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  • GWT. Exclude shared domain objects to separate Maven module

    - by MyTitle
    I have some Domain classes such as Student, User etc which are used on server and client (gwt) sides. Can I exclude this domain classes to separate maven-module, so I can add this module as dependency to other maven-modules (i.e. add this module as dependency to maven-module which contains gwt related stuff, so this domain classes will be generated to JavaScript, and add this module as dependency to "normal" (not gwt) Java maven-modules, so this domain classes won’t be generated to JavaScript)?

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  • Why doesn't the C++ default destructor destroy my objects?

    - by Oszkar
    The C++ specification says the default destructor deletes all non-static members. Nevertheless, I can't manage to achieve that. I have this: class N { public: ~N() { std::cout << "Destroying object of type N"; } }; class M { public: M() { n = new N; } // ~M() { //this should happen by default // delete n; // } private: N* n; }; Then this should print the given message, but it doesn't: M* m = new M(); delete m; //this should invoke the default destructor

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  • An efficient way to store view counts for objects?

    - by Nick Brooks
    I maintain an application where users are able to store images, and then share them. The system is powered by MongoDB at the back end. Most of the image depiction pages are cached as flat HTML files, but I can run some code just before loading the file. I've decided to implement a view count for the system. I am wondering what is the best storage place for that. It should be like Memcached but it should save the viewcounts every hour or so, so even if our server has to be restarted we won't lose the view counts. What is the best solution for that (preferably with a PHP extension as a client)?

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  • How to Pass complex objects in ASP.NET MVC using Get parameters?

    - by VJ
    I am wanting to pass something like the following to my view from my controller via GET not POST: public class MyDTO { public string val1 { get; set; } public string val2 { get; set; } public MyObject obj { get; set; } } public class MyObject { public int SomeInt { get; set; } public string ACoolValue { get; set; } public string YetAnotherCoolValue { get; set; } } And then the controller would like like this. (Note it is a GET): public ActionResult MyView(MyDTO dto) { return View(dto) } The problem is that the instance of MyObject is coming back as null, where val1 and val2 have data. Has anyone run across this?

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  • What is the right way to implement communication between java objects?

    - by imoschak
    I'm working on an academic project which simulates a rather large queuing procedure in java. The core of the simulator rests within one package where there exist 8 classes, each one implementing a single concept. Every class in the project follows SRP. These classes encapsulate the behavior of the simulator and inter-connect every other class in the project. The problem that has arisen is that most of these 8 classes are, as is logical i think, tightly coupled and each one has to have working knowledge of every other class in this package in order to be able to call methods from it when needed. The application needs only one instance of each class so it might be better to create static fields for each class in a new class and use that to make calls -instead of preserving a reference in each class for every other class in the package (which I'm certain that is incorrect)-, but is this considered a correct design solution? or is there a design pattern maybe that better suits my needs?

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  • VS2010 (older) installer project - two or more objects have the same target location.

    - by Hamish Grubijan
    This installer project was created back in 2004 and upgraded ever since. There are two offending dll files, which produce a total of 4 errors. I have searched online for this warning message and did not find a permanent fix (I did manage to make it go away once until I have done something like a clean, or built in Release, and then in Debug). I also tried cleaning, and then refreshing the dependencies. The duplicated entries are still in there. I also did not find a good explanation for what this error means. Additional warnings are of this nature: Warning 36 The version of the .NET Framework launch condition '.NET Framework 4' does not match the selected .NET Framework bootstrapper package. Update the .NET Framework launch condition to match the version of the .NET Framework selected in the Prerequisites Dialog Box. So, where is this prerequisites box? I want to make both things agree on .Net 4.0, just having a hard time locating both of them.

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  • How do you pass objects between View Controllers in Objective-C?

    - by editor
    I've been trudging through some code for two days trying to figure out why I couldn't fetch a global NSMutableArray variable I declared in the .h and implemented in .m and set in a the viewDidLoad function. It finally dawned on me: there's no such thing as a global variable in Objective-C, at least not in the PHP sense I've come to know. I didn't ever really read the XCode error warnings, but there it was, even if not quite plain English: "Instance variable 'blah' accessed in class method." My question: What am I supposed to do now? I've got two View Controllers that need to access a central NSMutableDictionary I generate from a JSON file via URL. It's basically an extended menu for all my Table View drill downs, and I'd like to have couple other "global" (non-static) variables. Do I have to grab the JSON each time I want to generate this NSMutableDictionary or is there some way to set it once and access it from various classes via #import? Do I have to write data to a file, or is there another way people usually do this?

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  • Should I share UI for objects that use common fields?

    - by wb
    I have a parent class that holds all of the fields that are common between all device types. From that, I have a few derived classes that each hold their unique fields. Say I have device type "Switch" and "Transformer". Both derived classes only have 2-3 of their own unique fields. When doing the UI design (windows forms) in this case. Should I create two separate forms for each device type or create a user control with all fields that are shared among all devices? Thank you.

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  • Copy not null and not empty fields from one object to another object of the same type(Objects are same type) in java

    - by Chinni
    I am using hibernate, struts, extjs in my project. I have a Customer object with these fields: custId, custName, address, phone and in my project from UI side I get an object customer with custName. So I need to update the above object(custName is unique). I have only one object with the same customer name. So I will get that object using customer name (object from DB). Now I have to save the object with the updated customer name. If I save as follows I have Customer Object from UI, is cust Customer cust1 = getCustomerByName(cust.getCustName()); cust.setCustId(cust1.getCustId()); save(cust); If I do this I lose the customer address and phone number. So, how can I copy one object not null or not empty field values to another object of same type. Can any one please help. I just stuck here. It's stopping me to save. Thanks in advance!

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  • How to $.extend 2 objects by adding numerical values together from keys with the same name?

    - by muudless
    I currently have 2 obj and using the jquery extend function, however it's overriding value from keys with the same name. How can I add the values together instead? obj1 = {"orange":2,"apple":1, "grape":1} obj2 = {"orange":5,"apple":1, "banana":1} mergedObj = $.extend({}, obj1, obj2); var printObj = typeof JSON != "undefined" ? JSON.stringify : function(obj) { var arr = []; $.each(obj, function(key, val) { var next = key + ": "; next += $.isPlainObject(val) ? printObj(val) : val; arr.push( next ); }); return "{ " + arr.join(", ") + " }"; }; console.log('all together: '+printObj(mergedObj) ); And I get obj1 = {"orange":5,"apple":1, "grape":1, "banana":1} What I need is obj1 = {"orange":7,"apple":2, "grape":1, "banana":1}

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  • How would you find the height of objects given an image?

    - by Ram Bhat
    Heyguys.. This isn't exactly a programming question exactly. I just want to know what your approach would be to a common problem in Digital image processing. Lets say you have an image of a a few trees in say jpg format. How would you go about finding the heights of each of these trees. The photo is the only input you have. I want to know the approaches you have not code. So it doesnt matter if your answers are vague, or non DIP-ish.

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  • CodePlex Daily Summary for Wednesday, April 14, 2010

    CodePlex Daily Summary for Wednesday, April 14, 2010New Projectsbitly.net: A bitly (useing Version 3 of their API's) client for .NET (Version 3.5)Chord Sheet Editor Add-In for Word: Transpose music chord sheets (guitar chord sheets, etc.) in Microsoft Word using this VSTO Add-In.CloudSponge.Net: Simple .Net wrapper for www.cloudsponge.com's REST API.Database Searcher: This is a small tool for searching a typed value inside all type matching columns and rows of a database. For connecting the database a .NET data p...Edu Math: PL: Program Edu Math, ma na celu ułatwienie wykonywania skomplikowanych obliczeń oraz analiz matematycznych. EN: Program Edu Math, aims to facilita...fluent AOP: This project is not yet publishedFNA Fractal Numerical Algorithm for a new encryption technology: FNA Fractal Numerical Algorithm for a new encryption technology is a symmetrical encryption method based on two algorithms that I developed for: 1....Image viewer cum editor: This is a project on image viewing and editing. The project have following features VIEWER: Album Password security for albums Inbuilt Browser...JEngine - Tile Map Editor v1: JEngine - Tile Map Editor v1Jeremy Knight: Code samples, snippets, etc from my personal blog.lcskey: lcs test codemoldme: testesds ssdfsdfsNanoPrompt: NanoPrompt makes it more pleasant to work on a command-line. Features: - syntax-highlighting - graphical output possible - up to 12 "displays" (cha...nirvana: for testOffInvoice Add-in for MS Office 2010: Project Description: The project it's based in the ability to extend funtionality in the Microsoft Office 2010 suite.PowerSlim - Acceptance Testing for Enterprise Applications: PowerSlim makes it possible to use PowerShell in the acceptance testing. It is a small but powerful plugin for the Fitnesse acceptance testing fram...Proxi [Proxy Interface]: Proxi is a light-weight library that allows to generate dynamic proxies using different providers. By utilizing Proxi frameworks and libraries can ...Reality show about ASP.NET development: This application is created with using ASP.NET and Microsoft SQL Server for the demo purposes with the following target goals: example of usage fo...RecordLogon.vbs login script: RecordLogon.vbs is a script applied at logon via Group or Local policy. It records specific user and computer information and writes the data to a ...SpaceGameApplet: A java game ;)SpaceShipsGame: A game with space ships ";..;"SysHard: Info for Linux system.System Etheral™ - Developer: SE Dev (System Etheral™ - Developer) is an OS (Operating System) that is a bit like UNIX but it is for you to edit! We have not gave you much but w...TimeSheet Reporting Silverlight: TimeSheet Reporting application in Silver light. Contains a data grid containing combo boxes bound to different data sources like Members and Proje...TrayBird: A minimalistic twitter client for windows.Twitter4You: This appliction for windows is a communication for twitter!WCF RIA Services (+ PRISM + MVVM) LoB Application: WCF RIA Services sample LoB application (case study) built on PRISM with Entity Framework Model. It's a simple application for a fictive company Te...New ReleasesBluetooth Radar: Version 1.9: Change Search and Close Icons Add Device Detail ViewCloudSponge.Net: Alpha: Initial alpha release very limited tested includes *CloudSponge.dll *Sponge.exe (simple cmd line utility to import contacts, and test API)Global Assembly Cache comparison tool: GAC Compare version 3.1: Version 3.1Added export assemblies to directory functionalityHTML Ruby: 6.21.2: Some style adjustments Ruby text spacing is spaced out to keep Firefox responsive Status bar is backJEngine - Tile Map Editor v1: JEngine - Tile Map Editor V1: JEngine - Tile Map Editor V1 Discription SoonJeremy Knight: SQL Padding Functions v1.0: The entire scripts, including if exists logic, for SQL Padding Functions are included in this download.jqGrid ASP.Net MVC Control: Version 1.1.0.0: UPDATE 14-04 Fixed a small problem with the custom column renderers controller, And added a new example for a cascading-dropdownlist grid column A...JulMar MVVM Helpers + Behaviors: Version 1.06: This version is an update to MVVM Helpers that is built on Visual Studio 2010 RTM. It includes some minor updates to classes and a few new convert...lcskey: v 1.0: v1.0 基本能跑，未详细测试LINQ To Blippr: LINQ to Blippr: Download to test out and play around LINQ to Blippr based from blog posts: http://consultingblogs.emc.com/jonsharrattLINQ to XSD: 1.1.0: The LINQ to XSD technology provides .NET developers with support for typed XML programming. LINQ to XSD contributes to the LINQ project (.NET Langu...LINQ to XSD: 2.0.0: It is the same code as version 1.1 but compiled for .NET framework 4.0. Requirements: .NET Framework 4.0.LocoSync: LocoSync v0.1r2010.04.12: Second Alpha version of LocoSync. Download unzip and run setup. It will download the .NET framework if needed. It will create an icon in the start ...mojoPortal: 2.3.4.2: see release note on mojoportal.com http://www.mojoportal.com/mojoportal-2342-released.aspxNanoPrompt: Setup (.NET 4.0) - 20100414-A Nightly: The setup for NanoPrompt 0.Xa for Intel-80386- (32 or 64 bits) or Intel-Itanium-compatible targets with installed .NET-Framework 4.0 Client Profile...Neural Cryptography in F#: Neural Cryptography 0.0.5: This release provides the basic functionality that this project was supposed to have from the very beginning: it can hash strings using neural netw...NodeXL: Network Overview, Discovery and Exploration for Excel: NodeXL Class Libraries, version 1.0.1.121: The NodeXL class libraries can be used to display network graphs in .NET applications. To include a NodeXL network graph in a WPF desktop or Windo...nRoute Framework: nRoute.Toolkit Release Version 0.4: Note, both "nRoute.Framework (x3)" and "nRoute.Toolkit (x3)" zip files contains binaries for Web, Desktop and Mobile targets. Also this release wa...Numina Application/Security Framework: Numina.Framework Core 50381: Rebuilt using .NET 4 RTM One minor change made to the web.config file - added System.Data.Linq to the assemblies list.PokeIn Comet Ajax Library: PokeIn Lib and Sample: Great sample with usefull comet ajax library! .Net 2.0 Note : It was very easy to build this project with Visual Studio 10 ;)Powershell Zip File Export/Import Cmdlet Module: PowershellZip 0.1.0.3: Powershell-Zip 0.1.0.3 contains the cmdlets Export-Zip and Import-ZipPowerSlim - Acceptance Testing for Enterprise Applications: PowerSlim 0.1: Just PowerSlim. http://vlasenko.org/2010/04/09/howto-setup-powerslim-step-by-step/RDA Collaboration Team Projects: SharePoint BPOS Logging Framework: RDA's SharePoint BPOS logging framework is a very lightweight WSP Builder project that provides the following items: A Site feature that creates a...RecordLogon.vbs login script: LogonSearchGadget: This is the Windows Gadget companion for RecordLogon.RecordLogon.vbs login script: LogonSearchTool.hta: This is the HTA standalone script that runs inside of an IE window. The HTA is what presents the data the recordlogon.vbs creates. Please remember...RecordLogon.vbs login script: recordlogon.vbs: This is the main script that grabs the logon and computer information and dumps the info as text files to a defined folder share. Make sure to chec...Rensea Image Viewer: RIV 0.4.3: New Release of RIV. Added many many features! You would love it. You would need .NET Framework 4.0 to make it run With separated RIV up-loader, to...SharePoint Site Configurator Feature: SharePoint Site Configurator V2.0: Updated for SharePoint 2010 and added quite a lot of new functions. Compatible with SP2010, MOSS and WSS 3.0Sharp Tests Ex: Sharp Tests Ex 1.0.0RC2: Project Description #TestsEx (Sharp Tests Extensions) is a set of extensible extensions. The main target is write short assertions where the Visual...SQL Server Extended Properties Quick Editor: Release 1.6.2: Whats new in 1.6.2: Fixed several errors in LinqToSQL generated classes, solved generation EntitySet members. Its highly recomended to download and...SSRS SDK for PHP: SugarCRM Sample for SSRSReport: The zip file contains a sample SugarCRM module that shows how the SSRS SDK for PHP can be used to add simple reporting capabilities to the SugarCRM...System Etheral™ - Developer: System Etheral Dev v1.00: Comes with a VERY basic text editor and the ability to shutdown. Hopefully we will have a lot more stuff in version 1.01! But this is fine for now....Text to HTML: 0.4.2.0: ¡Gracias a Martin Lemburg por avisar de los errores y por sus sugerencias! Cambios de la versiónSustitución de los caracteres especiales alemanes:...TimeSheet Reporting Silverlight: v1.0 Source Code: Source CodeTwitter4You: Twitter 4 You - Version 1.0 (TESTER): Serialcode: http://joeynl.blogspot.com/2010/04/test-version-of-t4yv1.html Thanks JoeyNLVCC: Latest build, v2.1.30413.0: Automatic drop of latest buildVisioAutomation: VisioAutomation 2.5.1: VisioAutomation 2.5.1- Moved to Visual Studio 2010 (Still using .NET Framework 3.5) Changes Since 2.5.0- Solution and Projects are all based on Vi...Most Popular ProjectsRawrWBFS ManagerAJAX Control ToolkitMicrosoft SQL Server Product Samples: DatabaseSilverlight ToolkitWindows Presentation Foundation (WPF)ASP.NETMicrosoft SQL Server Community & SamplesPHPExcelFacebook Developer ToolkitMost Active ProjectsRawrAutoPocopatterns & practices – Enterprise LibraryGMap.NET - Great Maps for Windows Forms & PresentationFarseer Physics EngineNB_Store - Free DotNetNuke Ecommerce Catalog ModuleBeanProxyjQuery Library for SharePoint Web ServicesBlogEngine.NETFacebook Developer Toolkit

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  • C#/.NET Little Wonders: The Predicate, Comparison, and Converter Generic Delegates

    - 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 last three weeks, we examined the Action family of delegates (and delegates in general), the Func family of delegates, and the EventHandler family of delegates and how they can be used to support generic, reusable algorithms and classes. This week I will be completing my series on the generic delegates in the .NET Framework with a discussion of three more, somewhat less used, generic delegates: Predicate<T>, Comparison<T>, and Converter<TInput, TOutput>. These are older generic delegates that were introduced in .NET 2.0, mostly for use in the Array and List<T> classes.  Though older, it’s good to have an understanding of them and their intended purpose.  In addition, you can feel free to use them yourself, though obviously you can also use the equivalents from the Func family of delegates instead. Predicate<T> – delegate for determining matches The Predicate<T> delegate was a very early delegate developed in the .NET 2.0 Framework to determine if an item was a match for some condition in a List<T> or T[].  The methods that tend to use the Predicate<T> include: Find(), FindAll(), FindLast() Uses the Predicate<T> delegate to finds items, in a list/array of type T, that matches the given predicate. FindIndex(), FindLastIndex() Uses the Predicate<T> delegate to find the index of an item, of in a list/array of type T, that matches the given predicate. The signature of the Predicate<T> delegate (ignoring variance for the moment) is: 1: public delegate bool Predicate<T>(T obj); So, this is a delegate type that supports any method taking an item of type T and returning bool.  In addition, there is a semantic understanding that this predicate is supposed to be examining the item supplied to see if it matches a given criteria. 1: // finds first even number (2) 2: var firstEven = Array.Find(numbers, n => (n % 2) == 0); 3:  4: // finds all odd numbers (1, 3, 5, 7, 9) 5: var allEvens = Array.FindAll(numbers, n => (n % 2) == 1); 6:  7: // find index of first multiple of 5 (4) 8: var firstFiveMultiplePos = Array.FindIndex(numbers, n => (n % 5) == 0); This delegate has typically been succeeded in LINQ by the more general Func family, so that Predicate<T> and Func<T, bool> are logically identical.  Strictly speaking, though, they are different types, so a delegate reference of type Predicate<T> cannot be directly assigned to a delegate reference of type Func<T, bool>, though the same method can be assigned to both. 1: // SUCCESS: the same lambda can be assigned to either 2: Predicate<DateTime> isSameDayPred = dt => dt.Date == DateTime.Today; 3: Func<DateTime, bool> isSameDayFunc = dt => dt.Date == DateTime.Today; 4:  5: // ERROR: once they are assigned to a delegate type, they are strongly 6: // typed and cannot be directly assigned to other delegate types. 7: isSameDayPred = isSameDayFunc; When you assign a method to a delegate, all that is required is that the signature matches.  This is why the same method can be assigned to either delegate type since their signatures are the same.  However, once the method has been assigned to a delegate type, it is now a strongly-typed reference to that delegate type, and it cannot be assigned to a different delegate type (beyond the bounds of variance depending on Framework version, of course). Comparison<T> – delegate for determining order Just as the Predicate<T> generic delegate was birthed to give Array and List<T> the ability to perform type-safe matching, the Comparison<T> was birthed to give them the ability to perform type-safe ordering. The Comparison<T> is used in Array and List<T> for: Sort() A form of the Sort() method that takes a comparison delegate; this is an alternate way to custom sort a list/array from having to define custom IComparer<T> classes. The signature for the Comparison<T> delegate looks like (without variance): 1: public delegate int Comparison<T>(T lhs, T rhs); The goal of this delegate is to compare the left-hand-side to the right-hand-side and return a negative number if the lhs < rhs, zero if they are equal, and a positive number if the lhs > rhs.  Generally speaking, null is considered to be the smallest value of any reference type, so null should always be less than non-null, and two null values should be considered equal. In most sort/ordering methods, you must specify an IComparer<T> if you want to do custom sorting/ordering.  The Array and List<T> types, however, also allow for an alternative Comparison<T> delegate to be used instead, essentially, this lets you perform the custom sort without having to have the custom IComparer<T> class defined. It should be noted, however, that the LINQ OrderBy(), and ThenBy() family of methods do not support the Comparison<T> delegate (though one could easily add their own extension methods to create one, or create an IComparer() factory class that generates one from a Comparison<T>). So, given this delegate, we could use it to perform easy sorts on an Array or List<T> based on custom fields.  Say for example we have a data class called Employee with some basic employee information: 1: public sealed class Employee 2: { 3: public string Name { get; set; } 4: public int Id { get; set; } 5: public double Salary { get; set; } 6: } And say we had a List<Employee> that contained data, such as: 1: var employees = new List<Employee> 2: { 3: new Employee { Name = "John Smith", Id = 2, Salary = 37000.0 }, 4: new Employee { Name = "Jane Doe", Id = 1, Salary = 57000.0 }, 5: new Employee { Name = "John Doe", Id = 5, Salary = 60000.0 }, 6: new Employee { Name = "Jane Smith", Id = 3, Salary = 59000.0 } 7: }; Now, using the Comparison<T> delegate form of Sort() on the List<Employee>, we can sort our list many ways: 1: // sort based on employee ID 2: employees.Sort((lhs, rhs) => Comparer<int>.Default.Compare(lhs.Id, rhs.Id)); 3:  4: // sort based on employee name 5: employees.Sort((lhs, rhs) => string.Compare(lhs.Name, rhs.Name)); 6:  7: // sort based on salary, descending (note switched lhs/rhs order for descending) 8: employees.Sort((lhs, rhs) => Comparer<double>.Default.Compare(rhs.Salary, lhs.Salary)); So again, you could use this older delegate, which has a lot of logical meaning to it’s name, or use a generic delegate such as Func<T, T, int> to implement the same sort of behavior.  All this said, one of the reasons, in my opinion, that Comparison<T> isn’t used too often is that it tends to need complex lambdas, and the LINQ ability to order based on projections is much easier to use, though the Array and List<T> sorts tend to be more efficient if you want to perform in-place ordering. Converter<TInput, TOutput> – delegate to convert elements The Converter<TInput, TOutput> delegate is used by the Array and List<T> delegate to specify how to convert elements from an array/list of one type (TInput) to another type (TOutput).  It is used in an array/list for: ConvertAll() Converts all elements from a List<TInput> / TInput[] to a new List<TOutput> / TOutput[]. The delegate signature for Converter<TInput, TOutput> is very straightforward (ignoring variance): 1: public delegate TOutput Converter<TInput, TOutput>(TInput input); So, this delegate’s job is to taken an input item (of type TInput) and convert it to a return result (of type TOutput).  Again, this is logically equivalent to a newer Func delegate with a signature of Func<TInput, TOutput>.  In fact, the latter is how the LINQ conversion methods are defined. So, we could use the ConvertAll() syntax to convert a List<T> or T[] to different types, such as: 1: // get a list of just employee IDs 2: var empIds = employees.ConvertAll(emp => emp.Id); 3:  4: // get a list of all emp salaries, as int instead of double: 5: var empSalaries = employees.ConvertAll(emp => (int)emp.Salary); Note that the expressions above are logically equivalent to using LINQ’s Select() method, which gives you a lot more power: 1: // get a list of just employee IDs 2: var empIds = employees.Select(emp => emp.Id).ToList(); 3:  4: // get a list of all emp salaries, as int instead of double: 5: var empSalaries = employees.Select(emp => (int)emp.Salary).ToList(); The only difference with using LINQ is that many of the methods (including Select()) are deferred execution, which means that often times they will not perform the conversion for an item until it is requested.  This has both pros and cons in that you gain the benefit of not performing work until it is actually needed, but on the flip side if you want the results now, there is overhead in the behind-the-scenes work that support deferred execution (it’s supported by the yield return / yield break keywords in C# which define iterators that maintain current state information). In general, the new LINQ syntax is preferred, but the older Array and List<T> ConvertAll() methods are still around, as is the Converter<TInput, TOutput> delegate. Sidebar: Variance support update in .NET 4.0 Just like our descriptions of Func and Action, these three early generic delegates also support more variance in assignment as of .NET 4.0.  Their new signatures are: 1: // comparison is contravariant on type being compared 2: public delegate int Comparison<in T>(T lhs, T rhs); 3:  4: // converter is contravariant on input and covariant on output 5: public delegate TOutput Contravariant<in TInput, out TOutput>(TInput input); 6:  7: // predicate is contravariant on input 8: public delegate bool Predicate<in T>(T obj); Thus these delegates can now be assigned to delegates allowing for contravariance (going to a more derived type) or covariance (going to a less derived type) based on whether the parameters are input or output, respectively. Summary Today, we wrapped up our generic delegates discussion by looking at three lesser-used delegates: Predicate<T>, Comparison<T>, and Converter<TInput, TOutput>.  All three of these tend to be replaced by their more generic Func equivalents in LINQ, but that doesn’t mean you shouldn’t understand what they do or can’t use them for your own code, as they do contain semantic meanings in their names that sometimes get lost in the more generic Func name.   Tweet Technorati Tags: C#,CSharp,.NET,Little Wonders,delegates,generics,Predicate,Converter,Comparison

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  • Dryad and DryadLINQ from MSR

    - by Daniel Moth
    Microsoft Research (MSR) researches technologies, incubates projects which many times result in technology that looks like a ready-to-use product (but it is important to understand that these are not the same as products built by the various… actual product teams here at Microsoft). A very popular MSR project has been DryadLINQ, which itself builds on Dryad. To learn more follow the project pages I just linked to and I also recommend this 1-hour channel 9 video. If you only have 3 minutes, watch this great elevator pitch instead. You can also stay tuned on the official blog, which includes a post that refers to internal adoption e.g by Bing, a quick DryadLINQ code example, and some history on how DryadLINQ generalizes the MapReduce pattern and makes it accessible to regular programmers (see this post and that post). Essentially, the DryadLINQ framework (building on the Dryad runtime) allows developers to re-use their LINQ skills for creating/generating programs that process large multi-gigabyte/terabyte datasets across 100s-1000s of machines. One way to think about it is that just as Parallel LINQ allows LINQ developers to seamlessly use multiple cores from a single process on a single machine, DryadLINQ allows LINQ developers to seamlessly use multiple machines for their data parallel algorithms. In the former scenario the motivation was speed of execution, in the latter it is speed of execution AND processing large datasets that simply don't fit on a single machine. Whenever I hear about execution of parallel code on multiple machines on the Microsoft platform, I immediately think of Windows HPC Server. Indeed Dryad and DryadLINQ were made available for Windows HPC Server and I encourage you to watch the PDC session on this topic: Data-Intensive Computing on Windows HPC Server with the DryadLINQ Framework. Watch this space… Comments about this post welcome at the original blog.

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  • Azure &ndash; Part 5 &ndash; Repository Pattern for Table Service

    - by Shaun
    In my last post I created a very simple WCF service with the user registration functionality. I created an entity for the user data and a DataContext class which provides some methods for operating the entities such as add, delete, etc. And in the service method I utilized it to add a new entity into the table service. But I didn’t have any validation before registering which is not acceptable in a real project. So in this post I would firstly add some validation before perform the data creation code and show how to use the LINQ for the table service.   LINQ to Table Service Since the table service utilizes ADO.NET Data Service to expose the data and the managed library of ADO.NET Data Service supports LINQ we can use it to deal with the data of the table service. Let me explain with my current example: I would like to ensure that when register a new user the email address should be unique. So I need to check the account entities in the table service before add. If you remembered, in my last post I mentioned that there’s a method in the TableServiceContext class – CreateQuery, which will create a IQueryable instance from a given type of entity. So here I would create a method under my AccountDataContext class to return the IQueryable<Account> which named Load. 1: public class AccountDataContext : TableServiceContext 2: { 3: private CloudStorageAccount _storageAccount; 4:  5: public AccountDataContext(CloudStorageAccount storageAccount) 6: : base(storageAccount.TableEndpoint.AbsoluteUri, storageAccount.Credentials) 7: { 8: _storageAccount = storageAccount; 9:  10: var tableStorage = new CloudTableClient(_storageAccount.TableEndpoint.AbsoluteUri, 11: _storageAccount.Credentials); 12: tableStorage.CreateTableIfNotExist("Account"); 13: } 14:  15: public void Add(Account accountToAdd) 16: { 17: AddObject("Account", accountToAdd); 18: SaveChanges(); 19: } 20:  21: public IQueryable<Account> Load() 22: { 23: return CreateQuery<Account>("Account"); 24: } 25: } The method returns the IQueryable<Account> so that I can perform the LINQ operation on it. And back to my service class, I will use it to implement my validation. 1: public bool Register(string email, string password) 2: { 3: var storageAccount = CloudStorageAccount.FromConfigurationSetting("DataConnectionString"); 4: var accountToAdd = new Account(email, password) { DateCreated = DateTime.Now }; 5: var accountContext = new AccountDataContext(storageAccount); 6:  7: // validation 8: var accountNumber = accountContext.Load() 9: .Where(a => a.Email == accountToAdd.Email) 10: .Count(); 11: if (accountNumber > 0) 12: { 13: throw new ApplicationException(string.Format("Your account {0} had been used.", accountToAdd.Email)); 14: } 15:  16: // create entity 17: try 18: { 19: accountContext.Add(accountToAdd); 20: return true; 21: } 22: catch (Exception ex) 23: { 24: Trace.TraceInformation(ex.ToString()); 25: } 26: return false; 27: } I used the Load method to retrieve the IQueryable<Account> and use Where method to find the accounts those email address are the same as the one is being registered. If it has I through an exception back to the client side. Let’s run it and test from my simple client application. Oops! Looks like we encountered an unexpected exception. It said the “Count” is not support by the ADO.NET Data Service LINQ managed library. That is because the table storage managed library (aka. TableServiceContext) is based on the ADO.NET Data Service and it supports very limit LINQ operation. Although I didn’t find a full list or documentation about which LINQ methods it supports I could even refer a page on msdn here. It gives us a roughly summary of which query operation the ADO.NET Data Service managed library supports and which doesn't. As you see the Count method is not in the supported list. Not only the query operation, there inner lambda expression in the Where method are limited when using the ADO.NET Data Service managed library as well. For example if you added (a => !a.DateDeleted.HasValue) in the Where method to exclude those deleted account it will raised an exception said "Invalid Input". Based on my experience you should always use the simple comparison (such as ==, >, <=, etc.) on the simple members (such as string, integer, etc.) and do not use any shortcut methods (such as string.Compare, string.IsNullOrEmpty etc.). 1: // validation 2: var accountNumber = accountContext.Load() 3: .Where(a => a.Email == accountToAdd.Email) 4: .ToList() 5: .Count; 6: if (accountNumber > 0) 7: { 8: throw new ApplicationException(string.Format("Your account {0} had been used.", accountToAdd.Email)); 9: } We changed the a bit and try again. Since I had created an account with my mail address so this time it gave me an exception said that the email had been used, which is correct.   Repository Pattern for Table Service The AccountDataContext takes the responsibility to save and load the account entity but only for that specific entity. Is that possible to have a dynamic or generic DataContext class which can operate any kinds of entity in my system? Of course yes. Although there's no typical database in table service we can threat the entities as the records, similar with the data entities if we used OR Mapping. As we can use some patterns for ORM architecture here we should be able to adopt the one of them - Repository Pattern in this example. We know that the base class - TableServiceContext provide 4 methods for operating the table entities which are CreateQuery, AddObject, UpdateObject and DeleteObject. And we can create a relationship between the enmity class, the table container name and entity set name. So it's really simple to have a generic base class for any kinds of entities. Let's rename the AccountDataContext to DynamicDataContext and make the type of Account as a type parameter if it. 1: public class DynamicDataContext<T> : TableServiceContext where T : TableServiceEntity 2: { 3: private CloudStorageAccount _storageAccount; 4: private string _entitySetName; 5:  6: public DynamicDataContext(CloudStorageAccount storageAccount) 7: : base(storageAccount.TableEndpoint.AbsoluteUri, storageAccount.Credentials) 8: { 9: _storageAccount = storageAccount; 10: _entitySetName = typeof(T).Name; 11:  12: var tableStorage = new CloudTableClient(_storageAccount.TableEndpoint.AbsoluteUri, 13: _storageAccount.Credentials); 14: tableStorage.CreateTableIfNotExist(_entitySetName); 15: } 16:  17: public void Add(T entityToAdd) 18: { 19: AddObject(_entitySetName, entityToAdd); 20: SaveChanges(); 21: } 22:  23: public void Update(T entityToUpdate) 24: { 25: UpdateObject(entityToUpdate); 26: SaveChanges(); 27: } 28:  29: public void Delete(T entityToDelete) 30: { 31: DeleteObject(entityToDelete); 32: SaveChanges(); 33: } 34:  35: public IQueryable<T> Load() 36: { 37: return CreateQuery<T>(_entitySetName); 38: } 39: } I saved the name of the entity type when constructed for performance matter. The table name, entity set name would be the same as the name of the entity class. The Load method returned a generic IQueryable instance which supports the lazy load feature. Then in my service class I changed the AccountDataContext to DynamicDataContext and that's all. 1: var accountContext = new DynamicDataContext<Account>(storageAccount); Run it again and register another account. The DynamicDataContext now can be used for any entities. For example, I would like the account has a list of notes which contains 3 custom properties: Account Email, Title and Content. We create the note entity class. 1: public class Note : TableServiceEntity 2: { 3: public string AccountEmail { get; set; } 4: public string Title { get; set; } 5: public string Content { get; set; } 6: public DateTime DateCreated { get; set; } 7: public DateTime? DateDeleted { get; set; } 8:  9: public Note() 10: : base() 11: { 12: } 13:  14: public Note(string email) 15: : base(email, string.Format("{0}_{1}", email, Guid.NewGuid().ToString())) 16: { 17: AccountEmail = email; 18: } 19: } And no need to tweak the DynamicDataContext we can directly go to the service class to implement the logic. Notice here I utilized two DynamicDataContext instances with the different type parameters: Note and Account. 1: public class NoteService : INoteService 2: { 3: public void Create(string email, string title, string content) 4: { 5: var storageAccount = CloudStorageAccount.FromConfigurationSetting("DataConnectionString"); 6: var accountContext = new DynamicDataContext<Account>(storageAccount); 7: var noteContext = new DynamicDataContext<Note>(storageAccount); 8:  9: // validate - email must be existed 10: var accounts = accountContext.Load() 11: .Where(a => a.Email == email) 12: .ToList() 13: .Count; 14: if (accounts <= 0) 15: throw new ApplicationException(string.Format("The account {0} does not exsit in the system please register and try again.", email)); 16:  17: // save the note 18: var noteToAdd = new Note(email) { Title = title, Content = content, DateCreated = DateTime.Now }; 19: noteContext.Add(noteToAdd); 20: } 21: } And updated our client application to test the service. I didn't implement any list service to show all notes but we can have a look on the local SQL database if we ran it at local development fabric.   Summary In this post I explained a bit about the limited LINQ support for the table service. And then I demonstrated about how to use the repository pattern in the table service data access layer and make the DataContext dynamically. The DynamicDataContext I created in this post is just a prototype. In fact we should create the relevant interface to make it testable and for better structure we'd better separate the DataContext classes for each individual kind of entity. So it should have IDataContextBase<T>, DataContextBase<T> and for each entity we would have class AccountDataContext<Account> : IDataContextBase<Account>, DataContextBase<Account> { … } class NoteDataContext<Note> : IDataContextBase<Note>, DataContextBase<Note> { … }   Besides the structured data saving and loading, another common scenario would be saving and loading some binary data such as images, files. In my next post I will show how to use the Blob Service to store the bindery data - make the account be able to upload their logo in my example.   Hope this helps, Shaun   All documents and related graphics, codes are provided "AS IS" without warranty of any kind. Copyright © Shaun Ziyan Xu. This work is licensed under the Creative Commons License.

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  • Help needed on an SQL configuration problem.

    - by user321048
    I have been banging my head with this one more the two weeks, and still don't know what the problem is ( I can't narrow it down). The problem is the following. I have a solution with 3 project in it all written in c# and I with LINQ. One project is the main web site, the other is the data layer (communication with the database) and the third one is a custom little CMS. The problem is the following: On a hosting provider when I publish the site it all works perfectly, but this site was needed to be hosted on the client server so I needed to do that. But the problem is that I also needed to configure the client server, because they don't have an Administrator employed (I know, I know ;) ). For the first time I some how managed, to set it up but a problem appear. My main web site is working just as it suppose to be - it reads (communicates with) the database, but My CMS is not. It shows the first log in page, but after that when I try to log in it throws the following error: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: TCP Provider, error: 0 - A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.) Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Data.SqlClient.SqlException: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: TCP Provider, error: 0 - A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.) Source Error: An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. Stack Trace: [SqlException (0x80131904): A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: TCP Provider, error: 0 - A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.)] System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) +4846887 System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) +194 System.Data.SqlClient.TdsParser.Connect(ServerInfo serverInfo, SqlInternalConnectionTds connHandler, Boolean ignoreSniOpenTimeout, Int64 timerExpire, Boolean encrypt, Boolean trustServerCert, Boolean integratedSecurity, SqlConnection owningObject) +4860189 System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, Boolean ignoreSniOpenTimeout, Int64 timerExpire, SqlConnection owningObject) +90 System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(String host, String newPassword, Boolean redirectedUserInstance, SqlConnection owningObject, SqlConnectionString connectionOptions, Int64 timerStart) +342 System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(SqlConnection owningObject, SqlConnectionString connectionOptions, String newPassword, Boolean redirectedUserInstance) +221 System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, Object providerInfo, String newPassword, SqlConnection owningObject, Boolean redirectedUserInstance) +189 System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection) +185 System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnection owningConnection, DbConnectionPool pool, DbConnectionOptions options) +31 System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject) +433 System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject) +66 System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject) +499 System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection) +65 System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory) +117 System.Data.SqlClient.SqlConnection.Open() +122 System.Data.Linq.SqlClient.SqlConnectionManager.UseConnection(IConnectionUser user) +44 System.Data.Linq.SqlClient.SqlProvider.get_IsSqlCe() +45 System.Data.Linq.SqlClient.SqlProvider.InitializeProviderMode() +20 System.Data.Linq.SqlClient.SqlProvider.System.Data.Linq.Provider.IProvider.Execute(Expression query) +57 System.Data.Linq.DataQuery`1.System.Linq.IQueryProvider.Execute(Expression expression) +23 System.Linq.Queryable.Count(IQueryable`1 source) +240 CMS.Security.UserProfile.LoginUser() in C:\Documents and Settings\Dimitar\Desktop\New Mepso Final 08_04\CMS\Classes\UserProfile.cs:132 CMS.Default.Login1_Authenticate(Object sender, AuthenticateEventArgs e) in C:\Documents and Settings\Dimitar\Desktop\New Mepso Final 08_04\CMS\Default.aspx.cs:37 System.Web.UI.WebControls.Login.OnAuthenticate(AuthenticateEventArgs e) +108 System.Web.UI.WebControls.Login.AttemptLogin() +115 System.Web.UI.WebControls.Login.OnBubbleEvent(Object source, EventArgs e) +101 System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args) +37 System.Web.UI.WebControls.Button.OnCommand(CommandEventArgs e) +118 System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +166 System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10 System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13 System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +36 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1565 Maybe this is a dumb question, but I cannot find the root of the problem, let alone the solution. So far I have tried the following: -setting time out on connection string to a higher value -configuration and after that turning off server firewall -checking the connection string over and over again (they are the same for all three projects and are saved in web.config) Important notes: I have tried executing the project from VS2008 with a connection string to the same database and the results are the same. That's why I think the problem is the SQL Server 2005 and not the IIS7. Any bit of information is more then welcomed.

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  • [C#] Not enough memory or not enough handles?

    - by Nayan
    I am working on a large scale project where a custom (pretty good and robust) framework has been provided and we have to use that for showing up forms and views. There is abstract class StrategyEditor (derived from some class in framework) which is instantiated whenever a new StrategyForm is opened. StrategyForm (a customized window frame) contains StrategyEditor. StrategyEditor contains StrategyTab. StrategyTab contains StrategyCanvas. This is a small portion of the big classes to clarify that there are many objects that will be created if one StrategyForm object is allocated in memory at run-time. My component owns all these classes mentioned above except StrategyForm whose code is not in my control. Now, at run-time, user opens up many strategy objects (which trigger creation of new StrategyForm object.) After creating approx. 44 strategy objects, we see that the USER OBJECT HANDLES (I'll use UOH from here onwards) created by the application reaches to about 20k+, while in registry the default amount for handles is 10k. Read more about User Objects here. Testing on different machines made it clear that the number of strategy objects opened is different for message to pop-up - on one m/c if it is 44, then it can be 40 on another. When we see the message pop-up, it means that the application is going to respond slowly. It gets worse with few more objects and then creation of window frames and subsequent objects fail. We first thought that it was not-enough-memory issue. But then reading more about new in C# helped in understanding that an exception would be thrown if app ran out of memory. This is not a memory issue then, I feel (task manager also showed 1.5GB+ available memory.) M/C specs Core 2 Duo 2GHz+ 4GB RAM 80GB+ free disk space for page file Virtual Memory set: 4000 - 6000 My questions Q1. Does this look like a memory issue and I am wrong that it is not? Q2. Does this point to exhaustion of free UOHs (as I'm thinking) and which is resulting in failure of creation of window handles? Q3. How can we avoid loading up of an StrategyEditor object (beyond a threshold, keeping an eye on the current usage of UOHs)? (we already know how to fetch number of UOHs in use, so don't go there.) Keep in mind that the call to new StrategyForm() is outside the control of my component. Q4. I am bit confused - what are Handles to user objects exactly? Is MSDN talking about any object that we create or only some specific objects like window handles, cursor handles, icon handles? Q5. What exactly cause to use up a UOH? (almost same as Q4) I would be really thankful to anyone who can give me some knowledgeable answers. Thanks much! :)

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