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• Client Id for Property (ASP.Net MVC)

  - by Felipe

  Hi guys... I'm begginer in asp.net mvc, and i have a doubs: I'm trying to do a label for a TextBox in my View and I'd like to know, how can I take a Id that will be render in client to generete scripts... for example: <label for="<%=x.Name.?ClientId?%>"> Name: </label> <%=Html.TextBoxFor(x=>x.Name) %> What need I put in "?ClientId?" to make sure that correct Id will be render to the corresponding control ? Thanks Cheers

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• [ASP.NET MVC] Problem with View - it does not refresh after db update

  - by crocodillez

  Hi, I am working with small ASP.NET MVC project - online store. I have addToCart method which adds selected product to cart - it updates cart table in my db and showing cart view with its content. But I have problems. while db is updating correctly the view does not. I see that quantity of the product in my db is incremented correctly but quantity in view is not changed. I have to stop debugging my app in visual studia and restart it - then my view is showing correct data. What can be wrong?

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• Parallelism in .NET – Part 1, Decomposition

  - by Reed

  The first step in designing any parallelized system is Decomposition.  Decomposition is nothing more than taking a problem space and breaking it into discrete parts.  When we want to work in parallel, we need to have at least two separate things that we are trying to run.  We do this by taking our problem and decomposing it into parts. There are two common abstractions that are useful when discussing parallel decomposition: Data Decomposition and Task Decomposition.  These two abstractions allow us to think about our problem in a way that helps leads us to correct decision making in terms of the algorithms we’ll use to parallelize our routine. To start, I will make a couple of minor points. I’d like to stress that Decomposition has nothing to do with specific algorithms or techniques.  It’s about how you approach and think about the problem, not how you solve the problem using a specific tool, technique, or library.  Decomposing the problem is about constructing the appropriate mental model: once this is done, you can choose the appropriate design and tools, which is a subject for future posts. Decomposition, being unrelated to tools or specific techniques, is not specific to .NET in any way.  This should be the first step to parallelizing a problem, and is valid using any framework, language, or toolset.  However, this gives us a starting point – without a proper understanding of decomposition, it is difficult to understand the proper usage of specific classes and tools within the .NET framework. Data Decomposition is often the simpler abstraction to use when trying to parallelize a routine.  In order to decompose our problem domain by data, we take our entire set of data and break it into smaller, discrete portions, or chunks.  We then work on each chunk in the data set in parallel. This is particularly useful if we can process each element of data independently of the rest of the data.  In a situation like this, there are some wonderfully simple techniques we can use to take advantage of our data.  By decomposing our domain by data, we can very simply parallelize our routines.  In general, we, as developers, should be always searching for data that can be decomposed. Finding data to decompose if fairly simple, in many instances.  Data decomposition is typically used with collections of data.  Any time you have a collection of items, and you’re going to perform work on or with each of the items, you potentially have a situation where parallelism can be exploited.  This is fairly easy to do in practice: look for iteration statements in your code, such as for and foreach. Granted, every for loop is not a candidate to be parallelized.  If the collection is being modified as it’s iterated, or the processing of elements depends on other elements, the iteration block may need to be processed in serial.  However, if this is not the case, data decomposition may be possible. Let’s look at one example of how we might use data decomposition.  Suppose we were working with an image, and we were applying a simple contrast stretching filter.  When we go to apply the filter, once we know the minimum and maximum values, we can apply this to each pixel independently of the other pixels.  This means that we can easily decompose this problem based off data – we will do the same operation, in parallel, on individual chunks of data (each pixel). Task Decomposition, on the other hand, is focused on the individual tasks that need to be performed instead of focusing on the data.  In order to decompose our problem domain by tasks, we need to think about our algorithm in terms of discrete operations, or tasks, which can then later be parallelized. Task decomposition, in practice, can be a bit more tricky than data decomposition.  Here, we need to look at what our algorithm actually does, and how it performs its actions.  Once we have all of the basic steps taken into account, we can try to analyze them and determine whether there are any constraints in terms of shared data or ordering.  There are no simple things to look for in terms of finding tasks we can decompose for parallelism; every algorithm is unique in terms of its tasks, so every algorithm will have unique opportunities for task decomposition. For example, say we want our software to perform some customized actions on startup, prior to showing our main screen.  Perhaps we want to check for proper licensing, notify the user if the license is not valid, and also check for updates to the program.  Once we verify the license, and that there are no updates, we’ll start normally.  In this case, we can decompose this problem into tasks – we have a few tasks, but there are at least two discrete, independent tasks (check licensing, check for updates) which we can perform in parallel.  Once those are completed, we will continue on with our other tasks. One final note – Data Decomposition and Task Decomposition are not mutually exclusive.  Often, you’ll mix the two approaches while trying to parallelize a single routine.  It’s possible to decompose your problem based off data, then further decompose the processing of each element of data based on tasks.  This just provides a framework for thinking about our algorithms, and for discussing the problem.

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• Getting Started With Knockout.js

  - by Pawan_Mishra

  Client side template binding in web applications is getting popular with every passing day. More and more libraries are coming up with enhanced support for client side binding. jQuery templates is one very popular mechanism for client side template bindings. The idea with client side template binding is simple. Define the html mark-up with appropriate place holder for data. User template engines like jQuery template to bind the data(JSON formatted data) with the previously defined mark-up.In this...(read more)

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• New and Improved Search Helpers Now Procurement Assistants!

  - by LuciaC

  Check out the new and improved Procurement Assistants (formerly Search Helpers). Let us guide you simply to Issue Resolution.  To access all our Procurement Search Helpers see Doc ID 1391694.2 our Procurement Information Center. Here you will see links to our Procurement Search Helpers: Assistants provide a collection of solutions based on the symptoms you enter. For example simply choose the radial button that pertains to your issue, as shown here: Then choose the additional symptom(s) that pertain and potential solution documents will be returned as shown here: Try these before logging a Service Request. Current Procurement Assistants: Doc ID Title 1361856.1     Assistant: Oracle Purchasing - Purchase Order and Requisition Approval (Search Helper) 1377764.1    Assistant: Oracle Purchasing PO Output for Communication / Supplier Notification Issues (Search Helper) 1364360.1    Assistant: Oracle Purchasing Requisition To Purchase Order (Search Helper) 1369663.1    Assistant: Oracle Purchasing Purchase Document Open Interface and API (Search Helper) 1391970.1    Assistant: Oracle Inventory Management RVTII-060 Errors in Receiving (Search Helper) 1394392.1    Assistant: Oracle Purchasing Buyer Work Center Search Helper (Search Helper) 1470034.1    Assistant: Oracle Purchasing - Document Control : Cancel and Close

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• .NET: Interface Problem VB.net Getter Only Interface

  - by snmcdonald

  Why does an interface override a class definition and violate class encapsulation? I have included two samples below, one in C# and one in VB.net? VB.net Module Module1 Sub Main() Dim testInterface As ITest = New TestMe Console.WriteLine(testInterface.Testable) ''// Prints False testInterface.Testable = True ''// Access to Private!!! Console.WriteLine(testInterface.Testable) ''// Prints True Dim testClass As TestMe = New TestMe Console.WriteLine(testClass.Testable) ''// Prints False ''//testClass.Testable = True ''// Compile Error Console.WriteLine(testClass.Testable) ''// Prints False End Sub End Module Public Class TestMe : Implements ITest Private m_testable As Boolean = False Public Property Testable As Boolean Implements ITest.Testable Get Return m_testable End Get Private Set(ByVal value As Boolean) m_testable = value End Set End Property End Class Interface ITest Property Testable As Boolean End Interface C# using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace InterfaceCSTest { class Program { static void Main(string[] args) { ITest testInterface = new TestMe(); Console.WriteLine(testInterface.Testable); testInterface.Testable = true; Console.WriteLine(testInterface.Testable); TestMe testClass = new TestMe(); Console.WriteLine(testClass.Testable); //testClass.Testable = true; Console.WriteLine(testClass.Testable); } } class TestMe : ITest { private bool m_testable = false; public bool Testable { get { return m_testable; } private set { m_testable = value; } } } interface ITest { bool Testable { get; set; } } } More Specifically How do I implement a interface in VB.net that will allow for a private setter. For example in C# I can declare: class TestMe : ITest { private bool m_testable = false; public bool Testable { get { return m_testable; } private set //No Compile Error here! { m_testable = value; } } } interface ITest { bool Testable { get; } } However, if I declare an interface property as readonly in VB.net I cannot create a setter. If I create a VB.net interface as just a plain old property then interface declarations will violate my encapsulation. Public Class TestMe : Implements ITest Private m_testable As Boolean = False Public ReadOnly Property Testable As Boolean Implements ITest.Testable Get Return m_testable End Get Private Set(ByVal value As Boolean) ''//Compile Error m_testable = value End Set End Property End Class Interface ITest ReadOnly Property Testable As Boolean End Interface So my question is, how do I define a getter only Interface in VB.net with proper encapsulation? I figured the first example would have been the best method. However, it appears as if interface definitions overrule class definitions. So I tried to create a getter only (Readonly) property like in C# but it does not work for VB.net. Maybe this is just a limitation of the language?

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• ASP.NET MVC + MySql Membership Provider, user cannot login

  - by Jason Miesionczek

  Hello, I've been playing around with using MySql as the membership provider for asp.net mvc forms authentication. I've got things configured correctly as far as i can tell, and i can create users via both the register action and asp.net web config site. however, when i try to login with one of the users, it does not work. it returns an error as if i had entered a wrong password, or if the account doesn't exist. i have verified in the database that the account does exist. I've followed the instructions here for reference: http://blog.tchami.com/post/ASPNET-MVC-2-and-MySQL-Membership-Provider.aspx here is my web.config: <?xml version="1.0"?> <!-- For more information on how to configure your ASP.NET application, please visit http://go.microsoft.com/fwlink/?LinkId=152368 --> <configuration> <connectionStrings> <add name="MySQLConn" connectionString="Server=localhost;Database=intereditor;Uid=<user>;Pwd=<password>;"/> </connectionStrings> <system.web> <compilation debug="true" targetFramework="4.0"> <assemblies> <add assembly="System.Web.Abstractions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /> <add assembly="System.Web.Routing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /> <add assembly="System.Web.Mvc, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /> </assemblies> </compilation> <authentication mode="Forms"> <forms loginUrl="~/Account/LogOn" timeout="2880" name=".ASPXFORM$" path="/" requireSSL="false" slidingExpiration="true" enableCrossAppRedirects="false" /> </authentication> <membership defaultProvider="MySqlMembershipProvider"> <providers> <clear/> <add name="MySqlMembershipProvider" type="MySql.Web.Security.MySQLMembershipProvider,MySql.Web,Version=6.3.4.0, Culture=neutral,PublicKeyToken=c5687fc88969c44d" autogenerateschema="true" connectionStringName="MySQLConn" enablePasswordRetrieval="false" enablePasswordReset="true" requiresQuestionAndAnswer="false" requiresUniqueEmail="false" passwordFormat="Hashed" maxInvalidPasswordAttempts="5" minRequiredPasswordLength="6" minRequiredNonalphanumericCharacters="0" passwordAttemptWindow="10" passwordStrengthRegularExpression="" applicationName="/" /> </providers> </membership> <profile defaultProvider="MySqlProfileProvider"> <providers> <clear/> <add name="MySqlProfileProvider" type="MySql.Web.Profile.MySQLProfileProvider,MySql.Web,Version=6.3.4.0,Culture=neutral,PublicKeyToken=c5687fc88969c44d" connectionStringName="MySQLConn" applicationName="/" /> </providers> </profile> <roleManager enabled="true" defaultProvider="MySqlRoleProvider"> <providers> <clear /> <add name="MySqlRoleProvider" type="MySql.Web.Security.MySQLRoleProvider,MySql.Web,Version=6.3.4.0,Culture=neutral,PublicKeyToken=c5687fc88969c44d" connectionStringName="MySQLConn" applicationName="/" /> </providers> </roleManager> <pages> <namespaces> <add namespace="System.Web.Mvc" /> <add namespace="System.Web.Mvc.Ajax" /> <add namespace="System.Web.Mvc.Html" /> <add namespace="System.Web.Routing" /> </namespaces> </pages> </system.web> <system.webServer> <validation validateIntegratedModeConfiguration="false"/> <modules runAllManagedModulesForAllRequests="true"/> </system.webServer> <runtime> <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1"> <dependentAssembly> <assemblyIdentity name="System.Web.Mvc" publicKeyToken="31bf3856ad364e35" /> <bindingRedirect oldVersion="1.0.0.0" newVersion="2.0.0.0" /> </dependentAssembly> </assemblyBinding> </runtime> </configuration> Can anyone please help me identify what is wrong so that users can login? UPDATE So after debugging the login process in the code of the membership provider itself, i discovered that there is a bug in the provider. There is a discrepancy between the password hash that is stored in the database, and the has that is generated based on the inputted password. As a workaround for my issue, i changed the password format to 'encrpyted' and added a machine key to my web.config. I am still interested in figuring out the issue with the hashed format in the provider, and will spend some more time debugging it, and if i can figure out the problem, i will put together a patch and submit it.

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• NullReferenceException makes me want to shoot myself

  - by rockinthesixstring

  Ok, so once upon a time, my code worked. Since then I did some refactoring (basic stuff so I thought) but now I'm getting a null reference exception, and I can't bloody well figure out why. Here's where it starts. note, this is the logout method, but all of my ActivityLogs sections are throwing this error Function LogOut(ByVal go As String) As ActionResult ActivityLogService.AddActivity(AuthenticationHelper.RetrieveAuthUser.ID, _ IActivityLogService.LogType.UserLogout, _ HttpContext.Request.UserHostAddress) ActivityLogService.SubmitChanges() ''# more stuff happens after this End Function The service is pretty straight forward (notice the ERROR THROWN HERE) Public Sub AddActivity(ByVal userid As Integer, ByVal activity As Integer, ByVal ip As String) Implements IActivityLogService.AddActivity Dim _activity As ActivityLog = New ActivityLog With {.Activity = activity, .UserID = userid, .UserIP = ip.IPAddressToNumber, .ActivityDate = DateTime.UtcNow} ActivityLogRepository.Create(_activity) ''#ERROR THROWN HERE End Sub And the Interface that the Service uses looks like this Public Interface IActivityLogService Sub AddActivity(ByVal userid As Integer, ByVal activity As Integer, ByVal ip As String) Function GetUsersLastActivity(ByVal UserID As Integer) As ActivityLog Sub SubmitChanges() ''' <summary> ''' The type of activity done by the user ''' </summary> ''' <remarks>Each int refers to an activity. ''' There can be no duplicates or modifications ''' after this application goes live</remarks> Enum LogType As Integer ''' <summary> ''' A new session started ''' </summary> SessionStarted = 1 ''' <summary> ''' A new user is Added/Created ''' </summary> UserAdded = 2 ''' <summary> ''' User has updated their profile ''' </summary> UserUpdated = 3 ''' <summary> ''' User has logged into they system ''' </summary> UserLogin = 4 ''' <summary> ''' User has logged out of the system ''' </summary> UserLogout = 5 ''' <summary> ''' A new event has been added ''' </summary> EventAdded = 6 ''' <summary> ''' An event has been updated ''' </summary> EventUpdated = 7 ''' <summary> ''' An event has been deleted ''' </summary> EventDeleted = 8 ''' <summary> ''' An event has received a Up/Down vote ''' </summary> EventVoted = 9 ''' <summary> ''' An event has been closed ''' </summary> EventCloseVoted = 10 ''' <summary> ''' A comment has been added to an event ''' </summary> CommentAdded = 11 ''' <summary> ''' A comment has been updated ''' </summary> CommentUpdated = 12 ''' <summary> ''' A comment has been deleted ''' </summary> CommentDeleted = 13 ''' <summary> ''' An event or comment has been reported as spam ''' </summary> SpamReported = 14 End Enum End Interface And the repository is equally straight forward Public Sub Create(ByVal activity As ActivityLog) Implements IActivityLogRepository.Create dc.ActivityLogs.InsertOnSubmit(activity) End Sub The stack trace is as follows [NullReferenceException: Object reference not set to an instance of an object.] MyApp.Core.Domain.ActivityLogService.AddActivity(Int32 userid, Int32 activity, String ip) in E:\Projects\MyApp\MyApp.Core\Domain\Services\ActivityLogService.vb:49 MyApp.Core.Controllers.UsersController.Authenticate(String go) in E:\Projects\MyApp\MyApp.Core\Controllers\UsersController.vb:258 lambda_method(Closure , ControllerBase , Object[] ) +163 System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters) +51 System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary2 parameters) +409 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary2 parameters) +52 System.Web.Mvc.<c_DisplayClass15.b_12() +127 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func1 continuation) +436 System.Web.Mvc.<>c__DisplayClass17.<InvokeActionMethodWithFilters>b__14() +61 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodWithFilters(ControllerContext controllerContext, IList1 filters, ActionDescriptor actionDescriptor, IDictionary2 parameters) +305 System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +830 System.Web.Mvc.Controller.ExecuteCore() +136 System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) +232 System.Web.Mvc.ControllerBase.System.Web.Mvc.IController.Execute(RequestContext requestContext) +39 System.Web.Mvc.<>c__DisplayClassb.<BeginProcessRequest>b__5() +68 System.Web.Mvc.Async.<>c__DisplayClass1.<MakeVoidDelegate>b__0() +44 System.Web.Mvc.Async.<>c__DisplayClass81.b__7(IAsyncResult ) +42 System.Web.Mvc.Async.WrappedAsyncResult`1.End() +141 System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +54 System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +40 System.Web.Mvc.<c_DisplayClasse.b_d() +61 System.Web.Mvc.SecurityUtil.b_0(Action f) +31 System.Web.Mvc.SecurityUtil.ProcessInApplicationTrust(Action action) +56 System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +110 System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +38 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +690 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +194 here's an image of the error when attached to the debugger. And here's an image of the DB schema in question Can anyone shed some light on what I might be missing here?

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• Parallelism in .NET – Part 10, Cancellation in PLINQ and the Parallel class

  - by Reed

  Many routines are parallelized because they are long running processes.  When writing an algorithm that will run for a long period of time, its typically a good practice to allow that routine to be cancelled.  I previously discussed terminating a parallel loop from within, but have not demonstrated how a routine can be cancelled from the caller’s perspective.  Cancellation in PLINQ and the Task Parallel Library is handled through a new, unified cooperative cancellation model introduced with .NET 4.0. Cancellation in .NET 4 is based around a new, lightweight struct called CancellationToken.  A CancellationToken is a small, thread-safe value type which is generated via a CancellationTokenSource.  There are many goals which led to this design.  For our purposes, we will focus on a couple of specific design decisions: Cancellation is cooperative.  A calling method can request a cancellation, but it’s up to the processing routine to terminate – it is not forced. Cancellation is consistent.  A single method call requests a cancellation on every copied CancellationToken in the routine. Let’s begin by looking at how we can cancel a PLINQ query.  Supposed we wanted to provide the option to cancel our query from Part 6: double min = collection .AsParallel() .Min(item => item.PerformComputation()); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } We would rewrite this to allow for cancellation by adding a call to ParallelEnumerable.WithCancellation as follows: var cts = new CancellationTokenSource(); // Pass cts here to a routine that could, // in parallel, request a cancellation try { double min = collection .AsParallel() .WithCancellation(cts.Token) .Min(item => item.PerformComputation()); } catch (OperationCanceledException e) { // Query was cancelled before it finished } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Here, if the user calls cts.Cancel() before the PLINQ query completes, the query will stop processing, and an OperationCanceledException will be raised.  Be aware, however, that cancellation will not be instantaneous.  When cts.Cancel() is called, the query will only stop after the current item.PerformComputation() elements all finish processing.  cts.Cancel() will prevent PLINQ from scheduling a new task for a new element, but will not stop items which are currently being processed.  This goes back to the first goal I mentioned – Cancellation is cooperative.  Here, we’re requesting the cancellation, but it’s up to PLINQ to terminate. If we wanted to allow cancellation to occur within our routine, we would need to change our routine to accept a CancellationToken, and modify it to handle this specific case: public void PerformComputation(CancellationToken token) { for (int i=0; i<this.iterations; ++i) { // Add a check to see if we've been canceled // If a cancel was requested, we'll throw here token.ThrowIfCancellationRequested(); // Do our processing now this.RunIteration(i); } } With this overload of PerformComputation, each internal iteration checks to see if a cancellation request was made, and will throw an OperationCanceledException at that point, instead of waiting until the method returns.  This is good, since it allows us, as developers, to plan for cancellation, and terminate our routine in a clean, safe state. This is handled by changing our PLINQ query to: try { double min = collection .AsParallel() .WithCancellation(cts.Token) .Min(item => item.PerformComputation(cts.Token)); } catch (OperationCanceledException e) { // Query was cancelled before it finished } PLINQ is very good about handling this exception, as well.  There is a very good chance that multiple items will raise this exception, since the entire purpose of PLINQ is to have multiple items be processed concurrently.  PLINQ will take all of the OperationCanceledException instances raised within these methods, and merge them into a single OperationCanceledException in the call stack.  This is done internally because we added the call to ParallelEnumerable.WithCancellation. If, however, a different exception is raised by any of the elements, the OperationCanceledException as well as the other Exception will be merged into a single AggregateException. The Task Parallel Library uses the same cancellation model, as well.  Here, we supply our CancellationToken as part of the configuration.  The ParallelOptions class contains a property for the CancellationToken.  This allows us to cancel a Parallel.For or Parallel.ForEach routine in a very similar manner to our PLINQ query.  As an example, we could rewrite our Parallel.ForEach loop from Part 2 to support cancellation by changing it to: try { var cts = new CancellationTokenSource(); var options = new ParallelOptions() { CancellationToken = cts.Token }; Parallel.ForEach(customers, options, customer => { // Run some process that takes some time... DateTime lastContact = theStore.GetLastContact(customer); TimeSpan timeSinceContact = DateTime.Now - lastContact; // Check for cancellation here options.CancellationToken.ThrowIfCancellationRequested(); // If it's been more than two weeks, send an email, and update... if (timeSinceContact.Days > 14) { theStore.EmailCustomer(customer); customer.LastEmailContact = DateTime.Now; } }); } catch (OperationCanceledException e) { // The loop was cancelled } Notice that here we use the same approach taken in PLINQ.  The Task Parallel Library will automatically handle our cancellation in the same manner as PLINQ, providing a clean, unified model for cancellation of any parallel routine.  The TPL performs the same aggregation of the cancellation exceptions as PLINQ, as well, which is why a single exception handler for OperationCanceledException will cleanly handle this scenario.  This works because we’re using the same CancellationToken provided in the ParallelOptions.  If a different exception was thrown by one thread, or a CancellationToken from a different CancellationTokenSource was used to raise our exception, we would instead receive all of our individual exceptions merged into one AggregateException.

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• Parallelism in .NET – Part 15, Making Tasks Run: The TaskScheduler

  - by Reed

  In my introduction to the Task class, I specifically made mention that the Task class does not directly provide it’s own execution.  In addition, I made a strong point that the Task class itself is not directly related to threads or multithreading.  Rather, the Task class is used to implement our decomposition of tasks.  Once we’ve implemented our tasks, we need to execute them.  In the Task Parallel Library, the execution of Tasks is handled via an instance of the TaskScheduler class. The TaskScheduler class is an abstract class which provides a single function: it schedules the tasks and executes them within an appropriate context.  This class is the class which actually runs individual Task instances.  The .NET Framework provides two (internal) implementations of the TaskScheduler class. Since a Task, based on our decomposition, should be a self-contained piece of code, parallel execution makes sense when executing tasks.  The default implementation of the TaskScheduler class, and the one most often used, is based on the ThreadPool.  This can be retrieved via the TaskScheduler.Default property, and is, by default, what is used when we just start a Task instance with Task.Start(). Normally, when a Task is started by the default TaskScheduler, the task will be treated as a single work item, and run on a ThreadPool thread.  This pools tasks, and provides Task instances all of the advantages of the ThreadPool, including thread pooling for reduced resource usage, and an upper cap on the number of work items.  In addition, .NET 4 brings us a much improved thread pool, providing work stealing and reduced locking within the thread pool queues.  By using the default TaskScheduler, our Tasks are run asynchronously on the ThreadPool. There is one notable exception to my above statements when using the default TaskScheduler.  If a Task is created with the TaskCreationOptions set to TaskCreationOptions.LongRunning, the default TaskScheduler will generate a new thread for that Task, at least in the current implementation.  This is useful for Tasks which will persist for most of the lifetime of your application, since it prevents your Task from starving the ThreadPool of one of it’s work threads. The Task Parallel Library provides one other implementation of the TaskScheduler class.  In addition to providing a way to schedule tasks on the ThreadPool, the framework allows you to create a TaskScheduler which works within a specified SynchronizationContext.  This scheduler can be retrieved within a thread that provides a valid SynchronizationContext by calling the TaskScheduler.FromCurrentSynchronizationContext() method. This implementation of TaskScheduler is intended for use with user interface development.  Windows Forms and Windows Presentation Foundation both require any access to user interface controls to occur on the same thread that created the control.  For example, if you want to set the text within a Windows Forms TextBox, and you’re working on a background thread, that UI call must be marshaled back onto the UI thread.  The most common way this is handled depends on the framework being used.  In Windows Forms, Control.Invoke or Control.BeginInvoke is most often used.  In WPF, the equivelent calls are Dispatcher.Invoke or Dispatcher.BeginInvoke. As an example, say we’re working on a background thread, and we want to update a TextBlock in our user interface with a status label.  The code would typically look something like: // Within background thread work... string status = GetUpdatedStatus(); Dispatcher.BeginInvoke(DispatcherPriority.Normal, new Action( () => { statusLabel.Text = status; })); // Continue on in background method .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This works fine, but forces your method to take a dependency on WPF or Windows Forms.  There is an alternative option, however.  Both Windows Forms and WPF, when initialized, setup a SynchronizationContext in their thread, which is available on the UI thread via the SynchronizationContext.Current property.  This context is used by classes such as BackgroundWorker to marshal calls back onto the UI thread in a framework-agnostic manner. The Task Parallel Library provides the same functionality via the TaskScheduler.FromCurrentSynchronizationContext() method.  When setting up our Tasks, as long as we’re working on the UI thread, we can construct a TaskScheduler via: TaskScheduler uiScheduler = TaskScheduler.FromCurrentSynchronizationContext(); We then can use this scheduler on any thread to marshal data back onto the UI thread.  For example, our code above can then be rewritten as: string status = GetUpdatedStatus(); (new Task(() => { statusLabel.Text = status; })) .Start(uiScheduler); // Continue on in background method This is nice since it allows us to write code that isn’t tied to Windows Forms or WPF, but is still fully functional with those technologies.  I’ll discuss even more uses for the SynchronizationContext based TaskScheduler when I demonstrate task continuations, but even without continuations, this is a very useful construct. In addition to the two implementations provided by the Task Parallel Library, it is possible to implement your own TaskScheduler.  The ParallelExtensionsExtras project within the Samples for Parallel Programming provides nine sample TaskScheduler implementations.  These include schedulers which restrict the maximum number of concurrent tasks, run tasks on a single threaded apartment thread, use a new thread per task, and more.

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• Parallelism in .NET – Part 18, Task Continuations with Multiple Tasks

  - by Reed

  In my introduction to Task continuations I demonstrated how the Task class provides a more expressive alternative to traditional callbacks.  Task continuations provide a much cleaner syntax to traditional callbacks, but there are other reasons to switch to using continuations… Task continuations provide a clean syntax, and a very simple, elegant means of synchronizing asynchronous method results with the user interface.  In addition, continuations provide a very simple, elegant means of working with collections of tasks. Prior to .NET 4, working with multiple related asynchronous method calls was very tricky.  If, for example, we wanted to run two asynchronous operations, followed by a single method call which we wanted to run when the first two methods completed, we’d have to program all of the handling ourselves.  We would likely need to take some approach such as using a shared callback which synchronized against a common variable, or using a WaitHandle shared within the callbacks to allow one to wait for the second.  Although this could be accomplished easily enough, it requires manually placing this handling into every algorithm which requires this form of blocking.  This is error prone, difficult, and can easily lead to subtle bugs. Similar to how the Task class static methods providing a way to block until multiple tasks have completed, TaskFactory contains static methods which allow a continuation to be scheduled upon the completion of multiple tasks: TaskFactory.ContinueWhenAll. This allows you to easily specify a single delegate to run when a collection of tasks has completed.  For example, suppose we have a class which fetches data from the network.  This can be a long running operation, and potentially fail in certain situations, such as a server being down.  As a result, we have three separate servers which we will “query” for our information.  Now, suppose we want to grab data from all three servers, and verify that the results are the same from all three. With traditional asynchronous programming in .NET, this would require using three separate callbacks, and managing the synchronization between the various operations ourselves.  The Task and TaskFactory classes simplify this for us, allowing us to write: var server1 = Task.Factory.StartNew( () => networkClass.GetResults(firstServer) ); var server2 = Task.Factory.StartNew( () => networkClass.GetResults(secondServer) ); var server3 = Task.Factory.StartNew( () => networkClass.GetResults(thirdServer) ); var result = Task.Factory.ContinueWhenAll( new[] {server1, server2, server3 }, (tasks) => { // Propogate exceptions (see below) Task.WaitAll(tasks); return this.CompareTaskResults( tasks[0].Result, tasks[1].Result, tasks[2].Result); }); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This is clean, simple, and elegant.  The one complication is the Task.WaitAll(tasks); statement. Although the continuation will not complete until all three tasks (server1, server2, and server3) have completed, there is a potential snag.  If the networkClass.GetResults method fails, and raises an exception, we want to make sure to handle it cleanly.  By using Task.WaitAll, any exceptions raised within any of our original tasks will get wrapped into a single AggregateException by the WaitAll method, providing us a simplified means of handling the exceptions.  If we wait on the continuation, we can trap this AggregateException, and handle it cleanly.  Without this line, it’s possible that an exception could remain uncaught and unhandled by a task, which later might trigger a nasty UnobservedTaskException.  This would happen any time two of our original tasks failed. Just as we can schedule a continuation to occur when an entire collection of tasks has completed, we can just as easily setup a continuation to run when any single task within a collection completes.  If, for example, we didn’t need to compare the results of all three network locations, but only use one, we could still schedule three tasks.  We could then have our completion logic work on the first task which completed, and ignore the others.  This is done via TaskFactory.ContinueWhenAny: var server1 = Task.Factory.StartNew( () => networkClass.GetResults(firstServer) ); var server2 = Task.Factory.StartNew( () => networkClass.GetResults(secondServer) ); var server3 = Task.Factory.StartNew( () => networkClass.GetResults(thirdServer) ); var result = Task.Factory.ContinueWhenAny( new[] {server1, server2, server3 }, (firstTask) => { return this.ProcessTaskResult(firstTask.Result); }); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Here, instead of working with all three tasks, we’re just using the first task which finishes.  This is very useful, as it allows us to easily work with results of multiple operations, and “throw away” the others.  However, you must take care when using ContinueWhenAny to properly handle exceptions.  At some point, you should always wait on each task (or use the Task.Result property) in order to propogate any exceptions raised from within the task.  Failing to do so can lead to an UnobservedTaskException.

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• JQuery / JSON + .Net Service Layer - to WCF or Not to WCF?

  - by hanzolo

  I Recently had a discussion with a colleague of mine about the pros / cons of WCF. He mentioned about how much code is generated to support WCF, and also the overhead required. It was mentioned that a simple jQuery /Ajax post to a .aspx page (or a handler for that matter) that returns JSON would work more efficiently and takes much less code to implement. I am also aware of the new WCF Web API and feel that technology may solve the "bloated"-ness required in attaining a proxy etc... by just outputting JSON. So when developing a relational DB (MSSQL) storage model, with a fairly complex Business Layer (C#) and Data Access Layer (EntityFW).. what's a good technology for creating a "service layer" which will spit out View Models represented in JSON, with a CQRS(Command Query..) approach in mind.. The app would use the service layer to support it's required UI, as well as provide an available subset of services (outputting JSON data) for service subscribers.. In other words an admin panel to support the admin UI, and service endpoints that return JSON to access the configurations made from the administration UI. What are some potential technologies to use as the transport / communication layer. I'd like to use a pure RESTful approach, but am not against doing some URL rewriting with IIS. Obviously some of the available technologies are: WCF WCF Web API (should this even be separate?) Straight request / response (query string to .aspx / handler) Would using MVC .Net solve this entire problem? maybe their single page app approach? any suggestions / feedback from developing this type of application? Thanks,

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• Visual Studio 2010 RC with .net 4 beta 2

  - by aip.cd.aish

  Does anyone know if it is possible to use Visual Studio 2010 RC with the beta 2 version of the .NET 4 framework? The reason I need to use the beta 2 version and not the RC is that there isn't an Expression Blend that can support the .NET 4 RC. I uninstalled the .NET 4 framework that installed with Visual Studio 2010, then I reinstalled the .NET 4 version Beta 2. But now when I launch Visual Studio, I get an error message saying "The operation could not be completed" and it shuts down. How can I make this work? Thanks!

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• HtmlForm.Action and .Net Framework 2.0/3.5 Query

  - by Brian

  Disappointingly, the members page for HtmlForm 2.0 is missing... My research seems to indicate that HtmlForm.Action is a property that was added in .Net Framework 3.5. However, I'm using VS2005 and my reference to System.Web (the namespace HtmlForm is under) is to a .Net Framework 2.0 runtime version. Further, my IIS status information also indicates I am using .Net Framework 2.0, when I force an error on my local IIS and read it. Despite this, I am able to use form1.Action successfully...but only on my local IIS. When I try it on vms and external servers, I get [MissingMethodException: Method not found: 'System.String System.Web.UI.HtmlControls.HtmlForm.get_Action()'.] errors. So, my question: 1) Why does it work on my local IIS? Does the fact that I have the 3.5 framework installed make a difference, here? 2) Why does it not work on other IIS? (I think this is because it's not part of .Net 2.0). I guess I just figure that if something is running on .Net Framework 2.0, the presence of 3.5 should not make a difference. Or maybe there's some other cause for these results.

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• asp.net mvc asp.net

  - by mazhar

  I want to Develop a similar sort of wizard mechanism for the design like in the picture above .How would I do that. Please reply how would i code the above mechanism . At this time I am completely blank so any idea will be great.

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• ASP.NET custom templates, still ASP.NET controls possible?

  - by Sha Le

  Hello: we currently do not use asp.net controls (no web forms). The way we do is: 1 Read HTML file from disk 2 lookup database, parse tags and populate data finally, Response.Write(page.ToString()); here there is no possibility of using asp.net controls. What I am wondering is, if we use asp.net controls in those HTML files, is there way to process them during step 2? Thanks and appreciate your response.

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• Recommend ASP.NET 3.5 SP1 Hosting Providers

  - by tyndall

  Would like to see a list of affordable ASP.NET 3.5 SP1 Hosting providers build up. Along with your review of the service, lacking features, special features, etc... Discount ASP.NET MochaHost At last update MochaHost does not offer SP1  they now offer SP1 CrystalTech Gearhost HostMySite please add more update: Anybody see a better deal for shared hosting ASP.NET than ASP.NETpro From GearHost? I would like to see more SQL storage, but I need keep the multiple domain capabilities. For about the same price.

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• Wordpress like dynamic permalinks in ASP.NET MVC2/3 or ASP.NET 4.0

  - by Aseem Gautam

  Scenario: There are two entities say 'Books' and 'Book Reviews'. There can be multiple books and each book can have multiple reviews. Each review and book should have a separate permalink. Books and Reviews can be added by users using separate input forms. As soon as any book/review is added it should be accessible by its permalink. Anyone can point me in the right direction on how should this be implemented?

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• Linq To Sql or classic ADO.net?

  - by Spyros

  I am asking my self many times before start writting a new app or data access library , should I use LinqToSql or classic ADO.net , I have used both and the development time I spend on building an app with Linq To sql is like the 1/3 compared to ADO.net. The only think I like using Linq to sql is that I dont have to design the domain objects Linq does that for me and saves me from spend my time on boring things :P But is Linq to sql suitable for large scale projects , is there an overhead that we can avoid when using ADO.net ?

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• Membership with Mysql, EF 1 and ASP.NET 3.5

  - by sanfra1983

  Hi, I created a web application with asp.net 3.5 and ado.net entity framework WebForms 1, but have not yet succeeded in creating a memebrship and roles. When I go on ASP.NET Configuration and click the Security Tab I get the following error: Keyword not supported. Parameter name: metadata Someone has already created an application with these same features to help me understand where is the problem? P.S.: I'm going crazy Thanks to all

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• ASP.NET MVC - Html.DropDownList - Value not set via ViewData.Model

  - by chrisb

  Have just started playing with ASP.NET MVC and have stumbled over the following situation. It feels a lot like a bug but if its not, an explanation would be appreciated :) The View contains pretty basic stuff <%=Html.DropDownList("MyList", ViewData["MyListItems"] as SelectList)%> <%=Html.TextBox("MyTextBox")%> When not using a model, the value and selected item are set as expected: //works fine public ActionResult MyAction(){ ViewData["MyListItems"] = new SelectList(items, "Value", "Text"); //items is an ienumerable of {Value="XXX", Text="YYY"} ViewData["MyList"] = "XXX"; //set the selected item to be the one with value 'XXX' ViewData["MyTextBox"] = "ABC"; //sets textbox value to 'ABC' return View(); } But when trying to load via a model, the textbox has the value set as expected, but the dropdown doesnt get a selected item set. //doesnt work public ActionResult MyAction(){ ViewData["MyListItems"] = new SelectList(items, "Value", "Text"); //items is an ienumerable of {Value="XXX", Text="YYY"} var model = new { MyList = "XXX", //set the selected item to be the one with value 'XXX' MyTextBox = "ABC" //sets textbox value to 'ABC' } return View(model); } Any ideas? My current thoughts on it are that perhaps when using a model, we're restricted to setting the selected item on the SelectList constructor instead of using the viewdata (which works fine) and passing the selectlist in with the model - which would have the benefit of cleaning the code up a little - I'm just wondering why this method doesnt work.... Many thanks for any suggestions

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• MVC controller is being called twice

  - by rboarman

  Hello, I have a controller that is being called twice from an ActionLink call. My home page has a link, that when clicked calls the Index method on the Play controller. An id of 100 is passed into the method. I think this is what is causing the issue. More on this below. Here are some code snippets: Home page: <%= Html.ActionLink(“Click Me”, "Index", "Play", new { id = 100 }, null) %> Play Controller: public ActionResult Index(int? id) { var settings = new Dictionary<string, string>(); settings.Add("Id", id.ToString()); ViewData["InitParams"] = settings.ToInitParams(); return View(); } Play view: <%@ Page Title="" Language="C#" Inherits="System.Web.Mvc.ViewPage" %> (html <head> omitted for brevity) <body> <form id="form1" runat="server" style="height:100%"> Hello </form> </body> If I get rid of the parameter to the Index method, everything is fine. If I leave the parameter in place, then the Index method is called with 100 as the id. After returning the View, the method is called a second time with a parameter of null. I can’t seem to figure out what is triggering the second call. My first thought was to add a specific route like this: routes.MapRoute( "Play", // Route name "Play/{id}", // URL with parameters new {controller = "Play", action = "Index"} // Parameter defaults ); This had no effect other than making a prettier looking link. I am not sure where to go from here. Thank you in advance. Rick

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• Asp.Net MVC EditorTemplate Model is lost after Post

  - by Farrell

  I have a controller with two simple Methods: UserController Methods: [AcceptVerbs(HttpVerbs.Get)] public ActionResult Details(string id) { User user = UserRepo.UserByID(id); return View(user); } [AcceptVerbs(HttpVerbs.Post)] public ActionResult Details(User user) { return View(user); } Then there is one simple view for displaying the details: <% using (Html.BeginForm("Details", "User", FormMethod.Post)) {%> <fieldset> <legend>Userinfo</legend> <%= Html.EditorFor(m => m.Name, "LabelTextBoxValidation")%> <%= Html.EditorFor(m => m.Email, "LabelTextBoxValidation")%> <%= Html.EditorFor(m => m.Telephone, "LabelTextBoxValidation")%> </fieldset> <input type="submit" id="btnChange" value="Change" /> <% } %> As you can see, I use an editor template "LabelTextBoxValidation": <%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<string>" %> <%= Html.Label("") %> <%= Html.TextBox(Model,Model)%> <%= Html.ValidationMessage("")%> Showing user information is no problem. The view renders perfectly user details. When I submit the form, the object user is lost. I debugged on the row "return View(User);" in the Post Details method, the user object is filled with nullable values. If I dont use the editor template, the user object is filled with correct data. So there has to be something wrong with the editor template, but can't figure out what it is. Suggestions?

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• Best way to escape characters before jquery post ASP.NET MVC

  - by Darcy

  Hello, I am semi-new to ASP.NET MVC. I am building an app that is used internally for my company. The scenario is this: There are two Html.Listbox's. One has all database information, and the other is initally empty. The user would add items from the database listbox to the empty listbox. Every time the user adds a command, I call a js function that calls an ActionResult "AddCommand" in my EditController. In the controller, the selected items that are added are saved to another database table. Here is the code (this gets called every time an item is added): function Add(listbox) { ... //skipping initializing code for berevity var url = "/Edit/AddCommand/" + cmd; $.post(url); } So the problem occurs when the 'cmd' is an item that has a '/', ':', '%', '?', etc (some kind of special character) So what I'm wondering is, what's the best way to escape these characters? Right now I'm checking the database's listbox item's text, and rebuilding the string, then in the Controller, I'm taking that built string and turning it back into its original state. So for example, if the item they are adding is 'Cats/Dogs', I am posting 'Cats[SLASH]Dogs' to the controller, and in the controller changing it back to 'Cats/Dogs'. Obviously this is a horrible hack, so I must be missing something. Any help would be greatly appreciated.

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• Using a custom MvcHttpHandler v2.0 Breaking change from 1.0 to 2.0 ?

  - by Myster

  Hi I have a site where part is webforms (Umbraco CMS) and part is MVC This is the HttpHandler to deal with the MVC functionality: public class Mvc : MvcHttpHandler { protected override void ProcessRequest(HttpContext httpContext) { httpContext.Trace.Write("Mvc.ashx", "Begin ProcessRequest"); string originalPath = httpContext.Request.Path; string newPath = httpContext.Request.QueryString["mvcRoute"]; if (string.IsNullOrEmpty(newPath)) newPath = "/"; httpContext.Trace.Write("Mvc.ashx", "newPath = "+newPath ); HttpContext.Current.RewritePath(newPath, false); base.ProcessRequest(HttpContext.Current); HttpContext.Current.RewritePath(originalPath, false); } } Full details of how this is implemented here This method works well in an MVC 1.0 website. However when I upgrade this site to MVC 2.0 following the steps in Microsoft's upgrade documentation; everything compiles, except at runtime I get this exception: Server Error in '/' Application. The resource cannot be found. Description: HTTP 404. The resource you are looking for (or one of its dependencies) could have been removed, had its name changed, or is temporarily unavailable. Please review the following URL and make sure that it is spelled correctly. Requested URL: /mvc.ashx Version Information: Microsoft .NET Framework Version:2.0.50727.4927; ASP.NET Version:2.0.50727.4927 This resource and it's dependencies are found fine in MVC 1.0 but not in MVC 2.0, is there an extra dependency I'd need to add? Is there something I'm missing? Is there a change in the way MVC 2.0 works?

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