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  • passing data to php in ajax [closed]

    - by MertMETIN
    i try to pass my data, actually checkboxes has some datas in their ids, and i read try to read them. like that, <input align="right" type=checkbox name="checkArtist[]" class="checkClass" id ="{$movieId}-{$mCast.id}"></li> dont worry about {$movieId}-{$mCast.id} They are template lite tags. I successfully read checkboxes datas in ajax side. The problem is that i cannot send these datas to my php. var artistIds = new Array(); $(".p16 input:checked").each()(function(){ artistIds.push($(this).attr('id')); }); $.post('/json/crewonly/deleteDataAjax2', { 'artistIds': artistIds },function(response){ if(response=='ok') alert("ok"); }); above code is my ajax but in php side $artistIds is always empty. I found a topic in stackoverflow http://stackoverflow.com/questions/5571646/how-to-pass-a-javascript-array-via-jquery-post-so-that-all-its-contents-are-acce It says how to pass js arrays $.post('/url/to/page', {'someKeyName': variableName}); This is same with my code. What's going wrong ?

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  • Asp.net tips and tricks

    - by ybbest
    Asp.net tips and tricks Here is a summary of articles I found very useful over the years while I am working on asp.net TRULY Understanding View state http://weblogs.asp.net/infinitiesloop/archive/2006/08/03/Truly-Understanding-Viewstate.aspx TRULY Understanding Dynamic Controls http://weblogs.asp.net/infinitiesloop/archive/2006/08/25/TRULY-Understanding-Dynamic-Controls-_2800_Part-1_2900_.aspx ASP.Net 2.0 – Master Pages: Tips, Tricks, and Traps http://odetocode.com/articles/450.aspx ASP.NET Tip – Use The Label Control Correctly http://haacked.com/archive/2007/02/15/asp.net_tip_-_use_the_label_control_correctly.aspx Asp.net httphandlers http://www.michaelflanakin.com/Articles/NET/NET1x/ImplementingHTTPHandlers/tabid/173/Default.aspx http://support.microsoft.com/default.aspx?scid=kb;EN-US;308001 http://msdn.microsoft.com/en-us/library/ms972974.aspx Asp.net ajax http://encosia.com/ ASP.NET 2.0 Tips, Tricks, Recipes and Gotchas http://weblogs.asp.net/scottgu/pages/ASP.NET-2.0-Tips_2C00_-Tricks_2C00_-Recipes-and-Gotchas.aspx Mastering Page-UserControl Communication http://www.codeproject.com/KB/user-controls/Page_UserControl.aspx Comparing Web Site Projects and Web Application Projects Web Deployment Projects .NET Radio Show http://www.dotnetrocks.com/ Herdingcode http://herdingcode.com/ Clean Code talk http://www.objectmentor.com/videos/video_index.html .NET Video Show http://www.dnrtv.com/ .Net User group http://chicagoalt.net/home http://exposureroom.com/members/RIAViewMirror.aspx/assets/ FAQ Why should you remove unnecessary C# using directives? http://stackoverflow.com/questions/136278/why-should-you-remove-unnecessary-c-using-directives http://stackoverflow.com/questions/2009471/what-is-the-benefit-of-removing-redundant-imports-in-vb-net-or-using-in-c-file http://codeclimber.net.nz/archive/2009/12/30/best-of-2009-the-5-most-popular-posts.aspx

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  • libgdx ActorGestureListener.pan() parameters not moving actor in smooth line

    - by Roar Skullestad
    I override the pan method in ActorGestureListener to implement dragging actors in libgdx (scene2d). When I move individual pieces on a board they move smoothly, but when moving the whole board, the x and y coordinates that is sent to pan is "jumping", and in an increasingly amount the longer it is dragged. These are an example of the deltaY coordinates sent to pan when dragging smoothly downwards: 1.1156368 -0.13125038 -1.0500145 0.98439217 -1.0500202 0.91877174 -0.984396 0.9187679 -0.98439026 0.9187641 -0.13125038 This is how I move the camera: public void pan (InputEvent event, float x, float y, float deltaX, float deltaY) { cam.translate(-deltaX, -deltaY); I have been using both the delta values sent to pan and the real position values, but similar results. And since it is the coordinates that are wrong, it doesn't matter whether I move the board itself or the camera. What could the cause be for this and what is the solution? When I move camera only half the delta-values, it moves smoothly but only at half the speed of the mouse pointer: cam.translate(-deltaX / 2, -deltaY / 2); It seems like the moving of camera or board affects the mouse input coordinates. How can I drag at "mouse speed" and still get smooth movements? (This question was also posted on stackoverflow: http://stackoverflow.com/questions/20693020/libgdx-actorgesturelistener-pan-parameters-not-moving-actor-in-smooth-line)

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  • How not to suffer from ideologists when you're a pragmatic person?

    - by Lukas Eder
    My story: I'm a pragmatic person. Sometimes, the most simple solution to a problem to get the job done is the one that fits best for me, if its not an utter blasphemy and reproach to any design principles. Check out my answer to this question on stackoverflow. Simple. Works. Was accepted. Could be improved. Is clearly not perfect. And along comes this guy. He downvotes me, comments on the question how his answer is better, more accurate etc and calls me "plain wrong". Reminds me of this comic strip. :-) While on stackoverflow I can laugh at these things because those people are far away, in the real world I'm suffering from ideologies every now and then. Heck, I'm not creating a miracle piece of software, I need to keep that huge legacy thing running, and it's an adventure to me every day. I don't have the time or passion to beautify my code (or other people's code) to that extent. My question(s): How do you deal with ideologies / ideologists, when you're a pragmatic person? How do you deal with pragmatism / pragmatists, when you're an ideologic person? I'm interested in both point of views. Tell me your experience. But please, be fair, somewhat objective, and understand that you may NOT be entirely correct and your opinion is NOT the only true one... :-)

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  • Squeezing all the SEO out of a URL as possible.

    - by John Isaacks
    I am working on an ecommerce site, I told our SEO consultant that I plan to make the URL scheme: /products/<id>/<name>. This is similar to Stackoverflow's URLs which are /questions/<id>/<title>. He asked me if I could change the URL scheme to /p/<id>/<name> instead. I know why he wants this change, the word "products" isn't needed to find the correct product, and it doesn't offer any SEO, so shortening it to just p would make the relevant keywords in the <name> weigh more. His main priority is maximizing SEO, but the part that I don't think he is considering is how this effects the semantics of the site. Also having the word "products" looks like it has meaning and a reason for being there, just having a p looks chaotic and ugly to me. I also don't think it makes that much of a difference does it? Stackoverflow doesn't use /q/<id>/<title> and they do just fine, I do realize that theres many factors at play here though, not just the URL. So I want some outside opinions on which is the better way and why?

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  • Script/tool to import series of snapshots, each being a new revision, into Subversion, populating source tree?

    - by Rob
    I've developed code locally and taken a fairly regular snapshot whenever I reach a significant point in development, e.g. a working build. So I have a long-ish list of about 40 folders, each folder being a snapshot e.g. in ascending date YYYYMMDD order, e.g.:- 20100523 20100614 20100721 20100722 20100809 20100901 20101001 20101003 20101104 20101119 20101203 20101218 20110102 I'm looking for a script to import each of these snapshots as a new subversion revision to the source tree. The end result being that the HEAD revision is the same as the last snapshot, and other revisions are as numbered. Some other requirements: that the HEAD revision is not cumulative of the previous snapshots, i.e., files that appeared in older snapshots but which don't appear in later ones (e.g. due to refactoring etc.) should not appear in the HEAD revision. meanwhile, there should be continuity between files that do persist between snapshots. Subversion should know that there are previous versions of these files and not treat them as brand new files within each revision. Some background about my aim: I need to formally revision control this work rather than keep local private snapshot copies. I plan to release this work as open source, so version controlling would be highly recommended I am evaluating some of the current popular version control systems (Subversion and GIT) BUT I definitely need a working solution in Subversion. I'm not looking to be persuaded to use one particular tool, I need a solution for each tool I am considering as I would also like a solution in GIT (I will post an answer separately for GIT so separate camps of folks who have expertise in GIT and Subversion will be able to give focused answers on one or the other). The same question but for GIT: Script/tool to import series of snapshots, each being a new edition, into GIT, populating source tree? An outline answer for Subversion in stackoverflow.com but not enough specifics about the script: what commands to use, code to check valid scenarios if necessary - i.e. a working script basically. http://stackoverflow.com/questions/2203818/is-there-anyway-to-import-xcode-snapshots-into-a-new-svn-repository

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  • Which web site gives the most accurate indication of a programmer's capabilities?

    - by Jerry Coffin
    If you were hiring programmers, and could choose between one of (say) the top 100 coders on topcoder.com, or one of the top 100 on stackoverflow.com, which would you choose? At least to me, it would appear that topcoder.com gives a more objective evaluation of pure ability to solve problems and write code. At the same time, despite obvious technical capabilities, this person may lack any hint of social skills -- he may be purely a "lone coder", with little or no ability to help/work with others, may lack mentoring ability to help transfer his technical skills to others, etc. On the other hand, stackoverflow.com would at least appear to give a much better indication of peers' opinion of the coder in question, and the degree to which his presence and useful and helpful to others on the "team". At the same time, the scoring system is such that somebody who just throws up a lot of mediocre (or even poor answers) will almost inevitably accumulate a positive total of "reputation" points -- a single up-vote (perhaps just out of courtesy) will counteract the effects of no fewer than 5 down-votes, and others are discouraged (to some degree) from down-voting because they have to sacrifice their own reputation points to do so. At the same time, somebody who makes little or no technical contribution seems unlikely to accumulate a reputation that lands them (even close to) the top of the heap, so to speak. So, which provides a more useful indication of the degree to which this particular coder is likely to be useful to your organization? If you could choose between them, which set of coders would you rather have working on your team?

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  • Live programming help

    - by frazras
    This idea has been floating around my head for a few years. I started some work on it but I just want to know if it is feasible, sensible, or if there is something else like it out there. Dont want to know I was wasting time on a solved issue. Whenever I have a programming issue, this is my sequence: Google it!: That usually brings up a lot of things: blogs, forums, stackoverflow, stackexchange, and even the official docs of the language/framework/cms. Ask on IRC: I format my question and try to get people on IRC to help me. Make a post: I create a post on forums/stackoverflow/stackexchange or shout on twitter with hashtags. Now a lot of the time I am in the middle of a project with a deadline. So I want answers NOW!!! Sometimes just 5-15 minutes worth of attention. Usually by the time I am failing at getting answers at #2, I am imagining how many people are ONLINE NOW with the skill and my exact answer but playing video games, watching youtube or idling online. However, if they were motivated, they would invest the 15 mintes helping me, that would make a world of a difference. I am even in positions where I would PAY for that 15 minutes of instant help. If your rate is as much as $100/hour (relatively good programmer) that is $25 that might save me 3 hours. This help would be live, text chat/skype/phone/screenshare. Should I continue developing this idea or is there a better alternative out there? Or is this even an unfeasible idea?

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  • Advanced PHP book [closed]

    - by Aaditi Sharma
    I've gone and stumbled across a lot of recommendations for PHP books, including on SO, however could not find a reasonable & convincible answer for this. Is there a really good advanced book for PHP. Background: I've done almost 8 months in PHP. I know the basics. I go through php.net very often. I've played around with Codeigniter, amongst other frameworks. I've been doing JavaScript for almost 2 years, and specifically thank Douglas Crockford for this, I completely changed the way I code JavaScript. I spend a lot of time travelling, and would love to read a book about PHP, that includes the awesome parts and even when something doesn't quite work in PHP. (As a note a lot of previous answers on SO and programmers give varied results.) I have to place an order through a library which has it's limitations. One book that some of experienced PHP programmers could recommend would be helpful. I have gone through http://stackoverflow.com/questions/1711/what-is-the-single-most-influential-book-every-programmer-should-read and http://stackoverflow.com/questions/194812/list-of-freely-available-programming-books, which do NOT have books related to PHP.

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  • How to retrieve the value of querystring from url using Javascript

    - by ybbest
    The following is a Javascript function I found on the internet , I keep here just in case I need to use it again. function getParameterByName(name) { name = name.replace(/[\[]/, "\\\[").replace(/[\]]/, "\\\]"); var regexS = "[\\?&]" + name + "=([^&#]*)"; var regex = new RegExp(regexS); var results = regex.exec(window.location.search); if(results == null) return ""; else return decodeURIComponent(results[1].replace(/\+/g, " ")); } You can also add this method to jquery as below. $.getParameterByName = function (name) { name = name.replace( /[\[]/ , "\\\[").replace( /[\]]/ , "\\\]"); var regexS = "[\\?&]" + name + "=([^&#]*)"; var regex = new RegExp(regexS); var results = regex.exec(window.location.search); if (results == null) return ""; else return decodeURIComponent(results[1].replace( /\+/g , " ")); }; $(document).ready(function () { alert($.getParameterByName("id")); }); References: http://stackoverflow.com/questions/901115/get-query-string-values-in-javascript http://blog.jeremymartin.name/2008/02/building-your-first-jquery-plugin-that.html http://stackoverflow.com/questions/7541218/writing-jquery-static-util-methods http://api.jquery.com/category/utilities/

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  • sharing life experience

    - by gcc
    I am a student of computer engineering. I have never done any programming before, and as you can understand, I don't know how to study it or how to make my own programs. My English is weak [edited for clarity - ed], and so if you don't like the choices I list, please feel free to provide others. How should I study? How should I learn programming languages? Study completely from a book. Don't study from a book, just try writing code. A mix of the two; study from a book, then try writing code. Study half the book, then write the code by hand on paper. Listed to the teacher, then try to solve general problems (those not from any specific chapter). I have send that question to stackoverflow before when I am at first year. Now, I want to construct webpage to guide fresh students by giving advise of yours and mines.Maybe, you wonder Why I want to construct webpage , I just want help the other student. I am giving a link to that question < http://stackoverflow.com/questions/3389465/how-should-i-study-programming-languagess If you have other advice, feel free. EDIT: This web cite, I think , is constructed to share member's life experience and also I know these experiences is valuable . So I have no right to want your opinion, But I want your opinion / experience even if you think it is not so helpful to other

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  • How should I approach learning programming languages?

    - by gcc
    I am a student of computer engineering. I have never done any programming before, and as you can understand, I don't know how to study it or how to make my own programs. My English is weak [edited for clarity - ed], and so if you don't like the choices I list, please feel free to provide others. How should I study? How should I learn programming languages? Study completely from a book. Don't study from a book, just try writing code. A mix of the two; study from a book, then try writing code. Study half the book, then write the code by hand on paper. Listed to the teacher, then try to solve general problems (those not from any specific chapter). I have send that question to stackoverflow before when I am at first year. Now, I want to construct webpage to guide fresh students by giving advise of yours and mines.Maybe, you wonder Why I want to construct webpage , I just want help the other student. I am giving a link to that question < http://stackoverflow.com/questions/3389465/how-should-i-study-programming-languagess If you have other advice, feel free. EDIT: This web cite, I think , is constructed to share member's life experience and also I know these experiences is valuable . So I have no right to want your opinion, But I want your opinion / experience even if you think it is not so helpful to other

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  • I am having a hard time learning Python, is it just me? [closed]

    - by Carpet
    For the past two weeks I am trying to learn Python and a framework for web development, while doing so I learned a lot but not what I was looking for. I did manage to get everything set up and running, followed tutorials, but I still have not managed to create a navigation bar and a simple template website. My goal is to create web applications (like a blog) and perhaps platforms similar to stackoverflow. In which language was stackoverflow created in? I believe that Python Django or Python Tornado (which I tried) is more for people who have learned desktop application development. It is hard for me to make sense out of the complex and fragmented system. I'm able to develop with PHP and have already created blogs and similar applications. If Python and a framework is not for me, what type of language would be for me, which languages are used for these type of platforms, I would like to develop myself? I only omitted PHP because I found it later on a bit too inheriting, and the code is hardly readable and becomes quickly cluttered, I love how readable Python code is.

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  • Prepping a conference

    - by Laurent Bugnion
    I have had the chance to talk at many conferences these past few years, and came up with a way to prepare them which works really well for me. Most importantly, it would make it quite easy to overcome an emergency (for example if my laptop would suddenly lose data). The whole code as well as the slides and other documents are in the cloud. I also use source control for my demos, so that I always have the latest and the greatest, but also a history of changes I made to my demos. Finally I have a system of code snippets which works great, and I often had very positive remarks from the audience regarding that. Putting everything in the cloud The one thing I used to be the most scared of was a sudden crash of my laptop, and being unable to restore in time for a conference. Most conferences ask speakers to send slides a few days (or weeks…) in advance, but let's face it, we all have last minute changes to our talks and I always come in the conference with updated slides that I pass to the management team. The answer to that dilemma used to be working off memory sticks, and that worked not bad. However last year I started putting all the documents relating to a conference in a DropBox folder, and that works great too. Obviously DropBox works only if you have connectivity, so if I for instance update slides while on an international flight, I cannot save to the cloud. The obvious answer to that is to backup everything on a memory stick… but I have to admit, I have been trusting my luck and working off my laptop HD and then synching everything to the cloud after landing. Of course on some US national flights you get WiFi on board, so in that case it is even simpler :) Usually after the conference is done, I remove the files from DropBox and copy them to their "final destination". They are backed up from there to BackBlaze, the great online backup service I am using routinely (I currently have about 90GB of data in BackBlaze). Outlining the presentations I like to have a written outline of my presentations written somewhere. I keep it simple, just write the various sections of the presentation with timing. I guess it is a remnant of the time when I was a private pilot, and using checklists for flight preparation. For example: Demo about designability 15' (0:37) Switch to Blend Open MainPage.xaml Create a DataTemplate ... Here I can immediately see during the presentation if I am taking too much time for my demo (0:37 is where I need to be when I am done with this section of the presentation, and 15' is the time that this particular section takes). I keep these sections reasonable, I don't detail every step of the preparation. Typically I have one such section for every 10-15 minutes of my talks. Yes, I am timing my presentations. I keep adjusting these numbers when I rehearse, and this really helps to feel more confident during the presentations. This is especially important for presentations that are long, like my MIX11 demo which clocked at 57 minutes (I had a lot of stuff to show…). Such presentations are risky, because if anything goes wrong, you will have to cut stuff, so the answer to that is: Rehearse, rehearse and when you're done rehearsing, rehearse a little more. I also have a "Preparation" section where I outline what I need to do before a presentation. For instance: Preparation Reboot in VHD Make sure MSN and Twitter are not running. Open VS10 and load demo Open Blend and load demo Run the WP7 emulator ... I typically start preparing my laptop an hour before the talk, starting everything I need to start and then putting my laptop to sleep. Saving and printing the outline, Timing Printing is a real problem because it is really hard to find a printer at most conference venues, and also quite hard in hotels. To solve that, I simply write everything in OneNote (synched to the cloud, now you start to know what I like ;) and then I print it to a PDF (I use CutePDFWriter) that I save to my Kindle. During the presentation, I read the outline off the Kindle (I mostly just need a quick check to see how I am timing). For timing during the presentation, I use the free tool ChronoGPS on my Windows Phone 7, but of course any phone these days has a clock/chrono application. In some conferences, they even have timers that the presenters can see, but they tend to count down and I prefer to count up… so I just use my own :) Source control for demos For demos, I create a separate folder and use Mercurial as source control. Mercurial has the huge advantage (over SVN or TFS) to work offline too, so I can commit while on a plane, and all the history is saved. Then when I have connectivity I push everything to the cloud (I am using the fantastic Trunksapp.com for my private repositories). Here too the obvious downside is the risk of losing my last changes if my laptop crashes before I can push to the cloud, and here too the obvious answer would be to work from a memory stick… though I have to admit I didn't do that lately (except when I was writing Silverlight 4 Unleashed, where I was really paranoid…) And code snippets? I am one of these presenters who hates to type in front of an audience. I can type really fast (writing two books has this advantage, it really teaches you to touch type and be fast at it) but in the context of an audience, on a stage where it is often damn cold (an issue I had a lot in past conferences, air conditioning can freeze your fingers and make it really hard to type), it doesn't work as well. I don't know for you, but I really dislike seeing a presentation where the speaker uses the backspace key more often than others ;) To solve that, I like to have my code ready in snippets, and drag them to the screen. Then I can spend time explaining each code snippet, while highlighting portions of the code (always highlight what you talk about, the audience often doesn't even see the cursor and doesn't know where you are on the screen!) Over the years I have used various solutions for code snippets, and now I have one which works really well… if you take a few precautions! I use the Visual Studio Toolbox. Preparing the code snippets You can store code snippets in the Toolbox for anything, XAML, C# etc. I arrange the snippets in the order in which I need them, which is a great way to remember what comes next in the presentation. I also separate them by topic, to make it easier to find them, for example when I switch to the slides and then back to the code. Remember that no matter how experienced you are, you will feel more nervous on stage than while you are preparing, so any way to make it easier for you is going to be beneficial to the audience. To store a code snippet, I do the following: Open the final demo that you want to show to the audience in Visual Studio. In your code, select a snippet of code that you want to explain in particular. Make sure that the Visual Studio Toolbox is open (menu View, Toolbox or Ctrl-Alt-X). Drag the selected snippet from the code window to the toolbox. (if needed) drag the snippet to the correct location (for example between two other code snippets so that you can access it as you speak through the demo). Right click on the snippet and select Rename Item from the context menu. Select a meaningful name. For me I use the following conventions: If it is a method, I use the method's name. If it is not a whole method, I use a descriptive name. If it is the content of a method (i.e. the body only, without the method's signature), I use "-> MethodName". This reminds me during the presentation that this is only the body, and that I need to insert that into an existing signature. This is the case, for instance, when I use Visual Studio to automatically generate the members of an interface’s implementation; then I only need to insert my snippet inside the generated method body. Saving the snippets This is the most important!! It happened to me a few times that VS10 lost its settings. When that happens, the snippets are lost too! Yeah that really sucks, especially (as it happened once) when this is the case about an hour before a talk… Stress and sweat follows, not good conditions to start a talk in front of an audience believe me. Thankfully, saving snippets is really easy with the following steps: Select the menu Tools, Import and Export Settings. Select Export selected environment settings and press Next. Uncheck All Settings. Then expand General Settings and select Toolbox (only!). Press Next. Select your source control folder and save under a meaningful name (for instance Snippets.vssettings). Commit to source control and push to the cloud. By the way, this also has the advantage of applying source control to the snippets file (which is an XML file), so you get history for free on that file! Reimporting the snippets If VS loses its settings and you need to reimport the snippets, this can be done super easily and very fast. Make sure that the Toolbox is empty. When you import snippets, they are merged with existing ones, they do not replace the content of the Toolbox. Unless merging is really what you want, make sure that your Toolbox is clean before you import, it is really easier. Select the menu Tools, Import and Export Settings. Select Import selected environment settings and press Next. Select No, just import new settings and press Next. Press Browse and select the Snippets.vssettings file. Press Finish. Et voila, all your snippets appear again in the Toolbox. Whew, the worst was averted and you can start your demo without sweating! (I had to do that once literally 5 minutes before the start of a demo, while my laptop was already hooked to the projector, and it went just fine). What about special tools? When using special tools (for example beta versions of tools you have an early access to), or a special configuration of your laptop, things can get tricky because you cannot really be sure that you will get a laptop with the same tools and the same configuration at the conference. To solve that, I use the following precautions: I make my demos from a Virtual Hard Disk. The great John Papa made a very easy-to-follow web page where he explains how to create a VHD and install Win7 to it. This gives you the full power of your laptop (as fast as booting from the metal). For me, I have a basic configuration that I saved on a USB harddrive (Win7 plus drivers, basic settings for desktop, folder options, taskbar etc) and Visual Studio 2010 SP1 on it. When preparing, I start by copying this "basis VHD" to my laptop. I install additional tools and configurations. I save the VHD back to the USB harddrive in a different folder. This would allow me to reinstall my demo environment quite fast, for example in case of harddrive failure. Replace the harddrive, copy the VHD to it, configure the BCD and you can start. Unfortunately this only works if the laptop itself still works. In the worst case of total failure, my security is to back all the installers up: The installers I use are synched on all my laptops and backed up to BackBlaze. If the worst happens and my laptop is absolutely broken, I can download the installer from BackBlaze and install on another laptop. This of course takes some time, and if that happens 5 minutes before a presentation, well… I don't have an answer to that, except of course crossing my fingers. Still, all that gives me additional security. Conclusion Remember folks, talking to an audience, large or small, will make you nervous. Just ask Scott Hanselman :) The goal here is to create the best possible conditions for you, and to create an environment where everything is saved and easy to restore, where everything is well known and provides you with additional confidence. The cooler you feel before the presentation (and during ;)), the better your presentation will be. Here too, the goal is to provide the best user experience you can have, which in turn will make it more enjoyable for your audience! Happy presenting :) Laurent   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • Windows Azure Service Bus Scatter-Gather Implementation

    - by Alan Smith
    One of the more challenging enterprise integration patterns that developers may wish to implement is the Scatter-Gather pattern. In this article I will show the basic implementation of a scatter-gather pattern using the topic-subscription model of the windows azure service bus. I’ll be using the implementation in demos, and also as a lab in my training courses, and the pattern will also be included in the next release of my free e-book the “Windows Azure Service Bus Developer Guide”. The Scatter-Gather pattern answers the following scenario. How do you maintain the overall message flow when a message needs to be sent to multiple recipients, each of which may send a reply? Use a Scatter-Gather that broadcasts a message to multiple recipients and re-aggregates the responses back into a single message. The Enterprise Integration Patterns website provides a description of the Scatter-Gather pattern here.   The scatter-gather pattern uses a composite of the publish-subscribe channel pattern and the aggregator pattern. The publish-subscribe channel is used to broadcast messages to a number of receivers, and the aggregator is used to gather the response messages and aggregate them together to form a single message. Scatter-Gather Scenario The scenario for this scatter-gather implementation is an application that allows users to answer questions in a poll based voting scenario. A poll manager application will be used to broadcast questions to users, the users will use a voting application that will receive and display the questions and send the votes back to the poll manager. The poll manager application will receive the users’ votes and aggregate them together to display the results. The scenario should be able to scale to support a large number of users.   Scatter-Gather Implementation The diagram below shows the overall architecture for the scatter-gather implementation.       Messaging Entities Looking at the scatter-gather pattern diagram it can be seen that the topic-subscription architecture is well suited for broadcasting a message to a number of subscribers. The poll manager application can send the question messages to a topic, and each voting application can receive the question message on its own subscription. The static limit of 2,000 subscriptions per topic in the current release means that 2,000 voting applications can receive question messages and take part in voting. The vote messages can then be sent to the poll manager application using a queue. The voting applications will send their vote messages to the queue, and the poll manager will receive and process the vote messages. The questions topic and answer queue are created using the Windows Azure Developer Portal. Each instance of the voting application will create its own subscription in the questions topic when it starts, allowing the question messages to be broadcast to all subscribing voting applications. Data Contracts Two simple data contracts will be used to serialize the questions and votes as brokered messages. The code for these is shown below.   [DataContract] public class Question {     [DataMember]     public string QuestionText { get; set; } }     To keep the implementation of the voting functionality simple and focus on the pattern implementation, the users can only vote yes or no to the questions.   [DataContract] public class Vote {     [DataMember]     public string QuestionText { get; set; }       [DataMember]     public bool IsYes { get; set; } }     Poll Manager Application The poll manager application has been implemented as a simple WPF application; the user interface is shown below. A question can be entered in the text box, and sent to the topic by clicking the Add button. The topic and subscriptions used for broadcasting the messages are shown in a TreeView control. The questions that have been broadcast and the resulting votes are shown in a ListView control. When the application is started any existing subscriptions are cleared form the topic, clients are then created for the questions topic and votes queue, along with background workers for receiving and processing the vote messages, and updating the display of subscriptions.   public MainWindow() {     InitializeComponent();       // Create a new results list and data bind it.     Results = new ObservableCollection<Result>();     lsvResults.ItemsSource = Results;       // Create a token provider with the relevant credentials.     TokenProvider credentials =         TokenProvider.CreateSharedSecretTokenProvider         (AccountDetails.Name, AccountDetails.Key);       // Create a URI for the serivce bus.     Uri serviceBusUri = ServiceBusEnvironment.CreateServiceUri         ("sb", AccountDetails.Namespace, string.Empty);       // Clear out any old subscriptions.     NamespaceManager = new NamespaceManager(serviceBusUri, credentials);     IEnumerable<SubscriptionDescription> subs =         NamespaceManager.GetSubscriptions(AccountDetails.ScatterGatherTopic);     foreach (SubscriptionDescription sub in subs)     {         NamespaceManager.DeleteSubscription(sub.TopicPath, sub.Name);     }       // Create the MessagingFactory     MessagingFactory factory = MessagingFactory.Create(serviceBusUri, credentials);       // Create the topic and queue clients.     ScatterGatherTopicClient =         factory.CreateTopicClient(AccountDetails.ScatterGatherTopic);     ScatterGatherQueueClient =         factory.CreateQueueClient(AccountDetails.ScatterGatherQueue);       // Start the background worker threads.     VotesBackgroundWorker = new BackgroundWorker();     VotesBackgroundWorker.DoWork += new DoWorkEventHandler(ReceiveMessages);     VotesBackgroundWorker.RunWorkerAsync();       SubscriptionsBackgroundWorker = new BackgroundWorker();     SubscriptionsBackgroundWorker.DoWork += new DoWorkEventHandler(UpdateSubscriptions);     SubscriptionsBackgroundWorker.RunWorkerAsync(); }     When the poll manager user nters a question in the text box and clicks the Add button a question message is created and sent to the topic. This message will be broadcast to all the subscribing voting applications. An instance of the Result class is also created to keep track of the votes cast, this is then added to an observable collection named Results, which is data-bound to the ListView control.   private void btnAddQuestion_Click(object sender, RoutedEventArgs e) {     // Create a new result for recording votes.     Result result = new Result()     {         Question = txtQuestion.Text     };     Results.Add(result);       // Send the question to the topic     Question question = new Question()     {         QuestionText = result.Question     };     BrokeredMessage msg = new BrokeredMessage(question);     ScatterGatherTopicClient.Send(msg);       txtQuestion.Text = ""; }     The Results class is implemented as follows.   public class Result : INotifyPropertyChanged {     public string Question { get; set; }       private int m_YesVotes;     private int m_NoVotes;       public event PropertyChangedEventHandler PropertyChanged;       public int YesVotes     {         get { return m_YesVotes; }         set         {             m_YesVotes = value;             NotifyPropertyChanged("YesVotes");         }     }       public int NoVotes     {         get { return m_NoVotes; }         set         {             m_NoVotes = value;             NotifyPropertyChanged("NoVotes");         }     }       private void NotifyPropertyChanged(string prop)     {         if(PropertyChanged != null)         {             PropertyChanged(this, new PropertyChangedEventArgs(prop));         }     } }     The INotifyPropertyChanged interface is implemented so that changes to the number of yes and no votes will be updated in the ListView control. Receiving the vote messages from the voting applications is done asynchronously, using a background worker thread.   // This runs on a background worker. private void ReceiveMessages(object sender, DoWorkEventArgs e) {     while (true)     {         // Receive a vote message from the queue         BrokeredMessage msg = ScatterGatherQueueClient.Receive();         if (msg != null)         {             // Deserialize the message.             Vote vote = msg.GetBody<Vote>();               // Update the results.             foreach (Result result in Results)             {                 if (result.Question.Equals(vote.QuestionText))                 {                     if (vote.IsYes)                     {                         result.YesVotes++;                     }                     else                     {                         result.NoVotes++;                     }                     break;                 }             }               // Mark the message as complete.             msg.Complete();         }       } }     When a vote message is received, the result that matches the vote question is updated with the vote from the user. The message is then marked as complete. A second background thread is used to update the display of subscriptions in the TreeView, with a dispatcher used to update the user interface. // This runs on a background worker. private void UpdateSubscriptions(object sender, DoWorkEventArgs e) {     while (true)     {         // Get a list of subscriptions.         IEnumerable<SubscriptionDescription> subscriptions =             NamespaceManager.GetSubscriptions(AccountDetails.ScatterGatherTopic);           // Update the user interface.         SimpleDelegate setQuestion = delegate()         {             trvSubscriptions.Items.Clear();             TreeViewItem topicItem = new TreeViewItem()             {                 Header = AccountDetails.ScatterGatherTopic             };               foreach (SubscriptionDescription subscription in subscriptions)             {                 TreeViewItem subscriptionItem = new TreeViewItem()                 {                     Header = subscription.Name                 };                 topicItem.Items.Add(subscriptionItem);             }             trvSubscriptions.Items.Add(topicItem);               topicItem.ExpandSubtree();         };         this.Dispatcher.BeginInvoke(DispatcherPriority.Send, setQuestion);           Thread.Sleep(3000);     } }       Voting Application The voting application is implemented as another WPF application. This one is more basic, and allows the user to vote “Yes” or “No” for the questions sent by the poll manager application. The user interface for that application is shown below. When an instance of the voting application is created it will create a subscription in the questions topic using a GUID as the subscription name. The application can then receive copies of every question message that is sent to the topic. Clients for the new subscription and the votes queue are created, along with a background worker to receive the question messages. The voting application is set to receiving mode, meaning it is ready to receive a question message from the subscription.   public MainWindow() {     InitializeComponent();       // Set the mode to receiving.     IsReceiving = true;       // Create a token provider with the relevant credentials.     TokenProvider credentials =         TokenProvider.CreateSharedSecretTokenProvider         (AccountDetails.Name, AccountDetails.Key);       // Create a URI for the serivce bus.     Uri serviceBusUri = ServiceBusEnvironment.CreateServiceUri         ("sb", AccountDetails.Namespace, string.Empty);       // Create the MessagingFactory     MessagingFactory factory = MessagingFactory.Create(serviceBusUri, credentials);       // Create a subcription for this instance     NamespaceManager mgr = new NamespaceManager(serviceBusUri, credentials);     string subscriptionName = Guid.NewGuid().ToString();     mgr.CreateSubscription(AccountDetails.ScatterGatherTopic, subscriptionName);       // Create the subscription and queue clients.     ScatterGatherSubscriptionClient = factory.CreateSubscriptionClient         (AccountDetails.ScatterGatherTopic, subscriptionName);     ScatterGatherQueueClient =         factory.CreateQueueClient(AccountDetails.ScatterGatherQueue);       // Start the background worker thread.     BackgroundWorker = new BackgroundWorker();     BackgroundWorker.DoWork += new DoWorkEventHandler(ReceiveMessages);     BackgroundWorker.RunWorkerAsync(); }     I took the inspiration for creating the subscriptions in the voting application from the chat application that uses topics and subscriptions blogged by Ovais Akhter here. The method that receives the question messages runs on a background thread. If the application is in receive mode, a question message will be received from the subscription, the question will be displayed in the user interface, the voting buttons enabled, and IsReceiving set to false to prevent more questing from being received before the current one is answered.   // This runs on a background worker. private void ReceiveMessages(object sender, DoWorkEventArgs e) {     while (true)     {         if (IsReceiving)         {             // Receive a question message from the topic.             BrokeredMessage msg = ScatterGatherSubscriptionClient.Receive();             if (msg != null)             {                 // Deserialize the message.                 Question question = msg.GetBody<Question>();                   // Update the user interface.                 SimpleDelegate setQuestion = delegate()                 {                     lblQuestion.Content = question.QuestionText;                     btnYes.IsEnabled = true;                     btnNo.IsEnabled = true;                 };                 this.Dispatcher.BeginInvoke(DispatcherPriority.Send, setQuestion);                 IsReceiving = false;                   // Mark the message as complete.                 msg.Complete();             }         }         else         {             Thread.Sleep(1000);         }     } }     When the user clicks on the Yes or No button, the btnVote_Click method is called. This will create a new Vote data contract with the appropriate question and answer and send the message to the poll manager application using the votes queue. The user voting buttons are then disabled, the question text cleared, and the IsReceiving flag set to true to allow a new message to be received.   private void btnVote_Click(object sender, RoutedEventArgs e) {     // Create a new vote.     Vote vote = new Vote()     {         QuestionText = (string)lblQuestion.Content,         IsYes = ((sender as Button).Content as string).Equals("Yes")     };       // Send the vote message.     BrokeredMessage msg = new BrokeredMessage(vote);     ScatterGatherQueueClient.Send(msg);       // Update the user interface.     lblQuestion.Content = "";     btnYes.IsEnabled = false;     btnNo.IsEnabled = false;     IsReceiving = true; }     Testing the Application In order to test the application, an instance of the poll manager application is started; the user interface is shown below. As no instances of the voting application have been created there are no subscriptions present in the topic. When an instance of the voting application is created the subscription will be displayed in the poll manager. Now that a voting application is subscribing, a questing can be sent from the poll manager application. When the message is sent to the topic, the voting application will receive the message and display the question. The voter can then answer the question by clicking on the appropriate button. The results of the vote are updated in the poll manager application. When two more instances of the voting application are created, the poll manager will display the new subscriptions. More questions can then be broadcast to the voting applications. As the question messages are queued up in the subscription for each voting application, the users can answer the questions in their own time. The vote messages will be received by the poll manager application and aggregated to display the results. The screenshots of the applications part way through voting are shown below. The messages for each voting application are queued up in sequence on the voting application subscriptions, allowing the questions to be answered at different speeds by the voters.

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  • DNS Problems (NIGHTMARES!) with BIND and Virtualmin

    - by Nyxynyx
    I have a webserver (Ubuntu 12.04 with LAMP) using Virtualmin / Webmin. Because I just moved from a Cpanel system, I am having a nightmare configuring the DNS! Using intoDNS.com, the failed reports are: Mismatched NS records WARNING: One or more of your nameservers did not return any of your NS records. DNS servers responded ERROR: One or more of your nameservers did not respond: The ones that did not respond are: 123.123.123.123 213.251.188.141x Multiple Nameservers ERROR: Looks like you have less than 2 nameservers. According to RFC2182 section 5 you must have at least 3 nameservers, and no more than 7. Having 2 nameservers is also ok by me. Missing nameservers reported by your nameserver You should already know that your NS records at your nameservers are missing, so here it is again: ns1.mydomain.com. sdns2.ovh.net. SOA record No valid SOA record came back! MX Records WWW A Record ERROR: I could not get any A records for www.mydomain.com! Step-by-Step of my Attempt In my domain registrar (Namecheap), I registered ns1.mydomain.com as a nameserver, pointing to the IP address of my web server which is running bind9. The domain is setup with DNS ns1.mydomain.com and sdns2.ovh.net. sdns2.ovh.net is a secondary DNS server (SLAVE and pointing mydomain.com to the IP address of my web server) Webserver domain: mydomain.com Webserver hostname: ns4000000.ip-123-123-123.net Webserver IP: 123.123.123.123 Under Virtualmin, I edited the default Virtual server template, BIND DNS records for new domains: ns1.mydomain.com Master DNS server hostname: ns1.mydomain.com Next I created a Virtual server using that server template. This is what I've done but its still not working! Any ideas? I've been stuck for days, thank you for all your help! service bind9 status * bind9 is running lsof -i :53 COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME named 6966 bind 20u IPv6 338583 0t0 TCP *:domain (LISTEN) named 6966 bind 21u IPv4 338588 0t0 TCP localhost.localdomain:domain (LISTEN) named 6966 bind 22u IPv4 338590 0t0 TCP ns4000000.ip-123-123-123.net:domain (LISTEN) named 6966 bind 512u IPv6 338582 0t0 UDP *:domain named 6966 bind 513u IPv4 338587 0t0 UDP localhost.localdomain:domain named 6966 bind 514u IPv4 338589 0t0 UDP ns4000000.ip-123-123-123.net:domain /etc/resolv.con (Not sure how 213.186.33.99 got here) nameserver 127.0.0.1 nameserver 213.186.33.99 search ovh.net host 123.123.123.123 (my web server's IP) 13.60.245.198.in-addr.arpa domain name pointer ns4000000.ip-123-123-123.net. nslookup 213.186.33.99 Server: 127.0.0.1 Address: 127.0.0.1#53 Non-authoritative answer: 99.33.186.213.in-addr.arpa name = cdns.ovh.net. Authoritative answers can be found from: 33.186.213.in-addr.arpa nameserver = ns.ovh.net. 33.186.213.in-addr.arpa nameserver = dns.ovh.net. nslookup ns1.mydomain.com ;; Got SERVFAIL reply from 127.0.0.1, trying next server ;; connection timed out; no servers could be reached nslookup ns2.mydomain.com ;; Got SERVFAIL reply from 127.0.0.1, trying next server ;; connection timed out; no servers could be reached nslookup www.mydomain.com ;; Got SERVFAIL reply from 127.0.0.1, trying next server ;; connection timed out; no servers could be reached dig mydomain.com ; <<>> DiG 9.8.1-P1 <<>> mydomain.com ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 43540 ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;mydomain.com. IN A ;; Query time: 0 msec ;; SERVER: 127.0.0.1#53(127.0.0.1) ;; WHEN: Thu Oct 11 11:30:09 2012 ;; MSG SIZE rcvd: 30 dig ns1.mydomain.com ; <<>> DiG 9.8.1-P1 <<>> ns1.mydomain.com ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 31254 ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;ns1.mydomain.com. IN A ;; Query time: 0 msec ;; SERVER: 127.0.0.1#53(127.0.0.1) ;; WHEN: Thu Oct 11 11:30:16 2012 ;; MSG SIZE rcvd: 34 /etc/bind/named.conf include "/etc/bind/named.conf.options"; include "/etc/bind/named.conf.local"; include "/etc/bind/named.conf.default-zones"; /etc/bind/named.conf.default-zones zone "." { type hint; file "/etc/bind/db.root"; }; zone "localhost" { type master; file "/etc/bind/db.local"; }; zone "127.in-addr.arpa" { type master; file "/etc/bind/db.127"; }; zone "0.in-addr.arpa" { type master; file "/etc/bind/db.0"; }; zone "255.in-addr.arpa" { type master; file "/etc/bind/db.255"; }; /etc/bind/named.conf.local zone "mydomain.com" { type master; file "/var/lib/bind/mydomain.com.hosts"; allow-transfer { 127.0.0.1; localnets; }; }; /etc/bind/named.conf.options options { directory "/var/cache/bind"; dnssec-validation auto; auth-nxdomain no; # conform to RFC1035 listen-on-v6 { any; }; // allow-recursion { 127.0.0.1; }; // transfer-source; }; named-checkconf -z dns_master_load: /var/lib/bind/mydomain.com.hosts:21: unexpected end of line dns_master_load: /var/lib/bind/mydomain.com.hosts:20: unexpected end of input /var/lib/bind/mydomain.com.hosts: file does not end with newline zone mydomain.com/IN: loading from master file /var/lib/bind/mydomain.com.hosts failed: unexpected end of input zone mydomain.com/IN: not loaded due to errors. _default/mydomain.com/IN: unexpected end of input zone localhost/IN: loaded serial 2 zone 127.in-addr.arpa/IN: loaded serial 1 zone 0.in-addr.arpa/IN: loaded serial 1 zone 255.in-addr.arpa/IN: loaded serial 1 iptables -L Chain INPUT (policy ACCEPT) target prot opt source destination ACCEPT udp -- anywhere anywhere udp dpt:domain ACCEPT tcp -- anywhere anywhere tcp dpt:20000 ACCEPT tcp -- anywhere anywhere tcp dpt:webmin ACCEPT tcp -- anywhere anywhere tcp dpt:https ACCEPT tcp -- anywhere anywhere tcp dpt:http ACCEPT tcp -- anywhere anywhere tcp dpt:imaps ACCEPT tcp -- anywhere anywhere tcp dpt:imap2 ACCEPT tcp -- anywhere anywhere tcp dpt:pop3s ACCEPT tcp -- anywhere anywhere tcp dpt:pop3 ACCEPT tcp -- anywhere anywhere tcp dpt:ftp-data ACCEPT tcp -- anywhere anywhere tcp dpt:ftp ACCEPT tcp -- anywhere anywhere tcp dpt:domain ACCEPT tcp -- anywhere anywhere tcp dpt:submission ACCEPT tcp -- anywhere anywhere tcp dpt:smtp ACCEPT tcp -- anywhere anywhere tcp dpt:ssh ACCEPT all -- anywhere anywhere Chain FORWARD (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination

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  • Soapi.CS : A fully relational fluent .NET Stack Exchange API client library

    - by Sky Sanders
    Soapi.CS for .Net / Silverlight / Windows Phone 7 / Mono as easy as breathing...: var context = new ApiContext(apiKey).Initialize(false); Question thisPost = context.Official .StackApps .Questions.ById(386) .WithComments(true) .First(); Console.WriteLine(thisPost.Title); thisPost .Owner .Questions .PageSize(5) .Sort(PostSort.Votes) .ToList() .ForEach(q=> { Console.WriteLine("\t" + q.Score + "\t" + q.Title); q.Timeline.ToList().ForEach(t=> Console.WriteLine("\t\t" + t.TimelineType + "\t" + t.Owner.DisplayName)); Console.WriteLine(); }); // if you can think it, you can get it. Output Soapi.CS : A fully relational fluent .NET Stack Exchange API client library 21 Soapi.CS : A fully relational fluent .NET Stack Exchange API client library Revision code poet Revision code poet Votes code poet Votes code poet Revision code poet Revision code poet Revision code poet Votes code poet Votes code poet Votes code poet Revision code poet Revision code poet Revision code poet Revision code poet Revision code poet Revision code poet Revision code poet Revision code poet Revision code poet Revision code poet Votes code poet Comment code poet Revision code poet Votes code poet Revision code poet Revision code poet Revision code poet Answer code poet Revision code poet Revision code poet 14 SOAPI-WATCH: A realtime service that notifies subscribers via twitter when the API changes in any way. Votes code poet Revision code poet Votes code poet Comment code poet Comment code poet Comment code poet Votes lfoust Votes code poet Comment code poet Comment code poet Comment code poet Comment code poet Revision code poet Comment lfoust Votes code poet Revision code poet Votes code poet Votes lfoust Votes code poet Revision code poet Comment Dave DeLong Revision code poet Revision code poet Votes code poet Comment lfoust Comment Dave DeLong Comment lfoust Comment lfoust Comment Dave DeLong Revision code poet 11 SOAPI-EXPLORE: Self-updating single page JavaSript API test harness Votes code poet Votes code poet Votes code poet Votes code poet Votes code poet Comment code poet Revision code poet Votes code poet Revision code poet Revision code poet Revision code poet Comment code poet Revision code poet Votes code poet Comment code poet Question code poet Votes code poet 11 Soapi.JS V1.0: fluent JavaScript wrapper for the StackOverflow API Comment George Edison Comment George Edison Comment George Edison Comment George Edison Comment George Edison Comment George Edison Answer George Edison Votes code poet Votes code poet Votes code poet Votes code poet Revision code poet Revision code poet Answer code poet Comment code poet Revision code poet Comment code poet Comment code poet Comment code poet Revision code poet Revision code poet Votes code poet Votes code poet Votes code poet Votes code poet Comment code poet Comment code poet Comment code poet Comment code poet Comment code poet 9 SOAPI-DIFF: Your app broke? Check SOAPI-DIFF to find out what changed in the API Votes code poet Revision code poet Comment Dennis Williamson Answer Dennis Williamson Votes code poet Votes Dennis Williamson Comment code poet Question code poet Votes code poet About A robust, fully relational, easy to use, strongly typed, end-to-end StackOverflow API Client Library. Out of the box, Soapi provides you with a robust client library that abstracts away most all of the messy details of consuming the API and lets you concentrate on implementing your ideas. A few features include: A fully relational model of the API data set exposed via a fully 'dot navigable' IEnumerable (LINQ) implementation. Simply tell Soapi what you want and it will get it for you. e.g. "On my first question, from the author of the first comment, get the first page of comments by that person on any post" my.Questions.First().Comments.First().Owner.Comments.ToList(); (yes this is a real expression that returns the data as expressed!) Full coverage of the API, all routes and all parameters with an intuitive syntax. Strongly typed Domain Data Objects for all API data structures. Eager and Lazy Loading of 'stub' objects. Eager\Lazy loading may be disabled. When finer grained control of requests is desired, the core RouteMap objects may be leveraged to request data from any of the API paths using all available parameters as documented on the help pages. A rich Asynchronous implementation. A configurable request cache to reduce unnecessary network traffic and to simplify your usage logic. There is no need to go out of your way to be frugal. You may set a distinct cache duration for any particular route. A configurable request throttle to ensure compliance with the api terms of usage and to simplify your code in that you do not have to worry about and respond to 50X errors. The RequestCache and Throttled Queue are thread-safe, so can make as many requests as you like from as many threads as you like as fast as you like and not worry about abusing the api or having to write reams of management/compensation code. Configurable retry threshold that will, by default, make up to 3 attempts to retrieve a request before failing. Every request made by Soapi is properly formed and directed so most any http error will be the result of a timeout or other network infrastructure. A retry buffer provides a level of fault tolerance that you can rely on. An almost identical javascript library, Soapi.JS, and it's full figured big brother, Soapi.JS2, that will enable you to leverage your server cycles and bandwidth for only those tasks that require it and offload things like status updates to the client's browser. License Licensed GPL Version 2 license. Why is Soapi.CS GPL? Can I get an LGPL license for Soapi.CS? (hint: probably) Platforms .NET 3.5 .NET 4.0 Silverlight 3 Silverlight 4 Windows Phone 7 Mono Download Source code lives @ http://soapics.codeplex.com. Binary releases are forthcoming. codeplex is acting up again. get the source and binaries @ http://bitbucket.org/bitpusher/soapi.cs/downloads The source is C# 3.5. and includes projects and solutions for the following IDEs Visual Studio 2008 Visual Studio 2010 ModoDevelop 2.4 Documentation Full documentation is available at http://soapi.info/help/cs/index.aspx Sample Code / Usage Examples Sample code and usage examples will be added as answers to this question. Full API Coverage all API routes are covered Full Parameter Parity If the API exposes it, Soapi giftwraps it for you. Building a simple app with Soapi.CS - a simple app that gathers all traces of a user in the whole stackiverse. Fluent Configuration - Setting up a Soapi.ApiContext could not be easier Bulk Data Import - A tiny app that quickly loads a SQLite data file with all users in the stackiverse. Paged Results - Soapi.CS transparently handles multi-page operations. Asynchronous Requests - Soapi.CS provides a rich asynchronous model that is especially useful when writing api apps in Silverlight or Windows Phone 7. Caching and Throttling - how and why Apps that use Soapi.CS Soapi.FindUser - .net utility for locating a user anywhere in the stackiverse Soapi.Explore - The entire API at your command Soapi.LastSeen - List users by last access time Add your app/site here - I know you are out there ;-) if you are not comfortable editing this post, simply add a comment and I will add it. The CS/SL/WP7/MONO libraries all compile the same code and with the exception of environmental considerations of Silverlight, the code samples are valid for all libraries. You may also find guidance in the test suites. More information on the SOAPI eco-system. Contact This library is currently the effort of me, Sky Sanders (code poet) and can be reached at gmail - sky.sanders Any who are interested in improving this library are welcome. Support Soapi You can help support this project by voting for Soapi's Open Source Ad post For more information about the origins of Soapi.CS and the rest of the Soapi eco-system see What is Soapi and why should I care?

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  • Building KPIs to monitor your business Its not really about the Technology

    When I have discussions with people about Business Intelligence, one of the questions the inevitably come up is about building KPIs and how to accomplish that. From a technical level the concept of a KPI is very simple, almost too simple in that it is like the tip of an iceberg floating above the water. The key to that iceberg is not really the tip, but the mass of the iceberg that is hidden beneath the surface upon which the tip sits. The analogy of the iceberg is not meant to indicate that the foundation of the KPI is overly difficult or complex. The disparity in size in meant to indicate that the larger thing that needs to be defined is not the technical tip, but the underlying business definition of what the KPI means. From a technical perspective the KPI consists of primarily the following items: Actual Value This is the actual value data point that is being measured. An example would be something like the amount of sales. Target Value This is the target goal for the KPI. This is a number that can be measured against Actual Value. An example would be $10,000 in monthly sales. Target Indicator Range This is the definition of ranges that define what type of indicator the user will see comparing the Actual Value to the Target Value. Most often this is defined by stoplight, but can be any indicator that is going to show a status in a quick fashion to the user. Typically this would be something like: Red Light = Actual Value more than 5% below target; Yellow Light = Within 5% of target either direction; Green Light = More than 5% higher than Target Value Status\Trend Indicator This is an optional attribute of a KPI that is typically used to show some kind of trend. The vast majority of these indicators are used to show some type of progress against a previous period. As an example, the status indicator might be used to show how the monthly sales compare to last month. With this type of indicator there needs to be not only a definition of what the ranges are for your status indictor, but then also what value the number needs to be compared against. So now we have an idea of what data points a KPI consists of from a technical perspective lets talk a bit about tools. As you can see technically there is not a whole lot to them and the choice of technology is not as important as the definition of the KPIs, which we will get to in a minute. There are many different types of tools in the Microsoft BI stack that you can use to expose your KPI to the business. These include Performance Point, SharePoint, Excel, and SQL Reporting Services. There are pluses and minuses to each technology and the right technology is based a lot on your goals and how you want to deliver the information to the users. Additionally, there are other non-Microsoft tools that can be used to expose KPI indicators to your business users. Regardless of the technology used as your front end, the heavy lifting of KPI is in the business definition of the values and benchmarks for that KPI. The discussion about KPIs is very dependent on the history of an organization and how much they are exposed to the attributes of a KPI. Often times when discussing KPIs with a business contact who has not been exposed to KPIs the discussion tends to also be a session educating the business user about what a KPI is and what goes into the definition of a KPI. The majority of times the business user has an idea of what their actual values are and they have been tracking those numbers for some time, generally in Excel and all manually. So they will know the amount of sales last month along with sales two years ago in the same month. Where the conversation tends to get stuck is when you start discussing what the target value should be. The actual value is answering the What and How much questions. When you are talking about the Target values you are asking the question Is this number good or bad. Typically, the user will know whether or not the value is good or bad, but most of the time they are not able to quantify what is good or bad. Their response is usually something like I just know. Because they have been watching the sales quantity for years now, they can tell you that a 5% decrease in sales this month might actually be a good thing, maybe because the salespeople are all waiting until next month when the new versions come out. It can sometimes be very hard to break the business people of this habit. One of the fears generally is that the status indicator is not subjective. Thus, in the scenario above, the business user is going to be fearful that their boss, just looking at a negative red indicator, is going to haul them out to the woodshed for a bad month. But, on the flip side, if all you are displaying is the amount of sales, only a person with knowledge of last month sales and the target amount for this month would have any idea if $10,000 in sales is good or not. Here is where a key point about KPIs needs to be communicated to both the business user and any user who might be viewing the results of that KPI. The KPI is just one tool that is used to report on business performance. The KPI is meant as a quick indicator of one business statistic. It is not meant to tell the entire story. It does not answer the question Why. Its primary purpose is to objectively and quickly expose an area of the business that might warrant more review. There is always going to be the need to do further analysis on any potential negative or neutral KPI. So, hopefully, once you have convinced your business user to come up with some target numbers and ranges for status indicators, you then need to take the next step and help them answer the Why question. The main question here to ask is, Okay, you see the indicator and you need to discover why the number is what is, where do you go?. The answer is usually a combination of sources. A sales manager might have some of the following items at their disposal (Marketing report showing a decrease in the promotional discounts for the month, Pricing Report showing the reduction of prices of older models, an Inventory Report showing the discontinuation of a particular product line, or a memo showing the ending of a large affiliate partnership. The answers to the question Why are never as simple as a single indicator value. Bring able to quickly get to this information is all about designing how a user accesses the KPIs and then also how easily they can get to the additional information they need. This is where a Dashboard mentality can come in handy. For example, the business user can have a dashboard that shows their KPIs, but also has links to some of the common reports that they run regarding Sales Data. The users boss may have the same KPIs on their dashboard, but instead of links to individual reports they are going to have a link to a status report that was created by the user that pulls together all the data about the KPI in a summary format the users boss can review. So some of the key things to think about when building or evaluating KPIs for your organization: Technology should not be the driving factor KPIs are of little value without some indicator for whether a value is good, bad or neutral. KPIs only give an answer to the Is this number good\bad? question Make sure the ability to drill into the Why of a KPI is close at hand and relevant to the user who is viewing the KPI. The KPI is a key business tool when defined properly to help monitor business performance across the enterprise in an objective and consistent manner. At times it might feel like the process of defining the business aspects of a KPI can sometimes be arduous, the payoff in the end can far outweigh the costs. Some of the benefits of going through this process are a better understanding of the key metrics for an organization and the measure of those metrics and a consistent snapshot of business performance that can be utilized across the organization. And I think that these are benefits to any organization regardless of the technology or the implementation.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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  • SQL SERVER – Weekly Series – Memory Lane – #034

    - by Pinal Dave
    Here is the list of selected articles of SQLAuthority.com across all these years. Instead of just listing all the articles I have selected a few of my most favorite articles and have listed them here with additional notes below it. Let me know which one of the following is your favorite article from memory lane. 2007 UDF – User Defined Function to Strip HTML – Parse HTML – No Regular Expression The UDF used in the blog does fantastic task – it scans entire HTML text and removes all the HTML tags. It keeps only valid text data without HTML task. This is one of the quite commonly requested tasks many developers have to face everyday. De-fragmentation of Database at Operating System to Improve Performance Operating system skips MDF file while defragging the entire filesystem of the operating system. It is absolutely fine and there is no impact of the same on performance. Read the entire blog post for my conversation with our network engineers. Delay Function – WAITFOR clause – Delay Execution of Commands How do you delay execution of the commands in SQL Server – ofcourse by using WAITFOR keyword. In this blog post, I explain the same with the help of T-SQL script. Find Length of Text Field To measure the length of TEXT fields the function is DATALENGTH(textfield). Len will not work for text field. As of SQL Server 2005, developers should migrate all the text fields to VARCHAR(MAX) as that is the way forward. Retrieve Current Date Time in SQL Server CURRENT_TIMESTAMP, GETDATE(), {fn NOW()} There are three ways to retrieve the current datetime in SQL SERVER. CURRENT_TIMESTAMP, GETDATE(), {fn NOW()} Explanation and Comparison of NULLIF and ISNULL An interesting observation is NULLIF returns null if it comparison is successful, whereas ISNULL returns not null if its comparison is successful. In one way they are opposite to each other. Here is my question to you - How to create infinite loop using NULLIF and ISNULL? If this is even possible? 2008 Introduction to SERVERPROPERTY and example SERVERPROPERTY is a very interesting system function. It returns many of the system values. I use it very frequently to get different server values like Server Collation, Server Name etc. SQL Server Start Time We can use DMV to find out what is the start time of SQL Server in 2008 and later version. In this blog you can see how you can do the same. Find Current Identity of Table Many times we need to know what is the current identity of the column. I have found one of my developers using aggregated function MAX () to find the current identity. However, I prefer following DBCC command to figure out current identity. Create Check Constraint on Column Some time we just need to create a simple constraint over the table but I have noticed that developers do many different things to make table column follow rules than just creating constraint. I suggest constraint is a very useful concept and every SQL Developer should pay good attention to this subject. 2009 List Schema Name and Table Name for Database This is one of the blog post where I straight forward display script. One of the kind of blog posts, which I still love to read and write. Clustered Index on Separate Drive From Table Location A table devoid of primary key index is called heap, and here data is not arranged in a particular order, which gives rise to issues that adversely affect performance. Data must be stored in some kind of order. If we put clustered index on it then the order will be forced by that index and the data will be stored in that particular order. Understanding Table Hints with Examples Hints are options and strong suggestions specified for enforcement by the SQL Server query processor on DML statements. The hints override any execution plan the query optimizer might select for a query. 2010 Data Pages in Buffer Pool – Data Stored in Memory Cache One of my earlier year article, which I still read it many times and point developers to read it again. It is clear from the Resultset that when more than one index is used, datapages related to both or all of the indexes are stored in Memory Cache separately. TRANSACTION, DML and Schema Locks Can you create a situation where you can see Schema Lock? Well, this is a very simple question, however during the interview I notice over 50 candidates failed to come up with the scenario. In this blog post, I have demonstrated the situation where we can see the schema lock in database. 2011 Solution – Puzzle – Statistics are not updated but are Created Once In this example I have created following situation: Create Table Insert 1000 Records Check the Statistics Now insert 10 times more 10,000 indexes Check the Statistics – it will be NOT updated Auto Update Statistics and Auto Create Statistics for database is TRUE Now I have requested two things in the example 1) Why this is happening? 2) How to fix this issue? Selecting Domain from Email Address This is a straight to script blog post where I explain how to select only domain name from entire email address. Solution – Generating Zero Without using Any Numbers in T-SQL How to get zero digit without using any digit? This is indeed a very interesting question and the answer is even interesting. Try to come up with answer in next 10 minutes and if you can’t come up with the answer the blog post read this post for solution. 2012 Simple Explanation and Puzzle with SOUNDEX Function and DIFFERENCE Function In simple words - SOUNDEX converts an alphanumeric string to a four-character code to find similar-sounding words or names. DIFFERENCE function returns an integer value. The  integer returned is the number of characters in the SOUNDEX values that are the same. Read Only Files and SQL Server Management Studio (SSMS) I have come across a very interesting feature in SSMS related to “Read Only” files. I believe it is a little unknown feature as well so decided to write a blog about the same. Identifying Column Data Type of uniqueidentifier without Querying System Tables How do I know if any table has a uniqueidentifier column and what is its value without using any DMV or System Catalogues? Only information you know is the table name and you are allowed to return any kind of error if the table does not have uniqueidentifier column. Read the blog post to find the answer. Solution – User Not Able to See Any User Created Object in Tables – Security and Permissions Issue Interesting question – “When I try to connect to SQL Server, it lets me connect just fine as well let me open and explore the database. I noticed that I do not see any user created instances but when my colleague attempts to connect to the server, he is able to explore the database as well see all the user created tables and other objects. Can you help me fix it?” Importing CSV File Into Database – SQL in Sixty Seconds #018 – Video Here is interesting small 60 second video on how to import CSV file into Database. ColumnStore Index – Batch Mode vs Row Mode Here is the logic behind when Columnstore Index uses Batch Mode and when it uses Row Mode. A batch typically represents about 1000 rows of data. Batch mode processing also uses algorithms that are optimized for the multicore CPUs and increased memory throughput. Follow up – Usage of $rowguid and $IDENTITY This is an excellent follow up blog post of my earlier blog post where I explain where to use $rowguid and $identity.  If you do not know the difference between them, this is a blog with a script example. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Memory Lane, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • elffile: ELF Specific File Identification Utility

    - by user9154181
    Solaris 11 has a new standard user level command, /usr/bin/elffile. elffile is a variant of the file utility that is focused exclusively on linker related files: ELF objects, archives, and runtime linker configuration files. All other files are simply identified as "non-ELF". The primary advantage of elffile over the existing file utility is in the area of archives — elffile examines the archive members and can produce a summary of the contents, or per-member details. The impetus to add elffile to Solaris came from the effort to extend the format of Solaris archives so that they could grow beyond their previous 32-bit file limits. That work introduced a new archive symbol table format. Now that there was more than one possible format, I thought it would be useful if the file utility could identify which format a given archive is using, leading me to extend the file utility: % cc -c ~/hello.c % ar r foo.a hello.o % file foo.a foo.a: current ar archive, 32-bit symbol table % ar r -S foo.a hello.o % file foo.a foo.a: current ar archive, 64-bit symbol table In turn, this caused me to think about all the things that I would like the file utility to be able to tell me about an archive. In particular, I'd like to be able to know what's inside without having to unpack it. The end result of that train of thought was elffile. Much of the discussion in this article is adapted from the PSARC case I filed for elffile in December 2010: PSARC 2010/432 elffile Why file Is No Good For Archives And Yet Should Not Be Fixed The standard /usr/bin/file utility is not very useful when applied to archives. When identifying an archive, a user typically wants to know 2 things: Is this an archive? Presupposing that the archive contains objects, which is by far the most common use for archives, what platform are the objects for? Are they for sparc or x86? 32 or 64-bit? Some confusing combination from varying platforms? The file utility provides a quick answer to question (1), as it identifies all archives as "current ar archive". It does nothing to answer the more interesting question (2). To answer that question, requires a multi-step process: Extract all archive members Use the file utility on the extracted files, examine the output for each file in turn, and compare the results to generate a suitable summary description. Remove the extracted files It should be easier and more efficient to answer such an obvious question. It would be reasonable to extend the file utility to examine archive contents in place and produce a description. However, there are several reasons why I decided not to do so: The correct design for this feature within the file utility would have file examine each archive member in turn, applying its full abilities to each member. This would be elegant, but also represents a rather dramatic redesign and re-implementation of file. Archives nearly always contain nothing but ELF objects for a single platform, so such generality in the file utility would be of little practical benefit. It is best to avoid adding new options to standard utilities for which other implementations of interest exist. In the case of the file utility, one concern is that we might add an option which later appears in the GNU version of file with a different and incompatible meaning. Indeed, there have been discussions about replacing the Solaris file with the GNU version in the past. This may or may not be desirable, and may or may not ever happen. Either way, I don't want to preclude it. Examining archive members is an O(n) operation, and can be relatively slow with large archives. The file utility is supposed to be a very fast operation. I decided that extending file in this way is overkill, and that an investment in the file utility for better archive support would not be worth the cost. A solution that is more narrowly focused on ELF and other linker related files is really all that we need. The necessary code for doing this already exists within libelf. All that is missing is a small user-level wrapper to make that functionality available at the command line. In that vein, I considered adding an option for this to the elfdump utility. I examined elfdump carefully, and even wrote a prototype implementation. The added code is small and simple, but the conceptual fit with the rest of elfdump is poor. The result complicates elfdump syntax and documentation, definite signs that this functionality does not belong there. And so, I added this functionality as a new user level command. The elffile Command The syntax for this new command is elffile [-s basic | detail | summary] filename... Please see the elffile(1) manpage for additional details. To demonstrate how output from elffile looks, I will use the following files: FileDescription configA runtime linker configuration file produced with crle dwarf.oAn ELF object /etc/passwdA text file mixed.aArchive containing a mixture of ELF and non-ELF members mixed_elf.aArchive containing ELF objects for different machines not_elf.aArchive containing no ELF objects same_elf.aArchive containing a collection of ELF objects for the same machine. This is the most common type of archive. The file utility identifies these files as follows: % file config dwarf.o /etc/passwd mixed.a mixed_elf.a not_elf.a same_elf.a config: Runtime Linking Configuration 64-bit MSB SPARCV9 dwarf.o: ELF 64-bit LSB relocatable AMD64 Version 1 /etc/passwd: ascii text mixed.a: current ar archive, 32-bit symbol table mixed_elf.a: current ar archive, 32-bit symbol table not_elf.a: current ar archive same_elf.a: current ar archive, 32-bit symbol table By default, elffile uses its "summary" output style. This output differs from the output from the file utility in 2 significant ways: Files that are not an ELF object, archive, or runtime linker configuration file are identified as "non-ELF", whereas the file utility attempts further identification for such files. When applied to an archive, the elffile output includes a description of the archive's contents, without requiring member extraction or other additional steps. Applying elffile to the above files: % elffile config dwarf.o /etc/passwd mixed.a mixed_elf.a not_elf.a same_elf.a config: Runtime Linking Configuration 64-bit MSB SPARCV9 dwarf.o: ELF 64-bit LSB relocatable AMD64 Version 1 /etc/passwd: non-ELF mixed.a: current ar archive, 32-bit symbol table, mixed ELF and non-ELF content mixed_elf.a: current ar archive, 32-bit symbol table, mixed ELF content not_elf.a: current ar archive, non-ELF content same_elf.a: current ar archive, 32-bit symbol table, ELF 64-bit LSB relocatable AMD64 Version 1 The output for same_elf.a is of particular interest: The vast majority of archives contain only ELF objects for a single platform, and in this case, the default output from elffile answers both of the questions about archives posed at the beginning of this discussion, in a single efficient step. This makes elffile considerably more useful than file, within the realm of linker-related files. elffile can produce output in two other styles, "basic", and "detail". The basic style produces output that is the same as that from 'file', for linker-related files. The detail style produces per-member identification of archive contents. This can be useful when the archive contents are not homogeneous ELF object, and more information is desired than the summary output provides: % elffile -s detail mixed.a mixed.a: current ar archive, 32-bit symbol table mixed.a(dwarf.o): ELF 32-bit LSB relocatable 80386 Version 1 mixed.a(main.c): non-ELF content mixed.a(main.o): ELF 64-bit LSB relocatable AMD64 Version 1 [SSE]

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  • Visual Tree Enumeration

    - by codingbloke
    I feel compelled to post this blog because I find I’m repeatedly posting this same code in silverlight and windows-phone-7 answers in Stackoverflow. One common task that we feel we need to do is burrow into the visual tree in a Silverlight or Windows Phone 7 application (actually more recently I found myself doing this in WPF as well).  This allows access to details that aren’t exposed directly by some controls.  A good example of this sort of requirement is found in the “Restoring exact scroll position of a listbox in Windows Phone 7”  question on stackoverflow.  This required that the scroll position of the scroll viewer internal to a listbox be accessed. A caveat One caveat here is that we should seriously challenge the need for this burrowing since it may indicate that there is a design problem.  Burrowing into the visual tree or indeed burrowing out to containing ancestors could represent significant coupling between module boundaries and that generally isn’t a good idea. Why isn’t this idea just not cast aside as a no-no?  Well the whole concept of a “Templated Control”, which are in extensive use in these applications, opens the coupling between the content of the visual tree and the internal code of a control.   For example, I can completely change the appearance and positioning of elements that make up a ComboBox.  The ComboBox control relies on specific template parts having set names of a specified type being present in my template.  Rightly or wrongly this does kind of give license to writing code that has similar coupling. Hasn’t this been done already? Yes it has.  There are number of blogs already out there with similar solutions.  In fact if you are using Silverlight toolkit the VisualTreeExtensions class already provides this feature.  However I prefer my specific code because of the simplicity principle I hold to.  Only write the minimum code necessary to give all the features needed.  In this case I add just two extension methods Ancestors and Descendents, note I don’t bother with “Get” or “Visual” prefixes.  Also I haven’t added Parent or Children methods nor additional “AndSelf” methods because all but Children is achievable with the addition of some other Linq methods.  I decided to give Descendents an additional overload for depth hence a depth of 1 is equivalent to Children but this overload is a little more flexible than simply Children. So here is the code:- VisualTreeEnumeration public static class VisualTreeEnumeration {     public static IEnumerable<DependencyObject> Descendents(this DependencyObject root, int depth)     {         int count = VisualTreeHelper.GetChildrenCount(root);         for (int i = 0; i < count; i++)         {             var child = VisualTreeHelper.GetChild(root, i);             yield return child;             if (depth > 0)             {                 foreach (var descendent in Descendents(child, --depth))                     yield return descendent;             }         }     }     public static IEnumerable<DependencyObject> Descendents(this DependencyObject root)     {         return Descendents(root, Int32.MaxValue);     }     public static IEnumerable<DependencyObject> Ancestors(this DependencyObject root)     {         DependencyObject current = VisualTreeHelper.GetParent(root);         while (current != null)         {             yield return current;             current = VisualTreeHelper.GetParent(current);         }     } }   Usage examples The following are some examples of how to combine the above extension methods with Linq to generate the other axis scenarios that tree traversal code might require. Missing Axis Scenarios var parent = control.Ancestors().Take(1).FirstOrDefault(); var children = control.Descendents(1); var previousSiblings = control.Ancestors().Take(1)     .SelectMany(p => p.Descendents(1).TakeWhile(c => c != control)); var followingSiblings = control.Ancestors().Take(1)     .SelectMany(p => p.Descendents(1).SkipWhile(c => c != control).Skip(1)); var ancestorsAndSelf = Enumerable.Repeat((DependencyObject)control, 1)     .Concat(control.Ancestors()); var descendentsAndSelf = Enumerable.Repeat((DependencyObject)control, 1)     .Concat(control.Descendents()); You might ask why I don’t just include these in the VisualTreeEnumerator.  I don’t on the principle of only including code that is actually needed.  If you find that one or more of the above  is needed in your code then go ahead and create additional methods.  One of the downsides to Extension methods is that they can make finding the method you actually want in intellisense harder. Here are some real world usage scenarios for these methods:- Real World Scenarios //Gets the internal scrollviewer of a ListBox ScrollViewer sv = someListBox.Descendents().OfType<ScrollViewer>().FirstOrDefault(); // Get all text boxes in current UserControl:- var textBoxes = this.Descendents().OfType<TextBox>(); // All UIElement direct children of the layout root grid:- var topLevelElements = LayoutRoot.Descendents(0).OfType<UIElement>(); // Find the containing `ListBoxItem` for a UIElement:- var container = elem.Ancestors().OfType<ListBoxItem>().FirstOrDefault(); // Seek a button with the name "PinkElephants" even if outside of the current Namescope:- var pinkElephantsButton = this.Descendents()     .OfType<Button>()     .FirstOrDefault(b => b.Name == "PinkElephants"); //Clear all checkboxes with the name "Selector" in a Treeview foreach (CheckBox checkBox in elem.Descendents()     .OfType<CheckBox>().Where(c => c.Name == "Selector")) {     checkBox.IsChecked = false; }   The last couple of examples above demonstrate a common requirement of finding controls that have a specific name.  FindName will often not find these controls because they exist in a different namescope. Hope you find this useful, if not I’m just glad to be able to link to this blog in future stackoverflow answers.

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  • Metrics - A little knowledge can be a dangerous thing (or 'Why you're not clever enough to interpret metrics data')

    - by Jason Crease
    At RedGate Software, I work on a .NET obfuscator  called SmartAssembly.  Various features of it use a database to store various things (exception reports, name-mappings, etc.) The user is given the option of using either a SQL-Server database (which requires them to have Microsoft SQL Server), or a Microsoft Access MDB file (which requires nothing). MDB is the default option, but power-users soon switch to using a SQL Server database because it offers better performance and data-sharing. In the fashionable spirit of optimization and metrics, an obvious product-management question is 'Which is the most popular? SQL Server or MDB?' We've collected data about this fact, using our 'Feature-Usage-Reporting' technology (available as part of SmartAssembly) and more recently our 'Application Metrics' technology: Parameter Number of users % of total users Number of sessions Number of usages SQL Server 28 19.0 8115 8115 MDB 114 77.6 1449 1449 (As a disclaimer, please note than SmartAssembly has far more than 132 users . This data is just a selection of one build) So, it would appear that SQL-Server is used by fewer users, but more often. Great. But here's why these numbers are useless to me: Only the original developers understand the data What does a single 'usage' of 'MDB' mean? Does this happen once per run? Once per option change? On clicking the 'Obfuscate Now' button? When running the command-line version or just from the UI version? Each question could skew the data 10-fold either way, and the answers only known by the developer that instrumented the application in the first place. In other words, only the original developer can interpret the data - product-managers cannot interpret the data unaided. Most of the data is from uninterested users About half of people who download and run a free-trial from the internet quit it almost immediately. Only a small fraction use it sufficiently to make informed choices. Since the MDB option is the default one, we don't know how many of those 114 were people CHOOSING to use the MDB, or how many were JUST HAPPENING to use this MDB default for their 20-second trial. This is a problem we see across all our metrics: Are people are using X because it's the default or are they using X because they want to use X? We need to segment the data further - asking what percentage of each percentage meet our criteria for an 'established user' or 'informed user'. You end up spending hours writing sophisticated and dubious SQL queries to segment the data further. Not fun. You can't find out why they used this feature Metrics can answer the when and what, but not the why. Why did people use feature X? If you're anything like me, you often click on random buttons in unfamiliar applications just to explore the feature-set. If we listened uncritically to metrics at RedGate, we would eliminate the most-important and more-complex features which people actually buy the software for, leaving just big buttons on the main page and the About-Box. "Ah, that's interesting!" rather than "Ah, that's actionable!" People do love data. Did you know you eat 1201 chickens in a lifetime? But just 4 cows? Interesting, but useless. Often metrics give you a nice number: '5.8% of users have 3 or more monitors' . But unless the statistic is both SUPRISING and ACTIONABLE, it's useless. Most metrics are collected, reviewed with lots of cooing. and then forgotten. Unless a piece-of-data could change things, it's useless collecting it. People get obsessed with significance levels The first things that lots of people do with this data is do a t-test to get a significance level ("Hey! We know with 99.64% confidence that people prefer SQL Server to MDBs!") Believe me: other causes of error/misinterpretation in your data are FAR more significant than your t-test could ever comprehend. Confirmation bias prevents objectivity If the data appears to match our instinct, we feel satisfied and move on. If it doesn't, we suspect the data and dig deeper, plummeting down a rabbit-hole of segmentation and filtering until we give-up and move-on. Data is only useful if it can change our preconceptions. Do you trust this dodgy data more than your own understanding, knowledge and intelligence?  I don't. There's always multiple plausible ways to interpret/action any data Let's say we segment the above data, and get this data: Post-trial users (i.e. those using a paid version after the 14-day free-trial is over): Parameter Number of users % of total users Number of sessions Number of usages SQL Server 13 9.0 1115 1115 MDB 5 4.2 449 449 Trial users: Parameter Number of users % of total users Number of sessions Number of usages SQL Server 15 10.0 7000 7000 MDB 114 77.6 1000 1000 How do you interpret this data? It's one of: Mostly SQL Server users buy our software. People who can't afford SQL Server tend to be unable to afford or unwilling to buy our software. Therefore, ditch MDB-support. Our MDB support is so poor and buggy that our massive MDB user-base doesn't buy it.  Therefore, spend loads of money improving it, and think about ditching SQL-Server support. People 'graduate' naturally from MDB to SQL Server as they use the software more. Things are fine the way they are. We're marketing the tool wrong. The large number of MDB users represent uninformed downloaders. Tell marketing to aggressively target SQL Server users. To choose an interpretation you need to segment again. And again. And again, and again. Opting-out is correlated with feature-usage Metrics tends to be opt-in. This skews the data even further. Between 5% and 30% of people choose to opt-in to metrics (often called 'customer improvement program' or something like that). Casual trial-users who are uninterested in your product or company are less likely to opt-in. This group is probably also likely to be MDB users. How much does this skew your data by? Who knows? It's not all doom and gloom. There are some things metrics can answer well. Environment facts. How many people have 3 monitors? Have Windows 7? Have .NET 4 installed? Have Japanese Windows? Minor optimizations.  Is the text-box big enough for average user-input? Performance data. How long does our app take to start? How many databases does the average user have on their server? As you can see, questions about who-the-user-is rather than what-the-user-does are easier to answer and action. Conclusion Use SmartAssembly. If not for the metrics (called 'Feature-Usage-Reporting'), then at least for the obfuscation/error-reporting. Data raises more questions than it answers. Questions about environment are the easiest to answer.

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  • Blogging locally and globally–my experience

    - by DigiMortal
    In Baltic MVP Summit 2011 there was discussion about having two blogs - one for local and another for global audience – and how to publish once written information in these blogs. There are many ways how to optimize your blogging activities if you have more than one audience and here you can find my experiences, best practices and advices about this topic. My two blogs I have to working blogs: this one here technology and programming blog for local market My local blog is almost five years old and it makes it one of the oldest company blogs in Estonia. It is still active and I write there as much as I have time for it. This blog here is active since September 2007, so it is about 3.5 years old right now. Both of these blogs are  my major hits in my MVP carrier and they have very good web statistics too. My local blog My local blog is about programming, web and technology. It has way wider target audience then this blog here has. By example, in my local blog I blog also about local events, cool new concept phones, different webs providing some interesting services etc. But local guys can find there also my postings about how to solve one or another programming problem and postings about Microsoft technologies I am playing with. This far my local blog has a lot of readers for such a small country that Estonia is. This blog has made me a lot of cool contacts and I have had there a lot of interesting discussions about different technical topics. Why I started this blog? Living in small country is different than living in big country. In small country you have less people and therefore smaller audience so you have to target more than one technical topic to find enough readers. In a same time you are still interested in your main topics and you want to reach to more people who are sharing same interests with you. Practically one day y will grow out from local market and you go global. This is how this blog was born. Was it worth to create, promote and mess with it? Every second I have put on my time to this blog has been worth of it. Thanks to this blog I have found new good friends and without them I think it is more boring to work on different problems and solutions. Defining target audiences One thing you should always do when having more than one blog is defining target audiences. If you are just technomaniac interested in sharing your stuff and make some new friends and have something to write to your MVP nomination form then you don’t have to go through complex targeting process. You can do it simple way and same effectively. Here is how I defined target audiences to my blogs: local blog – reader of my local blog is IT professional, software developer, technology innovator or just some guy who is interested in technology,   this blog – reader of this blog is experienced professional software developer who works on Microsoft technologies or software developer who is open minded and open to new technologies and interesting solutions to development problems. You can see how local blog – due to small market with less people – has wider definition for audience while this blog is heavily targeted to Microsoft technologies and specially to software development. On practical side these decisions are also made well I think because it is very hard to build up popular common IT blog. On global level it is better to target some specific niche and find readers who are professionals on your favorite topics. Thanks to this blog I have found new friends who are professional developers and I am very happy about all the discussions I have had with them. Publishing content to different blogs My local blog and this blog have some overlapping topics like .NET, databases and SEO. Due to this overlapping there is question: when I write posting to my local blog then should I have to publish same thing in my global blog? And if I write something to my global blog then should I publish same thing also in my local blog? Well, it really depends on the definition of your target audiences. If they match then of course it is good idea to translate you post and publish it also to another blog. But if you have different audiences then you may need to modify your posting before publishing it. The questions you have to answer are: is target audience interested in this topic? is target audience expecting more specific and deeper handling of this topic or are they expecting more general handling of topic? is the problem you are discussing actual for target audience or not? You have to answer these questions and after that make your decision. If you need to modify your original posting then take some time and do it. Provide quality to all your readers because they will respect you if you respect them. Cross-posting and referencing It is tempting to save time that preparing some blog post takes and if you have are done with posting in one blog it may seem like good idea to make short posting to another blog and add reference to first one where topic is discussed longer. Well, don’t do it – all your readers expect good quality content from you and jumping from one blog post to another is disturbing for them. Of course, there is problem with differences between target audiences. You may have wider target audience and some people may be interested in more specific handling of topic. In this case feel free to refer your blog you are writing in english. This is not working very well in opposite direction because almost all my global blog readers understand english but not estonian. By example, estonian language is complex one and online translating tools make very poor translations from estonian language. This is why I don’t even plan to publish postings here that refer to my local blog for more information. I am keeping these two blogs as two different worlds and if there is posting that fits well to both blogs I will write my posting to one blog and then answer previous three questions before posting same thing to another blog. Conclusion Growing out of your local market is not anything mysterious if you are living in small country. As it is harder to find people there who are interested in same topics with you then sooner or later you will start finding these new contacts from global audience. Global audience is bigger and to be visible there you must provide high quality content to your audience. It is something you will learn over time and you will learn every day something new when you are posting to your global blog. You may ask: if global blog is much more complex thing to do then is it worth to do at all? My answer is: yes, do it for sure. It is not easy thing to do when you start but if you work on your global blog and improve it over time you will get over all obstacles pretty soon. Just don’t forget one thing – content is king and your readers expect high quality from you.

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  • How do NTP Servers Manage to Stay so Accurate?

    - by Akemi Iwaya
    Many of us have had the occasional problem with our computers and other devices retaining accurate time settings, but a quick sync with an NTP server makes all well again. But if our own devices can lose accuracy, how do NTP servers manage to stay so accurate? Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites. Photo courtesy of LEOL30 (Flickr). The Question SuperUser reader Frank Thornton wants to know how NTP servers are able to remain so accurate: I have noticed that on my servers and other machines, the clocks always drift so that they have to sync up to remain accurate. How do the NTP server clocks keep from drifting and always remain so accurate? How do the NTP servers manage to remain so accurate? The Answer SuperUser contributor Michael Kjorling has the answer for us: NTP servers rely on highly accurate clocks for precision timekeeping. A common time source for central NTP servers are atomic clocks, or GPS receivers (remember that GPS satellites have atomic clocks onboard). These clocks are defined as accurate since they provide a highly exact time reference. There is nothing magical about GPS or atomic clocks that make them tell you exactly what time it is. Because of how atomic clocks work, they are simply very good at, having once been told what time it is, keeping accurate time (since the second is defined in terms of atomic effects). In fact, it is worth noting that GPS time is distinct from the UTC that we are more used to seeing. These atomic clocks are in turn synchronized against International Atomic Time or TAI in order to not only accurately tell the passage of time, but also the time. Once you have an exact time on one system connected to a network like the Internet, it is a matter of protocol engineering enabling transfer of precise times between hosts over an unreliable network. In this regard a Stratum 2 (or farther from the actual time source) NTP server is no different from your desktop system syncing against a set of NTP servers. By the time you have a few accurate times (as obtained from NTP servers or elsewhere) and know the rate of advancement of your local clock (which is easy to determine), you can calculate your local clock’s drift rate relative to the “believed accurate” passage of time. Once locked in, this value can then be used to continuously adjust the local clock to make it report values very close to the accurate passage of time, even if the local real-time clock itself is highly inaccurate. As long as your local clock is not highly erratic, this should allow keeping accurate time for some time even if your upstream time source becomes unavailable for any reason. Some NTP client implementations (probably most ntpd daemon or system service implementations) do this, and others (like ntpd’s companion ntpdate which simply sets the clock once) do not. This is commonly referred to as a drift file because it persistently stores a measure of clock drift, but strictly speaking it does not have to be stored as a specific file on disk. In NTP, Stratum 0 is by definition an accurate time source. Stratum 1 is a system that uses a Stratum 0 time source as its time source (and is thus slightly less accurate than the Stratum 0 time source). Stratum 2 again is slightly less accurate than Stratum 1 because it is syncing its time against the Stratum 1 source and so on. In practice, this loss of accuracy is so small that it is completely negligible in all but the most extreme of cases. Have something to add to the explanation? Sound off in the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.

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  • A Closer Look at the HiddenInput Attribute in MVC 2

    - by Steve Michelotti
    MVC 2 includes an attribute for model metadata called the HiddenInput attribute. The typical usage of the attribute looks like this (line #3 below): 1: public class PersonViewModel 2: { 3: [HiddenInput(DisplayValue = false)] 4: public int? Id { get; set; } 5: public string FirstName { get; set; } 6: public string LastName { get; set; } 7: } So if you displayed your PersonViewModel with Html.EditorForModel() or Html.EditorFor(m => m.Id), the framework would detect the [HiddenInput] attribute metadata and produce HTML like this: 1: <input id="Id" name="Id" type="hidden" value="21" /> This is pretty straight forward and allows an elegant way to keep the technical key for your model (e.g., a Primary Key from the database) in the HTML so that everything will be wired up correctly when the form is posted to the server and of course not displaying this value visually to the end user. However, when I was giving a recent presentation, a member of the audience asked me (quite reasonably), “When would you ever set DisplayValue equal to true when using a HiddenInput?” To which I responded, “Well, it’s an edge case. There are sometimes when…er…um…people might want to…um…display this value to the user.” It was quickly apparent to me (and I’m sure everyone else in the room) what a terrible answer this was. I realized I needed to have a much better answer here. First off, let’s look at what is produced if we change our view model to use “true” (which is equivalent to use specifying [HiddenInput] since “true” is the default) on line #3: 1: public class PersonViewModel 2: { 3: [HiddenInput(DisplayValue = true)] 4: public int? Id { get; set; } 5: public string FirstName { get; set; } 6: public string LastName { get; set; } 7: } Will produce the following HTML if rendered from Htm.EditorForModel() in your view: 1: <div class="editor-label"> 2: <label for="Id">Id</label> 3: </div> 4: <div class="editor-field"> 5: 21<input id="Id" name="Id" type="hidden" value="21" /> 6: <span class="field-validation-valid" id="Id_validationMessage"></span> 7: </div> The key is line #5. We get the text of “21” (which happened to be my DB Id in this instance) and also a hidden input element (again with “21”). So the question is, why would one want to use this? The best answer I’ve found is contained in this MVC 2 whitepaper: When a view lets users edit the ID of an object and it is necessary to display the value as well as to provide a hidden input element that contains the old ID so that it can be passed back to the controller. Well, that actually makes sense. Yes, it seems like something that would happen *rarely* but, for those instances, it would enable them easily. It’s effectively equivalent to doing this in your view: 1: <%: Html.LabelFor(m => m.Id) %> 2: <%: Model.Id %> 3: <%: Html.HiddenFor(m => m.Id) %> But it’s allowing you to specify it in metadata on your view model (and thereby take advantage of templated helpers like Html.EditorForModel() and Html.EditorFor()) rather than having to explicitly specifying everything in your view.

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