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  • Returning JsonResult From ASP.NET MVC 2.0 Controller and Unit Testing

    This post will show how to return a simple Json result from an ASP.NET MVC 2.0 web project.  It will show how to test that result inside a unit test and essentially pick apart the Json, just... This site is a resource for asp.net web programming. It has examples by Peter Kellner of techniques for high performance programming...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • RewriteRule not working at server level?

    - by Alexis Wilke
    I wanted to forbid some robots from doing certain things to my websites and decided to add a RewriteRule for that purpose. The rule works when put in one of my <VirtualHost *:80> tag and looks like this: RewriteEngine On RewriteCond %{HTTP_USER_AGENT} libwww-perl RewriteCond %{REQUEST_METHOD} POST RewriteRule . - [F,L] However, I wanted to apply that to all my websites instead of just one of them. So with the newest version of Apache2 settings, I decided to put that code in the security.conf file. This file is defined under /etc/apache2/conf-available/... (and yes, I have a softlink from the /etc/apache2/conf-enabled/... directory.) However, if the definition is only in the conf-available/security.conf files, it somehow gets ignored. From the documentation, it says that these Rewrite* commands all work at server level! Any idea of what I would be missing?

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  • C++ : Lack of Standardization at the Binary Level

    - by Nawaz
    Why ISO/ANSI didn't standardize C++ at the binary level? There are many portability issues with C++, which is only because of lack of it's standardization at the binary level. Don Box writes, (quoting from his book Essential COM, chapter COM As A Better C++) C++ and Portability Once the decision is made to distribute a C++ class as a DLL, one is faced with one of the fundamental weaknesses of C++, that is, lack of standardization at the binary level. Although the ISO/ANSI C++ Draft Working Paper attempts to codify which programs will compile and what the semantic effects of running them will be, it makes no attempt to standardize the binary runtime model of C++. The first time this problem will become evident is when a client tries to link against the FastString DLL's import library from a C++ developement environment other than the one used to build the FastString DLL. Are there more benefits Or loss of this lack of binary standardization?

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  • Silverlight 4 Twitter Client - Part 2

    - by Max
    We will create a few classes now to help us with storing and retrieving user credentials, so that we don't ask for it every time we want to speak with Twitter for getting some information. Now the class to sorting out the credentials. We will have this class as a static so as to ensure one instance of the same. This class is mainly going to include a getter setter for username and password, a method to check if the user if logged in and another one to log out the user. You can get the code here. Now let us create another class to facilitate easy retrieval from twitter xml format results for any queries we make. This basically involves just creating a getter setter for all the values that you would like to retrieve from the xml document returned. You can get the format of the xml document from here. Here is what I've in my Status.cs data structure class. using System; using System.Net; using System.Windows; using System.Windows.Controls; using System.Windows.Documents; using System.Windows.Ink; using System.Windows.Input; using System.Windows.Media; using System.Windows.Media.Animation; using System.Windows.Shapes;  namespace MaxTwitter.Classes { public class Status { public Status() {} public string ID { get; set; } public string Text { get; set; } public string Source { get; set; } public string UserID { get; set; } public string UserName { get; set; } } }  Now let us looking into implementing the Login.xaml.cs, first thing here is if the user is already logged in, we need to redirect the user to the homepage, this we can accomplish using the event OnNavigatedTo, which is fired when the user navigates to this particular Login page. Here you utilize the navigate to method of NavigationService to goto a different page if the user is already logged in. if (GlobalVariable.isLoggedin())         this.NavigationService.Navigate(new Uri("/Home", UriKind.Relative));  On the submit button click event, add the new event handler, which would save the perform the WebClient request and download the results as xml string. WebRequest.RegisterPrefix("https://", System.Net.Browser.WebRequestCreator.ClientHttp);  The following line allows us to create a web client to create a web request to a url and get back the string response. Something that came as a great news with SL 4 for many SL developers.   WebClient myService = new WebClient(); myService.AllowReadStreamBuffering = true; myService.UseDefaultCredentials = false; myService.Credentials = new NetworkCredential(TwitterUsername.Text, TwitterPassword.Password);  Here in the following line, we add an event that has to be fired once the xml string has been downloaded. Here you can do all your XLINQ stuff.   myService.DownloadStringCompleted += new DownloadStringCompletedEventHandler(TimelineRequestCompleted);   myService.DownloadStringAsync(new Uri("https://twitter.com/statuses/friends_timeline.xml"));  Now let us look at implementing the TimelineRequestCompleted event. Here we are not actually using the string response we get from twitter, I just use it to ensure the user is authenticated successfully and then save the credentials and redirect to home page. public void TimelineRequestCompleted(object sender, System.Net.DownloadStringCompletedEventArgs e) { if (e.Error != null) { MessageBox.Show("This application must be installed first"); }  If there is no error, we can save the credentials to reuse it later.   else { GlobalVariable.saveCredentials(TwitterUsername.Text, TwitterPassword.Password); this.NavigationService.Navigate(new System.Uri("/Home", UriKind.Relative)); } } Ok so now login page is done. Now the main thing – running this application. This credentials stuff would only work, if the application is run out of the browser. So we need fiddle with a few Silverlioght project settings to enable this. Here is how:    Right click on Silverlight > properties then check the "Enable running application out of browser".    Then click on Out-Of-Browser settings and check "Require elevated trust…" option. That's it, all done to run. Now press F5 to run the application, fix the errors if any. Then once the application opens up in browser with the login page, right click and choose install.  Once you install, it would automatically run and you can login and can see that you are redirected to the Home page. Here are the files that are related to this posts. We will look at implementing the Home page, etc… in the next post. Please post your comments and feedbacks; it would greatly help me in improving my posts!  Thanks for your time, catch you soon.

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  • Remote Display Config.sh Using SSH

    - by john.graves(at)oracle.com
    How often I see people look to VNC, NXMachine, RDP, etc to get a windowing environment on a remote system.  These products are great and I use them too, but there is a fancy feature in SSH to help. ssh –X remoteserver This is a great feature for hooking into headless VirtualBox machines and remote displaying an install wizard. The remote server must have some lines put in the /etc/ssh/sshd_conf file: X11Forwarding yes X11DisplayOffset 10 The second line is optional, but the first is required.  Restart sshd (sudo /etc/init.d/ssh restart). Now I can ssh –X remote server Then run /opt/app/wls10.3.4/wlserver_10.3/common/bin/config.sh to build a new domain. Note: For some reason, the jdk that comes with WebLogic often fails to work on the remote display.  In that case, I modify the config.sh to just use /usr/bin/java (from openjdk-6-jre package).

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  • How to Quickly Check If Your Computer Can Run a PC Game

    - by Chris Hoffman
    PC gaming isn’t quite as simple as console gaming. If you have a laptop with weak graphics hardware or an older PC, it’s important to check whether your computer can support a game before you spend your hard-earned cash. Gamers don’t have to upgrade their hardware as often as they used to. Even a gaming PC built years ago should be able to handle the newest games just fine. Laptops not build for gaming and older PCs are a different matter.    

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  • URL masking with .htaccess

    - by Michael Nguyen
    I need a hardcore programmer to help me with URL masking. So this is my situation. My website www.michaelfotograf.dk/blog/ is the main site that needs to be configured. I have another website/webhotel called www.umagepar.dk www.umagepar.dk is redirected to www.michaelfotograf.dk/blog/ The blog is an ongoing project where i post a lot of stuff to get my ranking higher on google. www.umagepar.dk which redirect to www.michaelfotograf.dk/blog/ is also a project on is own, so I do not want people to know, that it is a blog connected with www.michaelfotograf.dk/blog/ I therefore need to mask www.michaelfotograf.dk/blog/ so it will be called www.umagepar.dk in the URL in the searchbar at all times! What I need is a programmer that can do this for me. Name your price, and I'll see if I can affort it. Michael

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  • Understanding the problem when things break in production

    - by bitcycle
    Scenario: You push to production The push broke multiple things That same build did not break qa or dev As a developer, you don't have prod access. There is lots of pressure from above to get things working agian. Specifics: PHP/MVC application that is API-driven in Zend. Deployed to a few servers. My question: While investigating, lets say I have a hunch that something is wrong. But, I don't know for sure. And, of course, I can't test things in production. If I have a suggested fix based on that hunch, would it be wise to try and apply it and see if it works, before understanding what the problem is?

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  • Xen 4.0.1 not booting with device not found error

    - by Disco
    I'm trying to get Xen 4.0.1 run as dom0 on a fresh/clean install of 10.10 desktop (x64). Followed the step by step tutorial at http://wiki.xensource.com/xenwiki/Xen4.0 I have the pvops kernel in /boot, also included the ext4 fs support by recompiling the kernel by : make -j6 linux-2.6-pvops-config CONFIGMODE=menuconfig make -j6 linux-2.6-pvops-build make -j6 linux-2.6-pvops-install Here's my grub entry : menuentry 'Xen4' --class ubuntu --class gnu-linux --class gnu --class os { recordfail insmod part_msdos insmod ext2 insmod ext3 set root='(hd0,msdos1)' search --no-floppy --fs-uuid --set 2bf3177a-92fd-4196-901a-da8d810b04b4 multiboot /xen-4.0.gz dom0_mem=1024M loglvl=all guest_loglvl=all module /vmlinuz-2.6.32.27 root=UUID=2bf3177a-92fd-4196-901a-da8d810b04b4 ro module /initrd.img-2.6.32.27 } blkid /dev/sda1 gives the : /dev/sda1: UUID="2bf3177a-92fd-4196-901a-da8d810b04b4" TYPE="ext3" My partition shemes is : /boot (ext3) / (ext4) Whatever option i've tried i end up with : mounting none on /dev failed: no such file or directory And message complaining that it cannot find the device with uuid ... It's taking my hairs out, if somone has a clue ...

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  • Why does Google report a soft 404 when I redirect to the signup page?

    - by Hettomei
    In the last month, I've got an increased number of "soft 404" errors reported by Google webmaster tools which actually work well for users. Configuration (maybe useless): I have a website built with rails 3.1 Authentication is handled by the gem Devise Problem: On this page http://en.bemyboat.com/yacht-charter/9965-sailboat-beneteau-oceanis-43 Click on "Ask a Boat request" (a simple form, in GET to: http://en.bemyboat.com/boat_requests/new/9965) You are redirected with the HTTP status 302 to sign in You are then sent back to the new page if successfully sign in. Google tells me that the link on "ask a boat request" returns a soft 404. I can't make this form in "POST" (which will solve the problem) because we need to automatically redirect users back to the page after sign in. (the Gem Devise memorizes the "get" link.) To simplify, the question is: How to protect a private page with authentication, reached with a simple "GET" and not to be penalized by Google as a "soft 404".

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  • Should I use both WCF and ASP.NET Web API

    - by Mithir
    We already have a WCF API with basichttpbinding. Some of the calls have complex objects in both the response and request. We need to add RESTful abilities to the API. at first I tried adding a webHttp endpoint, but I got At most one body parameter can be serialized without wrapper elements If I made it Wrapped it wasn't pure as I need it to be. I got to read this, and this (which states "ASP.NET Web API is the new way to build RESTful service on .NET"). So my question is, should I make 2 APIs(2 different projects)? one for SOAP with WCF and one RESTful with ASP.NET Web API? is there anything wrong architecturally speaking with this approach?

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  • Artificial Intelligence implemented in x86 Assembly? [closed]

    - by Bigyellow Bastion
    Okay, so I decided that for my upcoming operating system, I do basically everything in x86 Assembly, using only 16-bit mode. I will need to write the software to host on it once I have something up and going, and I'll definitely post the source and VM-executable file. But as for now I'm stuck with the idea of implementing the AI code for some of the games I'm making to host on it. AI in Assembly is tedious, and sometimes almost impossible seeming, especially complex AI(I'm talking SNES Super Mario World 2: Yoshi's Island AI here, by the way, not pong AI). I was thinking that it'd be such a hassle that I'd have to bring a higher-level language to work some of this out here, like maybe C++ or C#, but I'd have to go through more work linking it into a fine binary that my OS will host, and that adds unnecessary work to the table I wanted to avoid(I don't want a complex system, I want everything as bare-bones as possible, avoiding libraries, APIs, and linkable formats for now, to make everything more directly accessible to the kernel's API).

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  • Idoc Script Plug-in for Notepad++

    - by Kyle Hatlestad
    For those of you that caught it in an earlier post, Arnoud Koot wrote a great Idoc Script plug-in for Notepad++.  Well, he's back at it and has written an update for 11g! Arnoud made his announcement a few days ago on the WebCenter Content forum. And it looks like Jonathan Hult caught it as well and posted to his blog. A great addition to his plug-in is context sensitive help.  Now you can look up the variables and functions without having to switch to the formal Oracle documentation. He's even provided a tool to update the help automatically based on the Oracle documentation.  A couple of things to look for that I had missed the instructions was the note about updating the LanguageHelp.ini with your own path to the iDoc11g.chm file as well as the <ctrl><space> keystroke for the auto-complete. Great work Arnoud!

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  • compiling compat-wireless fails at 'make' with 'make: *** [modules] Error 2'

    - by Paul Carter
    Trying to compile the compat-wireless-2012-09-25 driver module, without success. scrips/driver-select alx ; works make ; fails - scripts/Makefile.build:44 ~/sourcecode/compat-wireless-2012-09-25.2/drivers/net/ethernet/atheros/alx/Makefile: No such file or directory make[4]: ** No rule to make target '~/sourcecode/compat-wireless-2012-09-25.2/drivers/net/ethernet/atheros/alx/Makefile'. Stop. [snip] make: * [modules] Error 2 Device is Atheros AR8161 wired ethernet in a Dell Vostro 3460. I'd be very grateful for assistance in getting this to compile.

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  • Green Website Design

    - by Christofian
    This is kindove a strange question, but... There was a site called Blackle ( http://www.blackle.com/) which "claimed" to save energy by using a black background (it doesn't: see here: http://skeptics.stackexchange.com/questions/4373/how-much-energy-does-displaying-a-webpage-with-a-black-background-actually-save). However, blackle and it's idea of "green website design" interested me, and I was wondering if there are any ways to design an energy saving website that actually save energy. If anyone knows of any, please post them here. If nobody has any, then I guess there isn't a way to save energy through website design...

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  • Using YouTube as a CDN

    - by Syed
    Why isn't YouTube used as a CDN for video and audio files? Through YouTube's api and developer tools, it would be possible to post all media files to YouTube from a CMS and then make a call to them when needed. This seems like it's within YouTube's TOS, it's a cost-effective way to store, retrieve, and distribute media files, and it could also make for easy monetization. I ask because I'm working on a new project for a public radio station. I can't figure out the real downside to this sort of an implementation.

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  • TFS API Add Favorites programmatically

    - by Tarun Arora
    01 – What are we trying to achieve? In this blog post I’ll be showing you how to add work item queries as favorites, it is also possible to use the same technique to add build definition as favorites. Once a shared query or build definition has been added as favorite it will show up on the team web access.  In this blog post I’ll be showing you a work around in the absence of a proper API how you can add queries to team favorites. 02 – Disclaimer There is no official API for adding favorites programmatically. In the work around below I am using the Identity service to store this data in a property bag which is used during display of favorites on the team web site. This uses an internal data structure that could change over time, there is no guarantee about the key names or content of the values. What is shown below is a workaround for a missing API. 03 – Concept There is no direct API support for favorites, but you could work around it using the identity service in TFS.  Favorites are stored in the property bag associated with the TeamFoundationIdentity (either the ‘team’ identity or the users identity depending on if these are ‘team’ or ‘my’ favorites).  The data is stored as json in the property bag of the identity, the key being prefixed by ‘Microsoft.TeamFoundation.Framework.Server.IdentityFavorites’. References - Microsoft.TeamFoundation.WorkItemTracking.Client - using Microsoft.TeamFoundation.Client; - using Microsoft.TeamFoundation.Framework.Client; - using Microsoft.TeamFoundation.Framework.Common; - using Microsoft.TeamFoundation.ProcessConfiguration.Client; - using Microsoft.TeamFoundation.Server; - using Microsoft.TeamFoundation.WorkItemTracking.Client; Services - IIdentityManagementService2 - TfsTeamService - WorkItemStore 04 – Solution Lets start by connecting to TFS programmatically // Create an instance of the services to be used during the program private static TfsTeamProjectCollection _tfs; private static ProjectInfo _selectedTeamProject; private static WorkItemStore _wis; private static TfsTeamService _tts; private static TeamSettingsConfigurationService _teamConfig; private static IIdentityManagementService2 _ids; // Connect to TFS programmatically public static bool ConnectToTfs() { var isSelected = false; var tfsPp = new TeamProjectPicker(TeamProjectPickerMode.SingleProject, false); tfsPp.ShowDialog(); _tfs = tfsPp.SelectedTeamProjectCollection; if (tfsPp.SelectedProjects.Any()) { _selectedTeamProject = tfsPp.SelectedProjects[0]; isSelected = true; } return isSelected; } Lets get all the work item queries from the selected team project static readonly Dictionary<string, string> QueryAndGuid = new Dictionary<string, string>(); // Get all queries and query guid in the selected team project private static void GetQueryGuidList(IEnumerable<QueryItem> query) { foreach (QueryItem subQuery in query) { if (subQuery.GetType() == typeof(QueryFolder)) GetQueryGuidList((QueryFolder)subQuery); else { QueryAndGuid.Add(subQuery.Name, subQuery.Id.ToString()); } } }   Pass the name of a valid Team in your team project and a name of a valid query in your team project. The team details will be extracted using the team name and query GUID will be extracted using the query name. These details will be used to construct the key and value that will be passed to the SetProperty method in the Identity service.           Key           “Microsoft.TeamFoundation.Framework.Server.IdentityFavorites..<TeamProjectURI>.<TeamId>.WorkItemTracking.Queries.<newGuid1>”           Value           "{"data":"<QueryGuid>","id":"<NewGuid1>","name":"<QueryKey>","type":"Microsoft.TeamFoundation.WorkItemTracking.QueryItem”}"           // Configure a Work Item Query for the given team private static void ConfigureTeamFavorites(string teamName, string queryName) { _ids = _tfs.GetService<IIdentityManagementService2>(); var g = Guid.NewGuid(); var guid = string.Empty; var teamDetail = _tts.QueryTeams(_selectedTeamProject.Uri).FirstOrDefault(t => t.Name == teamName); foreach (var q in QueryAndGuid.Where(q => q.Key == queryName)) { guid = q.Value; } if(guid == string.Empty) { Console.WriteLine("Query '{0}' - Not found!", queryName); return; } var key = string.Format( "Microsoft.TeamFoundation.Framework.Server.IdentityFavorites..{0}.{1}.WorkItemTracking.Queries{2}", new Uri(_selectedTeamProject.Uri).Segments.LastOrDefault(), teamDetail.Identity.TeamFoundationId, g); var value = string.Format( @"{0}""data"":""{1}"",""id"":""{2}"",""name"":""{3}"",""type"":""Microsoft.TeamFoundation.WorkItemTracking.QueryItem""{4}", "{", guid, g, QueryAndGuid.FirstOrDefault(q => q.Value==guid).Key, "}"); teamDetail.Identity.SetProperty(IdentityPropertyScope.Local, key, value); _ids.UpdateExtendedProperties(teamDetail.Identity); Console.WriteLine("{0}Added Query '{1}' as Favorite", Environment.NewLine, queryName); }   If you have any questions or suggestions leave a comment. Enjoy!

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  • links worth clicking&hellip;

    - by Chris Williams
    Scanning my Twitter feed almost always proves to be fruitful when looking for cool/interesting links to share. Here are a few of the highlights: I read this blog post from Justin Angel today, pretty interesting stuff: Windows Phone 7 – Unlocked ROMs  Looks like there’s a lot of good stuff floating just under the surface in the latest build of the WP7 Emulator. (Courtesy of @JustinAngel) Next up is this video titled Game Design Tutorials: From Seconds to Hours of Gameplay. If you’re into Indie Game Development, or just like watching videos… this one is pretty short at 5 minutes, but contains some good information about increasing the duration of fun gameplay in your game. (Courtesy of @Kei_tchan) If you are a Firefly (or Castle, or Dr. Horrible’s Singalong Blog) fan, check out this Facebook campaign to get Nathan Fillion to host SNL: http://tinyurl.com/2dh5m67  It worked for Betty White, so why not, right? (Courtesy of @DGalloway42)

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  • Beginning android games, 2nd edition engine

    - by Benjamin Stephen
    I recently bought the book from Apress and have worked my way through it, unfortunately, it seems to just be dealing with side scrolling games and not Zelda-like top down games. I was wondering if anyone out there can tell me if it's possible to use their engine to create such a game? It doesn't go into how to build a top down tile map. Using the engine in their book, how can I make a tile map easily that has walls and things like that? Any help would be appreciated. Thanks in advance.

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  • IIS Not Accepting Login Credentials

    - by Dale Jay
    I have an ASP.NET web form using Microsoft's boilerplate Active Directory login page, set up exactly as suggested. (See http://msdn.microsoft.com/en-us/library/ms180890%28v=vs.80%29.aspx) Windows Authentication is activated on the "Default Website" and "MyWebsite" levels, and Domain\This.User is given "Allow" access to the site. After entering the valid credentials for This.User on the web form, a popup window appears asking me to enter my credentials yet again. Despite entering valid credentials for This.User (after attempting Domain\This.User and This.User formats), it rejects the credentials and returns an unauthorized user page. Active Directory user This.User is valid, the IP address of the AD server has been verified and SPN's have been set up for the server. Any thoughts as to what may be causing this? I can post code if needed.

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  • Become a Vi Master by Learning These 30+ Key Bindings

    - by Chris Hoffman
    Vi is a powerful text editor included on most Linux systems. Many people swear by vi and find it faster than any other editor once they’ve learned its key bindings. You can even use vi key bindings in Bash. We’ve already covered getting started with vi for beginners. If you haven’t used vi in a while, you might want to give that post a look to get a refresher on the basics. How To Customize Your Wallpaper with Google Image Searches, RSS Feeds, and More 47 Keyboard Shortcuts That Work in All Web Browsers How To Hide Passwords in an Encrypted Drive Even the FBI Can’t Get Into

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  • Using my own code in freelance projects.

    - by Witchunter
    I have been into freelance business for more than 2 years. While doing projects for other people, I've build a compilation of common tasks that I implement in projects and put them into code. It's kind of a library with some functions that I can reuse without having to rewrite the same thing dozen times. I'm talking about accessing Access databases, downloading information from FTP and similar stuff. Is this acceptable from a legal point of view? What's the difference in reusing the old code and rewriting it from the scratch (using you own brain again, therefore the exact same logic)? I do not hold any copyright to it, of course, and provide the source code for these classes to my clients.

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  • What's the best way to manage list item sort order with Drag & Drop UI?

    - by Reddy S R
    I have a list of Students that I should display to user on a web page in tabular format. The items are stored in DB along with SortOrder information. On the web page, user can rearrange the list order by dragging and dropping the items to their desired sort order, similar to this post. Below is a screenshot of my test page. In the above example, each row has sort order info attached to it. When I drop John Doe (Student Id 10) above the Student Id 1 row, the list order should now be: 2, 10, 1, 8, 11. What's the optimistic (less resource hungry) way to store and update Sort Order information? My only idea for now is, for every change in the list's sort order, every object's SortOrder value should be updated, which in my opinion is very resource hungry. Just FYI: I might have at most 25 rows in my table.

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  • Big Data – Buzz Words: What is HDFS – Day 8 of 21

    - by Pinal Dave
    In yesterday’s blog post we learned what is MapReduce. In this article we will take a quick look at one of the four most important buzz words which goes around Big Data – HDFS. What is HDFS ? HDFS stands for Hadoop Distributed File System and it is a primary storage system used by Hadoop. It provides high performance access to data across Hadoop clusters. It is usually deployed on low-cost commodity hardware. In commodity hardware deployment server failures are very common. Due to the same reason HDFS is built to have high fault tolerance. The data transfer rate between compute nodes in HDFS is very high, which leads to reduced risk of failure. HDFS creates smaller pieces of the big data and distributes it on different nodes. It also copies each smaller piece to multiple times on different nodes. Hence when any node with the data crashes the system is automatically able to use the data from a different node and continue the process. This is the key feature of the HDFS system. Architecture of HDFS The architecture of the HDFS is master/slave architecture. An HDFS cluster always consists of single NameNode. This single NameNode is a master server and it manages the file system as well regulates access to various files. In additional to NameNode there are multiple DataNodes. There is always one DataNode for each data server. In HDFS a big file is split into one or more blocks and those blocks are stored in a set of DataNodes. The primary task of the NameNode is to open, close or rename files and directory and regulate access to the file system, whereas the primary task of the DataNode is read and write to the file systems. DataNode is also responsible for the creation, deletion or replication of the data based on the instruction from NameNode. In reality, NameNode and DataNode are software designed to run on commodity machine build in Java language. Visual Representation of HDFS Architecture Let us understand how HDFS works with the help of the diagram. Client APP or HDFS Client connects to NameSpace as well as DataNode. Client App access to the DataNode is regulated by NameSpace Node. NameSpace Node allows Client App to connect to the DataNode based by allowing the connection to the DataNode directly. A big data file is divided into multiple data blocks (let us assume that those data chunks are A,B,C and D. Client App will later on write data blocks directly to the DataNode. Client App does not have to directly write to all the node. It just has to write to any one of the node and NameNode will decide on which other DataNode it will have to replicate the data. In our example Client App directly writes to DataNode 1 and detained 3. However, data chunks are automatically replicated to other nodes. All the information like in which DataNode which data block is placed is written back to NameNode. High Availability During Disaster Now as multiple DataNode have same data blocks in the case of any DataNode which faces the disaster, the entire process will continue as other DataNode will assume the role to serve the specific data block which was on the failed node. This system provides very high tolerance to disaster and provides high availability. If you notice there is only single NameNode in our architecture. If that node fails our entire Hadoop Application will stop performing as it is a single node where we store all the metadata. As this node is very critical, it is usually replicated on another clustered as well as on another data rack. Though, that replicated node is not operational in architecture, it has all the necessary data to perform the task of the NameNode in the case of the NameNode fails. The entire Hadoop architecture is built to function smoothly even there are node failures or hardware malfunction. It is built on the simple concept that data is so big it is impossible to have come up with a single piece of the hardware which can manage it properly. We need lots of commodity (cheap) hardware to manage our big data and hardware failure is part of the commodity servers. To reduce the impact of hardware failure Hadoop architecture is built to overcome the limitation of the non-functioning hardware. Tomorrow In tomorrow’s blog post we will discuss the importance of the relational database in Big Data. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Big Data, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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  • Qt Certification Exams

    - by karlphillip
    I'm wondering about doing a Qt Certification Exam this year, but I'm not 100% sure the investment is worth. I'm considering it because I think it could be a nice + on my resume, and as you know, I'm all for improving my software engineer persona. As I already earn a BSc and MSc degrees in computer stuff, I guess I see the certification process as some kind of adventure. Anyway, I know I'll spend a lot of time preparing myself for the exam and I just wanted to know if a Qt certification is worth the effort. Apparently there are 2 certificates that you can get in the Qt world: Nokia Certified Qt Developer (basic) Nokia Certified Qt Specialist (advanced) Nowadays I build cross-platform software in C++ and this exam would fit beautifully in my resume. My main concern is that, given the obscure future of Qt, I might be throwing time and money out the window. I'm looking for some advice regarding the usefulness of such certifications.

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