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  • Quick Quips on QR Codes

    - by Tim Dexter
    Yes, I'm an alliterating all-star; I missed my calling as a newspaper headline writer. I have recently received questions from several folks on support for QR codes. You know them they are everywhere you look, even here! How does Publisher handle QR codes then? In theory, exactly the same way we handle any other 2D barcode font. We need the font file, a mapping entry and an encoding class. With those three pieces we can embed QR codes into any output. To test the theory, I went off to IDAutomation, I have worked with them and many customers over the years and their fonts and encoders have worked great and have been very reliable. They kindly provide demo fonts which has made my life so much easier to be able to write posts like this. Their QR font and encoder is a little tough to find. I started here and then hit the Demo Now button. On the next page I hit the right hand Demo Now button. In the resulting zip file you'll need two files: AdditionalFonts.zip >> Automation2DFonts >> TrueType >> IDAutomation2D.ttf Java Class Encoder >> IDAutomation_JavaFontEncoder_QRCode.jar - the QRBarcodeExample.java is useful to see how to call the encoder. The font file needs to be installed into the windows/fonts directory, just copy and paste it in using file explorer and windows will install it for you. Remember, we are using the demo font here and you'll see if you get your phones decoder to looks a the font above there is a fixed string 'DEMO' at the beginning. You want that removed? Go buy the font from the IDAutomation folks. The Encoder Next you need to create your encoding wrapper class. Publisher does ship a class but its compiled and I do not recommend trying to modify it, you can just build your own. I have loaded up my class here. You do not need to be a java guru, its pretty straightforward. I'd recommend a java IDE like JDeveloper from a convenience point of view. I have annotated my class and added a main method to it so you can test your encoders from JDeveloper without having to deploy them first. You can load up the project form the zip file straight into JDeveloper.Next, take a look at IDAutomation's example java class and you'll see: QRCodeEncoder qre=new QRCodeEncoder();  String DataToEncode = "IDAutmation Inc.";  boolean ApplyTilde = false;  int EncodingMode = 0;  int Version = 0;  int ErrorCorrectionLevel = 0;  System.out.println( qre.FontEncode(DataToEncode, ApplyTilde, EncodingMode, Version, ErrorCorrectionLevel) ); You'll need to check what settings you need to set for the ApplyTilde, EncodingMode, Version and ErrorCorrectionLevel. They are covered in the user guide from IDAutomation here. If you do not want to hard code the values in the encoder then you can quite easily externalize them and read the values from a text file. I have not covered that scenario here, I'm going with IDAutomation's defaults and my phone app is reading the fonts no problem. Now you know how to call the encoder, you need to incorporate it into your encoder wrapper class. From my sample class:       Class[] clazz = new Class[] { "".getClass() };        ENCODERS.put("code128a",mUtility.getClass().getMethod("code128a", clazz));       ENCODERS.put("code128b",mUtility.getClass().getMethod("code128b", clazz));       ENCODERS.put("code128c",mUtility.getClass().getMethod("code128c", clazz));       ENCODERS.put("qrcode",mUtility.getClass().getMethod("qrcode", clazz)); I just added a new entry to register the encoder method 'qrcode' (in red). Then I created a new method inside the class to call the IDAutomation encoder. /** Call to IDAutomations QR Code encoder. Passing the data to encode      Returning the encoded string to the template for formatting **/ public static final String qrcode (String DataToEncode) {   QRCodeEncoder qre=new QRCodeEncoder();    boolean ApplyTilde = false;    int EncodingMode = 0;    int Version = 0;    int ErrorCorrectionLevel = 0; return qre.FontEncode(DataToEncode, ApplyTilde, EncodingMode, Version, ErrorCorrectionLevel); } Almost the exact same code in their sample class. The DataToEncode string is passed in rather than hardcoded of course. With the class done you can now compile it, but you need to ensure that the IDAutomation_JavaFontEncoder_QRCode.jar is in the classpath. In JDeveloper, open the project properties >> Libraries and Classpaths and then add the jar to the list. You'll need the publisher jars too. You can find those in the jlib directory in your Template Builder for Word directory.Note! In my class, I have used package oracle.psbi.barcode; As my package spec, yours will be different but you need to note it for later. Once you have it compiling without errors you will need to generate a jar file to keep it in. In JDeveloper highlight your project node >> New >> Deployment Profile >> JAR file. Once you have created the descriptor, just take the defaults. It will tell you where the jar is located. Go get it and then its time to copy it and the IDAutomation jar into the Template Builder for Word directory structure. Deploying the jars On your windows machine locate the jlib directory under the Template Builder for Word install directory. On my machine its here, F:\Program Files\Oracle\BI Publisher\BI Publisher Desktop\Template Builder for Word\jlib. Copy both of the jar files into the directory. The next step is to get the jars into the classpath for the Word plugin so that Publisher can find your wrapper class and it can then find the IDAutomation encoder. The most consistent way I have found so far, is to open up the RTF2PDF.jar in the same directory and make some mods. First make a backup of the jar file then open it using winzip or 7zip or similar and get into the META-INF directory. In there is a file, MANIFEST.MF. This contains the classpath for the plugin, open it in an editor and add the jars to the end of the classpath list. In mine I have: Manifest-Version: 1.0 Class-Path: ./activation.jar ./mail.jar ./xdochartstyles.jar ./bicmn.jar ./jewt4.jar ./share.jar ./bipres.jar ./xdoparser.jar ./xdocore.jar ./xmlparserv2.jar ./xmlparserv2-904.jar  ./i18nAPI_v3.jar ./versioninfo.jar ./barcodejar.jar ./IDAutomation_JavaFontEncoder_QRCode.jar Main-Class: RTF2PDF I have put in carriage returns above to make the Class-Path: entry more readable, make sure yours is all on one line. Be sure to use the ./ as a prefix to the jar name. Ensure the file is saved inside the jar file 7zip and winzip both have popups asking if you want to update the file in the jar file.Now you have the jars on the classpath, the Publisher plugin will be able to find our classes at run time. Referencing the Font The next step is to reference the font location so that the rendering engine can find it and embed a subset into the PDF output. Remember the other output formats rely on the font being present on the machine that is opening the document. The PDF is the only truly portable format. Inside the config directory under the Template Builder for Word install directory, mine is here, F:\Program Files\Oracle\BI Publisher\BI Publisher Desktop\Template Builder for Word\config. You'll find the file, 'xdo example.cfg'. Rename it to xdo.cfg and open it in a text editor. In the fonts section, create a new entry:       <font family="IDAutomation2D" style="normal" weight="normal">              <truetype path="C:\windows\fonts\IDAutomation2D.ttf" />       </font> Note, 'IDAutomation2D' (in red) is the same name as you can see when you open MSWord and look for the QRCode font. This must match exactly. When Publisher looks at the fonts in the RTF template at runtime it will see 'IDAutomation2D' it will then look at its font mapping entries to find where that font file resides on the disk. If the names do not match or the font is not present then the font will not get used and it will fall back on Helvetica. Building the Template Now you have the data encoder and the font in place and mapped; you can use it in the template. The two commands you will need to have present are: <?register-barcode-vendor:'ENCODER WRAPPER CLASS'; 'ENCODER NAME'?> for my encoder I have: <?register-barcode-vendor:'oracle.psbi.barcode.BarcodeUtil'; 'MyBarcodeEncoder'?> Notice the two parameters for the command. The first provides the package 'path' and class name (remember I said you need to remember that above.)The second is the name of the encoder, in my case 'MyBarcodeEncoder'. Check my full encoder class in the zip linked below to see where I named it. You can change it to something else, no problem.This command needs to be near the top of the template. The second command is the encoding command: <?format-barcode:DATAT_TO_ENCODE;'ENCODER_METHOD_NAME';'ENCODER_NAME'?> for my command I have <?format-barcode:DATATEXT;'qrcode';'MyBarcodeEncoder'?>DATATEXT is the XML element that contains the text to be encoded. If you want to hard code a piece of text just surround it with single quotes. qrcode is the name of my encoder method that calls the IDAutomation encoder. Remember this.MyBarcodeEncoder is the name of my encoder. Repetition? Yes but its needed again. Both of these commands are put inside their own form fields. Do not apply the QRCode font to the second field just yet. Lets make sure the encoder is working. Run you template with some data and you should get something like this for your encoded data: AHEEEHAPPJOPMOFADIPFJKDCLPAHEEEHA BNFFFNBPJGMDIDJPFOJGIGBLMPBNFFFNB APIBOHFJCFBNKHGGBMPFJFJLJBKGOMNII OANKPJFFLEPLDNPCLMNGNIJIHFDNLJFEH FPLFLHFHFILKFBLOIGMDFCFLGJGOPJJME CPIACDFJPBGDODOJCHALJOBPECKMOEDDF MFFNFNEPKKKCHAIHCHPCFFLDAHFHAGLMK APBBBPAPLDKNKJKKGIPDLKGMGHDDEPHLN HHHHHHHPHPHHPHPPHPPPPHHPHHPHPHPHP Grooovy huh? If you do not get the encoded text then go back and check that your jars are in the right spot and that you have the MANIFEST.MF file updated correctly. Once you do get the encoded text, highlight the field and apply the IDAutomation2D font to it. Then re-run the report and you will hopefully see the QR code in your output. If not, go back and check the xdo.cfg entry and make sure its in the right place and the font location is correct. That's it, you now have QR codes in Publisher outputs. Everything I have written above, has been tested with the 5.6.3, 10.1.3.4.2 codelines. I'll be testing the 11g code in the next day or two and will update you with any changes. One thing I have not covered yet and will do in the next few days is how to deploy all of this to your server. Look out for a follow up post. One note on the apparent white lines in the font (see the image above). Once printed they disappear and even viewing the code on a screen with the white lines, my phone app is still able to read and interpret the contents no problem. I have zipped up my encoder wrapper class as a JDeveloper 11.1.1.6 project here. Just dig into the src directories to find the BarcodeUtil.java file if you just want the code. I have put comments into the file to hopefully help the novice java programmer out. Happy QR'ing!

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  • Dynamically loading Assemblies to reduce Runtime Dependencies

    - by Rick Strahl
    I've been working on a request to the West Wind Application Configuration library to add JSON support. The config library is a very easy to use code-first approach to configuration: You create a class that holds the configuration data that inherits from a base configuration class, and then assign a persistence provider at runtime that determines where and how the configuration data is store. Currently the library supports .NET Configuration stores (web.config/app.config), XML files, SQL records and string storage.About once a week somebody asks me about JSON support and I've deflected this question for the longest time because frankly I think that JSON as a configuration store doesn't really buy a heck of a lot over XML. Both formats require the user to perform some fixup of the plain configuration data - in XML into XML tags, with JSON using JSON delimiters for properties and property formatting rules. Sure JSON is a little less verbose and maybe a little easier to read if you have hierarchical data, but overall the differences are pretty minor in my opinion. And yet - the requests keep rolling in.Hard Link Issues in a Component LibraryAnother reason I've been hesitant is that I really didn't want to pull in a dependency on an external JSON library - in this case JSON.NET - into the core library. If you're not using JSON.NET elsewhere I don't want a user to have to require a hard dependency on JSON.NET unless they want to use the JSON feature. JSON.NET is also sensitive to versions and doesn't play nice with multiple versions when hard linked. For example, when you have a reference to V4.4 in your project but the host application has a reference to version 4.5 you can run into assembly load problems. NuGet's Update-Package can solve some of this *if* you can recompile, but that's not ideal for a component that's supposed to be just plug and play. This is no criticism of JSON.NET - this really applies to any dependency that might change.  So hard linking the DLL can be problematic for a number reasons, but the primary reason is to not force loading of JSON.NET unless you actually need it when you use the JSON configuration features of the library.Enter Dynamic LoadingSo rather than adding an assembly reference to the project, I decided that it would be better to dynamically load the DLL at runtime and then use dynamic typing to access various classes. This allows me to run without a hard assembly reference and allows more flexibility with version number differences now and in the future.But there are also a couple of downsides:No assembly reference means only dynamic access - no compiler type checking or IntellisenseRequirement for the host application to have reference to JSON.NET or else get runtime errorsThe former is minor, but the latter can be problematic. Runtime errors are always painful, but in this case I'm willing to live with this. If you want to use JSON configuration settings JSON.NET needs to be loaded in the project. If this is a Web project, it'll likely be there already.So there are a few things that are needed to make this work:Dynamically create an instance and optionally attempt to load an Assembly (if not loaded)Load types into dynamic variablesUse Reflection for a few tasks like statics/enumsThe dynamic keyword in C# makes the formerly most difficult Reflection part - method calls and property assignments - fairly painless. But as cool as dynamic is it doesn't handle all aspects of Reflection. Specifically it doesn't deal with object activation, truly dynamic (string based) member activation or accessing of non instance members, so there's still a little bit of work left to do with Reflection.Dynamic Object InstantiationThe first step in getting the process rolling is to instantiate the type you need to work with. This might be a two step process - loading the instance from a string value, since we don't have a hard type reference and potentially having to load the assembly. Although the host project might have a reference to JSON.NET, that instance might have not been loaded yet since it hasn't been accessed yet. In ASP.NET this won't be a problem, since ASP.NET preloads all referenced assemblies on AppDomain startup, but in other executable project, assemblies are just in time loaded only when they are accessed.Instantiating a type is a two step process: Finding the type reference and then activating it. Here's the generic code out of my ReflectionUtils library I use for this:/// <summary> /// Creates an instance of a type based on a string. Assumes that the type's /// </summary> /// <param name="typeName">Common name of the type</param> /// <param name="args">Any constructor parameters</param> /// <returns></returns> public static object CreateInstanceFromString(string typeName, params object[] args) { object instance = null; Type type = null; try { type = GetTypeFromName(typeName); if (type == null) return null; instance = Activator.CreateInstance(type, args); } catch { return null; } return instance; } /// <summary> /// Helper routine that looks up a type name and tries to retrieve the /// full type reference in the actively executing assemblies. /// </summary> /// <param name="typeName"></param> /// <returns></returns> public static Type GetTypeFromName(string typeName) { Type type = null; // Let default name binding find it type = Type.GetType(typeName, false); if (type != null) return type; // look through assembly list var assemblies = AppDomain.CurrentDomain.GetAssemblies(); // try to find manually foreach (Assembly asm in assemblies) { type = asm.GetType(typeName, false); if (type != null) break; } return type; } To use this for loading JSON.NET I have a small factory function that instantiates JSON.NET and sets a bunch of configuration settings on the generated object. The startup code also looks for failure and tries loading up the assembly when it fails since that's the main reason the load would fail. Finally it also caches the loaded instance for reuse (according to James the JSON.NET instance is thread safe and quite a bit faster when cached). Here's what the factory function looks like in JsonSerializationUtils:/// <summary> /// Dynamically creates an instance of JSON.NET /// </summary> /// <param name="throwExceptions">If true throws exceptions otherwise returns null</param> /// <returns>Dynamic JsonSerializer instance</returns> public static dynamic CreateJsonNet(bool throwExceptions = true) { if (JsonNet != null) return JsonNet; lock (SyncLock) { if (JsonNet != null) return JsonNet; // Try to create instance dynamic json = ReflectionUtils.CreateInstanceFromString("Newtonsoft.Json.JsonSerializer"); if (json == null) { try { var ass = AppDomain.CurrentDomain.Load("Newtonsoft.Json"); json = ReflectionUtils.CreateInstanceFromString("Newtonsoft.Json.JsonSerializer"); } catch (Exception ex) { if (throwExceptions) throw; return null; } } if (json == null) return null; json.ReferenceLoopHandling = (dynamic) ReflectionUtils.GetStaticProperty("Newtonsoft.Json.ReferenceLoopHandling", "Ignore"); // Enums as strings in JSON dynamic enumConverter = ReflectionUtils.CreateInstanceFromString("Newtonsoft.Json.Converters.StringEnumConverter"); json.Converters.Add(enumConverter); JsonNet = json; } return JsonNet; }This code's purpose is to return a fully configured JsonSerializer instance. As you can see the code tries to create an instance and when it fails tries to load the assembly, and then re-tries loading.Once the instance is loaded some configuration occurs on it. Specifically I set the ReferenceLoopHandling option to not blow up immediately when circular references are encountered. There are a host of other small config setting that might be useful to set, but the default seem to be good enough in recent versions. Note that I'm setting ReferenceLoopHandling which requires an Enum value to be set. There's no real easy way (short of using the cardinal numeric value) to set a property or pass parameters from static values or enums. This means I still need to use Reflection to make this work. I'm using the same ReflectionUtils class I previously used to handle this for me. The function looks up the type and then uses Type.InvokeMember() to read the static property.Another feature I need is have Enum values serialized as strings rather than numeric values which is the default. To do this I can use the StringEnumConverter to convert enums to strings by adding it to the Converters collection.As you can see there's still a bit of Reflection to be done even in C# 4+ with dynamic, but with a few helpers this process is relatively painless.Doing the actual JSON ConversionFinally I need to actually do my JSON conversions. For the Utility class I need serialization that works for both strings and files so I created four methods that handle these tasks two each for serialization and deserialization for string and file.Here's what the File Serialization looks like:/// <summary> /// Serializes an object instance to a JSON file. /// </summary> /// <param name="value">the value to serialize</param> /// <param name="fileName">Full path to the file to write out with JSON.</param> /// <param name="throwExceptions">Determines whether exceptions are thrown or false is returned</param> /// <param name="formatJsonOutput">if true pretty-formats the JSON with line breaks</param> /// <returns>true or false</returns> public static bool SerializeToFile(object value, string fileName, bool throwExceptions = false, bool formatJsonOutput = false) { dynamic writer = null; FileStream fs = null; try { Type type = value.GetType(); var json = CreateJsonNet(throwExceptions); if (json == null) return false; fs = new FileStream(fileName, FileMode.Create); var sw = new StreamWriter(fs, Encoding.UTF8); writer = Activator.CreateInstance(JsonTextWriterType, sw); if (formatJsonOutput) writer.Formatting = (dynamic)Enum.Parse(FormattingType, "Indented"); writer.QuoteChar = '"'; json.Serialize(writer, value); } catch (Exception ex) { Debug.WriteLine("JsonSerializer Serialize error: " + ex.Message); if (throwExceptions) throw; return false; } finally { if (writer != null) writer.Close(); if (fs != null) fs.Close(); } return true; }You can see more of the dynamic invocation in this code. First I grab the dynamic JsonSerializer instance using the CreateJsonNet() method shown earlier which returns a dynamic. I then create a JsonTextWriter and configure a couple of enum settings on it, and then call Serialize() on the serializer instance with the JsonTextWriter that writes the output to disk. Although this code is dynamic it's still fairly short and readable.For full circle operation here's the DeserializeFromFile() version:/// <summary> /// Deserializes an object from file and returns a reference. /// </summary> /// <param name="fileName">name of the file to serialize to</param> /// <param name="objectType">The Type of the object. Use typeof(yourobject class)</param> /// <param name="binarySerialization">determines whether we use Xml or Binary serialization</param> /// <param name="throwExceptions">determines whether failure will throw rather than return null on failure</param> /// <returns>Instance of the deserialized object or null. Must be cast to your object type</returns> public static object DeserializeFromFile(string fileName, Type objectType, bool throwExceptions = false) { dynamic json = CreateJsonNet(throwExceptions); if (json == null) return null; object result = null; dynamic reader = null; FileStream fs = null; try { fs = new FileStream(fileName, FileMode.Open, FileAccess.Read); var sr = new StreamReader(fs, Encoding.UTF8); reader = Activator.CreateInstance(JsonTextReaderType, sr); result = json.Deserialize(reader, objectType); reader.Close(); } catch (Exception ex) { Debug.WriteLine("JsonNetSerialization Deserialization Error: " + ex.Message); if (throwExceptions) throw; return null; } finally { if (reader != null) reader.Close(); if (fs != null) fs.Close(); } return result; }This code is a little more compact since there are no prettifying options to set. Here JsonTextReader is created dynamically and it receives the output from the Deserialize() operation on the serializer.You can take a look at the full JsonSerializationUtils.cs file on GitHub to see the rest of the operations, but the string operations are very similar - the code is fairly repetitive.These generic serialization utilities isolate the dynamic serialization logic that has to deal with the dynamic nature of JSON.NET, and any code that uses these functions is none the wiser that JSON.NET is dynamically loaded.Using the JsonSerializationUtils WrapperThe final consumer of the SerializationUtils wrapper is an actual ConfigurationProvider, that is responsible for handling reading and writing JSON values to and from files. The provider is simple a small wrapper around the SerializationUtils component and there's very little code to make this work now:The whole provider looks like this:/// <summary> /// Reads and Writes configuration settings in .NET config files and /// sections. Allows reading and writing to default or external files /// and specification of the configuration section that settings are /// applied to. /// </summary> public class JsonFileConfigurationProvider<TAppConfiguration> : ConfigurationProviderBase<TAppConfiguration> where TAppConfiguration: AppConfiguration, new() { /// <summary> /// Optional - the Configuration file where configuration settings are /// stored in. If not specified uses the default Configuration Manager /// and its default store. /// </summary> public string JsonConfigurationFile { get { return _JsonConfigurationFile; } set { _JsonConfigurationFile = value; } } private string _JsonConfigurationFile = string.Empty; public override bool Read(AppConfiguration config) { var newConfig = JsonSerializationUtils.DeserializeFromFile(JsonConfigurationFile, typeof(TAppConfiguration)) as TAppConfiguration; if (newConfig == null) { if(Write(config)) return true; return false; } DecryptFields(newConfig); DataUtils.CopyObjectData(newConfig, config, "Provider,ErrorMessage"); return true; } /// <summary> /// Return /// </summary> /// <typeparam name="TAppConfig"></typeparam> /// <returns></returns> public override TAppConfig Read<TAppConfig>() { var result = JsonSerializationUtils.DeserializeFromFile(JsonConfigurationFile, typeof(TAppConfig)) as TAppConfig; if (result != null) DecryptFields(result); return result; } /// <summary> /// Write configuration to XmlConfigurationFile location /// </summary> /// <param name="config"></param> /// <returns></returns> public override bool Write(AppConfiguration config) { EncryptFields(config); bool result = JsonSerializationUtils.SerializeToFile(config, JsonConfigurationFile,false,true); // Have to decrypt again to make sure the properties are readable afterwards DecryptFields(config); return result; } }This incidentally demonstrates how easy it is to create a new provider for the West Wind Application Configuration component. Simply implementing 3 methods will do in most cases.Note this code doesn't have any dynamic dependencies - all that's abstracted away in the JsonSerializationUtils(). From here on, serializing JSON is just a matter of calling the static methods on the SerializationUtils class.Already, there are several other places in some other tools where I use JSON serialization this is coming in very handy. With a couple of lines of code I was able to add JSON.NET support to an older AJAX library that I use replacing quite a bit of code that was previously in use. And for any other manual JSON operations (in a couple of apps I use JSON Serialization for 'blob' like document storage) this is also going to be handy.Performance?Some of you might be thinking that using dynamic and Reflection can't be good for performance. And you'd be right… In performing some informal testing it looks like the performance of the native code is nearly twice as fast as the dynamic code. Most of the slowness is attributable to type lookups. To test I created a native class that uses an actual reference to JSON.NET and performance was consistently around 85-90% faster with the referenced code. This will change though depending on the size of objects serialized - the larger the object the more processing time is spent inside the actual dynamically activated components and the less difference there will be. Dynamic code is always slower, but how much it really affects your application primarily depends on how frequently the dynamic code is called in relation to the non-dynamic code executing. In most situations where dynamic code is used 'to get the process rolling' as I do here the overhead is small enough to not matter.All that being said though - I serialized 10,000 objects in 80ms vs. 45ms so this is hardly slouchy performance. For the configuration component speed is not that important because both read and write operations typically happen once on first access and then every once in a while. But for other operations - say a serializer trying to handle AJAX requests on a Web Server one would be well served to create a hard dependency.Dynamic Loading - Worth it?Dynamic loading is not something you need to worry about but on occasion dynamic loading makes sense. But there's a price to be paid in added code  and a performance hit which depends on how frequently the dynamic code is accessed. But for some operations that are not pivotal to a component or application and are only used under certain circumstances dynamic loading can be beneficial to avoid having to ship extra files adding dependencies and loading down distributions. These days when you create new projects in Visual Studio with 30 assemblies before you even add your own code, trying to keep file counts under control seems like a good idea. It's not the kind of thing you do on a regular basis, but when needed it can be a useful option in your toolset… © Rick Strahl, West Wind Technologies, 2005-2013Posted in .NET  C#   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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  • Utilizing Generics to make a Class structure more mutable…

    - by Keith Barrows
    While the ASP.NET GridView control supports automatic paging I found it faster to use custom paging in several situations.  I found myself rewriting the same code over and over just to add the basic sorting capabilities to an ASP.NET GridView object.  So today I took just a little bit of time to encapsulate it all into a Class I can use and reuse on any page with a GridView.  In fact, it will probably take longer to write this blog entry than it took to encapsulate the functionality...(read more)

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  • what's included in a typical computer architecture class? [closed]

    - by sq1020
    Does this description fit what's usually included in a computer architecture class? Computer Organization and Assembly Language An introduction to the hardware organization and assembly language of the Intel processor. Topics include memory hierarchy and design- CPU design- pipelining- addressing modes- subroutine linkage- polled input/output- interrupts- high level language interfacing and macros.

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  • Are UML class diagrams adequated to design javascript systems?

    - by Vandell
    Given that UML is oriented towards a more classic approach to object orientation, is it still usable in a reliable way to design javascript systems? One specific problem that I can see is that class diagrams are, in fact, a structural view of the system, and javascript is more behaviour driven, how can you deal with it? Please, keep in mind that I'm not talking abot the real world domain here, It's a model for the solution that I'm trying to achieve.

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  • A solution for a PHP website without a framework

    - by lortabac
    One of our customers asked us to add some dynamic functionality to an existent website, made of several static HTML pages. We normally work with an MVC framework (mostly CodeIgniter), but in this case moving everything to a framework would require too much time. Since it is not a big project, not having the full functionality of a framework is not a problem. But the question is how to keep code clean. The solution I came up with is to divide code in libraries (the application's API) and models. So inside HTML there will only be API calls, and readability will not be sacrificed. I implemented this with a sort of static Registry (sorry if I'm wrong, I am not a design pattern expert): <?php class Custom_framework { //Global database instance private static $db; //Registered models private static $models = array(); //Registered libraries private static $libraries = array(); //Returns a database class instance static public function get_db(){ if(isset(self::$db)){ //If instance exists, returns it return self::$db; } else { //If instance doesn't exists, creates it self::$db = new DB; return self::$db; } } //Returns a model instance static public function get_model($model_name){ if(isset(self::$models[$model_name])){ //If instance exists, returns it return self::$models[$model_name]; } else { //If instance doesn't exists, creates it if(is_file(ROOT_DIR . 'application/models/' . $model_name . '.php')){ include_once ROOT_DIR . 'application/models/' . $model_name . '.php'; self::$models[$model_name] = new $model_name; return self::$models[$model_name]; } else { return FALSE; } } } //Returns a library instance static public function get_library($library_name){ if(isset(self::$libraries[$library_name])){ //If instance exists, returns it return self::$libraries[$library_name]; } else { //If instance doesn't exists, creates it if(is_file(ROOT_DIR . 'application/libraries/' . $library_name . '.php')){ include_once ROOT_DIR . 'application/libraries/' . $library_name . '.php'; self::$libraries[$library_name] = new $library_name; return self::$libraries[$library_name]; } else { return FALSE; } } } } Inside HTML, API methods are accessed like this: <?php echo Custom_framework::get_library('My_library')->my_method(); ?> It looks to me as a practical solution. But I wonder what its drawbacks are, and what the possible alternatives.

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  • Why the static data members have to be defined outside the class separately in C++ (unlike Java)?

    - by iammilind
    class A { static int foo () {} // ok static int x; // <--- needed to be defined separately in .cpp file }; I don't see a need of having A::x defined separately in a .cpp file (or same file for templates). Why can't be A::x declared and defined at the same time? Has it been forbidden for historical reasons? My main question is, will it affect any functionality if static data members were declared/defined at the same time (same as Java) ?

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  • Are UML class diagrams adequate to design javascript systems?

    - by Vandell
    Given that UML is oriented towards a more classic approach to object orientation, is it still usable in a reliable way to design javascript systems? One specific problem that I can see is that class diagrams are, in fact, a structural view of the system, and javascript is more behaviour driven, how can you deal with it? Please, keep in mind that I'm not talking abot the real world domain here, It's a model for the solution that I'm trying to achieve.

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  • Java Grade Calculator program for class kepp geting the error "Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException." [migrated]

    - by user2880621
    this is my first question I've posted. I've used this site to look at other questions to help with similar problems I've had. After some cursory looking I couldn't find quite the answer I was looking for so I decided to finally succumb and create an account. I am fairly new to java, only a few weeks into my first class. Anyway, my project is to create a program which takes any amount of students and their grades, and then assign them a letter grade. The catch is, however, that it is on a sort of curve and the other grades' letter are dependent on the the highest. Anything equal to or 10 points below the best grade is an a, anything 11-20 points below is a b, and so on. I am to use an array, but I get this error when ran "Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException." I will go ahead and post my code down below. Thanks for any advice you may be able to give. package grade.calculator; import java.util.Scanner; /** * * @author nichol57 */ public class GradeCalculator { /** * @param args the command line arguments */ public static void main(String[] args) { Scanner input = new Scanner(System.in); System.out.println("Enter the number of students"); int number = input.nextInt(); double[]grades = new double [number]; for (int J = number; J >=0; J--) { System.out.println("Enter the students' grades"); grades[J] = input.nextDouble(); } double best = grades[0]; for (int J = 1; J < number; J++) { if (grades[J] >= best){ best = grades[J]; } } for (int J = 0;J < number; J++){ if (grades[J] >= best - 10){ System.out.println("Student " + J + " score is " + grades[J] + " and grade is " + "A"); } else if (grades[J] >= best - 20){ System.out.println("Student " + J + " score is " + grades[J] + " and grade is " + "B"); } else if (grades[J] >= best - 30) { System.out.println("Student " + J + " score is " + grades[J] + " and grade is " + "C"); } else if (grades[J] >= best - 40) { System.out.println("Student " + J + " score is " + grades[J] + " and grade is " + "D"); } else { System.out.println("Student " + J + " score is " + grades[J] + " and grade is " + "F"); } } // end for loop for output }// end main method }

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  • What class to use in order to have a number move around the screen?

    - by AllenZ41
    What i am trying to accomplish is have a randomly created number move around the screen but it is touchable. I am planning to have lots of numbers on the screen, so my question is what class is appropriate to use, so I could set a number randomly at run time and display it while it moves around the screen? I was planning the use a TextView, since I want to use a custom font of mine but I think creating a bunch at a time could cause a memory problem and to my understanding they cant move around the screen at runtime.

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  • How do I restore tab-completion on shell variables on the bash command-line?

    - by Eric
    I've long set my most-recently visited directories to shell variables d1, d2, etc. On an ancient Fedora machine I could type a command like $ cp $d1/ and the shell would replace $d1 with text like /home/acctname/projects/blog/ and would then show me the contents of .../blog, like any tab-completion. Now, both ubuntu wheezy/sid and fedora 16 just -escape the '$', and naturally there are no completions to show. You can see this behavior in action in an OSX Terminal window. On 10.8, do something like ls $HOME/ to see what I mean. Is there a bash shell variable or option that can restore the old behavior? man bash suggests this is a bug: complete (TAB) Attempt to perform completion on the text before point. Bash attempts completion treating the text as a variable (if the text begins with $), username (if the text begins with ~), hostname (if the text begins with @), or command (including aliases and functions) in turn. If none of these produces a match, filename completion is attempted. I get the above described completion when a token starts with '~' or a letter. It's just '$'-completion that's broken.

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  • Overriding Object.Equals() instance method in C#; now Code Analysis / FxCop warning CA2218: "should

    - by Chris W. Rea
    I've got a complex class in my C# project on which I want to be able to do equality tests. It is not a trivial class; it contains a variety of scalar properties as well as references to other objects and collections (e.g. IDictionary). For what it's worth, my class is sealed. To enable a performance optimization elsewhere in my system (an optimization that avoids a costly network round-trip), I need to be able to compare instances of these objects to each other for equality – other than the built-in reference equality – and so I'm overriding the Object.Equals() instance method. However, now that I've done that, Visual Studio 2008's Code Analysis a.k.a. FxCop, which I keep enabled by default, is raising the following warning: warning : CA2218 : Microsoft.Usage : Since 'MySuperDuperClass' redefines Equals, it should also redefine GetHashCode. I think I understand the rationale for this warning: If I am going to be using such objects as the key in a collection, the hash code is important. i.e. see this question. However, I am not going to be using these objects as the key in a collection. Ever. Feeling justified to suppress the warning, I looked up code CA2218 in the MSDN documentation to get the full name of the warning so I could apply a SuppressMessage attribute to my class as follows: [SuppressMessage("Microsoft.Naming", "CA2218:OverrideGetHashCodeOnOverridingEquals", Justification="This class is not to be used as key in a hashtable.")] However, while reading further, I noticed the following: How to Fix Violations To fix a violation of this rule, provide an implementation of GetHashCode. For a pair of objects of the same type, you must ensure that the implementation returns the same value if your implementation of Equals returns true for the pair. When to Suppress Warnings ----- Do not suppress a warning from this rule. [arrow & emphasis mine] So, I'd like to know: Why shouldn't I suppress this warning as I was planning to? Doesn't my case warrant suppression? I don't want to code up an implementation of GetHashCode() for this object that will never get called, since my object will never be the key in a collection. If I wanted to be pedantic, instead of suppressing, would it be more reasonable for me to override GetHashCode() with an implementation that throws a NotImplementedException? Update: I just looked this subject up again in Bill Wagner's good book Effective C#, and he states in "Item 10: Understand the Pitfalls of GetHashCode()": If you're defining a type that won't ever be used as the key in a container, this won't matter. Types that represent window controls, web page controls, or database connections are unlikely to be used as keys in a collection. In those cases, do nothing. All reference types will have a hash code that is correct, even if it is very inefficient. [...] In most types that you create, the best approach is to avoid the existence of GetHashCode() entirely. ... that's where I originally got this idea that I need not be concerned about GetHashCode() always.

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  • How does Visual Studio decide the order in which stack variables should be allocated?

    - by Jason
    I'm trying to turn some of the programs in gera's Insecure Programming by example into client/server applications that could be used in capture the flag scenarios to teach exploit development. The problem I'm having is that I'm not sure how Visual Studio (I'm using 2005 Professional Edition) decides where to allocate variables on the stack. When I compile and run example 1: int main() { int cookie; char buf[80]; printf("buf: %08x cookie: %08x\n", &buf, &cookie); gets(buf); if (cookie == 0x41424344) printf("you win!\n"); } I get the following result: buf: 0012ff14 cookie: 0012ff64 buf starts at an address eighty bytes lower than cookie, and any four bytes that are copied in buf after the first eighty will appear in cookie. The problem I'm having is when I place this code in some other function. When I compile and run the following code, I get a different result: buf appears at an address greater than cookie's. void ClientSocketHandler(SOCKET cs){ int cookie; char buf[80]; char stringToSend[160]; int numBytesRecved; int totalNumBytes; sprintf(stringToSend,"buf: %08x cookie: %08x\n",&buf,&cookie); send(cs,stringToSend,strlen(stringToSend),NULL); The result is: buf: 0012fd00 cookie: 0012fcfc Now there is no way to set cookie to arbitrary data via overwriting buf. Is there any way to tell Visual Studio to allocate cookie before buf? Is there any way to tell beforehand how the variables will be allocated? Thanks, Jason

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  • Mock versus Implementation. How to share both approaches in a single Test class ?

    - by Arthur Ronald F D Garcia
    Hi, See the following Mock Test by using Spring/Spring-MVC public class OrderTest { // SimpleFormController private OrderController controller; private OrderService service; private MockHttpServletRequest request; @BeforeMethod public void setUp() { request = new MockHttpServletRequest(); request.setMethod("POST"); Integer orderNumber = 421; Order order = new Order(orderNumber); // Set up a Mock service service = createMock(OrderService.class); service.save(order); replay(service); controller = new OrderController(); controller.setService(service); controller.setValidator(new OrderValidator()); request.addParameter("orderNumber", String.valueOf(orderNumber)); } @Test public void successSave() { controller.handleRequest(request, new MockHttpServletResponse()); // Our OrderService has been called by our controller verify(service); } @Test public void failureSave() { // Ops... our orderNumber is required request.removeAllParameters(); ModelAndView mav = controller.handleRequest(request, new MockHttpServletResponse()); BindingResult bindException = (BindingResult) mav.getModel().get(BindingResult.MODEL_KEY_PREFIX + "command"); assertEquals("Our Validator has thrown one FieldError", bindException.getAllErrors(), 1); } } As you can see, i do as proposed by Triple A pattern Arrange (setUp method) Act (controller.handleRequest) Assert (verify and assertEquals) But i would like to test both Mock and Implementation class (OrderService) by using this single Test class. So in order to retrieve my Implementation, i re-write my class as follows @ContextConfiguration(locations="/app.xml") public class OrderTest extends AbstractTestNGSpringContextTests { } So how should i write my single test to Arrange both Mock and Implementation OrderService without change my Test method (sucessSave and failureSave) I am using TestNG, but you can show in JUnit if you want regards,

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  • How to have a policy class implement a virtual function?

    - by dehmann
    I'm trying to design a policy-based class, where a certain interface is implemented by the policy itself, so the class derives from the policy, which itself is a template (I got this kind of thinking from Alexandrescu's book): #include <iostream> #include <vector> class TestInterface { public: virtual void test() = 0; }; class TestImpl1 { public: void test() {std::cerr << "Impl1" << std::endl;} }; template<class TestPolicy> class Foo : public TestInterface, TestPolicy { }; Then, in the main() function, I call test() on (potentially) various different objects that all implement the same interface: int main() { std::vector<TestInterface*> foos; foos.push_back(new Foo<TestImpl1>()); foos[0]->test(); delete foos[0]; return 0; } It doesn't compile, though, because the following virtual functions are pure within ‘Foo<TestImpl1>’: virtual void TestInterface::test() I thought TestInterface::test() is implemented because we derive from TestImpl1?

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  • How do I iterate through the id properties of R.java class ?

    - by mgpyone
    I've 16 textViews and need to set something like this done: for (int i=1; i<6; i++) { int $RidInt = R.id.s; tv[i] = (TextView)findViewById($RidInt); tv[i].setTypeface(face); tv[i].setClickable(true); tv[i].setOnClickListener(clickListener); } my R.java file is : public final class R { public static final class attr { } public static final class drawable { public static final int icon=0x7f020000; } public static final class id { public static final int s1=0x7f050000; public static final int s10=0x7f050009; public static final int s11=0x7f05000a; public static final int s12=0x7f05000b; public static final int s13=0x7f05000c; public static final int s14=0x7f05000d; public static final int s15=0x7f05000e; public static final int s16=0x7f05000f; public static final int s2=0x7f050001; public static final int s3=0x7f050002; public static final int s4=0x7f050003; public static final int s5=0x7f050004; public static final int s6=0x7f050005; public static final int s7=0x7f050006; public static final int s8=0x7f050007; public static final int s9=0x7f050008; } public static final class layout { public static final int main=0x7f030000; public static final int toast=0x7f030001; } public static final class string { public static final int app_name=0x7f040000; public static final int s2=0x7f040001; } }

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  • How can I prevent default_environment variables from getting set by Capistrano's sudo action?

    - by Logan Koester
    My deploy.rb sets some environment variables to use the regular user's local Ruby rather than the system-wide one. set :default_environment, { :PATH => '/home/myapp/.rvm/bin:/home/myapp/.rvm/bin:/home/myapp/.rvm/rubies/ruby-1.9.1-p378/bin:/home/myapp/.rvm/gems/ruby-1.9.1-p378/bin:/home/myapp/.rvm/gems/ruby-1.9.1-p378%global/bin:/home/myapp/bin:/usr/bin:/opt/local/bin:/opt/local/sbin:/usr/local/bin:/usr/local/sbin:/usr/sbin:/sbin:/bin:/usr/games', :RUBY_VERSION => 'ruby-1.9.1-p378', :GEM_HOME => '/home/myapp/.rvm/gems/ruby-1.9.1-p378', :GEM_PATH => '/home/myapp/.rvm/gems/ruby-1.9.1-p378:/home/myapp/.rvm/gems/ruby-1.9.1-p378%global' } Naturally, when a task is using sudo, I would expect the system-wide ruby to be used instead. But it seems the environment variables are being set anyway, which is obviously invalid for the root user and returns an error: executing "sudo -p 'sudo password: ' /etc/init.d/god stop" servers: ["myapp.com"] [myapp.com] executing command command finished failed: "env PATH=/home/myapp/.rvm/bin:/home/myapp/.rvm/bin:/home/myapp/.rvm/rubies/ruby-1.9.1-p378/bin:/home/myapp/.rvm/gems/ruby-1.9.1-p378/bin:/home/myapp/.rvm/gems/ruby-1.9.1-p378%global/bin:/home/myapp/bin:/usr/bin:/opt/local/bin:/opt/local/sbin:/usr/local/bin:/usr/local/sbin:/usr/sbin:/sbin:/bin:/usr/games RUBY_VERSION=ruby-1.9.1-p378 GEM_HOME=/home/myapp/.rvm/gems/ruby-1.9.1-p378 GEM_PATH=/home/myapp/.rvm/gems/ruby-1.9.1-p378:/home/myapp/.rvm/gems/ruby-1.9.1-p378%global sh -c 'sudo -p '\\''sudo password: '\\'' /etc/init.d/god stop'" on myapp.com It makes no difference whether I use capistrano's sudo "system call" or the regular run "sudo system call". How can I avoid this?

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  • How to redirect a URL with GET variables in routes.rb without Rails stripping out the variable first?

    - by Michael Hopkins
    I am building a website in Rails to replace an existing website. In routes.rb I am trying to redirect some of the old URLs to their new equivalents (some of the URL slugs are changing so a dynamic solution is not possible.) My routes.rb looks like this: match "/index.php?page=contact-us" => redirect("/contact-us") match "/index.php?page=about-us" => redirect("/about-us") match "/index.php?page=committees" => redirect("/teams") When I visit /index.php?page=contact-us I am not redirected to /contact-us. I have determined this is because Rails is removing the get variables and only trying to match /index.php. For example, If I pass /index.php?page=contact-us into the below routes I will be redirected to /foobar: match "/index.php?page=contact-us" => redirect("/contact-us") match "/index.php?page=about-us" => redirect("/about-us") match "/index.php?page=committees" => redirect("/teams") match "/index.php" => redirect("/foobar") How can I keep the GET variables in the string and redirect the old URLs the way I'd like? Does Rails have an intended mechanism for this?

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  • How do I create a class repository in Java and do I really need it?

    - by Roman
    I have a large number of objects which are identified by names (strings). So, I would like to have a kind of mapping from object name to the class instances. I was told that in this situation I can use a "repository" class which works like that: Server myServer = ServerRepository.getServer("NameOfServer"); So, if there is already an object (sever) with the "NameOfServer" it will be returned by the "getServer". If such an object does not exist yet, it will be created and returned by the "getServer". So, my question is how to program such a "repository" class? In this class I have to be able to check if there is an instance of a given class such that it has a given value of a given field. How can I do it? I need to have a kind of loop over all existing object of a given class? Another part of my question is why I cannot use associative arrays (associative container, map, mapping, dictionary, finite map)? (I am not sure how do you call it in Java) In more details, I have an "array" which maps names of objects to objects. So, whenever I create a new object, I add a new element to the array: myArray["NameOfServer"] = new Server("NameOfServer").

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  • How to traverse table in Jquery and add a class?

    - by SWL
    I have a simple table of two rows. The first column is required, but the others are not; however, I would like them to be required in pairs. So if the user enters a value for Quantity3, then Size3 should also now be required. As a fiddle: http://jsfiddle.net/NaRts/7/ <tr> <td><input name="qty1[492]" class="qty required" type="text"></td> <td><input name="qty2[492]" class="qty" type="text"></td> <td><input name="qty3[492]" class="qty" type="text"></td> </tr><tr> <td><input name="size1[492]" type="text" class="size required" ></td> <td><input name="size2[492]" type="text" class="size" ></td> <td><input name="size3[492]" type="text" class="size" ></td> </tr> And the simple jQuery I have is: $('.qty').keyup(function() { var s = $(this).attr('name'); // = qty3[418] var qtyID = s.replace(/[^1-9\[\]]/g, ""); // = 3[418] var SizeID = "size" + qtyID; var $sizeInput = $(this).closest('tr').next().find(SizeID); $sizeInput.css('background-color', 'green'); $sizeInput.addClass('required'); //I tried this too but it didn't work //$(this).parent().find(SizeID).addClass('required'); });? ? Any help is much appreciated.

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  • PHP: how to access variables inside a function that have been declared outside of it?

    - by Chris
    Please, I am very new and have not been confronted with OOP and all this related stuff, which I guess may be related to this issue (public, private, ...). So, any help and suggestions are very appreciated! :) At the very beginning of each page I include a file that starts the SESSION etc, lets call it session.php. In this file session.php, I include a file that contains a function, let's call it function1.php, because I need the function to be available in session.php. However, later in the main page I also include function2.php which needs to access variables set in session.php, so I additionally tried to include session.php in function2.php. The problem is that an error occurs as function1 will be declared multiple times... Fatal error: Cannot redeclare function1() (previously declared in ... So, what would be a more elegant and clean(er) solution for this? How could you solve it? Basically, I'd need to access variables inside a function that have been included in the main page before... Thank you very much in advance!

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  • Is it necessary to var scope loop variables in CFScript?

    - by Mel
    When using CFML and CF9 I usually var scope my loop variables; in this case local.i, for example: <cfloop list="#this.list#" index="local.i"> <cfif Len(local.i) GT 10> // do something </cfif> </cfloop> I recently started converting some stuff into CFScript, and (to my disappointment I found out that there is no way to loop over a list in CFScript) I'm wondering if I should still var scope my loop variables, and how: for (i = 1; LTE ListLen(this.list); i = i + 1 ) { if (Len(ListGetAt(this.list, i) GT 10)) { // do something } } Should I be doing local.i = 1 and local.i = local.i + 1 istead of the sample code in my example? Is it necessary? EDIT: I should also ask if the CFScript form of my CFML loop is correct; I ask because I just noticed that my CFML loop uses a , (comma and space) for the delimiter argument, which seems non-existence in the CFScript version of the loop.

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  • How can I extend a LINQ-to-SQL class without having to make changes every time the code is generated

    - by csharpnoob
    Hi, Update from comment: I need to extend linq-to-sql classes by own parameters and dont want to touch any generated classes. Any better suggestes are welcome. But I also don't want to do all attributes assignments all time again if the linq-to-sql classes are changing. so if vstudio generates new attribute to a class i have my own extended attributes kept separate, and the new innerited from the class itself Original question: i'm not sure if it's possible. I have a class car and a class mycar extended from class car. Class mycar has also a string list. Only difference. How can i cast now any car object to a mycar object without assigning all attributes each by hand. Like: Car car = new Car(); MyCar mcar = (MyCar) car; or MyCar mcar = new MyCar(car); or however i can extend car with own variables and don't have to do always Car car = new Car(); MyCar mcar = new MyCar(); mcar.name = car.name; mcar.xyz = car.xyz; ... Thanks.

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  • Is it possible to De-Serialize a new Derived class using Old Binary?

    - by Anand
    In my project I have a class which I Serialize in Binary format to the disk. Due to some new requirement I need to create a new class which is derived from the original class. eg [Serializable] public class Sample { String someString; int someInt; public Sample() { } public Sample(String _someString, int _someInt) { this.someInt = _someInt; this.someString = _someString; } public String SomeString { get { return someString; } } public int SomeInt { get { return someInt; } } } [Serializable] public class DerivedSample : Sample { String someMoreString; int someMoreInt; public DerivedSample () : base() { } public DerivedSample (String _someString, int _someInt, String _someMoreString, int _someMoreInt) : base(_someString, _someInt) { this.someMoreString = _someMoreString; this.someMoreInt = _someMoreInt; } public String SomeMoreString { get { return someMoreString; } } public int SomeMoreInt { get { return someMoreInt; } } } When I try to De serialize an old file which contains only object of Sample it works fine, in the current assembly. That means backward compatibility is there. But when I try to deserialize the file which contains object of DerivedSample using the previous version of the assembly application crashes. Which means forward compatibilty needs to be taken care off... It it possible to say read only the base class part of the object from new version of the file?

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  • How to check at runtime if a class implements certain interface?

    - by mare
    Let's say I have some content classes like Page, TabGroup, Tab, etc. Certain of those will be implementing my IWidgetContainer interface - it means they will geet an additional field named ContainedItems from the interface and some methods for manipulating this field. Now I need to reflect the fact that some class implements this interface by rendering out some special custom controls in my ASP.NET MVC Views (like jQuery Add/Remove/Move/Reorder buttons). For instance, TabGroup will implement IWidgetContainer because it will contain tabs but a tab will not implement it because it won't have the ability to contain anything. So I have to somehow check in my view, when I render my content objects (The problem is, I use my base class as strong type in my view not concrete classes), whether it implements IWidgetContainer. How is that possible or have I completely missed something? To rephrase the question, how do you reflect some special properties of a class (like interface implementation) in the UI in general (not necessarily ASP.NET MVC)? Here's my code so far: [DataContract] public class ContentClass { [DataMember] public string Slug; [DataMember] public string Title; [DataMember] protected ContentType Type; } [DataContract] public class Group : ContentClass, IWidgetContainer { public Group() { Type = ContentType.TabGroup; } public ContentList ContainedItems { get; set; } public void AddContent(ContentListItem toAdd) { throw new NotImplementedException(); } public void RemoveContent(ContentListItem toRemove) { throw new NotImplementedException(); } } [DataContract] public class GroupElement : ContentClass { public GroupElement() { Type = ContentType.Tab; } } Interface: interface IWidgetContainer { [DataMember] ContentList ContainedItems { get; set; } void AddContent(ContentListItem toAdd); void RemoveContent(ContentListItem toRemove); }

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