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Articles indexed Tuesday May 11 2010

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  • Help understanding .NET delegates, events, and eventhandlers

    - by Seth Spearman
    Hello, In the last couple of days I asked a couple of questions about delegates HERE and HERE. I confess...I don't really understand delegates. And I REALLY REALLY REALLY want to understand and master them. (I can define them--type safe function pointers--but since I have little experience with C type languages it is not really helpful.) Can anyone recommend some online resource(s) that will explain delegates in a way that presumes nothing? This is one of those moments where I suspect that VB actually handicaps me because it does some wiring for me behind the scenes. The ideal resource would just explain what delegates are, without reference to anything else like (events and eventhandlers), would show me how all everything is wired up, explain (as I just learned) that delegates are types and what makes them unique as a type (perhaps using a little ildasm magic)). That foundation would then expand to explain how delegates are related to events and eventhandlers which would need a pretty good explanation in there own right. Finally this resource could tie it all together using real examples and explain what wiring DOES happen automatically by the compiler, how to use them, etc. And, oh yeah, when you should and should not use delegates, in other words, downsides and alternatives to using delegates. What say ye? Can any of you point me to resource(s) that can help me begin my journey to mastery? EDIT One last thing. The ideal resource will explain how you can and cannot use delegates in an interface declaration. That is something that really tripped me up. Thanks for your help. Seth

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  • Date format strings in .Net and Java

    - by mizipzor
    I have an application that runs on both C# .Net and Java. Two entirely separate but identical code bases. The problem Im having is formatting date and numbers. For example: A user running the .Net variant is inputting a date and a format string. The 26th of April 1986 is formatted 1986-04-26. The actual date, along with the format string, is serialized to an XML file. Later another user running the Java variant opens said XML file and looks at the date. I want them to look the same. Whats the best approach here? There doesnt seem to be a one-to-one mapping between Java and .Nets format strings. Should I limit the possible formats to a selection I know I can represent fully in both .Net and Java?

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  • Linux - File was deleted and then reappeared when folder was zipped

    - by davee9
    Hello, I am using Backtrack 4 Final, which is a Linux distro that is Ubuntu based. I had a directory that contained around 5 files. I deleted one of the files, which sent it to the trash. I then zipped the directory up (now containing 4 files), using this command: zip -r directory.zip directory/ When I then unzipped directory.zip, the file I deleted was in there again. I couldn't believe this, so I zipped up the directory again, and the file reappeared again but this time could not be opened because the operating system said it didn't exist or something. I don't remember the exact error, and I cannot make this happen again. Would anyone happen to know why a file that was deleted from a directory would reappear in that directory after it was zipped up? Thank you.

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  • How do I find the ruby interpreter?

    - by The Doctor What
    Inside a ruby script, how do I get the path to the ruby interpreter? Example script: #!/path/to/ruby puts `#{RUBY_INTERPRETER_PATH} -e "puts 'hi'"` #EOF Where RUBY_INTERPRETER_PATH is a mythical way of finding /path/to/ruby. This is just an example, though. I realize in this case that I could just copy /path/to/ruby into the script, but I don't want to do that. I want this to work "correctly" regardless of what the #! line says. Even if running under windows. Ciao!

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  • m and s keys do not work over vnc connection to ubuntu server

    - by Don
    I'm new at setting a lot of this up, so bear with me. I installed Ubuntu 10.4 server on a 64 bit machine. Then I added vnc so I could manage it while it's racked. I start the server, SSH to it, and run vncserver :1 At this point, all keys work fine. Next I exit out of the SSH session and fire up my client vnc app. I connect via the IP :1, enter my password, and everything seems to be fine. Now when I enter a terminal (through the vnc connection) I cannot type lowercase "s" or "m" (upper case works). I've tried on two different pc's running the vnc client, but it's the same. I also installed the latest updates from Ubuntu as of today. Thanks for any help.

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  • How can I perform this query between related tables without using UNION?

    - by jeremy
    Suppose I have two separate tables that I watch to query. Both of these tables has a relation with a third table. How can I query both tables with a single, non UNION based query? I want the result of the search to rank the results by comparing a field on each table. Here's a theoretical example. I have a User table. That User can have both CDs and books. I want to find all of that user's books and CDs with a single query matching a string ("awesome" in this example). A UNION based query might look like this: SELECT "book" AS model, name, ranking FROM book WHERE name LIKE 'Awesome%' UNION SELECT "cd" AS model, name, ranking FROM cd WHERE name LIKE 'Awesome%' ORDER BY ranking DESC How can I perform a query like this without the UNION? If I do a simple left join from User to Books and CDs, we end up with a total number of results equal to the number of matching cds timse the number of matching books. Is there a GROUP BY or some other way of writing the query to fix this?

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  • Keep Hibernate Initializer from Crashing Program

    - by manyxcxi
    I have a Java program using a basic Hibernate session factory. I had an issue with a hibernate hbm.xml mapping file and it crashed my program even though I had the getSessionFactory() call in a try catch try { session = SessionFactoryUtil.getSessionFactory().openStatelessSession(); session.beginTransaction(); rh = getRunHistoryEntry(session); if(rh == null) { throw new Exception("No run history information found in the database for run id " + runId_ + "!"); } } catch(Exception ex) { logger.error("Error initializing hibernate"); } It still manages to break out of this try/catch and crash the main thread. How do I keep it from doing this? The main issue is I have a bunch of cleanup commands that NEED to be run before the main thread shuts down and need to be able to guarantee that even after a failure it still cleans up and goes down somewhat gracefully. The session factory looks like this: public class SessionFactoryUtil { private static final SessionFactory sessionFactory; static { try { // Create the SessionFactory from hibernate.cfg.xml sessionFactory = new Configuration().configure().buildSessionFactory(); } catch (Throwable ex) { // Make sure you log the exception, as it might be swallowed System.err.println("Initial SessionFactory creation failed." + ex); throw new ExceptionInInitializerError(ex); } } public static SessionFactory getSessionFactory() { try { return sessionFactory; } catch(Exception ex) { return null; } } }

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  • JAR files, don't they just bloat and slow Java down?

    - by Josamoto
    Okay, the question might seem dumb, but I'm asking it anyways. After struggling for hours to get a Spring + BlazeDS project up and running, I discovered that I was having problems with my project as a result of not including the right dependencies for Spring etc. There were .jars missing from my WEB-INF/lib folder, yes, silly me. After a while, I managed to get all the .jar files where they belong, and it comes at a whopping 12.5MB at that, and there's more than 30 of them! Which concerns me, but it probably and hopefully shouldn't be concerned. How does Java operate in terms of these JAR files, they do take up quite a bit of hard drive space, taking into account that it's compressed and compiled source code. So that can really quickly populate a lot of RAM and in an instant. My questions are: Does Java load an entire .jar file into memory when say for instance a class in that .jar is instantiated? What about stuff that's in the .jar that never gets used. Do .jars get cached somehow, for optimized application performance? When a single .jar is loaded, I understand that the thing sits in memory and is available across multiple HTTP requests (i.e. for the lifetime of the server instance running), unlike PHP where objects are created on the fly with each request, is this assumption correct? When using Spring, I'm thinking, I had to include all those fiddly .jars, wouldn't I just be better off just using native Java, with say at least and ORM solution like Hibernate? So far, Spring just took extra time configuring, extra hard drive space, extra memory, cpu consumption, so I'm concerned that the framework is going to cost too much application performance just to get for example, IoC implemented with my BlazeDS server. There still has to come ORM, a unit testing framework and bits and pieces here and there. It's just so easy to bloat up a project quickly and irresponsibly easily. Where do I draw the line?

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  • RelativeLayout does not shrink in height

    - by rudas
    Hi, I cannot get my relative layuot view to shrink when using it in the follwing layout, used as a dialog. In below example the scrollview always expands to fill the entire dialog which looks very ugly if there is not much actual content. I have tried most combinations of fill_parent, wrap_content etc without success. The problem seems to be that setting the button to "align_bottom" will cause the dialog to fill its height. But if I change the order and have to button placed below the scrollview the button will not be visible if a lot of content is shown... Please help /Rudas <RelativeLayout android:id="@+id/RelativeLayout01" xmlns:android="http://schemas.android.com/apk/res/android" android:layout_height="wrap_content" android:layout_width="wrap_content"> <ScrollView android:id="@+id/ScrollView01" android:layout_above="@+id/dialogCloseButton" android:layout_alignParentTop="true" android:layout_width="wrap_content" android:layout_height="wrap_content"> <LinearLayout android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/dialogContent" android:orientation="vertical" android:paddingBottom="10dp"> <TextView android:id="@+id/TextView01" android:layout_width="wrap_content" android:layout_height="wrap_content"> </TextView> </LinearLayout> </ScrollView> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Close" android:id="@+id/dialogCloseButton" android:layout_alignParentBottom="true" android:layout_centerHorizontal="true"></Button> </RelativeLayout>

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  • Django make model field name a link

    - by Daniel Garcia
    what Im looking to do is to have a link on the name of a field of a model. So when im filling the form using the admin interface i can access some information. I know this doesn't work but shows what i want to do class A(models.Model): item_type = models.CharField(max_length=100, choices=ITEMTYPE_CHOICES, verbose_name="<a href='http://www.quackit.com/html/codes'>Item Type</a>") Other option would be to put a description next to the field. Im not even sure where to start from.

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  • svn update overwrite local copy - can I retrieve local copy?

    - by Myx
    Hi: So I was editing a file on my local machine and I was ready to commit to the repository except that instead of running the svn commit, I ran svn update. Is there any way I can retrieve the changes that I had? I was working on a tex file in vim and I had closed the file before running svn update. Thanks. EDIT: I'm sorry - I completely was worried for nothing (project deadline in 30 mins and I thought I deleted all my changes). I realize that when I run svn update, it doesn't rewrite the local changes but tries to merge the files if there are no conflicts. Can someone tell me how to close or remove this post? Thanks.

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  • Codeigniter: Library function--I'm stuck

    - by Kevin Brown
    I have a library function that sets up my forms, and submits data. They're long, and they work, so I'll spare you reading my code. :) I simply need a way for my functions to determine how to handle the data. Until now, the function did one thing: Submit a report for the current user. NOW, the client has requested that an administrator also be able to complete a form--this means that the form would be filled out, and it would CREATE a user at the same time, whereas the current function EDITS and is accessed by an EXISTING user. Do I need a separate function to do essentially the same thing? How do I make one function perform two tasks? One to update a user, and if there is no user, create one. Current controller: function survey() { $id = $this->session->userdata('id'); $data['member'] = $this->home_model->getUser($id); //Convert the db Object to a row array $data['manager'] = $data['member']->row(); $manager_id = $data['manager']->manager_id; $data['manager'] = $this->home_model->getUser($manager_id); $data['manager'] = $data['manager']->row(); $data['header'] = "Home"; $this->survey_form_processing->survey_form($this->_container,$data, $method); } Current Library: function survey_form($container) { //Lots of validation stuff $this->CI->validation->set_rules($rules); if ( $this->CI->validation->run() === FALSE ) { // Output any errors $this->CI->validation->output_errors(); } else { // Submit form $this->_submit(); } $this->CI->load->view($container,$data); The submit function is huge too. Basically says, "Update table with data where user_id=current user" I hope this wasn't too confusing. I'll create two functions if need be, but I'd like to keep redundancy down! }

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  • Can I create a custom class that inherits from a strongly typed DataRow?

    - by Calvin Fisher
    I'm working on a huge, old project with a lot of brittle code, some of which has been around since the .NET 1.0 era, and it has been and will be worked on by other people... so I'd like to change as little as possible. I have one project in my solution that contains DataSet.xsd. This project compiles to a separate assembly (Data.dll). The database schema includes several tables arranged more or less hierarchically, but the only way the tables are actually linked together is through joins. I can get, e.g. DepartmentRow and EmployeeRow objects from the autogenerated code. EmployeeRow contains information from the employee's corresponding DepartmentRow through a join. I'm making a new report to view multiple departments and all their employees. If I use the existing data access scheme, all I will be able to get is a spreadsheet-like output where each employee is represented on one line, with department information repeated over and over in its appropriate columns. E.g.: Department1...Employee1... Department1...Employee2... Department2...Employee3... But what the customer would like is to have each department render like a heading, with a list of employees beneath each. E.g.: - Department1... Employee1... Employee2... + Department2... I'm trying to do this by inheriting hierarchical objects from the autogenerated Row objects. E.g.: public class Department : DataSet.DepartmentRow { public List<Employee> Employees; } That way I could nest the data in the report by using a collection of Department objects as the DataSource, each of which will put its list of Employees in a subreport. The problem is that this gives me a The type Data.DataSet.DepartmentRow has no constructors defined error. And when I try to make a constructor, e.g. public class Department : DataSet.DepartmentRow { private Department() { } public List<Employee> Employees; } I get a 'Data.DataSet.DepartmentRow(System.Data.DataRowBuilder)' is inaccessible due to its protection level. error in addition to the first one. Is there a way to accomplish what I'm trying to do? Or is there something else I should be trying entirely?

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  • javascript getMonth() gets me!

    - by Dave Noderer
    I’ve been working a lot with Microsoft CRM over the past few months and much of the screen level customization uses javascript. One thing I discovered today while breaking apart some dates was that the javascript getDate() returns the day of the month 1-31 as you would expect but the getMonth() returns 0-11… definitely not what I expected!!

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  • The theory of evolution applied to software

    - by Michel Grootjans
    I recently realized the many parallels you can draw between the theory of evolution and evolving software. Evolution is not the proverbial million monkeys typing on a million typewriters, where one of them comes up with the complete works of Shakespeare. We would have noticed by now, since the proverbial monkeys are now blogging on the Internet ;-) One of the main ideas of the theory of evolution is the balance between random mutations and natural selection. Random mutations happen all the time: millions of mutations over millions of years. Most of them are totally useless. Some of them are beneficial to the evolved species. Natural selection favors the beneficially mutated species. Less beneficial mutations die off. The mutated rabbit doesn't have to be faster than the fox. It just has to be faster than the other rabbits.   Theory of evolution Evolving software Random mutations happen all the time. Most of these mutations are so bad, the new species dies off, or cannot reproduce. Developers write new code all the time. New ideas come up during the act of writing software. The really bad ones don't get past the stage of idea. The bad ones don't get committed to source control. Natural selection favors the beneficial mutated species Good ideas and new code gets discussed in group during informal peer review. Less than good code gets refactored. Enhanced code makes it more readable, maintainable... A good set of traits makes the species superior to others. It becomes widespread A good design tends to make it easier to add new features, easier to understand the current implementations, easier to optimize for performance...thus superior. The best designs get carried over from project to project. They appear in blogs, articles and books about principles, patterns and practices.   Of course the act of writing software is deliberate. This can hardly be called random mutations. Though it sometimes might seem that code evolves through a will of its own ;-) Does this mean that evolving software (evolution) is better than a big design up front (creationism)? Not necessarily. It's a false idea to think that a project starts from scratch and everything evolves from there. Everyone carries his experience of what works and what doesn't. Up front design is necessary, but is best kept simple and minimal, just enough to get you started. Let the good experiences and ideas help to drive the process, whether they come from you or from others, from past experience or from the most junior developer on your team. Once again, balance is the keyword. Balance design up front with evolution on a daily basis. How do you know what balance is right? Through your own experience of what worked and what didn't (here's evolution again). Notes: The evolution of software can quickly degenerate without discipline. TDD is a discipline that leaves little to chance on that part. Write your test to describe the new behavior. Write just enough code to make it behave as specified. Refactor to evolve the code to a higher standard. The responsibility of good design rests continuously on each developers' shoulders. Promiscuous pair programming helps quickly spreading the design to the whole team.

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  • Mustek 1200 CP driver SFC4.SYS bluescreens with BAD_POOL_HEADER

    - by Slink84
    I have Windows XP SP2. Recently it started bluescreening right after starting up with 'BAD_POOL_HEADER', 0x00000019 error caused by SFC4.SYS driver. After googling for a while I've found out that this is my Mustek's 1200 CP scanner driver. Booting in safe mode and uninstalling it solved the problem... And created another one: now I can't use my scanner. The weird thing is, that it has been working for a while on this PC without any problems. It all started suddenly, and I can't remember installing anything that might have affected it. Reverting to several earlier system restore points didn't help. I've tried re-installing it from the Mustek website, just in case if my copy got corrupted or infected by a virus, but it did not help - it still bluescreens. Also, I've installed Avast and scanned my PC - there were no viruses found. If anyone had such a problem before or has an idea what might have caused it, please help. ED: @Michael Todd: ...try installing on another PC... I've installed it on my friends PC. He has the same OS version, with the latest updates just like mine (he wasn't too happy, even after I've assured him that it is easy to fix by uninstalling that driver :] ). It worked fine - no bluescreens or whatsoever. So I think I've narrowed it down to either BIOS settings, or some wicked driver conflict. Next thing I'm going to try is to re-install XP, or install windows 7. I'm not too happy with a prospect of mucking about with BIOS settings...

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  • How to subtract dates in YYYYMMDD format?

    - by NinjaBomb
    I have 2 integer fields that represent dates in the YYYYMMDD format. What is the best way to subtract 2 of these fields to get the correct # of days between them? For instance, if I take the difference between 20100511 and 20100428 I would like the result to be 13 and not 83. I know I need to convert the integer fields into date formats but everything I have tried either throws an exception or doesn't work correctly. What am I missing? Answers in vb.net please

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  • Cascading Dropdown List

    - by user333831
    I am working on a web app and trying to code a form with two dropdown lists. The list in the second dropdown will be dependent on the selection from the first one. The task itself isn’t too complicated except that once the first selection is made, I need to make a database call to pull the data for the second dropdown. This is where I am having difficulty. Both lists are in fact populated from a database. I am working on this in a python script and have been trying to do this w/ an onChange javascript function. The web app is built in Zope and page templates may be an option along w/ the python scripts.

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  • UpdatePanel on masterpage does postback on first button click

    - by gevjen
    I have an update panel on a masterpage and for reasons unbeknown to me our content placeholder is within the updatepanel. But when I click on a button on one of our pages that uses the masterpage the page postsback. If I then click the button for a second time it does not postback and does an ajax call. Im wondering why it does a postback the first time when I dont want it to. Below is how I have the updatepanel set up

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  • Winforms connection strings from App.config

    - by Geo Ego
    I have a Winforms app that I am developing in C# that will serve as a frontend for a SQL Server 2005 database. I rolled the executable out to a test machine and ran it. It worked perfectly fine on the test machine up until the last round of changes that I made. However, now on the test machine, it throws the following exception immediately upon opening: System.NullReferenceException: Object reference not set to an instance of an object. at PSRD_Specs_Database_Administrat.mainMenu.mainMenu_Load(Object sender, EventArgs e) at System.Windows.Forms.Form.OnLoad(EventArgs e) at System.Windows.Forms.Form.OnCreateControl() at System.Windows.Forms.Control.CreateControl(Boolean fIgnoreVisible) at System.Windows.Forms.Control.CreateControl() at System.Windows.Forms.Control.WmShowWindow(Message& m) at System.Windows.Forms.Control.WndProc(Message& m) at System.Windows.Forms.ScrollableControl.WndProc(Message& m) at System.Windows.Forms.ContainerControl.WndProc(Message& m) at System.Windows.Forms.Form.WmShowWindow(Message& m) at System.Windows.Forms.Form.WndProc(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m) at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam) The only thing that I changed in this version that pertains to mainMenu_Load is the way that the connection string to the database is called. Previously, I had set a string with the connection string on every form that I needed to call it from, like: string conString = "Data Source = SHAREPOINT;Trusted_Connection = yes;" + "database = CustomerDatabase;connection timeout = 15"; As my app grew and I added forms to it, I decided to add an App.config to the project. I defined the connection string in it: <connectionStrings> <add name="conString" providerName="System.Data.SqlClient" connectionString="Data Source = SHAREPOINT;Trusted_Connection = yes;database = CustomerDatabase;connection timeout = 15" /> </connectionStrings> I then created a static string that would return the conString: public static string GetConnectionString(string conName) { string strReturn = string.Empty; if (!(string.IsNullOrEmpty(conName))) { strReturn = ConfigurationManager.ConnectionStrings[conName].ConnectionString; } else { strReturn = ConfigurationManager.ConnectionStrings["conString"].ConnectionString; } return strReturn; } I removed the conString variable and now call the connection string like so: PublicMethods.GetConnectionString("conString").ToString() It appears that this is giving me the error. I changed these instances to directly call the connection string from App.config without using GetConnectionString. For instance, in a SQLConnection: using (SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["conString"].ConnectionString)) This also threw the exception. However, when I went back to using the conString variable on each form, I had no issues. What I don't understand is why all three methods work fine on my development machine, while using the App.config directly or via the static string I created throw exceptions.

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  • JQuery: using .LIVE problems

    - by TeddTedd
    I have the following JQuery code: $("#myDIV li:eq(0)").live('click',function(){ funcA(); }); $("#myDIV li:eq(1)").live('click',function(){ funcB(); }); $("#myDIV li:eq(2)").live('click',function(){ funcC(); }); $("#myDIV li:eq(3)").live('click',function(){ funcD(); }); And realized it's really inefficient. So I tried the following, which I believe is much more effect; however, the code does not work: var tab_node = $("#myDIV li"); tab_node.eq(0).live('click',function(){ funcA(); }); tab_node.eq(1).live('click',function(){ funcB(); }); tab_node.eq(2).live('click',function(){ funcC(); }); tab_node.eq(3).live('click',function(){ funcD(); }); Any idea how I can make my code more efficient while also work? UPDATE: From the answers below, it sounds like these two statements are not equalavent. New Question: Is there any way to run my original code more efficient?

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