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  • Problem with ebay AddItem API call [migrated]

    - by user1323572
    I am totally new to any sort of API application. Right now I am creating a listing application to list items on E-bay India site. API version being used is 767, sandbox url is https://api.sandbox.ebay.com/wsapi. I have sandbox account for ebay(buyer/seller) and developer account. I am getting error saying: 1) Sales Tax / VAT was dropped from the listing as per new sales tax / VAT policy. The items will be listed successfully, you may revise the listing to specify all inclusive price. 2) You have either not registered or are having problem with your payment method registration. ItemType type = new ItemType(); type.PaymentMethods = new BuyerPaymentMethodCodeTypeCollection(); type.PaymentMethods.Add(BuyerPaymentMethodCodeType.PaisaPayAccepted); Also do I have to specify taxation for each state? For VAT and shipping details here's my snippet: private ShippingDetailsType getShippingDetails() { // Shipping details. ShippingDetailsType sd = new ShippingDetailsType(); SalesTaxType salesTax = new SalesTaxType(); ReadSettings rs = new ReadSettings(); rs.GetSettings(); salesTax.SalesTaxPercent = 12f; salesTax.SalesTaxState = "MH"; SalesTaxType s = new SalesTaxType(); salesTax.ShippingIncludedInTax = true; salesTax.ShippingIncludedInTaxSpecified = true; sd.ApplyShippingDiscount = true; AmountType at = new AmountType(); at.Value = 2.8; at.currencyID = CurrencyCodeType.INR; sd.InsuranceFee = at; sd.InsuranceOption = InsuranceOptionCodeType.NotOffered; sd.PaymentInstructions = "These are my instructions."; VATDetailsType vd = new VATDetailsType(); vd.BusinessSeller = false; vd.BusinessSellerSpecified = false; vd.RestrictedToBusiness = false; vd.RestrictedToBusinessSpecified = false; vd.VATID = "VATSNO1234567890"; vd.VATPercent = 12f; vd.VATPercentSpecified = true; vd.VATSite = "None"; sd.ShippingType = ShippingTypeCodeType.Flat; // ShippingServiceOptionsType st1 = new ShippingServiceOptionsType(); sd.SalesTax = salesTax; st1.ShippingService = ShippingServiceCodeType.IN_Express.ToString(); at = new AmountType(); at.Value = 50; at.currencyID = CurrencyCodeType.INR; st1.ShippingServiceAdditionalCost = at; at = new AmountType(); at.Value = 50; at.currencyID = CurrencyCodeType.INR; st1.ShippingServiceCost = at; st1.ShippingServicePriority = 1; at = new AmountType(); at.Value = 1.0; at.currencyID = CurrencyCodeType.INR; st1.ShippingInsuranceCost = at; sd.ShippingServiceOptions = new ShippingServiceOptionsTypeCollection(new ShippingServiceOptionsType[] { st1 }); return sd; } Thank you for you efforts.

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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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  • Optional Parameters and Named Arguments in C# 4 (and a cool scenario w/ ASP.NET MVC 2)

    - by ScottGu
    [In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu] This is the seventeenth in a series of blog posts I’m doing on the upcoming VS 2010 and .NET 4 release. Today’s post covers two new language feature being added to C# 4.0 – optional parameters and named arguments – as well as a cool way you can take advantage of optional parameters (both in VB and C#) with ASP.NET MVC 2. Optional Parameters in C# 4.0 C# 4.0 now supports using optional parameters with methods, constructors, and indexers (note: VB has supported optional parameters for awhile). Parameters are optional when a default value is specified as part of a declaration.  For example, the method below takes two parameters – a “category” string parameter, and a “pageIndex” integer parameter.  The “pageIndex” parameter has a default value of 0, and as such is an optional parameter: When calling the above method we can explicitly pass two parameters to it: Or we can omit passing the second optional parameter – in which case the default value of 0 will be passed:   Note that VS 2010’s Intellisense indicates when a parameter is optional, as well as what its default value is when statement completion is displayed: Named Arguments and Optional Parameters in C# 4.0 C# 4.0 also now supports the concept of “named arguments”.  This allows you to explicitly name an argument you are passing to a method – instead of just identifying it by argument position.  For example, I could write the code below to explicitly identify the second argument passed to the GetProductsByCategory method by name (making its usage a little more explicit): Named arguments come in very useful when a method supports multiple optional parameters, and you want to specify which arguments you are passing.  For example, below we have a method DoSomething that takes two optional parameters: We could use named arguments to call the above method in any of the below ways: Because both parameters are optional, in cases where only one (or zero) parameters is specified then the default value for any non-specified arguments is passed. ASP.NET MVC 2 and Optional Parameters One nice usage scenario where we can now take advantage of the optional parameter support of VB and C# is with ASP.NET MVC 2’s input binding support to Action methods on Controller classes. For example, consider a scenario where we want to map URLs like “Products/Browse/Beverages” or “Products/Browse/Deserts” to a controller action method.  We could do this by writing a URL routing rule that maps the URLs to a method like so: We could then optionally use a “page” querystring value to indicate whether or not the results displayed by the Browse method should be paged – and if so which page of the results should be displayed.  For example: /Products/Browse/Beverages?page=2. With ASP.NET MVC 1 you would typically handle this scenario by adding a “page” parameter to the action method and make it a nullable int (which means it will be null if the “page” querystring value is not present).  You could then write code like below to convert the nullable int to an int – and assign it a default value if it was not present in the querystring: With ASP.NET MVC 2 you can now take advantage of the optional parameter support in VB and C# to express this behavior more concisely and clearly.  Simply declare the action method parameter as an optional parameter with a default value: C# VB If the “page” value is present in the querystring (e.g. /Products/Browse/Beverages?page=22) then it will be passed to the action method as an integer.  If the “page” value is not in the querystring (e.g. /Products/Browse/Beverages) then the default value of 0 will be passed to the action method.  This makes the code a little more concise and readable. Summary There are a bunch of great new language features coming to both C# and VB with VS 2010.  The above two features (optional parameters and named parameters) are but two of them.  I’ll blog about more in the weeks and months ahead. If you are looking for a good book that summarizes all the language features in C# (including C# 4.0), as well provides a nice summary of the core .NET class libraries, you might also want to check out the newly released C# 4.0 in a Nutshell book from O’Reilly: It does a very nice job of packing a lot of content in an easy to search and find samples format. Hope this helps, Scott

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  • IE9 RC fixed the “Internet Explorer cannot display the webpage” error when running an ASP.NET application in Visual Studio

    - by Jon Galloway
    One of the obstacles ASP.NET developers faced in using the Internet Explorer 9 Beta was the dreaded “Internet Explorer cannot display the webpage” error when running an ASP.NET application in Visual Studio. In the bug information on Connect (issue 601047), Eric Lawrence said that the problem was due to “caused by failure to failover from IPv6 to IPv4 when the connection is local.” Robert MacLean gives some more information as what was going wrong: “The problem is Windows, especially since it assumes IPv6 is better than IPv4. Note […] that when you ping localhost you get an IPv6 address. So what appears to be happening is when IE9 tries to go to localhost it uses IPv6, and the ASP.NET Development Server is IPv4 only and so nothing loads and we get the error.” The Simple Fix - Install IE 9 RC Internet Explorer 9 RC fixes this bug, so if you had tried IE 9 Beta and stopped using it due to problems with ASP.NET development, install the RC. The Workaround in IE 9 Beta If you're stuck on IE 9 Beta for some reason, you can follow Robert's workaround, which involves a one character edit to your hosts file. I've been using it for months, and it works great. Open notepad (running as administrator) and edit the hosts file (found in %systemroot%\system32\drivers\etc) Remove the # comment character before the line starting with 127.0.0.1 Save the file - if you have problems saving, it's probably because you weren't running as administrator When you're done, your hosts file will end with the following lines (assuming you were using a default hosts file setup beforehand): # localhost name resolution is handled within DNS itself.     127.0.0.1       localhost #    ::1             localhost Note: more information on editing your hosts file here. This causes Windows to default to IPv4 when resolving localhost, which will point to 127.0.0.1, which is right where Cassini - I mean the ASP.NET Web Development Server - is waiting for it.

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  • SQLAuthority News – Social Media Series – YouTube and Movies

    - by pinaldave
    Pinal Dave on Youtube! Some people might not know it, but YouTube is actually more than a place to watch funny cat videos and people singing their favorite pop songs – it’s actually a social media site.  When you are a member of YouTube you can follow people who regularly post videos, post video responses of your own, and even gain a following for your own videos.  I myself was not aware of YouTube’s potential until recently, when I started to make SQL Server in Sixty Seconds videos. YouTube is very different than other types of social media, and a big factor is that anyone can look at videos without being a member.  Unlike other social media sites, like Twitter and Facebook, you have to have an account in order to participate.  But on YouTube you are even more anonymous.  To make and post videos you need an account, but anyone who comes to the site can look at what you’ve made without signing in or leaving any trace of having seen your material.  This makes YouTube very anonymous and hard to track. However, we should not overlook the power of video on the internet.  Over the past few months I have been making SQL Server in Sixty Second videos and have come to love it.  It is very exciting to be able to talk about a subject that mostly I write about, and for many people video is far more accessible and easy to understand.   I have really enjoyed diving into something new, and would love to have more people check out these videos and give me feedback.  You can find me at www.youtube.com/user/pinaldave. I am very excited with all the possibilities on YouTube and it might just be the technology evangelist in me, but I would love for other people to discover how fun and exciting this site can be, too.  Don’t think of it as just a place to find funny videos and waste a few minutes of your time, think of it as a place to learn and interact with interesting people.  Come watch a few of my videos, while you’re there.  Remember, everything is free and there are no contracts to sign, but I hope that you get as excited as I am and join up.  We need more people creating good content on this site! Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology Tagged: Social Media

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  • Deploying ASP.NET Web Applications

    - by Ben Griswold
    In this episode, Noah and I explain how to use Web Deployment Projects to deploy your web application. This screencast will get you up and running, but in a future screencast, we discuss more advanced topics like excluding files, swapping out the right config files per environment, and alternate solution configurations.  This screencast (and the next) are based on a write-up I did about ASP.NET Web Application deployment with Web Deployment Projects a while back.  Multi-media knowledge sharing.  You have to love it! This is the first video hosted on Vimeo.  What do you think?

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  • YouTube: Tips by Bitwise Courses on NetBeans

    - by Geertjan
    I really like the potential of YouTube in providing a platform for short info clips that take not much time to produce and about as much time to consume. Huw Collingbourne's Bitwise Courses channel is full of exactly this kind of YouTube clip. Several of his YouTube clips are about or make use of NetBeans. The related Twitter account is @bitwisecourses and the homepage is bitwisecourses.com. Here's a great example, the latest YouTube clip created by Bitwise Courses. Very clear and simple explanation, on a specific and narrow topic, and very short and sweet. And very useful! Didn't know about this feature myself. Direct link to the movie: https://www.youtube.com/watch?v=b0fKT_hFQpU Here's to more of these, they're wonderful. More such YouTube clips are needed, short and precise, on very specific topics. And I'm very happy to promote them, as you can see.

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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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  • Will new Twitter API 1.1 allow hashtag/tweet/trend queries without any authentication, i.e. for a client that does not use an user's account at all?

    - by P5music
    I see that, even not being logged in Twitter with an account, if I google hashtags or twitter accounts, twitter show them. I think it should be also possible to get those tweets programmatically but I do not know it for sure, so I ask for confirmation here, especially for the future with the new Twitter API resctrictions. I mean, will it be possible to get tweets from hashtags or accounts without logging in an user account, and so not wanting to access the user settings, subscriptions, etc (because I do not need it), thus not having to respect any token limit? I found these API 1.1 faqs, have I to be concerned? Will an application have to request user authorization just to make public API calls? When API v1.1 is released, user authorization (and access tokens) are required for all API 1.1 requests. In the weeks following release, some methods will require only application-based authentication for certain "userless" contexts. Will an application have to request user authorization just to make public API calls? When API v1.1 is released, user authorization (and access tokens) are required for all API 1.1 requests. In the weeks following release, some methods will require only application-based authentication for certain "userless" contexts. Will the Search API require authentication? The Search API is now part of the official REST API in version 1.1. In addition to serving results in a format consistent with other Tweet resources, usage will also require authentication.

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  • How to use a Proxy with Youtube API? (Python)

    - by Kate
    Hi, I'm working a script that will upload videos to YouTube with different accounts. Is there a way to use HTTPS or SOCKS proxies to filter all the requests. My client doesn't want to leave any footprints for Google. The only way I found was to set the proxy environment variable beforehand but this seems cumbersome. Is there some way I'm missing? Thanks :)

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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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  • Google Fonts API JSON Data in WordPress Options-Framework-Theme

    - by Rob
    I'm developing a child-theme off of the new Twenty Twelve theme using Wordpress 3.4.2 and the development version of the Options Theme Framework by Devin Price. In Devin's tutorial, it shows of a way to implement 15 Google Web Fonts into the Theme Options page, but not all of them (roughly 560). I know I can create a "manual list", like in the tutorial that states each one with fallbacks, but this is time consuming and unproductive as Google may or may not add to, update, change or remove some of these fonts from their list. The list I've created above will ultimately store unavailable fonts the user thinks is there because of what they can see in the drop-down menu and it won't have any new ones - making the list and some selections obsolete. On the Google Developer API Web Fonts page, it talks briefly on retrieving a "dynamic list" using JSON/JavaScript. I was wondering how would I be able to pull the Google Web Fonts API into my Wordpress Theme Options page so I'm not creating my own list or have to constantly release an update to solve this issue. Could someone please walk me through what I would need to paste into my options.php, functions.php, /inc/options-framework.php file etc. or even in a new one to implement this? I've also had a look into some screencasts, plugins and tutorials on how it works, but none of them are specific enough for people just starting out. Please keep in mind I'm not the best coder... Thank you.

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  • DB API for shell scripting (any shell)

    - by foampile
    I am faced with some legacy shell scripts that run batch data processing jobs in Oracle using SQL+. For the most part, the data tier does not have to communicate back to the script with retrieved data to be passed for shell-level processing but in a few cases it does. The problem is, SQL+ is really meant to be an end user app and not an API that can communicate with other clients programmaticaly. That is why people have invented APIs such as DBD::DBI for Perl, JDBC for Java, ODBC etc. The way it is done is they invoke SQL+ and then parse the output, which is clearly designed for human eye consumption, using tools like sed and awk. The whole thing is at best a hack and very prone to bugs. Since this client is rather conservative with their technology, they don't want to scale their scripts up to Perl or Python where there are data access APIs. So I am wondering whether there are similar APIs for shell, e.g. K or bash. What I would like is if an API would return data in a 2-dimensional array or strings (for the lack of type setting) so that I can just read DB data like that. The way they do it now is akin to parsing regular web page HTML to get a single stock quote rather than cleanly calling a web service and be done with it. Anybody know of a product I can use? Thanks

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  • Balancing dependency injection with public API design

    - by kolektiv
    I've been contemplating how to balance testable design using dependency injection with providing simple fixed public API. My dilemma is: people would want to do something like var server = new Server(){ ... } and not have to worry about creating the many dependencies and graph of dependencies that a Server(,,,,,,) may have. While developing, I don't worry too much, as I use an IoC/DI framework to handle all that (I'm not using the lifecycle management aspects of any container, which would complicate things further). Now, the dependencies are unlikely to be re-implemented. Componentisation in this case is almost purely for testability (and decent design!) rather than creating seams for extension, etc. People will 99.999% of the time wish to use a default configuration. So. I could hardcode the dependencies. Don't want to do that, we lose our testing! I could provide a default constructor with hard-coded dependencies and one which takes dependencies. That's... messy, and likely to be confusing, but viable. I could make the dependency receiving constructor internal and make my unit tests a friend assembly (assuming C#), which tidies the public API but leaves a nasty hidden trap lurking for maintenance. Having two constructors which are implicitly connected rather than explicitly would be bad design in general in my book. At the moment that's about the least evil I can think of. Opinions? Wisdom?

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  • Reflective discovery of an inner class in an API

    - by wassup
    Let me ask you, as this bothers me for quite a while but appears to be subjectively the best solution for my problem, if reflective discovery of an inner class for API purposes is that bad idea? First, let me explain what I mean by saying "reflective discovery" and all that stuff. I am sketching an API for a Java database system, that'll be centered around block-based entities (don't ask me what that means - that's a long story), and those entities can be read and returned to the Java code as objects subclassed from the Entity class. I have an Entity.Factory class, that, by means of fluent interfaces, takes a Class<? extends Entity> argument and then, uses an instance of Section.Builder, Property.Builder, or whatever builder the entity has, to put it into the back-end storage. The idea about registering all entity types and their builders just doesn't appeal to me, so I thought that the closest solution to the problem that'd suffice my design needs would be to discover, using reflection, all inner classes of Entity classes and find one that's called Builder. Looking for some expert insight :) And if I missed some important design details (which could happen as I tried to make this question as concise as possible), just tell me and I'll add them.

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  • Yelp, Google's API for restaurants help

    - by chris
    Ok I have looked into this, and I'm not sure if anyone else has experience with it. I'm having termendous difficulties with Yelp and Google's API. To help explain what I am trying to do here is the concept of the website. We would have to pull restaurants based on user distance, and then randomize them based on quality of restaurant based on feedback from review websites (Yelp, Google, urbanspoon, zagat, opentable, kudzu, yahoo - doesn't have to be from all), and feedback from our users (on results page for the random restaurant users can select good recommendation/bad recommendation). There’s a lot we could calculate for our formula. Things that will dictate your results will be based on if you’re at home or work. If you’re at home you will have more time to drive out to the city to grab some dinner or lunch. If you’re at work we would have to recommend restaurants nearby as lunch is typically 30 minutes to a hour. A 30 minute lunch would require take out most likely or quick service. A hour lunch break you could dine in at a local fine dining restaurant. So in a nutshell, user comes to website. Select if they're at home or work, click submit and we will have a random restaurant selected for them to go. If they don't like it they can click retry and a new restaurant can show. The issue I am having is using the API to gather all the restaurants in the US. I know it can be done because there are similiar websites/apps that pull restaurants that are closest to you such as Ness, Alfred, and I believe there's two more but I can't remember the names. Anyone know if this can be accomplish?

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  • MSBuild (.NET 4.0) access problems

    - by JMP
    I'm using Cruise Control .NET as my build server (Windows 2008 Server). Yesterday I upgraded my ASP.NET MVC project from VS 2008/.NET 3.5 to VS 2010/.NET 4.0. The only change I made to my ccnet.config's MSBuild task was the location of MSBuild.exe. Ever since I made that change, the build has been broken with the error: MSB4019 - The imported project "C:\Program Files (x86)\MSBuild\Microsoft\VisualStudio\v10.0\WebApplications\Microsoft.WebApplication.targets" was not found. Confirm that the path in the declaration is correct, and that the file exists on disk. This file does, in fact, exist in the location specified (I solved a problem similar to this when setting up the build server for VS2008/.NET 3.5 by copying the files from my dev environment to my build environment). So I RDP'ed into the build machine and opened a command prompt, used MSBUILD to attempt to build my project. MSBUILD returns the error: MSB3021 - Unable to copy file "obj\debug....dll". Access to the path 'bin....dll' is denied. Since I'm running MSBUILD from the command prompt, logged in with an account that has administrative privileges, I'm assuming that MSBUILD is running with the same privileges that I have. Next, I tried to copy the file that MSBUILD was attempting to copy. In this case, I get the UAC dialog that makes me click the [Continue] button to complete the copy. I'd like to avoid installing Visual Studio 2010 on my build machine, can anyone suggest other fixes I might try?

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  • Error Running MVC2 application in IIS on .NET 4.0

    - by Matt Wrock
    I recently installed the RTM version of 4.0. I now receive an error when running MVC2 websites in a .net 4 app pool. The error is "User is not available in this context." All works fine on .net 2.0 app pools or if I run the app within the VS10 web server. The error only occurs in IIS on .net 4.0. To verify that it was not something specific to my app, I created a new MVC test app from the VS template and even that app encounters this error. My next step is to reinstall .net 4.0. Has anyone else seen this error?

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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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  • ASP.NET MVC, Spring.NET, NHibernate initial setup/example/tutorial.

    - by Bubba88
    Hello! Have you been doing some ASP.NET MVC developement involving Spring.NET and NHibernate both? I would like to see an informative example of such setup, so I could build my own project off that. I tried googling, found some pretty things like S#arp Architecture, an article about regular ASP.NET (WebForms) integrated with the frameworks and so on. Still, I'm missing a good tutorial on ASP.NET MVC & the subj. P.S.: I do know how Spring and Hibernate works, I just need to plug them into an MVC application. Don't want to use S#arp Architecture by now. P.P.S: I'll update the links later, including this one:

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  • ASP.Net MVC 2 - Need To Add A Default Property To A Strongly Typed Html.Textbox Helper In Asp.Net MV

    - by Sara
    I'm having a problem with something that I'm sure is very simple. I have been using Asp.Net MVC and I decided to start using Asp.Net MVC 2. Something has changed and now I need a little help. The strongly typed helpers are now written like this - <%= Html.TextBoxFor(model => model.State) %> I need to add a default value to a textbox. In the prior version of Asp.Net MVC it was easy to assign a default value. I thought doing the following would work in MVC 2- <%= Html.TextBoxFor(model => model.CountyId, new{ value = 840 })%> This, however, does not work for me in Asp.Net MVC 2. The value is still blank for the textbox. I want to make sure that this isn't some random error that I am having. Has anyone else encountered the same problem? I have searched and searched to find more information on the default property for the html helpers in MVC 2, but I can't find anything. Does anyone out there know how to correctly assign a default value to a textbox in Asp.Net MVC 2?

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