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  • How to use an OSGi service from a web application?

    - by Jaime Soriano
    I'm trying to develop a web application that is going to be launched from a HTTP OSGi service, this application needs to use other OSGi service (db4o OSGi), for what I need a reference to a BundleContext. I have tried two different approaches to get the OSGi context in the web application: Store the BundleContext of the Activator in an static field of a class that the web service can import and use. Use FrameworkUtil.getBundle(this.getClass()).getBundleContext() (being this an instance of MainPage, a class of the web application). I think that first option is completely wrong, but anyway I'm having problems with the class loaders in both options. In the second one it raises a LinkageError: java.lang.LinkageError: loader constraint violation: loader (instance of org/apache/felix/framework/ModuleImpl$ModuleClassLoader) previously initiated loading for a different type with name "com/db4o/ObjectContainer" Also tried with Equinox and I have a similar error: java.lang.LinkageError: loader constraint violation: loader (instance of org/eclipse/osgi/internal/baseadaptor/DefaultClassLoader) previously initiated loading for a different type with name "com/db4o/ObjectContainer" The code that provokes the exception is: ServiceReference reference = context.getServiceReference(Db4oService.class.getName()); Db4oService service = (Db4oService)context.getService(reference); database = service.openFile("foo.db"); The exception is raised in the last line, database class is ObjectContainer, if I change the type of this variable to Object exception is not raised, but It's not useful as an Object :)

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  • Objective C, Core Data issue

    - by Jaime Rae
    I'm following a tutorial in "More iPhone 3 Development. In the code, they have a line: NSManagedObjectContext *managedObjectContext = appDelegate.managedObjectContext; I get an error: "accessing unknown 'managedObjectContext' getter method" on that line. I've downloaded his sample code and his program runs fine with that line of code. I've tried rewriting the code and I've even copied and pasted his code into my program, but I still get the error. I am using the newest SDK, and I'm wondering if something might have changed so this getter method doesn't work anymore, but I do not get any warning about deprecation. Does anyone know what is going on, or better yet, a better way to write this line and not get the error. Thanks LadyDev

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  • What is the sequence followed by the Linux kernel to configure a device?

    - by Jaime Soriano
    As I understood after reading the chapter related to The Linux Device Model in the Linux Device Drivers 3rd Edition, when a new device is configured, the kernel follows more or less this sequence: The Device is registered in the driver core (device_register(), what includes device initialization) A kobject is registered in the device model It provokes a hotplug event Bus and drivers are checked to see which one matches with the device Probe Device is binded to the driver My main doubt is, in step 1, when is device_register() called and what info should be yet in the device struct? Is it called by the bus to which the device is connected? Any example in the code? Have I misunderstood something? :)

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  • How to profile the execution of an OSGi deployment?

    - by Jaime Soriano
    I'm starting the development of an OSGi bundle for an application that will be deployed in a device with some hardware limitations. I'd like to know how could I profile the execution of that bundle to be always sure that it's going to fit with its dependencies in the final device. It would be nice to have a profiler to know how much memory is each bundle using, to localize bottle necks and to compare different implementations of the same service. Is there any profiler for OSGi deployments or should I use a general Java profiler? For developing I'm using Pax runner with Apache felix to run the bundle and maven to manage project dependencies and building.

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  • GPU YUV to RGB. Worth the effort?

    - by Jaime Pardos
    Hello, I have to convert several full PAL videos (720x576@25) from YUV 4:2:2 to RGB, in real time, and probably a custom resize for each. I have thought of using the GPU, as I have seen some example that does just this (except that it's 4:4:4 so the bpp is the same in source and destiny)-- http://www.fourcc.org/source/YUV420P-OpenGL-GLSLang.c However, I don't have any experience with using GPU's and I'm not sure of what can be done. The example, as I understand it, just converts the video frame to YUV and displays it in the screen. Is it possible to get the processed frame instead? Would it be worth the effort to send it to the GPU, get it transformed, and sending it again to main memory, or would it kill performance? Being a bit platform-specific, assuming I work on windows, is it possible to get an OpenGL or DirectDraw surface from a window so the GPU can draw directly to it?

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  • How to debug a GWT application running on OSGi?

    - by Jaime Soriano
    I'm developing a web UI using GWT. While working only with the widgets I could debug from Eclipse using the Firefox extension, but now that I'm integrating the UI with other OSGi bundles I cannot use this solution. For deploying the GWT application I create the .war and convert it to an OSGi bundle using BND. Then I launch the OSGi container with all the bundles using Pax Runner and Pax Web and the application works correctly, but when something fails in the generated javascript code I don't have any decent output error or debugging facility. Is there any way to launch the GWT application in "debug mode" from OSGi? Any other idea that could help in this scenario?

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  • Alternative to c++ static virtual methods

    - by Jaime Pardos
    In C++ is not possible to declare a static virtual function, neither cast a non-static function to a C style function pointer. Now, I have a plain ol' C SDK that uses function pointers heavily. I have to fill a structure with several function pointers. I was planning to use an abstract class with a bunch of static pure virtual methods, and redefine them in derived classes and fill the structure with them. It wasn't until then that I realized that static virtual are not allowed in C++. Is there any good alternative? The best I can think of is defining some pure virtual methods GetFuncA(), GetFuncB(),... and some static members FuncA()/FuncB() in each derived class, which would be returned by the GetFuncX(). Then a function in the abstract class would call those functions to get the pointers and fill the structure.

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  • Image in absolute DIV is not positioning from containing DIV

    - by Jaime Schuster
    I have a DIV with position:absolute inside another with position:relative. But the inside DIV is flowing out of the other and positioning it self based on the browser not the containing DIV. Any ideas why this is happening? You can see the problem here: https://www.luxedesignerhandbags.com/Articles.asp?ID=239 Look at the botton right "Get Cash for your handbags" The image is in div id="sell_bag" and that is contained in div id="wrapper" The css is as follows: #wrapper { position:inherit; font-family: Quicksand, Arial, Helvetica, sans-serif; width: 980px; left: 24px; margin: auto; } #sell_bag { position:absolute; right: 190px; width: 260px; } Any help would be greatly appreciated! Thanks,

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  • What does a linux device need to be seen by Hal?

    - by Jaime Soriano
    I'm trying to learn about device drivers on Linux Kernel, for that I've created three modules with: A bus type A device driver A fake device that does nothing now, only is registered Everything works fine, I can load the bus, the driver and the module that creates the device. Everything appears on sysfs, including the link between the device and the device driver that indicates that they are binded. And when the driver and device are loaded, I can see using udevadm monitor that also some events are provoked: KERNEL[1275564332.144997] add /module/bustest_driver (module) KERNEL[1275564332.145289] add /bus/bustest/drivers/bustest_example (drivers) UDEV [1275564332.157428] add /module/bustest_driver (module) UDEV [1275564332.157483] add /bus/bustest/drivers/bustest_example (drivers) KERNEL[1275564337.656650] add /module/bustest_device (module) KERNEL[1275564337.656817] add /devices/bustest_device (bustest) UDEV [1275564337.658294] add /module/bustest_device (module) UDEV [1275564337.664707] add /devices/bustest_device (bustest) But after everything, the device doesn't appear on hal. What else need a device to be seen by hal?

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  • How to nicely inform to the user that an unknown error has happened?

    - by Jaime Soriano
    There are several guidelines for error reporting, that are usually based on giving to the user useful information when he or she does something wrong, but to give this kind of information you need to be handling the error and know that it can happen. There are also tons of articles about designing 404 error pages. But, what can you do when it's a new, unhandled error provoked by a failure in the shoftware? Are there some guidelines about how to nicely report totally unexpected errors in a web site, as an unexpected error 500? What header message should be shown in that case? something like "Sorry, an unexpected error has ocurred" would be enough? What information should be given? Should it have mechanisms to help to report the failure to developers? Which ones?

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  • How do you save a Neural Network to file using Ruby's ai4r gem?

    - by Jaime Bellmyer
    I'm using ruby's ai4r gem, building a neural network. Version 1.1 of the gem allowed me to simply do a Marshal.dump(network) to a file, and I could load the network back up whenever I wanted. With version 1.9 a couple years later, I'm no longer able to do this. It generates this error when I try: no marshal_dump is defined for class Proc I know the reason for the error - Marshal can't handle procs in an object. Fair enough. So is there something built in to ai4r? I've been searching with no luck. I can't imagine any practical use for a neural network you have to rebuild from scratch every time you want to use it.

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  • S.redirectTo leads always to a blank screen

    - by Jaime Ocampo
    I am now playing a little bit with lift (2.8.0), and all the features in LiftRules work as intended. But I haven't been able to use S.redirectTo at all. I always ends with a blank screen, no matter what. No error messages at all! As an example, I have the following form: ... <lift:logIn.logInForm form="post"> <p><login:name /></p> <p><login:password /></p> <p><login:submit /></p> </lift:logIn.logInForm> ... And the code is: object LogIn extends helper.LogHelper { ... def logInForm(in: NodeSeq): NodeSeq = { var name = "" var password = "" def login() = { logger.info("name: " + name) logger.info("password: " + password) if (name == "test1") S.redirectTo("/example") if (name == "test2") S.redirectTo("/example.html") if (name == "test3") S.redirectTo("example.html") S.redirectTo("/") } bind("login", in, "name" -> SHtml.text(name, name = _), "password" -> SHtml.password(password, password = _), "submit" -> SHtml.submit("Login", login)) } } The method 'login' is invoked, I can check that in the log information. But as I said, no matter which name I enter, I always end with a blank screen, although 'examples.html' is available when being accessed directly in the browser. How should I invoke S.redirectoTo in order to navigate to 'examples.html'? Also, why don't I receive an error message (I am logging at a debug level)? I think all the configuration in Boot is correct, since all LitRules examples (statelessRewrite, dispatch, viewDispatch, snippets) work fine.

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  • How to change size of STL container in C++

    - by Jaime Pardos
    I have a piece of performance critical code written with pointers and dynamic memory. I would like to rewrite it with STL containers, but I'm a bit concerned with performance. Is there a way to increase the size of a container without initializing the data? For example, instead of doing ptr = new BYTE[x]; I want to do something like vec.insert(vec.begin(), x, 0); However this initializes every byte to 0. Isn't there a way to just make the vector grow? I know about reserve() but it just allocates memory, it doesn't change the size of the vector, and doesn't allows me to access it until I have inserted valid data. Thank you everyone.

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  • Custom Control in Silverlight ListBox

    - by jaime
    I have a custom control I created from a expression design I created and exported to xaml. I have put in it a bound itemtemplate/datatemplate of a ListBox contorl. It doesn't seem to be rendering more than once and/or it is rendering each item in the same place(kind of like the same x,y coordinates.

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  • PHP: Parsing of a given form input variable

    - by Jaime Cross
    How would I go about parsing incoming form data where the name changes based on section of site like: <input type="radio" name="Motorola section" value="Ask a question"> where 'Motorola section may be that, or Verizon section, or Blackberry section, etc. I do not have any control over changing the existing forms unfortunately, so must find a way to work with what is there. Basically, I need to be able to grab both the name="" data as well as its coresponding value="" data to be able to populate the email that gets sent properly.

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  • Silverlight Cream for March 31, 2010 -- #826

    - by Dave Campbell
    In this Issue: Andrea Boschin, Radenko Zec, Andrej Tozon, Bobby Diaz, Brad Abrams, Wolf Schmidt, Colin Eberhardt, Anand Iyer, Matthias Shapiro, Jaime Rodriguez, Bill Reiss, and Lee. Shoutouts: Cigdem has a post up about here MIX10 Interviewing experiences: MIX10 SilverlightShow Interviews Ian T. Lackey has his material up from his talk Silverlight SEO at the St. Louis .Net Users Group Not Silverlight but definitely WP7 cool, Michael Klucher reports that there are New Windows Phone Samples on Creators Club Online Tim Heuer posted a survey: What tools are the minimum to get started in Silverlight? From SilverlightCream.com: A RoleManager to apply roles declaratively to user interface Andrea Boschin also has a new post at SilverlightShow discussing the use of a RoleManager in WCF RIA Services to apply user roles to elements of the UI... good stuff, Andrea. Virtualization in Silverlight 4 RC Radenko Zec has a post out at SilverlightShow where he explains UI and Data Virtualization then gives some examples of their use in Silverlight 4RC, and some issues as well. MS Word Mail Merge with Silverlight 4 COM Automation Andrej Tozon has a post up at SilverlightShow that I missed in the rush of MIX10. He's doing MailMerge with COM automation and Silverlight 4... actually prett cool stuff and all the source! KISS and Tell - MVVM and the ViewModelLocator Bobby Diaz is blogging about a very popular subject right now: ViewModelLocator. He's not showing production code, but it's a thought... check it out. Silverlight 4 + RIA Services - Ready for Business: Validating Data I'm running behind, but Brad Abrams' next post in his series is about validating data in the business application. He also discusses setting up shared code validation. A One-stop Shopping XAML Namespace for Silverlight Client SDK Controls Wolf Schmidt at the Silverlight SDK has a post up highlighting the SL4 XAML namespace prefix. He starts with SL3 then demonstrates the feature's use in SL4. Binding a Silverlight 3 DataGrid to dynamic data via IDictionary (Updated) Colin Eberhardt has an update to his previous article of the same title. This one is a bug fix on an upgrade to SL3 and also an expansion of the previous post. Demo Apps from MIX10 on Windows Phone 7 Anand Iyer posted links to all the WP7 demos used at MIX10 and at least in the case of FourSquare, the source is on CodePlex. XAML Files for Location Visualizations in Silverlight and WPF Matthias Shapiro has graciously provided XAML for us for Silverlight and WPF for a bunch of different US maps... too cool, now we don't have to be asking 'where did you get that map?'... thanks Matthias! Theming in Windows Phone Jaime Rodriguez has a post up that deep-dives theming in general and demonstrates using it on WP7... end-user configurations and developer stuff. Space Rocks game step 7: Moving the ship It appears that in the heat of battle (blogging) I said Bill Reiss' Space Rocks game he's building is for WP7... obviously it's not, but it's a game folks... :) THis is Episode 7 and he's moving the ship now. SL4(RC) RichTextBox and Access Violation Lee has some code that looks like it should work for a RichTextBox in SL4RC, and it's throwing an error... see if you have a solution for him... or is it a bug? Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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  • Silverlight Cream for May 08, 2010 -- #858

    - by Dave Campbell
    In this Issue: Phil Middlemiss, Jaime Rodriguez, Senthil Kumar, Mike Snow, DaveDev, Gergely Orosz, Kirupa, Cheryl Simmons, András Velvárt, Dan Wahlin, Michael D. Brown, and Ben Rush. Shoutouts: Erik Mork and crew have their latest up: This Week In Silverlight – Where’s the Tablet? Chris Rouw has a good link post and instructions on WCF RIA services: Deploying and Configuring Silverlight 4 and WCF RIA Services From SilverlightCream.com: Quick and Easy Sscalable Rounded Bevels Phil Middlemiss duplicates some bevel-edged rectangles in Blend, and they look great. Now you don't have to import all the other PhotoShop bits to get those things looking the way you want! A transparent Windows PHONE FAQ Jaime Rodriguez combined a bunch of information into a WP7 FAQ that he's going to keep up to date, so bookmark the page. He also has links to the Training Kit, on and offline versions. Windows Phone Developer Training Kit April Refresh is now available for Download Thanks to Senthil Kumar, I found out there is an April refresh of the WP7 Training kit at Channel 9 -- go get yours now --- I'll still be here when you get back! Silverlight Tip of the Day #16 – Working with IgnoreImageCache Mike Snow's Tip of the day #16 covers IgnoreImageCache and like many other things in life, until you read Mike's post you may be surprised at how it works. DoodlePad – A fun, free, sketching application for Windows Phone 7 DaveDev has a new WP7 App up that lets you or your kids 'Doodle' on the phone... could be a note, or could be a drawing... good post with all the links you need to get this cranked up on the emulator. Printing in Silverlight: Printing Charts and Auto Scaling Gergely Orosz's latest post is a very useful one on auto-scaling charts to fit a printed page and then getting them to print. Smoothly Scrolling a ListBox Check out the smooth scrolling Kirupa has on the ListBox near the top of his post... all good stuff... you wanna know how to do that! Plus... it's dead simple and all in Blend :) http://www.sparklingclient.com/wheres-the-silverlight-tablet/ Cheryl Simmons has a great tip up at the SilverlightSDK if you haven't burned through to figure it out yet ... changing the watermark on a DatePicker control... looks great! The story of a wicked bug András Velvárt tells a story of a bug that just defied logic or being found. Read how he tracked it down and what it actually was... could save you some time. Story learned: if I have a problem that bad, I'm calling András :) Text Trimming in Silverlight 4 Dan Wahlin gives a quick run-through of what TextBox trimming is, and then by a good real example... check it out and start using it in your projects. Enterprise Patterns with WCF RIA Services Michael D. Brown has an article in MSDN Magazine on RIA Services. Great information and link-packed article, with all the source avialable for download. Building Custom Players with the Silverlight Media Framework Ben Rush has a nice long tutorial on the Silverlight Media Framework up on the MSDN Magazine site ... lots of information in there. Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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  • C#/.NET Little Wonders: The Joy of Anonymous Types

    - by James Michael Hare
    Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. In the .NET 3 Framework, Microsoft introduced the concept of anonymous types, which provide a way to create a quick, compiler-generated types at the point of instantiation.  These may seem trivial, but are very handy for concisely creating lightweight, strongly-typed objects containing only read-only properties that can be used within a given scope. Creating an Anonymous Type In short, an anonymous type is a reference type that derives directly from object and is defined by its set of properties base on their names, number, types, and order given at initialization.  In addition to just holding these properties, it is also given appropriate overridden implementations for Equals() and GetHashCode() that take into account all of the properties to correctly perform property comparisons and hashing.  Also overridden is an implementation of ToString() which makes it easy to display the contents of an anonymous type instance in a fairly concise manner. To construct an anonymous type instance, you use basically the same initialization syntax as with a regular type.  So, for example, if we wanted to create an anonymous type to represent a particular point, we could do this: 1: var point = new { X = 13, Y = 7 }; Note the similarity between anonymous type initialization and regular initialization.  The main difference is that the compiler generates the type name and the properties (as readonly) based on the names and order provided, and inferring their types from the expressions they are assigned to. It is key to remember that all of those factors (number, names, types, order of properties) determine the anonymous type.  This is important, because while these two instances share the same anonymous type: 1: // same names, types, and order 2: var point1 = new { X = 13, Y = 7 }; 3: var point2 = new { X = 5, Y = 0 }; These similar ones do not: 1: var point3 = new { Y = 3, X = 5 }; // different order 2: var point4 = new { X = 3, Y = 5.0 }; // different type for Y 3: var point5 = new {MyX = 3, MyY = 5 }; // different names 4: var point6 = new { X = 1, Y = 2, Z = 3 }; // different count Limitations on Property Initialization Expressions The expression for a property in an anonymous type initialization cannot be null (though it can evaluate to null) or an anonymous function.  For example, the following are illegal: 1: // Null can't be used directly. Null reference of what type? 2: var cantUseNull = new { Value = null }; 3:  4: // Anonymous methods cannot be used. 5: var cantUseAnonymousFxn = new { Value = () => Console.WriteLine(“Can’t.”) }; Note that the restriction on null is just that you can’t use it directly as the expression, because otherwise how would it be able to determine the type?  You can, however, use it indirectly assigning a null expression such as a typed variable with the value null, or by casting null to a specific type: 1: string str = null; 2: var fineIndirectly = new { Value = str }; 3: var fineCast = new { Value = (string)null }; All of the examples above name the properties explicitly, but you can also implicitly name properties if they are being set from a property, field, or variable.  In these cases, when a field, property, or variable is used alone, and you don’t specify a property name assigned to it, the new property will have the same name.  For example: 1: int variable = 42; 2:  3: // creates two properties named varriable and Now 4: var implicitProperties = new { variable, DateTime.Now }; Is the same type as: 1: var explicitProperties = new { variable = variable, Now = DateTime.Now }; But this only works if you are using an existing field, variable, or property directly as the expression.  If you use a more complex expression then the name cannot be inferred: 1: // can't infer the name variable from variable * 2, must name explicitly 2: var wontWork = new { variable * 2, DateTime.Now }; In the example above, since we typed variable * 2, it is no longer just a variable and thus we would have to assign the property a name explicitly. ToString() on Anonymous Types One of the more trivial overrides that an anonymous type provides you is a ToString() method that prints the value of the anonymous type instance in much the same format as it was initialized (except actual values instead of expressions as appropriate of course). For example, if you had: 1: var point = new { X = 13, Y = 42 }; And then print it out: 1: Console.WriteLine(point.ToString()); You will get: 1: { X = 13, Y = 42 } While this isn’t necessarily the most stunning feature of anonymous types, it can be handy for debugging or logging values in a fairly easy to read format. Comparing Anonymous Type Instances Because anonymous types automatically create appropriate overrides of Equals() and GetHashCode() based on the underlying properties, we can reliably compare two instances or get hash codes.  For example, if we had the following 3 points: 1: var point1 = new { X = 1, Y = 2 }; 2: var point2 = new { X = 1, Y = 2 }; 3: var point3 = new { Y = 2, X = 1 }; If we compare point1 and point2 we’ll see that Equals() returns true because they overridden version of Equals() sees that the types are the same (same number, names, types, and order of properties) and that the values are the same.   In addition, because all equal objects should have the same hash code, we’ll see that the hash codes evaluate to the same as well: 1: // true, same type, same values 2: Console.WriteLine(point1.Equals(point2)); 3:  4: // true, equal anonymous type instances always have same hash code 5: Console.WriteLine(point1.GetHashCode() == point2.GetHashCode()); However, if we compare point2 and point3 we get false.  Even though the names, types, and values of the properties are the same, the order is not, thus they are two different types and cannot be compared (and thus return false).  And, since they are not equal objects (even though they have the same value) there is a good chance their hash codes are different as well (though not guaranteed): 1: // false, different types 2: Console.WriteLine(point2.Equals(point3)); 3:  4: // quite possibly false (was false on my machine) 5: Console.WriteLine(point2.GetHashCode() == point3.GetHashCode()); Using Anonymous Types Now that we’ve created instances of anonymous types, let’s actually use them.  The property names (whether implicit or explicit) are used to access the individual properties of the anonymous type.  The main thing, once again, to keep in mind is that the properties are readonly, so you cannot assign the properties a new value (note: this does not mean that instances referred to by a property are immutable – for more information check out C#/.NET Fundamentals: Returning Data Immutably in a Mutable World). Thus, if we have the following anonymous type instance: 1: var point = new { X = 13, Y = 42 }; We can get the properties as you’d expect: 1: Console.WriteLine(“The point is: ({0},{1})”, point.X, point.Y); But we cannot alter the property values: 1: // compiler error, properties are readonly 2: point.X = 99; Further, since the anonymous type name is only known by the compiler, there is no easy way to pass anonymous type instances outside of a given scope.  The only real choices are to pass them as object or dynamic.  But really that is not the intention of using anonymous types.  If you find yourself needing to pass an anonymous type outside of a given scope, you should really consider making a POCO (Plain Old CLR Type – i.e. a class that contains just properties to hold data with little/no business logic) instead. Given that, why use them at all?  Couldn’t you always just create a POCO to represent every anonymous type you needed?  Sure you could, but then you might litter your solution with many small POCO classes that have very localized uses. It turns out this is the key to when to use anonymous types to your advantage: when you just need a lightweight type in a local context to store intermediate results, consider an anonymous type – but when that result is more long-lived and used outside of the current scope, consider a POCO instead. So what do we mean by intermediate results in a local context?  Well, a classic example would be filtering down results from a LINQ expression.  For example, let’s say we had a List<Transaction>, where Transaction is defined something like: 1: public class Transaction 2: { 3: public string UserId { get; set; } 4: public DateTime At { get; set; } 5: public decimal Amount { get; set; } 6: // … 7: } And let’s say we had this data in our List<Transaction>: 1: var transactions = new List<Transaction> 2: { 3: new Transaction { UserId = "Jim", At = DateTime.Now, Amount = 2200.00m }, 4: new Transaction { UserId = "Jim", At = DateTime.Now, Amount = -1100.00m }, 5: new Transaction { UserId = "Jim", At = DateTime.Now.AddDays(-1), Amount = 900.00m }, 6: new Transaction { UserId = "John", At = DateTime.Now.AddDays(-2), Amount = 300.00m }, 7: new Transaction { UserId = "John", At = DateTime.Now, Amount = -10.00m }, 8: new Transaction { UserId = "Jane", At = DateTime.Now, Amount = 200.00m }, 9: new Transaction { UserId = "Jane", At = DateTime.Now, Amount = -50.00m }, 10: new Transaction { UserId = "Jaime", At = DateTime.Now.AddDays(-3), Amount = -100.00m }, 11: new Transaction { UserId = "Jaime", At = DateTime.Now.AddDays(-3), Amount = 300.00m }, 12: }; So let’s say we wanted to get the transactions for each day for each user.  That is, for each day we’d want to see the transactions each user performed.  We could do this very simply with a nice LINQ expression, without the need of creating any POCOs: 1: // group the transactions based on an anonymous type with properties UserId and Date: 2: byUserAndDay = transactions 3: .GroupBy(tx => new { tx.UserId, tx.At.Date }) 4: .OrderBy(grp => grp.Key.Date) 5: .ThenBy(grp => grp.Key.UserId); Now, those of you who have attempted to use custom classes as a grouping type before (such as GroupBy(), Distinct(), etc.) may have discovered the hard way that LINQ gets a lot of its speed by utilizing not on Equals(), but also GetHashCode() on the type you are grouping by.  Thus, when you use custom types for these purposes, you generally end up having to write custom Equals() and GetHashCode() implementations or you won’t get the results you were expecting (the default implementations of Equals() and GetHashCode() are reference equality and reference identity based respectively). As we said before, it turns out that anonymous types already do these critical overrides for you.  This makes them even more convenient to use!  Instead of creating a small POCO to handle this grouping, and then having to implement a custom Equals() and GetHashCode() every time, we can just take advantage of the fact that anonymous types automatically override these methods with appropriate implementations that take into account the values of all of the properties. Now, we can look at our results: 1: foreach (var group in byUserAndDay) 2: { 3: // the group’s Key is an instance of our anonymous type 4: Console.WriteLine("{0} on {1:MM/dd/yyyy} did:", group.Key.UserId, group.Key.Date); 5:  6: // each grouping contains a sequence of the items. 7: foreach (var tx in group) 8: { 9: Console.WriteLine("\t{0}", tx.Amount); 10: } 11: } And see: 1: Jaime on 06/18/2012 did: 2: -100.00 3: 300.00 4:  5: John on 06/19/2012 did: 6: 300.00 7:  8: Jim on 06/20/2012 did: 9: 900.00 10:  11: Jane on 06/21/2012 did: 12: 200.00 13: -50.00 14:  15: Jim on 06/21/2012 did: 16: 2200.00 17: -1100.00 18:  19: John on 06/21/2012 did: 20: -10.00 Again, sure we could have just built a POCO to do this, given it an appropriate Equals() and GetHashCode() method, but that would have bloated our code with so many extra lines and been more difficult to maintain if the properties change.  Summary Anonymous types are one of those Little Wonders of the .NET language that are perfect at exactly that time when you need a temporary type to hold a set of properties together for an intermediate result.  While they are not very useful beyond the scope in which they are defined, they are excellent in LINQ expressions as a way to create and us intermediary values for further expressions and analysis. Anonymous types are defined by the compiler based on the number, type, names, and order of properties created, and they automatically implement appropriate Equals() and GetHashCode() overrides (as well as ToString()) which makes them ideal for LINQ expressions where you need to create a set of properties to group, evaluate, etc. Technorati Tags: C#,CSharp,.NET,Little Wonders,Anonymous Types,LINQ

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  • Google I/O 2010 - Fireside chat with the GWT team

    Google I/O 2010 - Fireside chat with the GWT team Google I/O 2010 - Fireside chat with the GWT team Fireside Chats, GWT Bruce Johnson, Joel Webber, Ray Ryan, Amit Manjhi, Jaime Yap, Kathrin Probst, Eric Ayers, lan Stewart, Christian Dupuis, Chris Ramsdale (moderator) If you're interested in what the GWT team has been up to since 2.0, here's your chance. We'll have several of the core engineers available to discuss the new features and frameworks in GWT, as well as to answer any questions that you might have. For all I/O 2010 sessions, please go to code.google.com From: GoogleDevelopers Views: 140 0 ratings Time: 58:32 More in Science & Technology

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  • Thank you South Florida for a successful SPSouthFLA

    - by Leonard Mwangi
    I wanted to officially thank the organizers, speakers, volunteers and the attendees of SharePoint Saturday South Florida. Being the first event in South Florida the reception was phenomenon and the group of speakers from keynote by Joel Oleson to session’s speakers from well renowned speakers like John Holliday, Randy Disgrill, Richard Harbridge, Ameet Phadnis, Fabian Williams, Chris McNulty, Jaime Velez to organizers like Michael Hinckley amongst others. With my Business Intelligence (BI) presentation being on the last track of the day, I spent very quality time networking with these great guys and getting the insider scope on International SharePoint Community from Joel and his son which was mesmerizing. I had a very active audience to a point where we couldn’t accommodate all the contents within the 1hr allocated time because they were very engaged and wanted a deep dive session on news features like PowerPivot, enhancements on PerformancePoint, Excel Services amongst others in order to understand the business value and how SharePoint 2010 is making the self-service BI become a reality. These community events allows the attendees experience technology first hand and network with MVPs, authors, experts providing high quality educational sessions usually for free which is a reason to attend. I have made the slides for my session available for download for those interested http://goo.gl/VaH5x

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  • Silverlight Cream for May 05, 2010 -- #856

    - by Dave Campbell
    In this Issue: Jeremy Alles(-2-), Kunal Chowdhury, anand iyer, Yochay Kiriaty(-2-, -3-), Max Paulousky, David Kelley, smartyP, Tim Heuer, and Dan Wahlin. Shoutout: Tim Heuer provides links for all the Ways to give feedback on Silverlight From SilverlightCream.com: [WP7] Bug when using NavigationService in Windows Phone 7 Jeremy Alles has blogged about a bug he found using the Navigation service in WP7. He gives the steps to reproduce and a couple possible workarounds. [WP7] Using the camera in the emulator Jeremy Alles is also digging into the camera functionality in the emulator. He has code demonstrating launching a camera task, and a list of other tasks available. Silverlight Tutorials Chapter 3: Introduction to Panels Kunal Chowdhury has Chapter 3 of his Silverlight 4 Tutorial series up and he's talking about Panels this time out. Push Notifications in Windows Phone 7 developer tools CTP April Refresh anand iyer is discussing the Push Notifications, only from a code perspective. Good information and good additional links to follow. Windows Phone Application Life Cycle Yochay Kiriaty talks with Tudor Toma and Jaime Rodriguez about the WP7 application lifecycle on Channel 9. Understanding Microsoft Push Notifications for Windows Phones Yochay Kiriaty has a 2-part post up on WP7 Push Notifications. The first part is explaining what Push Notifications are and why we need them... as a developer and as an end user viewing Toast or Tile notifications. Understanding How Microsoft Push Notification Works – Part 2 In the 2nd part of his Push Notification series, Yochay Kiriaty discusses how the Push Notification works under the covers. To Remember: Deployment of Silverlight Applications With Wcf Ria Services Max Paulousky has a post up for reference on what to look into when you get "Load Operation Failed" in WCF RIA services. Launching a URL from an OOB Silverlight Application David Kelley has a quick post up on launching URLs from an OOB app. If you haven't tried it, you may be surprised as he was at first. Creating a Windows Phone 7 XNA Game in Landscape Orientation smartyP is looking at recreating a landscape WP7 game in XNA and is detailing some of the issues he's been dealing with, and is also sharing a project file. New Silverlight 4 Themes available–get the raw bits Tim Heuer provided 'raw' versions of 3 new themes. Read his post to see exactly what he means by 'raw' ... they're definitely good looking, and are going to get a lot of play. Handling WCF Service Paths in Silverlight 4 – Relative Path Support Dan Wahlin shares his technique for avoiding the pain involved with ServiceReferences.ClientConfig by using Silverlight 4 relative path support. Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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