Html.HiddenFor(m => m.ArticleID); @Html.LabelFor(m => m.Article.Tags) @* @Html.ListBoxFor(m => m.Article.Tags, Model.Tags.Select(t => new SelectListItem { Text = t.Name, Value = t.TagID.ToString() }), new { Multiple = "multiple" }) *@ @Html.ListBoxFor(m => m.Article.Tags, Model.mslTags); @Html.LabelFor(m => m.Article.LastWorn) @Html.TextBoxFor(m => m.Article.LastWorn, new { @class = "datepicker" }) @Html.LabelFor(m => m.Article.DatePurchased) @Html.TextBoxFor(m => m.Article.DatePurchased, new { @class = "datepicker" }) <p> <input type="submit" value="Save" /> </p> } EDITED Ok, I changed around the constructor of the MultiSelectList to have a list of TagID in the selected value arg instead of a list of Tag objects. This shows the correct tags as selected in the results view when I watch the mslTags object in debug mode. However, it still isn't rendering correctly to the page. public class ArticleViewModel { public int ArticleID { get; set; } public List<Tag> Tags { get; set; } public MultiSelectList mslTags { get; set; } public virtual Article Article { get; set; } public ArticleViewModel(int ArticleID) { using (ctContext db = new ctContext()) { this.Article = db.Articles.Find(ArticleID); this.Tags = db.Tags.ToList(); this.mslTags = new MultiSelectList(this.Tags, "TagID", "Name", this.Article.Tags.Select(t => t.TagID).ToList()); } } }

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• Android: Having trouble creating a subclass of application to share data with multiple Activities

  - by Mike

  Hello, I just finished a couple of activities in my game and now I was going to start to wire them both up to use real game data, instead of the test data I was using just to make sure each piece worked. Since multiple Activities will need access to this game data, I started researching the best way to pass this data to my Activities. I know about using putExtra with intents, but my GameData class has quite a bit of data and not just simple key value pairs. Besides quite a few basic data types, it also has large arrays. I didn't really want to try and pass all that, unless I can pass the entire object, instead of just key/data pairs. I read the following post and thought it would be the way to go, but so far, I haven't got it to work. Android: How to declare global variables? I created a simple test app to try this method out, but it keeps crashing and my code seems to look the same as in the post above - except I changed the names. Here is the error I am getting. Can someone help me understand what I am doing wrong? 12-23 00:50:49.762: ERROR/AndroidRuntime(608): Caused by: java.lang.ClassCastException: android.app.Application It crashes on the following statement: GameData newGameData = ((GameData)getApplicationContext()); Here is my code: package mrk.examples.StaticGameData; import android.app.Application; public class GameData extends Application { private int intTest; GameData () { intTest = 0; } public int getIntTest(){ return intTest; } public void setIntTest(int value){ intTest = value; } } // My main activity package mrk.examples.StaticGameData; import android.app.Activity; import android.content.Intent; import android.os.Bundle; import android.util.Log; public class StaticGameData extends Activity { int intStaticTest; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); GameData newGameData = ((GameData)getApplicationContext()); newGameData.setIntTest(0); intStaticTest = newGameData.getIntTest(); Log.d("StaticGameData", "Well: IntStaticTest = " + intStaticTest); newGameData.setIntTest(1); Log.d("StaticGameData", "Well: IntStaticTest = " + intStaticTest + " newGameData: " + newGameData.getIntTest()); Intent intentNew = new Intent(this, PassData2Activity.class); startActivity (intentNew); } } // My test Activity to see if it can access the data and its previous state from the last activity package mrk.examples.StaticGameData; import android.app.Activity; import android.os.Bundle; import android.util.Log; public class PassData2Activity extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); GameData gamedataPass = ((GameData)getApplicationContext()); Log.d("PassData2Activity", "IntTest = " + gamedataPass.getIntTest()); } } Below is the relevant portion of my manifest: <application android:icon="@drawable/icon" android:label="@string/app_name"> <activity android:name=".StaticGameData" android:label="@string/app_name"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> <activity android:name=".PassData2Activity"></activity> </application> <application android:name=".GameData" android:icon="@drawable/icon" android:label="@string/app_name"> </application> Thanks in advance for helping me understand why this code is crashing. Also, if you think this is just the wrong approach to let multiple activities have access to the same data, please give your suggestion. Please keep in mind that I am talking about quite a few variables and some large arrays.

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• Windows DD-esque implementation in Qt 5

  - by user1777667

  I'm trying to get into Qt and as a project I want to try and pull a binary image from a hard drive in Windows. This is what I have: QFile dsk("//./PhysicalDrive1"); dsk.open(QIODevice::ReadOnly); QByteArray readBytes = dsk.read(512); dsk.close(); QFile img("C:/out.bin"); img.open(QIODevice::WriteOnly); img.write(readBytes); img.close(); When I run it, it creates the file, but when I view it in a hex editor, it says: ëR.NTFS ..........ø..?.ÿ.€.......€.€.ÿç......UT..............ö.......ì§á.Íá.`....ú3ÀŽÐ¼.|ûhÀ...hf.ˈ...f.>..NTFSu.´A»ªUÍ.r..ûUªu.÷Á..u.éÝ..ƒì.h..´HŠ...‹ô..Í.ŸƒÄ.žX.rá;...uÛ£..Á.....Z3Û¹. +Èfÿ.......ŽÂÿ...èK.+Èwï¸.»Í.f#Àu-f.ûTCPAu$.ù..r..h.».hp..h..fSfSfU...h¸.fa..Í.3À¿(.¹Ø.üóªé_...f`..f¡..f.....fh....fP.Sh..h..´BŠ.....‹ôÍ.fY[ZfYfY..‚..fÿ.......ŽÂÿ...u¼..faàø.è.. û.è..ôëý´.‹ð¬<.t.´.»..Í.ëòÃ..A disk read error occurred...BOOTMGR is missing...BOOTMGR is compressed...Press Ctrl+Alt+Del to restart...Œ©¾Ö..Uª Is there a better way of doing this? I tried running it as admin, but still no dice. Any help would be much appreciated. Update: I changed the code a bit. Now if I specify a dd images as the input it writes the image perfectly, but when I try to use a disk as the input it only writes 0x00. QTextStream(stdout) << "Start\n"; QFile dsk("//./d:"); //QFile dsk("//./PhysicalDrive1"); //QFile dsk("//?/Device/Harddisk1/Partition0"); //QFile dsk("//./Volume{e988ffc3-3512-11e3-99d8-806e6f6e6963}"); //QFile dsk("//./Volume{04bbc7e2-a450-11e3-a9d9-902b34d5484f}"); //QFile dsk("C:/out_2.bin"); if (!dsk.open(QIODevice::ReadOnly)) qDebug() << "Failed to open:" << dsk.errorString(); qDebug() << "Size:" << dsk.size() << "\n"; // Blank out image file QFile img(dst); img.open(QIODevice::WriteOnly); img.write(0); img.close(); // Read and write operations while (!dsk.atEnd()) { QByteArray readBytes = dsk.readLine(); qDebug() << "Reading: " << readBytes.size() << "\n"; QFile img(dst); if (!img.open(QIODevice::Append)) qDebug() << "Failed to open:" << img.errorString(); img.write(readBytes); } QTextStream(stdout) << "End\n"; I guess the real problem I'm having is how to open a volume with QFile in Windows. I tried a few variants, but to no avail.

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• SetPixelFormat is not creating an alpha channel for OpenGL

  - by i_photon

  I've been able to do this before, and I don't know what changed between two weeks ago and the last windows update, but for some reason SetPixelFormat isn't creating an alpha channel. gDebugger shows that the window's back buffer only has 3 channels. White+0 alpha renders as white. So there is something inherently wrong with what I was doing, or an update broke it. The code below should be paste-able into an empty VS project. #include <Windows.h> #include <dwmapi.h> #include <gl/GL.h> #pragma comment(lib,"opengl32.lib") #pragma comment(lib,"dwmapi.lib") HWND hWnd = 0; HDC hDC = 0; HGLRC hRC = 0; LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM); int APIENTRY WinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow ) { WNDCLASSEX wcex = {0}; wcex.cbSize = sizeof(WNDCLASSEX); wcex.lpfnWndProc = WndProc; wcex.hCursor = LoadCursor(NULL, IDC_ARROW); wcex.lpszClassName = TEXT("why_class"); RegisterClassEx(&wcex); // no errors hWnd = CreateWindowEx( NULL, TEXT("why_class"), TEXT("why_window"), WS_OVERLAPPEDWINDOW, 128,128, 256,256, NULL, NULL, hInstance, NULL ); // no errors PIXELFORMATDESCRIPTOR pfd = {0}; pfd.nSize = sizeof(pfd); pfd.nVersion = 1; pfd.dwFlags = PFD_DRAW_TO_WINDOW| PFD_SUPPORT_OPENGL| PFD_DOUBLEBUFFER| PFD_SUPPORT_COMPOSITION; pfd.cColorBits = 32; pfd.cAlphaBits = 8; // need an alpha channel pfd.cDepthBits = 24; pfd.cStencilBits = 8; hDC = GetDC(hWnd); int i = ChoosePixelFormat(hDC,&pfd); SetPixelFormat(hDC,i,&pfd); // no errors hRC = wglCreateContext(hDC); // no errors wglMakeCurrent(hDC,hRC); // no errors // EDIT: Turn on alpha testing (which actually won't // fix the clear color problem below) glEnable(GL_BLEND); glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA); // EDIT: Regardless of whether or not GL_BLEND is enabled, // a clear color with an alpha of 0 should (or did at one time) // make this window transparent glClearColor( 0,0,0, // if this is (1,1,1), the window renders // solid white regardless of the alpha 0 // changing the alpha here has some effect ); DWM_BLURBEHIND bb = {0}; bb.dwFlags = DWM_BB_ENABLE|DWM_BB_TRANSITIONONMAXIMIZED; bb.fEnable = TRUE; bb.fTransitionOnMaximized = TRUE; DwmEnableBlurBehindWindow(hWnd,&bb); // no errors ShowWindow(hWnd, SW_SHOWNORMAL); UpdateWindow(hWnd); // no errors MSG msg = {0}; while(true){ GetMessage(&msg,NULL,NULL,NULL); if(msg.message == WM_QUIT){ return (int)msg.wParam; } TranslateMessage(&msg); DispatchMessage(&msg); glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT); glBegin(GL_TRIANGLES); // this vertex should be transparent, // as it was when I last built this test // // it renders as white glColor4f(1,1,1,0); glVertex2f(0,0); glColor4f(0,1,1,1); glVertex2f(1,0); glColor4f(1,0,1,1); glVertex2f(0,1); glEnd(); SwapBuffers(hDC); } return (int)msg.wParam; } LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) { switch (message) { case WM_DESTROY: { PostQuitMessage(0); }return 0; default: break; } return DefWindowProc(hWnd, message, wParam, lParam); }

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• Supporting Piping (A Useful Hello World)

  - by blastthisinferno

  I am trying to write a collection of simple C++ programs that follow the basic Unix philosophy by: Make each program do one thing well. Expect the output of every program to become the input to another, as yet unknown, program. I'm having an issue trying to get the output of one to be the input of the other, and getting the output of one be the input of a separate instance of itself. Very briefly, I have a program add which takes arguments and spits out the summation. I want to be able to pipe the output to another add instance. ./add 1 2 | ./add 3 4 That should yield 6 but currently yields 10. I've encountered two problems: The cin waits for user input from the console. I don't want this, and haven't been able to find a simple example showing a the use of standard input stream without querying the user in the console. If someone knows of an example please let me know. I can't figure out how to use standard input while supporting piping. Currently, it appears it does not work. If I issue the command ./add 1 2 | ./add 3 4 it results in 7. The relevant code is below: add.cpp snippet // ... COMMAND LINE PROCESSING ... std::vector<double> numbers = multi.getValue(); // using TCLAP for command line parsing if (numbers.size() > 0) { double sum = numbers[0]; double arg; for (int i=1; i < numbers.size(); i++) { arg = numbers[i]; sum += arg; } std::cout << sum << std::endl; } else { double input; // right now this is test code while I try and get standard input streaming working as expected while (std::cin) { std::cin >> input; std::cout << input << std::endl; } } // ... MORE IRRELEVANT CODE ... So, I guess my question(s) is does anyone see what is incorrect with this code in order to support piping standard input? Are there some well known (or hidden) resources that explain clearly how to implement an example application supporting the basic Unix philosophy? @Chris Lutz I've changed the code to what's below. The problem where cin still waits for user input on the console, and doesn't just take from the standard input passed from the pipe. Am I missing something trivial for handling this? I haven't tried Greg Hewgill's answer yet, but don't see how that would help since the issue is still with cin. // ... COMMAND LINE PROCESSING ... std::vector<double> numbers = multi.getValue(); // using TCLAP for command line parsing double sum = numbers[0]; double arg; for (int i=1; i < numbers.size(); i++) { arg = numbers[i]; sum += arg; } // right now this is test code while I try and get standard input streaming working as expected while (std::cin) { std::cin >> arg; std::cout << arg << std::endl; } std::cout << sum << std::endl; // ... MORE IRRELEVANT CODE ...

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• More localized, efficient Lowest Common Ancestor algorithm given multiple binary trees?

  - by mstksg

  I have multiple binary trees stored as an array. In each slot is either nil (or null; pick your language) or a fixed tuple storing two numbers: the indices of the two "children". No node will have only one child -- it's either none or two. Think of each slot as a binary node that only stores pointers to its children, and no inherent value. Take this system of binary trees: 0 1 / \ / \ 2 3 4 5 / \ / \ 6 7 8 9 / \ 10 11 The associated array would be: 0 1 2 3 4 5 6 7 8 9 10 11 [ [2,3] , [4,5] , [6,7] , nil , nil , [8,9] , nil , [10,11] , nil , nil , nil , nil ] I've already written simple functions to find direct parents of nodes (simply by searching from the front until there is a node that contains the child) Furthermore, let us say that at relevant times, both all trees are anywhere between a few to a few thousand levels deep. I'd like to find a function P(m,n) to find the lowest common ancestor of m and n -- to put more formally, the LCA is defined as the "lowest", or deepest node in which have m and n as descendants (children, or children of children, etc.). If there is none, a nil would be a valid return. Some examples, given our given tree: P( 6,11) # => 2 P( 3,10) # => 0 P( 8, 6) # => nil P( 2,11) # => 2 The main method I've been able to find is one that uses an Euler trace, which turns the given tree, with a node A to be the invisible parent of 0 and 1 with a depth of -1, into: A-0-2-6-2-7-10-7-11-7-2-0-3-0-A-1-4-1-5-8-5-9-5-1-A And from that, simply find the node between your given m and n that has the lowest number; For example, to find P(6,11), look for a 6 and an 11 on the trace. The number between them that is the lowest is 2, and that's your answer. If A is in between them, return nil. -- Calculating P(6,11) -- A-0-2-6-2-7-10-7-11-7-2-0-3-0-A-1-4-1-5-8-5-9-5-1-A ^ ^ ^ | | | m lowest n Unfortunately, I do believe that finding the Euler trace of a tree that can be several thousands of levels deep is a bit machine-taxing...and because my tree is constantly being changed throughout the course of the programming, every time I wanted to find the LCA, I'd have to re-calculate the Euler trace and hold it in memory every time. Is there a more memory efficient way, given the framework I'm using? One that maybe iterates upwards? One way I could think of would be the "count" the generation/depth of both nodes, and climb the lowest node until it matched the depth of the highest, and increment both until they find someone similar. But that'd involve climbing up from level, say, 3025, back to 0, twice, to count the generation, and using a terribly inefficient climbing-up algorithm in the first place, and then re-climbing back up. Are there any other better ways?

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• window.open() in an iPad on load of a frame does not work

  - by user278859

  I am trying to modify a site that uses "Morten's JavaScript Tree Menu" to display PDFs in a frames set using the Adobe Reader plug-in. On the iPad the frame is useless, so I want to open the PDF in a new tab. Not wanting to mess with the tree menu I thought I could use JavaScript in the web page being opened in the viewer frame to open a new tab with the PDF. I am using window.open() in $(document).ready(function() to open the pdf in the new tab. The problem is that window.open() does not want to work in the iPad. The body of the HTML normally looks like this... <body> <object data="MypdfFileName.pdf#toolbar=1&amp;navpanes=1&amp;scrollbar=0&amp;page=1&amp;view=FitH" type="application/pdf" width="100%" height="100%"> </object> </body> I changed it to only have a div like this... <body> <div class="myviewer" ></div> </body> Then used the following script... $(document).ready(function() { var isMobile = { Android : function() { return navigator.userAgent.match(/Android/i) ? true : false; }, BlackBerry : function() { return navigator.userAgent.match(/BlackBerry/i) ? true : false; }, iOS : function() { return navigator.userAgent.match(/iPhone|iPad|iPod/i) ? true : false; }, Windows : function() { return navigator.userAgent.match(/IEMobile/i) ? true : false; }, any : function() { return (isMobile.Android() || isMobile.BlackBerry() || isMobile.iOS() || isMobile.Windows()); } }; if(isMobile.any()) { var file = "MypdfFileName.pdf"; window.open(file); }else { var markup = "<object data='MypdfFileName.pdf#toolbar=1&amp;navpanes=1&amp;scrollbar=0&amp;page=1&amp;view=FitH' type='application/pdf' width='100%' height='100%'></object>"; $('.myviewer').append(markup); }; }); Everthing works except for window.open() on the iPad. If I switch things around widow.open() works fine on a computer. In another project I am using window.open() successfully on the iPad from an onclick function. I tried using a timer function. I also tried adding an onclick function to the div and posting a click event. In both cases they worked on a computer but not an iPad. I am stumped. I know it would make more sense to handle the ipad in the tree menu frame, but that code is so complex I can't figure out where to put/modify the onclick event. Is there a way to change the object so that it opens in a new tab? Is anyone familiar enough with Mortens Tree Menu code that can tell me how to channge the on click event so that it opens the pdf in a new tab instead of opening a page in the frame? Thanks

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• Self-updating collection concurrency issues

  - by DEHAAS

  I am trying to build a self-updating collection. Each item in the collection has a position (x,y). When the position is changed, an event is fired, and the collection will relocate the item. Internally the collection is using a “jagged dictionary”. The outer dictionary uses the x-coordinate a key, while the nested dictionary uses the y-coordinate a key. The nested dictionary then has a list of items as value. The collection also maintains a dictionary to store the items position as stored in the nested dictionaries – item to stored location lookup. I am having some trouble making the collection thread safe, which I really need. Source code for the collection: public class PositionCollection<TItem, TCoordinate> : ICollection<TItem> where TItem : IPositionable<TCoordinate> where TCoordinate : struct, IConvertible { private readonly object itemsLock = new object(); private readonly Dictionary<TCoordinate, Dictionary<TCoordinate, List<TItem>>> items; private readonly Dictionary<TItem, Vector<TCoordinate>> storedPositionLookup; public PositionCollection() { this.items = new Dictionary<TCoordinate, Dictionary<TCoordinate, List<TItem>>>(); this.storedPositionLookup = new Dictionary<TItem, Vector<TCoordinate>>(); } public void Add(TItem item) { if (item.Position == null) { throw new ArgumentException("Item must have a valid position."); } lock (this.itemsLock) { if (!this.items.ContainsKey(item.Position.X)) { this.items.Add(item.Position.X, new Dictionary<TCoordinate, List<TItem>>()); } Dictionary<TCoordinate, List<TItem>> xRow = this.items[item.Position.X]; if (!xRow.ContainsKey(item.Position.Y)) { xRow.Add(item.Position.Y, new List<TItem>()); } xRow[item.Position.Y].Add(item); if (this.storedPositionLookup.ContainsKey(item)) { this.storedPositionLookup[item] = new Vector<TCoordinate>(item.Position); } else { this.storedPositionLookup.Add(item, new Vector<TCoordinate>(item.Position)); // Store a copy of the original position } item.Position.PropertyChanged += (object sender, PropertyChangedEventArgs eventArgs) => this.UpdatePosition(item, eventArgs.PropertyName); } } private void UpdatePosition(TItem item, string propertyName) { lock (this.itemsLock) { Vector<TCoordinate> storedPosition = this.storedPositionLookup[item]; this.RemoveAt(storedPosition, item); this.storedPositionLookup.Remove(item); } } } I have written a simple unit test to check for concurrency issues: [TestMethod] public void TestThreadedPositionChange() { PositionCollection<Crate, int> collection = new PositionCollection<Crate, int>(); Crate crate = new Crate(new Vector<int>(5, 5)); collection.Add(crate); Parallel.For(0, 100, new Action<int>((i) => crate.Position.X += 1)); Crate same = collection[105, 5].First(); Assert.AreEqual(crate, same); } The actual stored position varies every time I run the test. I appreciate any feedback you may have.

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• How to design a data model that deals with (real) contracts?

  - by Geoffrey

  I was looking for some advice on designing a data model for contract administration. The general life cycle of a contract is thus: Contract is created and in a "draft" state. It is viewable internally and changes may be made. Contract goes out to vendor, status is set to "pending" Contract is rejected by vendor. At this state, nothing can be done to the contract. No statuses may be added to the collection. Contract is accepted by vendor. At this state, nothing can be done to the contract. No statuses may be added to the collection. I obviously want to avoid a situation where the contract is accepted and, say, the amount is changed. Here are my classes: [EnforceNoChangesAfterDraftState] public class VendorContract { public virtual Vendor Vendor { get; set; } public virtual decimal Amount { get; set; } public virtual VendorContact VendorContact { get; set; } public virtual string CreatedBy { get; set; } public virtual DateTime CreatedOn { get; set; } public virtual FileStore Contract { get; set; } public virtual IList<VendorContractStatus> ContractStatus { get; set; } } [EnforceCorrectWorkflow] public class VendorContractStatus { public virtual VendorContract VendorContract { get; set; } public virtual FileStore ExecutedDocument { get; set; } public virtual string Status { get; set; } public virtual string Reason { get; set; } public virtual string CreatedBy { get; set; } public virtual DateTime CreatedOn { get; set; } } I've omitted the filestore class, which is basically a key/value lookup to find the document based on its guid. The VendorContractStatus is mapped as a many-to-one in Nhibernate. I then use a custom validator as described here. If anything but draft is returned in the VendorContractStatus collection, no changes are allowed. Furthermore the VendorContractStatus must follow the correct workflow (you can add a rejected after a pending, but you can't add anything else to the collection if a reject or accepted exists, etc.). All sounds alright? Well a colleague has argued that we should simply add an "IsDraft" bool property to VendorContract and not accept updates if IsDraft is false. Then we should setup a method inside of VendorContractStatus for updating the status, if something gets added after a draft, it sets the IsDraft property of VendorContract to false. I do not like this as it feels like I'm dirtying up the POCOs and adding logic that should persist in the validation area, that no rules should really exist in these classes and they shouldn't be aware of their states. Any thoughts on this and what is the better practice from a DDD perspective? From my view, if in the future we want more complex rules, my way will be more maintainable over the long run. Say we have contracts over a certain amount to be approved by a manager. I would think it would be better to have a one-to-one mapping with a VendorContractApproval class, rather than adding IsApproved properties, but that's just speculation. This might be splitting hairs, but this is the first real gritty enterprise software project we've done. Any advice would be appreciated!

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