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  • Using RIA DomainServices with ASP.NET and MVC 2

    - by Bobby Diaz
    Recently, I started working on a new ASP.NET MVC 2 project and I wanted to reuse the data access (LINQ to SQL) and business logic methods (WCF RIA Services) that had been developed for a previous project that used Silverlight for the front-end.  I figured that I would be able to instantiate the various DomainService classes from within my controller’s action methods, because after all, the code for those services didn’t look very complicated.  WRONG!  I didn’t realize at first that some of the functionality is handled automatically by the framework when the domain services are hosted as WCF services.  After some initial searching, I came across an invaluable post by Joe McBride, which described how to get RIA Service .svc files to work in an MVC 2 Web Application, and another by Brad Abrams.  Unfortunately, Brad’s solution was for an earlier preview release of RIA Services and no longer works with the version that I am running (PDC Preview). I have not tried the RC version of WCF RIA Services, so I am not sure if any of the issues I am having have been resolved, but I wanted to come up with a way to reuse the shared libraries so I wouldn’t have to write a non-RIA version that basically did the same thing.  The classes I came up with work with the scenarios I have encountered so far, but I wanted to go ahead and post the code in case someone else is having the same trouble I had.  Hopefully this will save you a few headaches! 1. Querying When I first tried to use a DomainService class to perform a query inside one of my controller’s action methods, I got an error stating that “This DomainService has not been initialized.”  To solve this issue, I created an extension method for all DomainServices that creates the required DomainServiceContext and passes it to the service’s Initialize() method.  Here is the code for the extension method; notice that I am creating a sort of mock HttpContext for those cases when the service is running outside of IIS, such as during unit testing!     public static class ServiceExtensions     {         /// <summary>         /// Initializes the domain service by creating a new <see cref="DomainServiceContext"/>         /// and calling the base DomainService.Initialize(DomainServiceContext) method.         /// </summary>         /// <typeparam name="TService">The type of the service.</typeparam>         /// <param name="service">The service.</param>         /// <returns></returns>         public static TService Initialize<TService>(this TService service)             where TService : DomainService         {             var context = CreateDomainServiceContext();             service.Initialize(context);             return service;         }           private static DomainServiceContext CreateDomainServiceContext()         {             var provider = new ServiceProvider(new HttpContextWrapper(GetHttpContext()));             return new DomainServiceContext(provider, DomainOperationType.Query);         }           private static HttpContext GetHttpContext()         {             var context = HttpContext.Current;   #if DEBUG             // create a mock HttpContext to use during unit testing...             if ( context == null )             {                 var writer = new StringWriter();                 var request = new SimpleWorkerRequest("/", "/",                     String.Empty, String.Empty, writer);                   context = new HttpContext(request)                 {                     User = new GenericPrincipal(new GenericIdentity("debug"), null)                 };             } #endif               return context;         }     }   With that in place, I can use it almost as normally as my first attempt, except with a call to Initialize():     public ActionResult Index()     {         var service = new NorthwindService().Initialize();         var customers = service.GetCustomers();           return View(customers);     } 2. Insert / Update / Delete Once I got the records showing up, I was trying to insert new records or update existing data when I ran into the next issue.  I say issue because I wasn’t getting any kind of error, which made it a little difficult to track down.  But once I realized that that the DataContext.SubmitChanges() method gets called automatically at the end of each domain service submit operation, I could start working on a way to mimic the behavior of a hosted domain service.  What I came up with, was a base class called LinqToSqlRepository<T> that basically sits between your implementation and the default LinqToSqlDomainService<T> class.     [EnableClientAccess()]     public class NorthwindService : LinqToSqlRepository<NorthwindDataContext>     {         public IQueryable<Customer> GetCustomers()         {             return this.DataContext.Customers;         }           public void InsertCustomer(Customer customer)         {             this.DataContext.Customers.InsertOnSubmit(customer);         }           public void UpdateCustomer(Customer currentCustomer)         {             this.DataContext.Customers.TryAttach(currentCustomer,                 this.ChangeSet.GetOriginal(currentCustomer));         }           public void DeleteCustomer(Customer customer)         {             this.DataContext.Customers.TryAttach(customer);             this.DataContext.Customers.DeleteOnSubmit(customer);         }     } Notice the new base class name (just change LinqToSqlDomainService to LinqToSqlRepository).  I also added a couple of DataContext (for Table<T>) extension methods called TryAttach that will check to see if the supplied entity is already attached before attempting to attach it, which would cause an error! 3. LinqToSqlRepository<T> Below is the code for the LinqToSqlRepository class.  The comments are pretty self explanatory, but be aware of the [IgnoreOperation] attributes on the generic repository methods, which ensures that they will be ignored by the code generator and not available in the Silverlight client application.     /// <summary>     /// Provides generic repository methods on top of the standard     /// <see cref="LinqToSqlDomainService&lt;TContext&gt;"/> functionality.     /// </summary>     /// <typeparam name="TContext">The type of the context.</typeparam>     public abstract class LinqToSqlRepository<TContext> : LinqToSqlDomainService<TContext>         where TContext : System.Data.Linq.DataContext, new()     {         /// <summary>         /// Retrieves an instance of an entity using it's unique identifier.         /// </summary>         /// <typeparam name="TEntity">The type of the entity.</typeparam>         /// <param name="keyValues">The key values.</param>         /// <returns></returns>         [IgnoreOperation]         public virtual TEntity GetById<TEntity>(params object[] keyValues) where TEntity : class         {             var table = this.DataContext.GetTable<TEntity>();             var mapping = this.DataContext.Mapping.GetTable(typeof(TEntity));               var keys = mapping.RowType.IdentityMembers                 .Select((m, i) => m.Name + " = @" + i)                 .ToArray();               return table.Where(String.Join(" && ", keys), keyValues).FirstOrDefault();         }           /// <summary>         /// Creates a new query that can be executed to retrieve a collection         /// of entities from the <see cref="DataContext"/>.         /// </summary>         /// <typeparam name="TEntity">The type of the entity.</typeparam>         /// <returns></returns>         [IgnoreOperation]         public virtual IQueryable<TEntity> GetEntityQuery<TEntity>() where TEntity : class         {             return this.DataContext.GetTable<TEntity>();         }           /// <summary>         /// Inserts the specified entity.         /// </summary>         /// <typeparam name="TEntity">The type of the entity.</typeparam>         /// <param name="entity">The entity.</param>         /// <returns></returns>         [IgnoreOperation]         public virtual bool Insert<TEntity>(TEntity entity) where TEntity : class         {             //var table = this.DataContext.GetTable<TEntity>();             //table.InsertOnSubmit(entity);               return this.Submit(entity, null, DomainOperation.Insert);         }           /// <summary>         /// Updates the specified entity.         /// </summary>         /// <typeparam name="TEntity">The type of the entity.</typeparam>         /// <param name="entity">The entity.</param>         /// <returns></returns>         [IgnoreOperation]         public virtual bool Update<TEntity>(TEntity entity) where TEntity : class         {             return this.Update(entity, null);         }           /// <summary>         /// Updates the specified entity.         /// </summary>         /// <typeparam name="TEntity">The type of the entity.</typeparam>         /// <param name="entity">The entity.</param>         /// <param name="original">The original.</param>         /// <returns></returns>         [IgnoreOperation]         public virtual bool Update<TEntity>(TEntity entity, TEntity original)             where TEntity : class         {             if ( original == null )             {                 original = GetOriginal(entity);             }               var table = this.DataContext.GetTable<TEntity>();             table.TryAttach(entity, original);               return this.Submit(entity, original, DomainOperation.Update);         }           /// <summary>         /// Deletes the specified entity.         /// </summary>         /// <typeparam name="TEntity">The type of the entity.</typeparam>         /// <param name="entity">The entity.</param>         /// <returns></returns>         [IgnoreOperation]         public virtual bool Delete<TEntity>(TEntity entity) where TEntity : class         {             //var table = this.DataContext.GetTable<TEntity>();             //table.TryAttach(entity);             //table.DeleteOnSubmit(entity);               return this.Submit(entity, null, DomainOperation.Delete);         }           protected virtual bool Submit(Object entity, Object original, DomainOperation operation)         {             var entry = new ChangeSetEntry(0, entity, original, operation);             var changes = new ChangeSet(new ChangeSetEntry[] { entry });             return base.Submit(changes);         }           private TEntity GetOriginal<TEntity>(TEntity entity) where TEntity : class         {             var context = CreateDataContext();             var table = context.GetTable<TEntity>();             return table.FirstOrDefault(e => e == entity);         }     } 4. Conclusion So there you have it, a fully functional Repository implementation for your RIA Domain Services that can be consumed by your ASP.NET and MVC applications.  I have uploaded the source code along with unit tests and a sample web application that queries the Customers table from inside a Controller, as well as a Silverlight usage example. As always, I welcome any comments or suggestions on the approach I have taken.  If there is enough interest, I plan on contacting Colin Blair or maybe even the man himself, Brad Abrams, to see if this is something worthy of inclusion in the WCF RIA Services Contrib project.  What do you think? Enjoy!

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  • CodePlex Daily Summary for Monday, June 20, 2011

    CodePlex Daily Summary for Monday, June 20, 2011Popular ReleasesBlogEngine.NET: BlogEngine.NET 2.5 RC: BlogEngine.NET Hosting - Click Here! 3 Months FREE – BlogEngine.NET Hosting – Click Here! This is a Release Candidate version for BlogEngine.NET 2.5. The most current, stable version of BlogEngine.NET is version 2.0. Find out more about the BlogEngine.NET 2.5 RC here. If you want to extend or modify BlogEngine.NET, you should download the source code. Also, please note at this time the Mercurial source code repository on the Source Code tab is having issues, but will be fixed shortly. I...Microsoft All-In-One Code Framework - a centralized code sample library: All-In-One Code Framework 2011-06-19: Alternatively, you can install Sample Browser or Sample Browser VS extension, and download the code samples from Sample Browser. Improved and Newly Added Examples:For an up-to-date code sample index, please refer to All-In-One Code Framework Sample Catalog. NEW Samples for Windows Azure Sample Description Owner CSAzureStartupTask The sample demonstrates using the startup tasks to install the prerequisites or to modify configuration settings for your environment in Windows Azure Rafe Wu ...Facebook C# SDK: 5.0.40: This is a RTW release which adds new features to v5.0.26 RTW. Support for multiple FacebookMediaObjects in one request. Allow FacebookMediaObjects in batch requests. Removes support for Cassini WebServer (visual studio inbuilt web server). Better support for unit testing and mocking. updated SimpleJson to v0.6 Refer to CHANGES.txt for details. For more information about this release see the following blog posts: Facebook C# SDK - Multiple file uploads in Batch Requests Faceb...Candescent NUI: Candescent NUI (7774): This is the binary version of the source code in change set 7774.Media Companion: MC 3.408b weekly: Some minor fixes..... Fixed messagebox coming up during batch scrape Added <originaltitle></originaltitle> to movie nfo's - when a new movie is scraped, the original title will be set as the returned title. The end user can of course change the title in MC, however the original title will not change. The original title can be seen by hovering over the movie title in the right pane of the main movie tab. To update all of your current nfo's to add the original title the same as your current ...NLog - Advanced .NET Logging: NLog 2.0 Release Candidate: Release notes for NLog 2.0 RC can be found at http://nlog-project.org/nlog-2-rc-release-notesGendering Add-In for Microsoft Office Word 2010: Gendering Add-In: This is the first stable Version of the Gendering Add-In. Unzip the package and start "setup.exe". The .reg file shows how to config an alternate path for suggestion table.TerrariViewer: TerrariViewer v3.1 [Terraria Inventory Editor]: This version adds tool tips. Almost every picture box you mouse over will tell you what item is in that box. I have also cleaned up the GUI a little more to make things easier on my end. There are various bug fixes including ones associated with opening different characters in the same instance of the program. As always, please bring any bugs you find to my attention.Kinect Paint: KinectPaint V1.0: This is version 1.0 of Kinect Paint. To run it, follow the steps: Install the Kinect SDK for Windows (available at http://research.microsoft.com/en-us/um/redmond/projects/kinectsdk/download.aspx) Connect your Kinect device to the computer and to the power. Download the Zip file. Unblock the Zip file by right clicking on it, and pressing the Unblock button in the file properties (if available). Extract the content of the Zip file. Run KinectPaint.exe.CommonLibrary.NET: CommonLibrary.NET - 0.9.7 Beta: A collection of very reusable code and components in C# 3.5 ranging from ActiveRecord, Csv, Command Line Parsing, Configuration, Holiday Calendars, Logging, Authentication, and much more. Samples in <root>\src\Lib\CommonLibrary.NET\Samples CommonLibrary.NET 0.9.7Documentation 6738 6503 New 6535 Enhancements 6583 6737DropBox Linker: DropBox Linker 1.2: Public sub-folders are now monitored for changes as well (thanks to mcm69) Automatic public sync folder detection (thanks to mcm69) Non-Latin and special characters encoded correctly in URLs Pop-ups are now slot-based (use first free slot and will never be overlapped — test it while previewing timeout) Public sync folder setting is hidden when auto-detected Timeout interval is displayed in popup previews A lot of major and minor code refactoring performed .NET Framework 4.0 Client...Terraria World Viewer: Version 1.3.1: Update June 20th Removed "Draw Markers" checkbox from main window because of redundancy/confusing. (Select all or no items from the Settings tab for the same effect.) Fixed Marker preferences not being saved. It is now possible to render more than one map without having to restart the application. World file will not be locked while the world is being rendered. Note: The World Viewer might render an inaccurate map or even crash if Terraria decides to modify the World file during the pro...MVC Controls Toolkit: Mvc Controls Toolkit 1.1.5 RC: Added Extended Dropdown allows a prompt item to be inserted as first element. RequiredAttribute, if present, trggers if no element is chosen Client side javascript function to set/get the values of DateTimeInput, TypedTextBox, TypedEditDisplay, and to bind/unbind a "change" handler The selected page in the pager is applied the attribute selected-page="selected" that can be used in the definition of CSS rules to style the selected page items controls now interpret a null value as an empr...Umbraco CMS: Umbraco CMS 5.0 CTP 1: Umbraco 5 Community Technology Preview Umbraco 5 will be the next version of everyone's favourite, friendly ASP.NET CMS that already powers over 100,000 websites worldwide. Try out our first CTP of version 5 today! If you're new to Umbraco and would like to get a quick low-down on our popular and easy-to-learn approach to content management, check out our intro video here. What's in the v5 CTP box? This is a preview version of version 5 and includes support for the following familiar Umbr...Ribbon Browser for Microsoft Dynamics CRM 2011: Ribbon Browser (1.0.514.30): Initial releaseCoding4Fun Kinect Toolkit: Coding4Fun.Kinect Toolkit: Version 1.0Kinect Mouse Cursor: Kinect Mouse Cursor v1.0: The initial release of the Kinect Mouse Cursor project!patterns & practices: Project Silk: Project Silk Community Drop 11 - June 14, 2011: Changes from previous drop: Many code changes: please see the readme.mht for details. New "Client Data Management and Caching" chapter. Updated "Application Notifications" chapter. Updated "Architecture" chapter. Updated "jQuery UI Widget" chapter. Updated "Widget QuickStart" appendix and code. Guidance Chapters Ready for Review The Word documents for the chapters are included with the source code in addition to the CHM to help you provide feedback. The PDF is provided as a separat...Orchard Project: Orchard 1.2: Build: 1.2.41 Published: 6/14/2010 How to Install Orchard To install Orchard using Web PI, follow these instructions: http://www.orchardproject.net/docs/Installing-Orchard.ashx. Web PI will detect your hardware environment and install the application. Alternatively, to install the release manually, download the Orchard.Web.1.2.41.zip file. http://orchardproject.net/docs/Manually-installing-Orchard-zip-file.ashx The zip contents are pre-built and ready-to-run. Simply extract the contents o...Snippet Designer: Snippet Designer 1.4.0: Snippet Designer 1.4.0 for Visual Studio 2010 Change logSnippet Explorer ChangesReworked language filter UI to work better in the side bar. Added result count drop down which lets you choose how many results to see. Language filter and result count choices are persisted after Visual Studio is closed. Added file name to search criteria. Search is now case insensitive. Snippet Editor Changes Snippet Editor ChangesAdded menu option for the $end$ symbol which indicates where the c...New Projects.NET Dev Tools Dashboard: .NET Dev Tools Dashboard is a WPF application that implements the Prism 4 standards. Modules can be added at runtime and after install of the base Dashboard shell. The first module is a WPF Gui for NAnt based on Colin Svingen's Gui for NAnt open source app for Windows Forms.Chutzpah - A JavaScript Test Runner: Chutzpah helps you integrate JavaScript unit testing into your website. It enables you to run JavaScript unit tests from the command line and from inside of Visual Studio. It also supports running in the TeamCity continuous integration server.Cow connect: Ziel des Projektes Cow connect, ist es ein Tool zu schrieben das Verschiedene Datenbanken, unterschiedlicher Herdenmanagement Tool z.b: Helm Multikuh, Westfalia C21, Holdi,…. Synchron zu halten. oder eine neue Datenbank zu GenerrierenCqrs CWDNUG Demo: A very simple CQRS demo for a presentation at the Canary Wharf Dot Net User Group. Uses Ncqrs, ASP.NET MVC 3. Not best practices - just something to get your teeth into if you're new to CQRS and Event Sourcing.Down123: down123EssionCalendar: EssionCal EssionCalGuardian: Protects reference type parameters and return values from NULL values.Honest Flex Time Management System: A Japanese time management system to handle worker hourlies. Will include some basic reporting functions as well.iStatServer.NET: Server implementation for iPhone iStat app. Windows analogue to iStat Server on OS x or iStatd on linux/solaris. Keolis Service Wrapper: Keolis Service WrapperKinectContrib: A set of extensions and helpers that will facilitate the use of the Microsoft Kinect motion sensor with the Kinect SDK.kingdomwp7: kingdomwp7Laboratório de Engenharia de Software - Projeto: Criado para estudar e aplicar novas tecnologias web.Multi Touch Digit OCR With Matlab Neural Network Wpf Project: Multi Touch Digit OCR Project is a wpf project that works on multi touch devices but it works well on normal devices , this project uses matlab core , that creates 4 feed forward neural network and train them with Back Propagation Algorithm for detecting numbers that you draw .PhoneGap Extensions - Alpha Version: This project was created to solve some issues about PhoneGap. The first issue to solve is how to reuse HTML code through include files. SABnzbd UI: This application is a Windows 7 enabled UI for SABnzbd, so that you don't have to navigate to the website, but instead you can view a slick UI on your desktop.SP:Social: A community project for providing integration points between SharePoint and other social networks like Facebook, LinkedIn, Live etc.Whisk: An extremely simplistic but cross-platform network rending environment for Blender.Windows phone 7, Game framewok: Windows phone 7, Game framewokWP7 - Multi Select Wrapped ListBox: Its a WP 7.1 project which contains a list box that can wrap listBoxItems and can scroll vertically.

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  • How to model a relationship that NHibernate (or Hibernate) doesn’t easily support

    - by MylesRip
    I have a situation in which the ideal relationship, I believe, would involve Value Object Inheritance. This is unfortunately not supported in NHibernate so any solution I come up with will be less than perfect. Let’s say that: “Item” entities have a “Location” that can be in one of multiple different formats. These formats are completely different with no overlapping fields. We will deal with each Location in the format that is provided in the data with no attempt to convert from one format to another. Each Item has exactly one Location. “SpecialItem” is a subtype of Item, however, that is unique in that it has exactly two Locations. “Group” entities aggregate Items. “LocationGroup” is as subtype of Group. LocationGroup also has a single Location that can be in any of the formats as described above. Although I’m interested in Items by Group, I’m also interested in being able to find all items with the same Location, regardless of which group they are in. I apologize for the number of stipulations listed above, but I’m afraid that simplifying it any further wouldn’t really reflect the difficulties of the situation. Here is how the above could be diagrammed: Mapping Dilemma Diagram: (http://www.freeimagehosting.net/uploads/592ad48b1a.jpg) (I tried placing the diagram inline, but Stack Overflow won't allow that until I have accumulated more points. I understand the reasoning behind it, but it is a bit inconvenient for now.) Hmmm... Apparently I can't have multiple links either. :-( Analyzing the above, I make the following observations: I treat Locations polymorphically, referring to the supertype rather than the subtype. Logically, Locations should be “Value Objects” rather than entities since it is meaningless to differentiate between two Location objects that have all the same values. Thus equality between Locations should be based on field comparisons, not identifiers. Also, value objects should be immutable and shared references should not be allowed. Using NHibernate (or Hibernate) one would typically map value objects using the “component” keyword which would cause the fields of the class to be mapped directly into the database table that represents the containing class. Put another way, there would not be a separate “Locations” table in the database (and Locations would therefore have no identifiers). NHibernate (or Hibernate) do not currently support inheritance for value objects. My choices as I see them are: Ignore the fact that Locations should be value objects and map them as entities. This would take care of the inheritance mapping issues since NHibernate supports entity inheritance. The downside is that I then have to deal with aliasing issues. (Meaning that if multiple objects share a reference to the same Location, then changing values for one object’s Location would cause the location to change for other objects that share the reference the same Location record.) I want to avoid this if possible. Another downside is that entities are typically compared by their IDs. This would mean that two Location objects would be considered not equal even if the values of all their fields are the same. This would be invalid and unacceptable from the business perspective. Flatten Locations into a single class so that there are no longer inheritance relationships for Locations. This would allow Locations to be treated as value objects which could easily be handled by using “component” mapping in NHibernate. The downside in this case would be that the domain model becomes weaker, more fragile and less maintainable. Do some “creative” mapping in the hbm files in order to force Location fields to be mapped into the containing entities’ tables without using the “component” keyword. This approach is described by Colin Jack here. My situation is more complicated than the one he describes due to the fact that SpecialItem has a second Location and the fact that a different entity, LocatedGroup, also has Locations. I could probably get it to work, but the mappings would be non-intuitive and therefore hard to understand and maintain by other developers in the future. Also, I suspect that these tricky mappings would likely not be possible using Fluent NHibernate so I would use the advantages of using that tool, at least in that situation. Surely others out there have run into similar situations. I’m hoping someone who has “been there, done that” can share some wisdom. :-) So here’s the question… Which approach should be preferred in this situation? Why?

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  • Curious about IObservable? Here’s a quick example to get you started!

    - by Roman Schindlauer
    Have you heard about IObservable/IObserver support in Microsoft StreamInsight 1.1? Then you probably want to try it out. If this is your first incursion into the IObservable/IObserver pattern, this blog post is for you! StreamInsight 1.1 introduced the ability to use IEnumerable and IObservable objects as event sources and sinks. The IEnumerable case is pretty straightforward, since many data collections are already surfacing as this type. This was already covered by Colin in his blog. Creating your own IObservable event source is a little more involved but no less exciting – here is a primer: First, let’s look at a very simple Observable data source. All it does is publish an integer in regular time periods to its registered observers. (For more information on IObservable, see http://msdn.microsoft.com/en-us/library/dd990377.aspx ). sealed class RandomSubject : IObservable<int>, IDisposable {     private bool _done;     private readonly List<IObserver<int>> _observers;     private readonly Random _random;     private readonly object _sync;     private readonly Timer _timer;     private readonly int _timerPeriod;       /// <summary>     /// Random observable subject. It produces an integer in regular time periods.     /// </summary>     /// <param name="timerPeriod">Timer period (in milliseconds)</param>     public RandomSubject(int timerPeriod)     {         _done = false;         _observers = new List<IObserver<int>>();         _random = new Random();         _sync = new object();         _timer = new Timer(EmitRandomValue);         _timerPeriod = timerPeriod;         Schedule();     }       public IDisposable Subscribe(IObserver<int> observer)     {         lock (_sync)         {             _observers.Add(observer);         }         return new Subscription(this, observer);     }       public void OnNext(int value)     {         lock (_sync)         {             if (!_done)             {                 foreach (var observer in _observers)                 {                     observer.OnNext(value);                 }             }         }     }       public void OnError(Exception e)     {         lock (_sync)         {             foreach (var observer in _observers)             {                 observer.OnError(e);             }             _done = true;         }     }       public void OnCompleted()     {         lock (_sync)         {             foreach (var observer in _observers)             {                 observer.OnCompleted();             }             _done = true;         }     }       void IDisposable.Dispose()     {         _timer.Dispose();     }       private void Schedule()     {         lock (_sync)         {             if (!_done)             {                 _timer.Change(_timerPeriod, Timeout.Infinite);             }         }     }       private void EmitRandomValue(object _)     {         var value = (int)(_random.NextDouble() * 100);         Console.WriteLine("[Observable]\t" + value);         OnNext(value);         Schedule();     }       private sealed class Subscription : IDisposable     {         private readonly RandomSubject _subject;         private IObserver<int> _observer;           public Subscription(RandomSubject subject, IObserver<int> observer)         {             _subject = subject;             _observer = observer;         }           public void Dispose()         {             IObserver<int> observer = _observer;             if (null != observer)             {                 lock (_subject._sync)                 {                     _subject._observers.Remove(observer);                 }                 _observer = null;             }         }     } }   So far, so good. Now let’s write a program that consumes data emitted by the observable as a stream of point events in a Streaminsight query. First, let’s define our payload type: class Payload {     public int Value { get; set; }       public override string ToString()     {         return "[StreamInsight]\tValue: " + Value.ToString();     } }   Now, let’s write the program. First, we will instantiate the observable subject. Then we’ll use the ToPointStream() method to consume it as a stream. We can now write any query over the source - here, a simple pass-through query. class Program {     static void Main(string[] args)     {         Console.WriteLine("Starting observable source...");         using (var source = new RandomSubject(500))         {             Console.WriteLine("Started observable source.");             using (var server = Server.Create("Default"))             {                 var application = server.CreateApplication("My Application");                   var stream = source.ToPointStream(application,                     e => PointEvent.CreateInsert(DateTime.Now, new Payload { Value = e }),                     AdvanceTimeSettings.StrictlyIncreasingStartTime,                     "Observable Stream");                   var query = from e in stream                             select e;                   [...]   We’re done with consuming input and querying it! But you probably want to see the output of the query. Did you know you can turn a query into an observable subject as well? Let’s do precisely that, and exploit the Reactive Extensions for .NET (http://msdn.microsoft.com/en-us/devlabs/ee794896.aspx) to quickly visualize the output. Notice we’re subscribing “Console.WriteLine()” to the query, a pattern you may find useful for quick debugging of your queries. Reminder: you’ll need to install the Reactive Extensions for .NET (Rx for .NET Framework 4.0), and reference System.CoreEx and System.Reactive in your project.                 [...]                   Console.ReadLine();                 Console.WriteLine("Starting query...");                 using (query.ToObservable().Subscribe(Console.WriteLine))                 {                     Console.WriteLine("Started query.");                     Console.ReadLine();                     Console.WriteLine("Stopping query...");                 }                 Console.WriteLine("Stopped query.");             }             Console.ReadLine();             Console.WriteLine("Stopping observable source...");             source.OnCompleted();         }         Console.WriteLine("Stopped observable source.");     } }   We hope this blog post gets you started. And for bonus points, you can go ahead and rewrite the observable source (the RandomSubject class) using the Reactive Extensions for .NET! The entire sample project is attached to this article. Happy querying! Regards, The StreamInsight Team

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  • Reading input from a text file, omits the first and adds a nonsense value to the end?

    - by Greenhouse Gases
    Hi there When I input locations from a txt file I am getting a peculiar error where it seems to miss off the first entry, yet add a garbage entry to the end of the link list (it is designed to take the name, latitude and longitude for each location you will notice). I imagine this to be an issue with where it starts collecting the inputs and where it stops but I cant find the error!! It reads the first line correctly but then skips to the next before adding it because during testing for the bug it had no record of the first location Lisbon though whilst stepping into the method call it was reading it. Very bizarre but hopefully someone knows the issue. Here is firstly my header file: #include <string> struct locationNode { char nodeCityName [35]; double nodeLati; double nodeLongi; locationNode* Next; void CorrectCase() // Correct upper and lower case letters of input { int MAX_SIZE = 35; int firstLetVal = this->nodeCityName[0], letVal; int n = 1; // variable for name index from second letter onwards if((this->nodeCityName[0] >90) && (this->nodeCityName[0] < 123)) // First letter is lower case { firstLetVal = firstLetVal - 32; // Capitalise first letter this->nodeCityName[0] = firstLetVal; } while(n <= MAX_SIZE - 1) { if((this->nodeCityName[n] >= 65) && (this->nodeCityName[n] <= 90)) { letVal = this->nodeCityName[n] + 32; this->nodeCityName[n] = letVal; } n++; } //cityNameInput = this->nodeCityName; } }; class Locations { private: int size; public: Locations(){ }; // constructor for the class locationNode* Head; //int Add(locationNode* Item); }; And here is the file containing main: // U08221.cpp : main project file. #include "stdafx.h" #include "Locations.h" #include <iostream> #include <string> #include <fstream> using namespace std; int n = 0,x, locationCount = 0, MAX_SIZE = 35; string cityNameInput; char targetCity[35]; bool acceptedInput = false, userInputReq = true, match = false, nodeExists = false;// note: addLocation(), set to true to enable user input as opposed to txt file locationNode *start_ptr = NULL; // pointer to first entry in the list locationNode *temp, *temp2; // Part is a pointer to a new locationNode we can assign changing value followed by a call to Add locationNode *seek, *bridge; void setElementsNull(char cityParam[]) { int y=0, count =0; while(cityParam[y] != NULL) { y++; } while(y < MAX_SIZE) { cityParam[y] = NULL; y++; } } void addLocation() { temp = new locationNode; // declare the space for a pointer item and assign a temporary pointer to it if(!userInputReq) // bool that determines whether user input is required in adding the node to the list { cout << endl << "Enter the name of the location: "; cin >> temp->nodeCityName; temp->CorrectCase(); setElementsNull(temp->nodeCityName); cout << endl << "Please enter the latitude value for this location: "; cin >> temp->nodeLati; cout << endl << "Please enter the longitude value for this location: "; cin >> temp->nodeLongi; cout << endl; } temp->Next = NULL; //set to NULL as when one is added it is currently the last in the list and so can not point to the next if(start_ptr == NULL){ // if list is currently empty, start_ptr will point to this node start_ptr = temp; } else { temp2 = start_ptr; // We know this is not NULL - list not empty! while (temp2->Next != NULL) { temp2 = temp2->Next; // Move to next link in chain until reach end of list } temp2->Next = temp; } ++locationCount; // increment counter for number of records in list if(!userInputReq){ cout << "Location sucessfully added to the database! There are " << locationCount << " location(s) stored" << endl; } } void populateList(){ ifstream inputFile; inputFile.open ("locations.txt", ios::in); userInputReq = true; temp = new locationNode; // declare the space for a pointer item and assign a temporary pointer to it do { inputFile.get(temp->nodeCityName, 35, ' '); setElementsNull(temp->nodeCityName); inputFile >> temp->nodeLati; inputFile >> temp->nodeLongi; setElementsNull(temp->nodeCityName); if(temp->nodeCityName[0] == 10) //remove linefeed from input { for(int i = 0; temp->nodeCityName[i] != NULL; i++) { temp->nodeCityName[i] = temp->nodeCityName[i + 1]; } } addLocation(); } while(!inputFile.eof()); userInputReq = false; cout << "Successful!" << endl << "List contains: " << locationCount << " entries" << endl; cout << endl; inputFile.close(); } bool nodeExistTest(char targetCity[]) // see if entry is present in the database { match = false; seek = start_ptr; int letters = 0, letters2 = 0, x = 0, y = 0; while(targetCity[y] != NULL) { letters2++; y++; } while(x <= locationCount) // locationCount is number of entries currently in list { y=0, letters = 0; while(seek->nodeCityName[y] != NULL) // count letters in the current name { letters++; y++; } if(letters == letters2) // same amount of letters in the name { y = 0; while(y <= letters) // compare each letter against one another { if(targetCity[y] == seek->nodeCityName[y]) { match = true; y++; } else { match = false; y = letters + 1; // no match, terminate comparison } } } if(match) { x = locationCount + 1; //found match so terminate loop } else{ if(seek->Next != NULL) { bridge = seek; seek = seek->Next; x++; } else { x = locationCount + 1; // end of list so terminate loop } } } return match; } void deleteRecord() // complete this { int junction = 0; locationNode *place; cout << "Enter the name of the city you wish to remove" << endl; cin >> targetCity; setElementsNull(targetCity); if(nodeExistTest(targetCity)) //if this node does exist { if(seek == start_ptr) // if it is the first in the list { junction = 1; } if(seek != start_ptr && seek->Next == NULL) // if it is last in the list { junction = 2; } switch(junction) // will alter list accordingly dependant on where the searched for link is { case 1: start_ptr = start_ptr->Next; delete seek; --locationCount; break; case 2: place = seek; seek = bridge; delete place; --locationCount; break; default: bridge->Next = seek->Next; delete seek; --locationCount; break; } } else { cout << targetCity << "That entry does not currently exist" << endl << endl << endl; } } void searchDatabase() { char choice; cout << "Enter search term..." << endl; cin >> targetCity; if(nodeExistTest(targetCity)) { cout << "Entry: " << endl << endl; } else { cout << "Sorry, that city is not currently present in the list." << endl << "Would you like to add this city now Y/N?" << endl; cin >> choice; /*while(choice != ('Y' || 'N')) { cout << "Please enter a valid choice..." << endl; cin >> choice; }*/ switch(choice) { case 'Y': addLocation(); break; case 'N': break; default : cout << "Invalid choice" << endl; break; } } } void printDatabase() { temp = start_ptr; // set temp to the start of the list do { if (temp == NULL) { cout << "You have reached the end of the database" << endl; } else { // Display details for what temp points to at that stage cout << "Location : " << temp->nodeCityName << endl; cout << "Latitude : " << temp->nodeLati << endl; cout << "Longitude : " << temp->nodeLongi << endl; cout << endl; // Move on to next locationNode if one exists temp = temp->Next; } } while (temp != NULL); } void nameValidation(string name) { n = 0; // start from first letter x = name.size(); while(!acceptedInput) { if((name[n] >= 65) && (name[n] <= 122)) // is in the range of letters { while(n <= x - 1) { while((name[n] >=91) && (name[n] <=97)) // ERROR!! { cout << "Please enter a valid city name" << endl; cin >> name; } n++; } } else { cout << "Please enter a valid city name" << endl; cin >> name; } if(n <= x - 1) { acceptedInput = true; } } cityNameInput = name; } int main(array<System::String ^> ^args) { //main contains test calls to functions at present cout << "Populating list..."; populateList(); printDatabase(); deleteRecord(); printDatabase(); cin >> cityNameInput; } The text file contains this (ignore the names, they are just for testing!!): Lisbon 45 47 Fattah 45 47 Darius 42 49 Peter 45 27 Sarah 85 97 Michelle 45 47 John 25 67 Colin 35 87 Shiron 40 57 George 34 45 Sean 22 33 The output omits Lisbon, but adds on a garbage entry with nonsense values. Any ideas why? Thank you in advance.

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