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• How does memory management in Java and C# differ?

  - by David Johnstone

  I was reading through 2010 CWE/SANS Top 25 Most Dangerous Programming Errors and one of the entries is for Buffer Copy without Checking Size of Input. It suggests using a language with features to prevent or mitigate this problem, and says: For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. I was not aware that Java and C# differed in any meaningful way with regard to memory management. How is it that Java is not subject to buffer overflows, while C# only protects against overflows? And how is it possible to disable this protection in C#?

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• Deselecting a form input and waiting for a function before submitting

  - by blcArmadillo

  I have a form with an input field where a user enters a unique identifier. I then have some jQuery code that upon the user moving away from the input field (blur) goes out and fetches details about the part and populates some fields on the page. The problem is if the user clicks the submit button before moving out of the input field the jQuery code never has a chance to load in the data and populate the necessary fields. Whats the best way to go about doing this? I thought about maybe setting the focus to body and then having an infinite loop that keeps checking the page until all fields that should be filled in have been filled in but I feel like some sort of event based solution would be better than unpredictable infinite loops. Any ideas?

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• Counting multiple entries in a MySQL database?

  - by Aaron

  Hi all, I'm trying to count multiple entries in a MySQL database, I know how to use COUNT(), but the exact syntax I want to get the results I need eludes me. The problem: Table structure: ID, CODE, AUTHOR, COUNTRY, TIMESTAMP. Code, Author and Country overlap many times in the table. I am trying to discover if there is one simple query that can be ran to return (using WHERE clause on COUNTRY) the author field, the code field, and then a final field that counts the number of times the CODE was present in the query result. So, theoretically I could end up with an array like: array('author', 'code', 'codeAppearsNTimes'); Authors also have varying codes associated with them, so I don't want the results merged. I suppose the end result would be: 'This author is associated with this code this many times'. Is this possible with MySQL? Thanks in advance.

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• How to calculate the sum of a column in an MS Access table for a given date (a single day, month or year)

  - by cMinor

  I have a table in Access in a custom format saved as dd/MM/yyyy hh:mm:ss tt , Also A form in VB.NET 2010, I get a specific day, month and year with no problem but the problem comes when I want to query the sum of a column named value depending on a specific month or day or year.... The table is like: +-----+-----------+-------------------------+ | id | value | date | +-----+-----------+-------------------------+ | id1 | 1499 | 01/01/2012 07:30:11 p.m.| | id2 | 1509 | 11/02/2012 07:30:11 p.m.| | id3 | 1611 | 21/10/2012 07:30:11 p.m.| | id1 | 1115 | 11/10/2012 07:30:11 p.m.| | id1 | 1499 | 17/05/2012 07:30:11 p.m.| | id2 | 1709 | 11/06/2012 07:30:11 p.m.| | id3 | 1911 | 30/07/2012 07:30:11 p.m.| | id1 | 1015 | 01/08/2012 07:30:11 p.m.| | id1 | 1000 | 11/05/2012 07:30:11 p.m.| |+-----+-----------+------------------------+ So I Know the query SELECT SUM(value) FROM mytable WHERE date in='01/05/2012 00:00:00' ... How to tell the query I want the month of May so I would get 1499+1000= 2499 Or how to tell I want the year 2012 so I would get the sum of all the table Which would be the correct syntax...

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• Watching a variable for changes without polling.

  - by milkfilk

  I'm using a framework called Processing which is basically a Java applet. It has the ability to do key events because Applet can. You can also roll your own callbacks of sorts into the parent. I'm not doing that right now and maybe that's the solution. For now, I'm looking for a more POJO solution. So I wrote some examples to illustrate my question. Please ignore using key events on the command line (console). Certainly this would be a very clean solution but it's not possible on the command line and my actual app isn't a command line app. In fact, a key event would be a good solution for me but I'm trying to understand events and polling beyond just keyboard specific problems. Both these examples flip a boolean. When the boolean flips, I want to fire something once. I could wrap the boolean in an Object so if the Object changes, I could fire an event too. I just don't want to poll with an if() statement unnecessarily. import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; /* * Example of checking a variable for changes. * Uses dumb if() and polls continuously. */ public class NotAvoidingPolling { public static void main(String[] args) { boolean typedA = false; String input = ""; System.out.println("Type 'a' please."); while (true) { InputStreamReader isr = new InputStreamReader(System.in); BufferedReader br = new BufferedReader(isr); try { input = br.readLine(); } catch (IOException ioException) { System.out.println("IO Error."); System.exit(1); } // contrived state change logic if (input.equals("a")) { typedA = true; } else { typedA = false; } // problem: this is polling. if (typedA) System.out.println("Typed 'a'."); } } } Running this outputs: Type 'a' please. a Typed 'a'. On some forums people suggested using an Observer. And although this decouples the event handler from class being observed, I still have an if() on a forever loop. import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.Observable; import java.util.Observer; /* * Example of checking a variable for changes. * This uses an observer to decouple the handler feedback * out of the main() but still is polling. */ public class ObserverStillPolling { boolean typedA = false; public static void main(String[] args) { // this ObserverStillPolling o = new ObserverStillPolling(); final MyEvent myEvent = new MyEvent(o); final MyHandler myHandler = new MyHandler(); myEvent.addObserver(myHandler); // subscribe // watch for event forever Thread thread = new Thread(myEvent); thread.start(); System.out.println("Type 'a' please."); String input = ""; while (true) { InputStreamReader isr = new InputStreamReader(System.in); BufferedReader br = new BufferedReader(isr); try { input = br.readLine(); } catch (IOException ioException) { System.out.println("IO Error."); System.exit(1); } // contrived state change logic // but it's decoupled now because there's no handler here. if (input.equals("a")) { o.typedA = true; } } } } class MyEvent extends Observable implements Runnable { // boolean typedA; ObserverStillPolling o; public MyEvent(ObserverStillPolling o) { this.o = o; } public void run() { // watch the main forever while (true) { // event fire if (this.o.typedA) { setChanged(); // in reality, you'd pass something more useful notifyObservers("You just typed 'a'."); // reset this.o.typedA = false; } } } } class MyHandler implements Observer { public void update(Observable obj, Object arg) { // handle event if (arg instanceof String) { System.out.println("We received:" + (String) arg); } } } Running this outputs: Type 'a' please. a We received:You just typed 'a'. I'd be ok if the if() was a NOOP on the CPU. But it's really comparing every pass. I see real CPU load. This is as bad as polling. I can maybe throttle it back with a sleep or compare the elapsed time since last update but this is not event driven. It's just less polling. So how can I do this smarter? How can I watch a POJO for changes without polling? In C# there seems to be something interesting called properties. I'm not a C# guy so maybe this isn't as magical as I think. private void SendPropertyChanging(string property) { if (this.PropertyChanging != null) { this.PropertyChanging(this, new PropertyChangingEventArgs(property)); } }

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• Django DecimalField returns "None" instead of empty value

  - by Ed

  Is there a way to force django to display nothing instead of "None" for a Decimal Field that's been left blank? In my template, I show a list of all the values for a particular field. Each value is hyperlinked to a page that displays the results of a query filtered on that value. But because there are some entries with null value, my list includes actual DecimalField entries and "None" for all those that are empty. When a user clicks on None, django throws a validation error because you cannot query a DecimalField using a string. I could write if statements checking all instances of decimal fields for Nones and skipping them, but that is far from an elegant solution. Any advice? This is one part of the code, though there are other templates that derive the None value in slightly different manners: {% for item in choices %} <a href={% url app_views.field_choice item %}>{{ item }}</a><br> {% endfor %}

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• LINQ: Dot Notation vs Query Expression

  - by Martín Marconcini

  I am beginning to use LINQ in general (so far toXML and toSQL). I've seen that sometimes there are two or more ways to achieve the same results. Take this simple example, as far as I understand both return exactly the same thing: SomeDataContext dc = new SomeDataContext(); var queue = from q in dc.SomeTable where q.SomeDate <= DateTime.Now && q.Locked != true orderby (q.Priority, q.TimeCreated) select q; var queue2 = dc.SomeTable .Where( q => q.SomeDate <= DateTime.Now && q.Locked != true ) .OrderBy(q => q.Priority) .ThenBy(q => q.TimeCreated); Besides any mistake I may have made in the syntax or a missing parameter or difference, the idea is that there are two ways to express the same thing; I understand that the first method has some limitations and that the "dot notation" is more complete, but besides that, are there any other advantages?

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• perl debugger freezes

  - by vbNewbie

  First time perl user and I am trying to debug some script to follow project logic and of course syntax. Using cygwin after entering $perl -d sample.pl Loading DB routines from perl5db.pl version 1.3 Editor support available. Enter h or h h' for help, orperldoc perldebug' for more help. main::(sample2.pl:7): looper(); DB<1 It hangs at the DB<1 line. I cannot enter anything at the prompt. Is there a reason why this post is inappropriate? or how is this not clear?

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• How do I avoid symlinks using an Ant FileSet?

  - by Will

  I have a directory tree that includes a symlink to . (the current directory). When I attempt to iterate over this using an Ant FileSet, I get the following error: Caught error while checking for symbolic links at org.apache.tools.ant.DirectoryScanner.causesIllegalSymlinkLoop(DirectoryScanner.java:1859) The code that I am using to generate the scanner is: FileSet files = new FileSet(); Project project = new Project(); project.setBasedir( dir ); files.setProject( project ); files.setDir( project.getBaseDir() ); files.getDirectoryScanner().setFollowSymlinks( false ); for( Iterator iter = files.iterator(); iter.hasNext(); ) {}

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• Does SQL Server Compact Edition (SqlCe) have a SNAPSHOT table like Oracle Lite?

  - by MusiGenesis

  In Oracle Lite, you can create a SNAPSHOT table which is like a normal table except that it tracks changes to itself. The syntax is CREATE SNAPSHOT TABLE tblWhatever ... and you can perform CRUD operations on it like a normal table. To get the change information, you query the table like this: SELECT * FROM tblWhatever + WHERE ... which returns all the rows in the table (including deleted ones) meeting the WHERE clause, and you can access each row's row_state column as a normal field (which is invisible to a normal SELECT * FROM tblWhatever WHERE ... query). Is there some way to do the same thing with Sql Compact Edition (3.5) - i.e. create a table that tracks changes without using RDA?

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• SoundPlayer causing Memory Leaks?

  - by Nick Udell

  I'm writing a basic writing app in C# and I wanted to have the program make typewriter sounds as you typed. I've hooked the KeyPress event on my RichTextBox to a function that uses a SoundPlayer to play a short wav file every time a key is pressed, however I've noticed after a while my computer slows to a crawl and checking my processes, audiodlg.exe was using 5 GIGABYTES of RAM. The code I'm using is as follows: I initialise the SoundPlayer as a global variable on program start with SoundPlayer sp = new SoundPlayer("typewriter.wav") Then on the KeyPress event I simply call sp.Play(); Does anybody know what's causing the heavy memory usage? The file is less than a second long, so it shouldn't be clogging the thing up too much.

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• How to determine if an event is already subscribed

  - by Ram

  Hi, In my .NET application I am subscribing to events from another class. The subscription is conditional. I am subscribing to events when the control is visible and de-subscribing it when it become invisible. However in some conditions I do not want to de-subscribe the event even if the control is not visible as I want the result of an operation which is happening on background thread . Is there any way through which I can determine if a that class has already subscribed to that event. I know we can do it in the class which will raise that event by checking event with null but I don not know how to do it in a class which will subscribe to that event.

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• How can I copy a file from VMS to Windows and back again?

  - by Matt Joslin

  I am trying to copy C source files from a vms alpha to a windows machine to allow easier editing of the code. (VMS editor is just a text editor and it would be nice to have syntax highlighting etc) I can copy this across using Exceed FTP and this handles the issue of duplicate filenames with version suffix that vms has: File.c;1 File.c;2 Flle.c;3 But when I open a file I've transferred, all the line breaks have been lost and the entire file is just one line. Can anyone recommend a solution to this or offer any hints? Thanks in advance ps. I need to be able to copy the files back to vms and still maintain format.

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• How to compile a program which needs a newer version of glib

  - by michael

  Hi, I am trying to compile Webkit on Ubuntu 8.04. But when i run autogen.sh, I get the following error saying it needs a newer version of glib. So what is the safest way to install glib without screwing up the rest of my OS (since the rest needs 2.16 while webkit compile needs 2.21)? checking for GLIB... configure: error: Package requirements (glib-2.0 >= 2.21.3 gobject-2.0 >= 2.0 gthread-2.0 >= 2.0) were not met: Requested 'glib-2.0 >= 2.21.3' but version of GLib is 2.16.6 Consider adjusting the PKG_CONFIG_PATH environment variable if you installed software in a non-standard prefix. Alternatively, you may set the environment variables GLIB_CFLAGS and GLIB_LIBS to avoid the need to call pkg-config. See the pkg-config man page for more details.

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• XSLT: How to escape square brackets in Urls

  - by ilariac

  I have a set of records from Solr where field[@name='url'] can have the following format: http://url/blabla/blabla.aspx?sv=[keyword%20keyword,%201] My understanding is that the square brackets denote an array syntax and I would like to use XSLT to remove the square brackets from all Urls. The reason for this is that I am using an Open URL resolver, which does not currently handle well those characters. The best option would be to strip the square brackets from all URLs before such resources are mediated by the Open URL resolver. There are cases where I have multiple occurrences of square brackets per Url. Can you please help me with this? Thanks for your help, I.

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• understanding this regex

  - by DarthVader

  I m trying to understand what the following does. ^([^=]+)(?:(?:\\=)(.+))?$ Any ideas? This is being used here. Obviously it s command line parser but i m trying to understand the syntax so i can actually run the program. This is from commandline-jmxclient , they have no documents on setting JMX properties but in their source code, there is such an option, so i just want to understand how i can invoke that method. Matcher m = Client.CMD_LINE_ARGS_PATTERN.matcher(command); if ((m == null) || (!m.matches())) { throw new ParseException("Failed parse of " + command, 0); } this.cmd = m.group(1); if ((m.group(2) != null) && (m.group(2).length() > 0)) this.args = m.group(2).split(","); else this.args = null;

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• PEP8: conflict between W292 and W391

  - by seler

  As far as I know in unix it's a good practice to always have blank line at the end of file - or to put it in other words: every line should end with \n. While checking my python code with PEP8 I noticed that it also states that there should be \n at end of file: W292 no newline at end of file JCR: The last line should have a newline. What's strange, it conflicts with W391: W391 blank line at end of file JCR: Trailing blank lines are superfluous. Okay: spam(1) W391: spam(1)\n How it should be? Should I have blank line at the end of file or not?

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• Setting properties of auto-generated listboxitem

  - by DerKlaus

  I am trying to set the inputbindings of the auto-generated ListBoxItems of a databound ListBox. The code below does not work. The compiler complains that "The Property Setter 'InputBindings' cannot be set because it does not have an accessible set accessor." What is the correct syntax to set the InputBindings? <ListBox.ItemContainerStyle> <Style TargetType="{x:Type ListBoxItem}"> <Setter Property="ListBoxItem.InputBindings"> <Setter.Value> <MouseBinding Command="{Binding OpenCommand}" Gesture="LeftDoubleClick"/> </Setter.Value> </Setter> </Style> </ListBox.ItemContainerStyle> PS: Posting does not work with Opera 10.51

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• Collaborative editing for .NET development - what are the possibilities

  - by Olav

  What are the best options for real-time collaborative editing for .NET development? (C#,VB.NET, ASP.NET - not Mono unless it is the best way to get collaboration) 1) Anything possible with visual studio? 2) Collaborative editors? I know Eclipse has real-time collaboration, but I don't know how far you can combine it with .NET support. 3) Web-based tools? 4) Desktop sharing tools like VNC, NX etc. The main points is that 2 developers in different locations should be able to see edits in real time. Both should be able to edit, or it should be easy to switch control. Regarding .NET, syntax highlighting etc is better than nothing.

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• Saving a "project"-type document (containing sub-documents)

  - by andyvn22

  I'm trying to create a "project"-like document, in that it contains subdocuments in a specified directory. I'd like a brand new save of a document to set up that directory with appropriate subdirectories. I'd like a "Save As" to copy all those subdirectories and any files within them to the new location. But I'd like a "Save" to only update certain data files and (of course) not overwrite all the subdocuments! What's the "safe" way to do this? I tried keeping track of the file's location in my document, and checking to see if it was the same or different than the save location, but it feels messy, and I'm worried that Apple is doing something behind the scenes that will make this direct URL-to-URL comparison fail in some circumstances. Is there a standard way to do something like this?

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• git: How to diff changed files versus previous versions after a pull?

  - by doug

  I'm new to git, using it via Terminal on Snow Leopard. When I run "git pull" I often want to know what changed between the last version of a file and the new one. Say I want to know what someone else committed to a particular file. How is that done? I'm assuming it's "git diff" with some parameters for commit x versus commit y but I can't seem to get the syntax. I also find "git log" confusing a bit and am not sure where to get the commit ID of my latest version of the file versus the new one.

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• problems with mysql "or"

  - by Simon

  i have a problem with "and" "or" syntax!!! here is my query. . . SELECT `act1`.`name`, `act1`.`surname`, `act2`.`name`, `act2`.`surname`, `act3`.`name`, `act3`.`surname` FROM videos, actors AS act1, actors AS act2, actors AS act3 WHERE videos.ident = 'somethink' AND ( act1.id = videos.id_actor1 OR act2.id = videos.id_actor2 OR act3.id = videos.id_actor3 ) it returns me all variations of {name, surname}, but why!!! i want the name and surname of first axactly, second and thirth, if they exist!!! halp me please

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• Enable access for assistive device programmatically

  - by Dheeraj

  Hi All, I want to enable Access for assistive devices in System Preferences programmatically. But Problem is that my application is not running as root user and i do not want my application to be as root user and also should not ask for any authentication in between. I want to tap all keyboard events globally. I am using CGEventTapCreate() for the same.In the documentation of CGEventTapCreate() API it is mentioned that, Event taps receive key up and key down events if one of the following conditions is true: The current process is running as the root user. Access for assistive devices is enabled. In Mac OS X v10.4 & later, you can enable this feature using System Preferences, Universal Access panel, Keyboard view. I tried manually by checking the Enable Access for assistive devices from System Preference and it gives me expected output. So is there any way to do the same via program without asking for authentication and also application is not running as root user? Thanks, Dheeraj.

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• How To create a Simple NDK Program in Android NDK

  - by Rakesh

  Hi I am new to android Programming and NDK.Yet i am not clear with working in NDK.I just downloaded android ndk r4.If i want to develop appln using NDK,and i refered http://marakana.com/forums/android/android_examples/49.html for reference,But still not clear how to create the header file and implementation,I did nt have any previuos exp in c language.And they asked for run javah tool to create the JNI header file. I dont know how to use javah tool,but i found it in java bin directory and i tried using cmd javah -jni com.pathname.classname is this correct syntax? if so i tried doing it in android bin directory.I want to know ,what classname represents,is this name of header file class that i try to create Regards Rakesh Shankar.P

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• LLBL Gen Predicate Filter

  - by Neil

  I am new to LLBLGen Pro and am checking for duplicate, I have the following SQL: SQL: select a.TopicId,atc.TopicCategoryId,a.Headline from article a inner join ArticleTopicCategory atc on atc.ArticleId = a.Id where a.TopicId = 'C0064FAE-093B-466E-8745-230534867D2F' and a.Headline = 'Test' and atc.TopicCategoryId in ('004D64F7-474C-48F9-9887-17B1E7532A84') Whenever I step though my function, it always returns 0: LLBLGen Code: public bool CheckDuplicateArticle(Guid topicId, List<Guid> categories, string headline) { ArticleCollection articles = new ArticleCollection(); PredicateExpression filter = new PredicateExpression(); RelationCollection relation = new RelationCollection(); relation.Add(ArticleEntity.Relations.ArticleTopicCategoryEntityUsingArticleId); filter.AddWithAnd(ArticleFields.TopicId == topicId); filter.AddWithAnd(ArticleTopicCategoryFields.Id == categories); filter.AddWithAnd(ArticleFields.Headline == headline); articles.GetMulti(filter, 0, null, relation); return articles.Count > 0; } Any help would be appreciated!

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