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• Performance and Optimization Isn’t Evil

  - by Reed

  Donald Knuth is a fairly amazing guy.  I consider him one of the most influential contributors to computer science of all time.  Unfortunately, most of the time I hear his name, I cringe.  This is because it’s typically somebody quoting a small portion of one of his famous statements on optimization: “premature optimization is the root of all evil.” I mention that this is only a portion of the entire quote, and, as such, I feel that Knuth is being quoted out of context.  Optimization is important.  It is a critical part of every software development effort, and should never be ignored.  A developer who ignores optimization is not a professional.  Every developer should understand optimization – know what to optimize, when to optimize it, and how to think about code in a way that is intelligent and productive from day one. I want to start by discussing my own, personal motivation here.  I recently wrote about a performance issue I ran across, and was slammed by multiple comments and emails that effectively boiled down to: “You’re an idiot.  Premature optimization is the root of all evil.  This doesn’t matter.”  It didn’t matter that I discovered this while measuring in a profiler, and that it was a portion of my code base that can take “many hours to complete.”  Even so, multiple people instantly jump to “it’s premature – it doesn’t matter.” This is a common thread I see.  For example, StackOverflow has many pages of posts with answers that boil down to (mis)quoting Knuth.  In fact, just about any question relating to a performance related issue gets this quote thrown at it immediately – whether it deserves it or not.  That being said, I did receive some positive comments and emails as well.  Many people want to understand how to optimize their code, approaches to take, tools and techniques they can use, and any other advice they can discover. First, lets get back to Knuth – I mentioned before that Knuth is being quoted out of context.  Lets start by looking at the entire quote from his 1974 paper Structured Programming with go to Statements: “We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil. Yet we should not pass up our opportunities in that critical 3%. A good programmer will not be lulled into complacency by such reasoning, he will be wise to look carefully at the critical code; but only after that code has been identified.” Ironically, if you read Knuth’s original paper, this statement was made in the middle of a discussion of how Knuth himself had changed how he approaches optimization.  It was never a statement saying “don’t optimize”, but rather, “optimizing intelligently provides huge advantages.”  His approach had three benefits: “a) it doesn’t take long” … “b) the payoff is real”, c) you can “be less efficient in the other parts of my programs, which therefore are more readable and more easily written and debugged.” Looking at Knuth’s premise here, and reading that section of his paper, really leads to a few observations: Optimization is important  “he will be wise to look carefully at the critical code” Normally, 3% of your code – three lines out of every 100 you write, are “critical code” and will require some optimization: “we should not pass up our opportunities in that critical 3%” Optimization, if done well, should not be time consuming: “it doesn’t take long” Optimization, if done correctly, provides real benefits: “the payoff is real” None of this is new information.  People who care about optimization have been discussing this for years – for example, Rico Mariani’s Designing For Performance (a fantastic article) discusses many of the same issues very intelligently. That being said, many developers seem unable or unwilling to consider optimization.  Many others don’t seem to know where to start.  As such, I’m going to spend some time writing about optimization – what is it, how should we think about it, and what can we do to improve our own code.

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• Parallelism in .NET – Part 19, TaskContinuationOptions

  - by Reed

  My introduction to Task continuations demonstrates continuations on the Task class.  In addition, I’ve shown how continuations allow handling of multiple tasks in a clean, concise manner.  Continuations can also be used to handle exceptional situations using a clean, simple syntax. In addition to standard Task continuations , the Task class provides some options for filtering continuations automatically.  This is handled via the TaskContinationOptions enumeration, which provides hints to the TaskScheduler that it should only continue based on the operation of the antecedent task. This is especially useful when dealing with exceptions.  For example, we can extend the sample from our earlier continuation discussion to include support for handling exceptions thrown by the Factorize method: // Get a copy of the UI-thread task scheduler up front to use later var uiScheduler = TaskScheduler.FromCurrentSynchronizationContext(); // Start our task var factorize = Task.Factory.StartNew( () => { int primeFactor1 = 0; int primeFactor2 = 0; bool result = Factorize(10298312, ref primeFactor1, ref primeFactor2); return new { Result = result, Factor1 = primeFactor1, Factor2 = primeFactor2 }; }); // When we succeed, report the results to the UI factorize.ContinueWith(task => textBox1.Text = string.Format("{0}/{1} [Succeeded {2}]", task.Result.Factor1, task.Result.Factor2, task.Result.Result), CancellationToken.None, TaskContinuationOptions.NotOnFaulted, uiScheduler); // When we have an exception, report it factorize.ContinueWith(task => textBox1.Text = string.Format("Error: {0}", task.Exception.Message), CancellationToken.None, TaskContinuationOptions.OnlyOnFaulted, uiScheduler); .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; } The above code works by using a combination of features.  First, we schedule our task, the same way as in the previous example.  However, in this case, we use a different overload of Task.ContinueWith which allows us to specify both a specific TaskScheduler (in order to have your continuation run on the UI’s synchronization context) as well as a TaskContinuationOption.  In the first continuation, we tell the continuation that we only want it to run when there was not an exception by specifying TaskContinuationOptions.NotOnFaulted.  When our factorize task completes successfully, this continuation will automatically run on the UI thread, and provide the appropriate feedback. However, if the factorize task has an exception – for example, if the Factorize method throws an exception due to an improper input value, the second continuation will run.  This occurs due to the specification of TaskContinuationOptions.OnlyOnFaulted in the options.  In this case, we’ll report the error received to the user. We can use TaskContinuationOptions to filter our continuations by whether or not an exception occurred and whether or not a task was cancelled.  This allows us to handle many situations, and is especially useful when trying to maintain a valid application state without ever blocking the user interface.  The same concepts can be extended even further, and allow you to chain together many tasks based on the success of the previous ones.  Continuations can even be used to create a state machine with full error handling, all without blocking the user interface thread.

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• Launching a WPF Window in a Separate Thread, Part 1

  - by Reed

  Typically, I strongly recommend keeping the user interface within an application’s main thread, and using multiple threads to move the actual “work” into background threads.  However, there are rare times when creating a separate, dedicated thread for a Window can be beneficial.  This is even acknowledged in the MSDN samples, such as the Multiple Windows, Multiple Threads sample.  However, doing this correctly is difficult.  Even the referenced MSDN sample has major flaws, and will fail horribly in certain scenarios.  To ease this, I wrote a small class that alleviates some of the difficulties involved. The MSDN Multiple Windows, Multiple Threads Sample shows how to launch a new thread with a WPF Window, and will work in most cases.  The sample code (commented and slightly modified) works out to the following: // Create a thread Thread newWindowThread = new Thread(new ThreadStart( () => { // Create and show the Window Window1 tempWindow = new Window1(); tempWindow.Show(); // Start the Dispatcher Processing System.Windows.Threading.Dispatcher.Run(); })); // Set the apartment state newWindowThread.SetApartmentState(ApartmentState.STA); // Make the thread a background thread newWindowThread.IsBackground = true; // Start the thread newWindowThread.Start(); .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 sample creates a thread, marks it as single threaded apartment state, and starts the Dispatcher on that thread. That is the minimum requirements to get a Window displaying and handling messages correctly, but, unfortunately, has some serious flaws. The first issue – the created thread will run continuously until the application shuts down, given the code in the sample.  The problem is that the ThreadStart delegate used ends with running the Dispatcher.  However, nothing ever stops the Dispatcher processing.  The thread was created as a Background thread, which prevents it from keeping the application alive, but the Dispatcher will continue to pump dispatcher frames until the application shuts down. In order to fix this, we need to call Dispatcher.InvokeShutdown after the Window is closed.  This would require modifying the above sample to subscribe to the Window’s Closed event, and, at that point, shutdown the Dispatcher: // Create a thread Thread newWindowThread = new Thread(new ThreadStart( () => { Window1 tempWindow = new Window1(); // When the window closes, shut down the dispatcher tempWindow.Closed += (s,e) => Dispatcher.CurrentDispatcher.BeginInvokeShutdown(DispatcherPriority.Background); tempWindow.Show(); // Start the Dispatcher Processing System.Windows.Threading.Dispatcher.Run(); })); // Setup and start thread as before This eliminates the first issue.  Now, when the Window is closed, the new thread’s Dispatcher will shut itself down, which in turn will cause the thread to complete. The above code will work correctly for most situations.  However, there is still a potential problem which could arise depending on the content of the Window1 class.  This is particularly nasty, as the code could easily work for most windows, but fail on others. The problem is, at the point where the Window is constructed, there is no active SynchronizationContext.  This is unlikely to be a problem in most cases, but is an absolute requirement if there is code within the constructor of Window1 which relies on a context being in place. While this sounds like an edge case, it’s fairly common.  For example, if a BackgroundWorker is started within the constructor, or a TaskScheduler is built using TaskScheduler.FromCurrentSynchronizationContext() with the expectation of synchronizing work to the UI thread, an exception will be raised at some point.  Both of these classes rely on the existence of a proper context being installed to SynchronizationContext.Current, which happens automatically, but not until Dispatcher.Run is called.  In the above case, SynchronizationContext.Current will return null during the Window’s construction, which can cause exceptions to occur or unexpected behavior. Luckily, this is fairly easy to correct.  We need to do three things, in order, prior to creating our Window: Create and initialize the Dispatcher for the new thread manually Create a synchronization context for the thread which uses the Dispatcher Install the synchronization context Creating the Dispatcher is quite simple – The Dispatcher.CurrentDispatcher property gets the current thread’s Dispatcher and “creates a new Dispatcher if one is not already associated with the thread.”  Once we have the correct Dispatcher, we can create a SynchronizationContext which uses the dispatcher by creating a DispatcherSynchronizationContext.  Finally, this synchronization context can be installed as the current thread’s context via SynchronizationContext.SetSynchronizationContext.  These three steps can easily be added to the above via a single line of code: // Create a thread Thread newWindowThread = new Thread(new ThreadStart( () => { // Create our context, and install it: SynchronizationContext.SetSynchronizationContext( new DispatcherSynchronizationContext( Dispatcher.CurrentDispatcher)); Window1 tempWindow = new Window1(); // When the window closes, shut down the dispatcher tempWindow.Closed += (s,e) => Dispatcher.CurrentDispatcher.BeginInvokeShutdown(DispatcherPriority.Background); tempWindow.Show(); // Start the Dispatcher Processing System.Windows.Threading.Dispatcher.Run(); })); // Setup and start thread as before This now forces the synchronization context to be in place before the Window is created and correctly shuts down the Dispatcher when the window closes. However, there are quite a few steps.  In my next post, I’ll show how to make this operation more reusable by creating a class with a far simpler API…

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• Parallelism in .NET – Part 8, PLINQ’s ForAll Method

  - by Reed

  Parallel LINQ extends LINQ to Objects, and is typically very similar.  However, as I previously discussed, there are some differences.  Although the standard way to handle simple Data Parellelism is via Parallel.ForEach, it’s possible to do the same thing via PLINQ. PLINQ adds a new method unavailable in standard LINQ which provides new functionality… LINQ is designed to provide a much simpler way of handling querying, including filtering, ordering, grouping, and many other benefits.  Reading the description in LINQ to Objects on MSDN, it becomes clear that the thinking behind LINQ deals with retrieval of data.  LINQ works by adding a functional programming style on top of .NET, allowing us to express filters in terms of predicate functions, for example. PLINQ is, generally, very similar.  Typically, when using PLINQ, we write declarative statements to filter a dataset or perform an aggregation.  However, PLINQ adds one new method, which provides a very different purpose: ForAll. The ForAll method is defined on ParallelEnumerable, and will work upon any ParallelQuery<T>.  Unlike the sequence operators in LINQ and PLINQ, ForAll is intended to cause side effects.  It does not filter a collection, but rather invokes an action on each element of the collection. At first glance, this seems like a bad idea.  For example, Eric Lippert clearly explained two philosophical objections to providing an IEnumerable<T>.ForEach extension method, one of which still applies when parallelized.  The sole purpose of this method is to cause side effects, and as such, I agree that the ForAll method “violates the functional programming principles that all the other sequence operators are based upon”, in exactly the same manner an IEnumerable<T>.ForEach extension method would violate these principles.  Eric Lippert’s second reason for disliking a ForEach extension method does not necessarily apply to ForAll – replacing ForAll with a call to Parallel.ForEach has the same closure semantics, so there is no loss there. Although ForAll may have philosophical issues, there is a pragmatic reason to include this method.  Without ForAll, we would take a fairly serious performance hit in many situations.  Often, we need to perform some filtering or grouping, then perform an action using the results of our filter.  Using a standard foreach statement to perform our action would avoid this philosophical issue: // Filter our collection var filteredItems = collection.AsParallel().Where( i => i.SomePredicate() ); // Now perform an action foreach (var item in filteredItems) { // These will now run serially item.DoSomething(); } .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 would cause a loss in performance, since we lose any parallelism in place, and cause all of our actions to be run serially. We could easily use a Parallel.ForEach instead, which adds parallelism to the actions: // Filter our collection var filteredItems = collection.AsParallel().Where( i => i.SomePredicate() ); // Now perform an action once the filter completes Parallel.ForEach(filteredItems, item => { // These will now run in parallel item.DoSomething(); }); This is a noticeable improvement, since both our filtering and our actions run parallelized.  However, there is still a large bottleneck in place here.  The problem lies with my comment “perform an action once the filter completes”.  Here, we’re parallelizing the filter, then collecting all of the results, blocking until the filter completes.  Once the filtering of every element is completed, we then repartition the results of the filter, reschedule into multiple threads, and perform the action on each element.  By moving this into two separate statements, we potentially double our parallelization overhead, since we’re forcing the work to be partitioned and scheduled twice as many times. This is where the pragmatism comes into play.  By violating our functional principles, we gain the ability to avoid the overhead and cost of rescheduling the work: // Perform an action on the results of our filter collection .AsParallel() .Where( i => i.SomePredicate() ) .ForAll( i => i.DoSomething() ); The ability to avoid the scheduling overhead is a compelling reason to use ForAll.  This really goes back to one of the key points I discussed in data parallelism: Partition your problem in a way to place the most work possible into each task.  Here, this means leaving the statement attached to the expression, even though it causes side effects and is not standard usage for LINQ. This leads to my one guideline for using ForAll: The ForAll extension method should only be used to process the results of a parallel query, as returned by a PLINQ expression. Any other usage scenario should use Parallel.ForEach, instead.

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• Parallelism in .NET – Part 17, Think Continuations, not Callbacks

  - by Reed

  In traditional asynchronous programming, we’d often use a callback to handle notification of a background task’s completion.  The Task class in the Task Parallel Library introduces a cleaner alternative to the traditional callback: continuation tasks. Asynchronous programming methods typically required callback functions.  For example, MSDN’s Asynchronous Delegates Programming Sample shows a class that factorizes a number.  The original method in the example has the following signature: public static bool Factorize(int number, ref int primefactor1, ref int primefactor2) { //... .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; } However, calling this is quite “tricky”, even if we modernize the sample to use lambda expressions via C# 3.0.  Normally, we could call this method like so: int primeFactor1 = 0; int primeFactor2 = 0; bool answer = Factorize(10298312, ref primeFactor1, ref primeFactor2); Console.WriteLine("{0}/{1} [Succeeded {2}]", primeFactor1, primeFactor2, answer); If we want to make this operation run in the background, and report to the console via a callback, things get tricker.  First, we need a delegate definition: public delegate bool AsyncFactorCaller( int number, ref int primefactor1, ref int primefactor2); Then we need to use BeginInvoke to run this method asynchronously: int primeFactor1 = 0; int primeFactor2 = 0; AsyncFactorCaller caller = new AsyncFactorCaller(Factorize); caller.BeginInvoke(10298312, ref primeFactor1, ref primeFactor2, result => { int factor1 = 0; int factor2 = 0; bool answer = caller.EndInvoke(ref factor1, ref factor2, result); Console.WriteLine("{0}/{1} [Succeeded {2}]", factor1, factor2, answer); }, null); This works, but is quite difficult to understand from a conceptual standpoint.  To combat this, the framework added the Event-based Asynchronous Pattern, but it isn’t much easier to understand or author. Using .NET 4’s new Task<T> class and a continuation, we can dramatically simplify the implementation of the above code, as well as make it much more understandable.  We do this via the Task.ContinueWith method.  This method will schedule a new Task upon completion of the original task, and provide the original Task (including its Result if it’s a Task<T>) as an argument.  Using Task, we can eliminate the delegate, and rewrite this code like so: var background = Task.Factory.StartNew( () => { int primeFactor1 = 0; int primeFactor2 = 0; bool result = Factorize(10298312, ref primeFactor1, ref primeFactor2); return new { Result = result, Factor1 = primeFactor1, Factor2 = primeFactor2 }; }); background.ContinueWith(task => Console.WriteLine("{0}/{1} [Succeeded {2}]", task.Result.Factor1, task.Result.Factor2, task.Result.Result)); This is much simpler to understand, in my opinion.  Here, we’re explicitly asking to start a new task, then continue the task with a resulting task.  In our case, our method used ref parameters (this was from the MSDN Sample), so there is a little bit of extra boiler plate involved, but the code is at least easy to understand. That being said, this isn’t dramatically shorter when compared with our C# 3 port of the MSDN code above.  However, if we were to extend our requirements a bit, we can start to see more advantages to the Task based approach.  For example, supposed we need to report the results in a user interface control instead of reporting it to the Console.  This would be a common operation, but now, we have to think about marshaling our calls back to the user interface.  This is probably going to require calling Control.Invoke or Dispatcher.Invoke within our callback, forcing us to specify a delegate within the delegate.  The maintainability and ease of understanding drops.  However, just as a standard Task can be created with a TaskScheduler that uses the UI synchronization context, so too can we continue a task with a specific context.  There are Task.ContinueWith method overloads which allow you to provide a TaskScheduler.  This means you can schedule the continuation to run on the UI thread, by simply doing: Task.Factory.StartNew( () => { int primeFactor1 = 0; int primeFactor2 = 0; bool result = Factorize(10298312, ref primeFactor1, ref primeFactor2); return new { Result = result, Factor1 = primeFactor1, Factor2 = primeFactor2 }; }).ContinueWith(task => textBox1.Text = string.Format("{0}/{1} [Succeeded {2}]", task.Result.Factor1, task.Result.Factor2, task.Result.Result), TaskScheduler.FromCurrentSynchronizationContext()); This is far more understandable than the alternative.  By using Task.ContinueWith in conjunction with TaskScheduler.FromCurrentSynchronizationContext(), we get a simple way to push any work onto a background thread, and update the user interface on the proper UI thread.  This technique works with Windows Presentation Foundation as well as Windows Forms, with no change in methodology.

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• How do I configure postfix starttls

  - by Michael Temeschinko

  I need to install postfix on my webserver couse I need to use sendmail for my website. I only need to send mail not recieve or relay. send with starttls (port 587) via relay smtp.strato.de here is what happens Jul 15 00:02:38 negrita postfix/smtp[7120]: Host offered STARTTLS: [smtp.strato.de] Jul 15 00:02:38 negrita postfix/smtp[7120]: C717A181252: to=<[email protected]>, relay=smtp.strato.de[81.169.145.133]:587, delay=0.31, delays=0.09/0/0.16/0.04, dsn=5.7.0, status=bounced (host smtp.strato.de[81.169.145.133] said: 530 5.7.0 Bitte konfigurieren Sie ihr E-Mailprogramm fuer Authentifizierung am SMTP Server, wie auf www.strato.de/email-hilfe beschrieben. - Please configure your mail client for using SMTP Server Authentication (in reply to MAIL FROM command)) Jul 15 00:02:38 negrita postfix/cleanup[7118]: 29F5F181254: message-id=<20120714220238.29F5F181254@negrita> Jul 15 00:02:38 negrita postfix/qmgr[7102]: 29F5F181254: from=<>, size=2548, nrcpt=1 (queue active) Jul 15 00:02:38 negrita postfix/bounce[7121]: C717A181252: sender non-delivery notification: 29F5F181254 Jul 15 00:02:38 negrita postfix/qmgr[7102]: C717A181252: removed Jul 15 00:02:39 negrita postfix/local[7122]: 29F5F181254: to=<michael@negrita>, relay=local, delay=1.1, delays=0.04/0/0/1.1, dsn=2.0.0, status=sent (delivered to command: procmail -a "$EXTENSION") Jul 15 00:02:39 negrita postfix/qmgr[7102]: 29F5F181254: removed Jul 15 08:05:18 negrita postfix/master[1083]: daemon started -- version 2.9.1, configuration /etc/postfix Jul 15 08:05:29 negrita postfix/master[1083]: reload -- version 2.9.1, configuration /etc/postfix and my config michael@negrita:~$ postconf -n biff = no config_directory = /etc/postfix delay_warning_time = 4h home_mailbox = /home/michael/Maildir/ html_directory = /usr/share/doc/postfix/html inet_interfaces = localhost mailbox_command = procmail -a "$EXTENSION" mailbox_size_limit = 0 mydomain = example.com myhostname = negrita mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128 notify_classes = resource, software, protocol readme_directory = /usr/share/doc/postfix recipient_delimiter = + relayhost = [smtp.strato.de]:587 smtp_sasl_password_maps = hash:/etc/postfix/sasl/passwd smtp_tls_enforce_peername = no smtp_tls_note_starttls_offer = yes smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu) smtpd_sasl_auth_enable = yes smtpd_sasl_security_options = noanonymous smtpd_tls_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem smtpd_tls_key_file = /etc/ssl/private/ssl-cert-snakeoil.key smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache smtpd_use_tls = yes soft_bounce = yes the user and password is ok couse I can send mail with my thunderbird thanks in advance mike

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• 2010 Visual C# MVP Award

  - by Reed

  I received a pleasant surprise today.  I was presented this morning with the 2010 Microsoft® MVP Award for Visual C#.  According to the award email, this “award is given to exceptional technical community leaders who actively share their high quality, real world expertise with others.” I feel honored and proud to receive this award, and hope that I can continue to be a valuable member of the community in the future.  Thank you to everyone who nominated me!

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• Silverlight Cream for November 20, 2011 -- #1169

  - by Dave Campbell

  In this Issue: Andrea Boschin, Michael Crump, Michael Sync, WindowsPhoneGeek, Jesse Liberty, Derik Whittaker, Sumit Dutta, Jeff Blankenburg(-2-), and Beth Massi. Above the Fold: WP7: "Silver VNC 1.0 for Windows Phone "Mango"" Andrea Boschin Metro/WinRT/W8: "Lighting up your C# Metro apps by being a Share Source" Derik Whittaker LightSwitch: "Using the Save and Query Pipeline to “Archive” Deleted Records" Beth Massi Shoutouts: Michael Palermo's latest Desert Mountain Developers is up Michael Washington's latest Visual Studio #LightSwitch Daily is up From SilverlightCream.com: Silver VNC 1.0 for Windows Phone "Mango" Andrea Boschin published the first release of his "Silver VNC" version 1.0 on CodePlex. Check out the video on the blog post to see the capabilities, then go grab it from CodePlex. Fixing a broken toolbox (In Visual Studio 2010 SP1) Not Silverlight or Metro, but near to us all is Visual Studio... read how Michael Crump resolves the 'broken' toolbox that we all get now and then Windows Phone 7 – USB Device Not Recognized Error Michael Sync is looking for ideas about an error he gets any time he updates his phone. Windows Phone Toolkit MultiselectList in depth| Part2: Data Binding WindowsPhoneGeek has up the second part of his tutorial series on the MultiselectList from the Windows Phone Toolkit... this part is about data binding, complete with lots of code, discussion, pictures, and project to download New Mini-Tutorial Video Series Jesse Liberty started a new video series based on his Mango Mini tutorials. They will be on Channel 9, and he has a link on this post to the index. The firs of the series is on animation without code Lighting up your C# Metro apps by being a Share Source Derik Whittaker continues investigating Metro with this post about how to set your app up to share its content with other apps Part 21 - Windows Phone 7 - Toast Push Notification Sumit Dutta has part 21 of his WP7 series up and is talking about Toast Notification by creating a Windows form app for sending notifications to the WP7 app for viewing 31 Days of Mango | Day #6: Motion Jeff Blankenburg's Day 6 in his Mango series is about the Motion class which combines the data we get from the Accelerometer, Compass, and Gyroscope of the last couple days of posts 31 Days of Mango | Day #7: Raw Camera Data In Day 7, Jeff Blankenburg talks about the Camera on the WP7 and how to use the raw data in your own application Using the Save and Query Pipeline to “Archive” Deleted Records Beth Massi's latest LightSwith post is this one on tapping into the Save and Query pipelines to perform some data processing prior to saving or pulling data Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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• Reflections on GiveCamp

  - by Reed

  I participated in the Seattle GiveCamp over the weekend, and am entirely impressed.  GiveCamp is a great event – I especially like how rewarding it is for everybody involved.  I strongly encourage any and all developers to watch for future GiveCamp events, and consider participating, for many reasons… GiveCamp provides real value to organizations that truly need help.  The Seattle event alone succeeded in helping sixteen non-profit organizations in many different ways.  The projects involved varied dramatically, including website redesigns, SEO, reworking data management workflows, and even game development.  Many non-profits have a strong need for good, quality technical help.  However, nearly every non-profit organization has an incredibly limited budget.  GiveCamp is a way to really give back, and provide incredibly valuable help to organizations that truly benefit. My experience has shown many developers to be incredibly generous – this is a chance to dedicate your energy to helping others in a way that really takes advantage of your expertise.  Your time as a developer is incredibly valuable, and this puts something of incredible value directly into the hands of places its needed. First, and foremost, GiveCamp is about providing technical help to non-profit organizations in need. GiveCamp can make you a better developer.  This is a fantastic opportunity for us, as developers, to work with new people, in a new setting.  The incredibly short time frame (one weekend for a deliverable project) and intense motivation to succeed provides a huge opportunity for learning from peers.  I’d personally like to thank off the developers with whom I worked – I learned something from each and every one of you.  I hope to see and work with all of you again someday. GiveCamp provides an opportunity for you to work outside of your comfort zone. While it’s always nice to be an expert, it’s also valuable to work on a project where you have little or no direct experience.  My team focused on a complete reworking of our organizations message and a complete new website redesign and deployment using WordPress.  While I’d used WordPress for my blog, and had some experience, this is completely unrelated to my professional work.  In fact, nobody on our team normally worked directly with the technologies involved – yet together we managed to succeed in delivering our goals.  As developers, it’s easy to want to stay abreast of new technology surrounding our expertise, but its rare that we get a chance to sit down and work on something practical that is completely outside of our normal realm of work.  I’m a desktop developer by trade, and spent much of the weekend working with CSS and Photoshop.  Many of the projects organizations need don’t match perfectly with the skill set in the room – yet all of the software professionals rose to the occasion and delivered practical, usable applications. GiveCamp is a short term, known commitment. While this seems obvious, I think it’s an important aspect to remember.  This is a huge part of what makes it successful – you can work, completely focused, on a project, then walk away completely when you’re done.  There is no expectation of continued involvement.  While many of the professionals I’ve talked to are willing to contribute some amount of their time beyond the camp, this is not expected. The freedom this provides is immense.  In addition, the motivation this brings is incredibly valuable.  Every developer in the room was very focused on delivering in time – you have one shot to get it as good as possible, and leave it with the organization in a way that can be maintained by them.  This is a rare experience – and excellent practice at time management for everyone involved. GiveCamp provides a great way to meet and network with your peers. Not only do you get to network with other software professionals in your area – you get to network with amazing people.  Every single person in the room is there to try to help people.  The balance of altruism, intelligence, and expertise in the room is something I’ve never before experienced. During the presentations of what was accomplished, I felt blessed to participate.  I know many people in the room were incredibly touched by the level of dedication and accomplishment over the weekend. GiveCamp is fun. At the end of the experience, I would have signed up again, even if it was a painful, tedious weekend – merely due to the amazing accomplishments achieved throughout the event.  However, the event is fun.  Everybody I talked to, the entire weekend, was having a good time.  While there were many faces focused into a near grimace at times (including mine, I’ll admit), this was always in response to a particularly challenging problem or task.  The challenges just added to the overall enjoyment of the weekend – part of why I became a developer in the first place is my love for challenge and puzzles, and a short deadline using unfamiliar technology provided plenty of opportunity for puzzles.  As soon as people would stand up, it was another smile.   If you’re a developer, I’d recommend looking at GiveCamp more closely.  Watch for an event in your area.  If there isn’t one, consider building a team and organizing an event.  The experience is worth the commitment. 

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• Silverlight Cream for November 25, 2011 -- #1174

  - by Dave Campbell

  In this Issue: Michael Collier, Samidip Basu, Jesse Liberty, Dhananjay Kumar, and Michael Crump. Above the Fold: WP7: "31 Days of Mango | Day #16: Isolated Storage Explorer" Samidip Basu Metro/WinRT/W8: "1360x768x32 Resolution in Windows 8 in VirtualBox" Michael Crump Shoutouts: Michael Palermo's latest Desert Mountain Developers is up Michael Washington's latest Visual Studio #LightSwitch Daily is up Alex Golesh releases a Silverlight 5-friendly version of his external map manifest file tool: Utility: Extmap Maker v1.1From SilverlightCream.com:31 Days of Mango | Day #17: Using Windows AzureMichael Collier has Jeff Blankenburg's Day 17 and is talking about Azure services for your Phone apps... great discussion on this... good diagrams, code, and entire project to download31 Days of Mango | Day #16: Isolated Storage ExplorerSamidip Basu has Jeff Blankenburg's 31 Days for Day 16, and is discussing ISO, and the Isolated Storage Explorer which helps peruse ISO either in the emulator or on your deviceTest Driven Development–Testing Private ValuesJesse Liberty's got a post up discussing TDD in his latest Full Stack excerpt wherein he and Jon Galloway are building a Pomodoro timer app. He has a solution for dealing with private member variables and is looking for feedbackVideo on How to work with System Tray Progress Indicator in Windows Phone 7Dhananjay Kumar's latest video tutorial is up... covering working with the System Tray Progress Indicator in WP7, as the title says :)1360x768x32 Resolution in Windows 8 in VirtualBoxMichael Crump is using a non-standard resolution with Win8 preview and demosntrates how to make that all work with VirtualBoxMichaelStay in the 'Light!Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCreamJoin me @ SilverlightCream | Phoenix Silverlight User GroupTechnorati Tags:Silverlight    Silverlight 3    Silverlight 4    Windows PhoneMIX10

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• C# Performance Pitfall – Interop Scenarios Change the Rules

  - by Reed

  C# and .NET, overall, really do have fantastic performance in my opinion.  That being said, the performance characteristics dramatically differ from native programming, and take some relearning if you’re used to doing performance optimization in most other languages, especially C, C++, and similar.  However, there are times when revisiting tricks learned in native code play a critical role in performance optimization in C#. I recently ran across a nasty scenario that illustrated to me how dangerous following any fixed rules for optimization can be… The rules in C# when optimizing code are very different than C or C++.  Often, they’re exactly backwards.  For example, in C and C++, lifting a variable out of loops in order to avoid memory allocations often can have huge advantages.  If some function within a call graph is allocating memory dynamically, and that gets called in a loop, it can dramatically slow down a routine. This can be a tricky bottleneck to track down, even with a profiler.  Looking at the memory allocation graph is usually the key for spotting this routine, as it’s often “hidden” deep in call graph.  For example, while optimizing some of my scientific routines, I ran into a situation where I had a loop similar to: for (i=0; i<numberToProcess; ++i) { // Do some work ProcessElement(element[i]); } .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 loop was at a fairly high level in the call graph, and often could take many hours to complete, depending on the input data.  As such, any performance optimization we could achieve would be greatly appreciated by our users. After a fair bit of profiling, I noticed that a couple of function calls down the call graph (inside of ProcessElement), there was some code that effectively was doing: // Allocate some data required DataStructure* data = new DataStructure(num); // Call into a subroutine that passed around and manipulated this data highly CallSubroutine(data); // Read and use some values from here double values = data->Foo; // Cleanup delete data; // ... return bar; Normally, if “DataStructure” was a simple data type, I could just allocate it on the stack.  However, it’s constructor, internally, allocated it’s own memory using new, so this wouldn’t eliminate the problem.  In this case, however, I could change the call signatures to allow the pointer to the data structure to be passed into ProcessElement and through the call graph, allowing the inner routine to reuse the same “data” memory instead of allocating.  At the highest level, my code effectively changed to something like: DataStructure* data = new DataStructure(numberToProcess); for (i=0; i<numberToProcess; ++i) { // Do some work ProcessElement(element[i], data); } delete data; Granted, this dramatically reduced the maintainability of the code, so it wasn’t something I wanted to do unless there was a significant benefit.  In this case, after profiling the new version, I found that it increased the overall performance dramatically – my main test case went from 35 minutes runtime down to 21 minutes.  This was such a significant improvement, I felt it was worth the reduction in maintainability. In C and C++, it’s generally a good idea (for performance) to: Reduce the number of memory allocations as much as possible, Use fewer, larger memory allocations instead of many smaller ones, and Allocate as high up the call stack as possible, and reuse memory I’ve seen many people try to make similar optimizations in C# code.  For good or bad, this is typically not a good idea.  The garbage collector in .NET completely changes the rules here. In C#, reallocating memory in a loop is not always a bad idea.  In this scenario, for example, I may have been much better off leaving the original code alone.  The reason for this is the garbage collector.  The GC in .NET is incredibly effective, and leaving the allocation deep inside the call stack has some huge advantages.  First and foremost, it tends to make the code more maintainable – passing around object references tends to couple the methods together more than necessary, and overall increase the complexity of the code.  This is something that should be avoided unless there is a significant reason.  Second, (unlike C and C++) memory allocation of a single object in C# is normally cheap and fast.  Finally, and most critically, there is a large advantage to having short lived objects.  If you lift a variable out of the loop and reuse the memory, its much more likely that object will get promoted to Gen1 (or worse, Gen2).  This can cause expensive compaction operations to be required, and also lead to (at least temporary) memory fragmentation as well as more costly collections later. As such, I’ve found that it’s often (though not always) faster to leave memory allocations where you’d naturally place them – deep inside of the call graph, inside of the loops.  This causes the objects to stay very short lived, which in turn increases the efficiency of the garbage collector, and can dramatically improve the overall performance of the routine as a whole. In C#, I tend to: Keep variable declarations in the tightest scope possible Declare and allocate objects at usage While this tends to cause some of the same goals (reducing unnecessary allocations, etc), the goal here is a bit different – it’s about keeping the objects rooted for as little time as possible in order to (attempt) to keep them completely in Gen0, or worst case, Gen1.  It also has the huge advantage of keeping the code very maintainable – objects are used and “released” as soon as possible, which keeps the code very clean.  It does, however, often have the side effect of causing more allocations to occur, but keeping the objects rooted for a much shorter time. Now – nowhere here am I suggesting that these rules are hard, fast rules that are always true.  That being said, my time spent optimizing over the years encourages me to naturally write code that follows the above guidelines, then profile and adjust as necessary.  In my current project, however, I ran across one of those nasty little pitfalls that’s something to keep in mind – interop changes the rules. In this case, I was dealing with an API that, internally, used some COM objects.  In this case, these COM objects were leading to native allocations (most likely C++) occurring in a loop deep in my call graph.  Even though I was writing nice, clean managed code, the normal managed code rules for performance no longer apply.  After profiling to find the bottleneck in my code, I realized that my inner loop, a innocuous looking block of C# code, was effectively causing a set of native memory allocations in every iteration.  This required going back to a “native programming” mindset for optimization.  Lifting these variables and reusing them took a 1:10 routine down to 0:20 – again, a very worthwhile improvement. Overall, the lessons here are: Always profile if you suspect a performance problem – don’t assume any rule is correct, or any code is efficient just because it looks like it should be Remember to check memory allocations when profiling, not just CPU cycles Interop scenarios often cause managed code to act very differently than “normal” managed code. Native code can be hidden very cleverly inside of managed wrappers

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• Setting useLegacyV2RuntimeActivationPolicy At Runtime

  - by Reed

  Version 4.0 of the .NET Framework included a new CLR which is almost entirely backwards compatible with the 2.0 version of the CLR.  However, by default, mixed-mode assemblies targeting .NET 3.5sp1 and earlier will fail to load in a .NET 4 application.  Fixing this requires setting useLegacyV2RuntimeActivationPolicy in your app.Config for the application.  While there are many good reasons for this decision, there are times when this is extremely frustrating, especially when writing a library.  As such, there are (rare) times when it would be beneficial to set this in code, at runtime, as well as verify that it’s running correctly prior to receiving a FileLoadException. Typically, loading a pre-.NET 4 mixed mode assembly is handled simply by changing your app.Config file, and including the relevant attribute in the startup element: <?xml version="1.0" encoding="utf-8" ?> <configuration> <startup useLegacyV2RuntimeActivationPolicy="true"> <supportedRuntime version="v4.0"/> </startup> </configuration> .csharpcode { background-color: #ffffff; font-family: consolas, "Courier New", courier, monospace; color: black; font-size: small } .csharpcode pre { background-color: #ffffff; font-family: consolas, "Courier New", courier, monospace; color: black; font-size: small } .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; margin: 0em; width: 100% } .csharpcode .lnum { color: #606060 } This causes your application to run correctly, and load the older, mixed-mode assembly without issues. For full details on what’s happening here and why, I recommend reading Mark Miller’s detailed explanation of this attribute and the reasoning behind it. Before I show any code, let me say: I strongly recommend using the official approach of using app.config to set this policy. That being said, there are (rare) times when, for one reason or another, changing the application configuration file is less than ideal. While this is the supported approach to handling this issue, the CLR Hosting API includes a means of setting this programmatically via the ICLRRuntimeInfo interface.  Normally, this is used if you’re hosting the CLR in a native application in order to set this, at runtime, prior to loading the assemblies.  However, the F# Samples include a nice trick showing how to load this API and bind this policy, at runtime.  This was required in order to host the Managed DirectX API, which is built against an older version of the CLR. This is fairly easy to port to C#.  Instead of a direct port, I also added a little addition – by trapping the COM exception received if unable to bind (which will occur if the 2.0 CLR is already bound), I also allow a runtime check of whether this property was setup properly: public static class RuntimePolicyHelper { public static bool LegacyV2RuntimeEnabledSuccessfully { get; private set; } static RuntimePolicyHelper() { ICLRRuntimeInfo clrRuntimeInfo = (ICLRRuntimeInfo)RuntimeEnvironment.GetRuntimeInterfaceAsObject( Guid.Empty, typeof(ICLRRuntimeInfo).GUID); try { clrRuntimeInfo.BindAsLegacyV2Runtime(); LegacyV2RuntimeEnabledSuccessfully = true; } catch (COMException) { // This occurs with an HRESULT meaning // "A different runtime was already bound to the legacy CLR version 2 activation policy." LegacyV2RuntimeEnabledSuccessfully = false; } } [ComImport] [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)] [Guid("BD39D1D2-BA2F-486A-89B0-B4B0CB466891")] private interface ICLRRuntimeInfo { void xGetVersionString(); void xGetRuntimeDirectory(); void xIsLoaded(); void xIsLoadable(); void xLoadErrorString(); void xLoadLibrary(); void xGetProcAddress(); void xGetInterface(); void xSetDefaultStartupFlags(); void xGetDefaultStartupFlags(); [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime)] void BindAsLegacyV2Runtime(); } } Using this, it’s possible to not only set this at runtime, but also verify, prior to loading your mixed mode assembly, whether this will succeed. In my case, this was quite useful – I am working on a library purely for internal use which uses a numerical package that is supplied with both a completely managed as well as a native solver.  The native solver uses a CLR 2 mixed-mode assembly, but is dramatically faster than the pure managed approach.  By checking RuntimePolicyHelper.LegacyV2RuntimeEnabledSuccessfully at runtime, I can decide whether to enable the native solver, and only do so if I successfully bound this policy. There are some tricks required here – To enable this sort of fallback behavior, you must make these checks in a type that doesn’t cause the mixed mode assembly to be loaded.  In my case, this forced me to encapsulate the library I was using entirely in a separate class, perform the check, then pass through the required calls to that class.  Otherwise, the library will load before the hosting process gets enabled, which in turn will fail. This code will also, of course, try to enable the runtime policy before the first time you use this class – which typically means just before the first time you check the boolean value.  As a result, checking this early on in the application is more likely to allow it to work. Finally, if you’re using a library, this has to be called prior to the 2.0 CLR loading.  This will cause it to fail if you try to use it to enable this policy in a plugin for most third party applications that don’t have their app.config setup properly, as they will likely have already loaded the 2.0 runtime. As an example, take a simple audio player.  The code below shows how this can be used to properly, at runtime, only use the “native” API if this will succeed, and fallback (or raise a nicer exception) if this will fail: public class AudioPlayer { private IAudioEngine audioEngine; public AudioPlayer() { if (RuntimePolicyHelper.LegacyV2RuntimeEnabledSuccessfully) { // This will load a CLR 2 mixed mode assembly this.audioEngine = new AudioEngineNative(); } else { this.audioEngine = new AudioEngineManaged(); } } public void Play(string filename) { this.audioEngine.Play(filename); } } Now – the warning: This approach works, but I would be very hesitant to use it in public facing production code, especially for anything other than initializing your own application.  While this should work in a library, using it has a very nasty side effect: you change the runtime policy of the executing application in a way that is very hidden and non-obvious.

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• C# 5 Async, Part 2: Asynchrony Today

  - by Reed

  The .NET Framework has always supported asynchronous operations.  However, different mechanisms for supporting exist throughout the framework.  While there are at least three separate asynchronous patterns used through the framework, only the latest is directly usable with the new Visual Studio Async CTP.  Before delving into details on the new features, I will talk about existing asynchronous code, and demonstrate how to adapt it for use with the new pattern. The first asynchronous pattern used in the .NET framework was the Asynchronous Programming Model (APM).  This pattern was based around callbacks.  A method is used to start the operation.  It typically is named as BeginSomeOperation.  This method is passed a callback defined as an AsyncCallback, and returns an object that implements IAsyncResult.  Later, the IAsyncResult is used in a call to a method named EndSomeOperation, which blocks until completion and returns the value normally directly returned from the synchronous version of the operation.  Often, the EndSomeOperation call would be called from the callback function passed, which allows you to write code that never blocks. While this pattern works perfectly to prevent blocking, it can make quite confusing code, and be difficult to implement.  For example, the sample code provided for FileStream’s BeginRead/EndRead methods is not simple to understand.  In addition, implementing your own asynchronous methods requires creating an entire class just to implement the IAsyncResult. Given the complexity of the APM, other options have been introduced in later versions of the framework.  The next major pattern introduced was the Event-based Asynchronous Pattern (EAP).  This provides a simpler pattern for asynchronous operations.  It works by providing a method typically named SomeOperationAsync, which signals its completion via an event typically named SomeOperationCompleted. The EAP provides a simpler model for asynchronous programming.  It is much easier to understand and use, and far simpler to implement.  Instead of requiring a custom class and callbacks, the standard event mechanism in C# is used directly.  For example, the WebClient class uses this extensively.  A method is used, such as DownloadDataAsync, and the results are returned via the DownloadDataCompleted event. While the EAP is far simpler to understand and use than the APM, it is still not ideal.  By separating your code into method calls and event handlers, the logic of your program gets more complex.  It also typically loses the ability to block until the result is received, which is often useful.  Blocking often requires writing the code to block by hand, which is error prone and adds complexity. As a result, .NET 4 introduced a third major pattern for asynchronous programming.  The Task<T> class introduced a new, simpler concept for asynchrony.  Task and Task<T> effectively represent an operation that will complete at some point in the future.  This is a perfect model for thinking about asynchronous code, and is the preferred model for all new code going forward.  Task and Task<T> provide all of the advantages of both the APM and the EAP models – you have the ability to block on results (via Task.Wait() or Task<T>.Result), and you can stay completely asynchronous via the use of Task Continuations.  In addition, the Task class provides a new model for task composition and error and cancelation handling.  This is a far superior option to the previous asynchronous patterns. The Visual Studio Async CTP extends the Task based asynchronous model, allowing it to be used in a much simpler manner.  However, it requires the use of Task and Task<T> for all operations.

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• Attached Property port of my Window Close Behavior

  - by Reed

  Nishant Sivakumar just posted a nice article on The Code Project.  It is a port of the MVVM-friendly Blend Behavior I wrote about in a previous article to WPF using Attached Properties. While similar to the WindowCloseBehavior code I posted on the Expression Code Gallery, Nishant Sivakumar’s version works in WPF without taking a dependency on the Expression Blend SDK. I highly recommend reading this article: Handling a Window’s Closed and Closing Events in the View-Model.  It is a very nice alternative approach to this common problem in MVVM.

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• Async CTP Refresh for Visual Studio 2010 SP1 Released

  - by Reed

  The Visual Studio team today released an update to the Visual Studio Async CTP which allows it to be used with Visual Studio SP1.  This new CTP includes some very nice new additions over the previous CTP.  The main highlights of this release include: Compatibility with Visual Studio SP1 APIs for Windows Phone 7 Compatibility with non-English installations Compatibility with Visual Studio Express Edition More efficient Async methods due to a change in the API Numerous bug fixes New EULA which allows distribution in production environments Anybody using the Async CTP should consider upgrading to the new version immediately.  For details, visit the Visual Studio Asynchronous Programming page on MSDN.

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• C# 5 Async, Part 3: Preparing Existing code For Await

  - by Reed

  While the Visual Studio Async CTP provides a fantastic model for asynchronous programming, it requires code to be implemented in terms of Task and Task<T>.  The CTP adds support for Task-based asynchrony to the .NET Framework methods, and promises to have these implemented directly in the framework in the future.  However, existing code outside the framework will need to be converted to using the Task class prior to being usable via the CTP. Wrapping existing asynchronous code into a Task or Task<T> is, thankfully, fairly straightforward.  There are two main approaches to this. Code written using the Asynchronous Programming Model (APM) is very easy to convert to using Task<T>.  The TaskFactory class provides the tools to directly convert APM code into a method returning a Task<T>.  This is done via the FromAsync method.  This method takes the BeginOperation and EndOperation methods, as well as any parameters and state objects as arguments, and returns a Task<T> directly. For example, we could easily convert the WebRequest BeginGetResponse and EndGetResponse methods into a method which returns a Task<WebResponse> via: Task<WebResponse> task = Task.Factory .FromAsync<WebResponse>( request.BeginGetResponse, request.EndGetResponse, null); .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; } Event-based Asynchronous Pattern (EAP) code can also be wrapped into a Task<T>, though this requires a bit more effort than the one line of code above.  This is handled via the TaskCompletionSource<T> class.  MSDN provides a detailed example of using this to wrap an EAP operation into a method returning Task<T>.  It demonstrates handling cancellation and exception handling as well as the basic operation of the asynchronous method itself. The basic form of this operation is typically: Task<YourResult> GetResultAsync() { var tcs = new TaskCompletionSource<YourResult>(); // Handle the event, and setup the task results... this.GetResultCompleted += (o,e) => { if (e.Error != null) tcs.TrySetException(e.Error); else if (e.Cancelled) tcs.TrySetCanceled(); else tcs.TrySetResult(e.Result); }; // Call the asynchronous method this.GetResult(); // Return the task from the TaskCompletionSource return tcs.Task; } We can easily use these methods to wrap our own code into a method that returns a Task<T>.  Existing libraries which cannot be edited can be extended via Extension methods.  The CTP uses this technique to add appropriate methods throughout the framework. The suggested naming for these methods is to define these methods as “Task<YourResult> YourClass.YourOperationAsync(…)”.  However, this naming often conflicts with the default naming of the EAP.  If this is the case, the CTP has standardized on using “Task<YourResult> YourClass.YourOperationTaskAsync(…)”. Once we’ve wrapped all of our existing code into operations that return Task<T>, we can begin investigating how the Async CTP can be used with our own code.

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• ConcurrentDictionary<TKey,TValue> used with Lazy<T>

  - by Reed

  In a recent thread on the MSDN forum for the TPL, Stephen Toub suggested mixing ConcurrentDictionary<T,U> with Lazy<T>.  This provides a fantastic model for creating a thread safe dictionary of values where the construction of the value type is expensive.  This is an incredibly useful pattern for many operations, such as value caches. The ConcurrentDictionary<TKey, TValue> class was added in .NET 4, and provides a thread-safe, lock free collection of key value pairs.  While this is a fantastic replacement for Dictionary<TKey, TValue>, it has a potential flaw when used with values where construction of the value class is expensive. The typical way this is used is to call a method such as GetOrAdd to fetch or add a value to the dictionary.  It handles all of the thread safety for you, but as a result, if two threads call this simultaneously, two instances of TValue can easily be constructed. If TValue is very expensive to construct, or worse, has side effects if constructed too often, this is less than desirable.  While you can easily work around this with locking, Stephen Toub provided a very clever alternative – using Lazy<TValue> as the value in the dictionary instead. This looks like the following.  Instead of calling: MyValue value = dictionary.GetOrAdd( key, () => new MyValue(key)); .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 instead use a ConcurrentDictionary<TKey, Lazy<TValue>>, and write: MyValue value = dictionary.GetOrAdd( key, () => new Lazy<MyValue>( () => new MyValue(key))) .Value; This simple change dramatically changes how the operation works.  Now, if two threads call this simultaneously, instead of constructing two MyValue instances, we construct two Lazy<MyValue> instances. However, the Lazy<T> class is very cheap to construct.  Unlike “MyValue”, we can safely afford to construct this twice and “throw away” one of the instances. We then call Lazy<T>.Value at the end to fetch our “MyValue” instance.  At this point, GetOrAdd will always return the same instance of Lazy<MyValue>.  Since Lazy<T> doesn’t construct the MyValue instance until requested, the actual MyClass instance returned is only constructed once.

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• Slides and Code from “Using C#’s Async Effectively”

  - by Reed

  The slides and code from my talk on the new async language features in C# and VB.Net are now available on https://github.com/ReedCopsey/Effective-Async This includes the complete slide deck, and all 4 projects, including: FakeService: Simple WCF service to run locally and simulate network service calls. AsyncService: Simple WCF service which wraps FakeService to demonstrate converting sync to async SimpleWPFExample: Simplest example of converting a method call to async from a synchronous version AsyncExamples: Windows Store application demonstrating main concepts, pitfalls, tips, and tricks from the slide deck

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• SQL Joing on a one-to-many relationship

  - by Harley

  Ok, here was my original question; Table one contains ID|Name 1 Mary 2 John Table two contains ID|Color 1 Red 2 Blue 2 Green 2 Black I want to end up with is ID|Name|Red|Blue|Green|Black 1 Mary Y Y 2 John Y Y Y It seems that because there are 11 unique values for color and 1000's upon 1000's of records in table one that there is no 'good' way to do this. So, two other questions. Is there an efficient way to get this result? I can then create a crosstab in my application to get the desired result. ID|Name|Color 1 Mary Red 1 Mary Blue 2 John Blue 2 John Green 2 John Black If I wanted to limit the number of records returned how could I do something like this? Where ((color='blue') AND (color<>'red' OR color<>'green')) So using the above example I would then get back ID|Name|Color 1 Mary Blue 2 John Blue 2 John Black I connect to Visual FoxPro tables via ADODB. Thanks!

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• How to detect if certain characters are at the end of an NSString?

  - by Sheehan Alam

  Let's assume I can have the following strings: "hey @john..." "@john, hello" "@john(hello)" I am tokenizing the string to get every word separated by a space: [myString componentsSeparatedByString:@" "]; My array of tokens now contain: @john... @john, @john(hello) For these cases. How can I make sure only @john is tokenized, while retaining the trailing characters: ... , (hello) Note: I would like to be able to handle all cases of characters at the end of a string. The above are just 3 examples.

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• JavaScript function binding (this keyword) is lost after assignment

  - by Ding

  this is one of most mystery feature in JavaScript, after assigning the object method to other variable, the binding (this keyword) is lost var john = { name: 'John', greet: function(person) { alert("Hi " + person + ", my name is " + this.name); } }; john.greet("Mark"); // Hi Mark, my name is John var fx = john.greet; fx("Mark"); // Hi Mark, my name is my question is: 1) what is happening behind the assignment? var fx = john.greet; is this copy by value or copy by reference? fx and john.greet point to two diferent function, right? 2) since fx is a global method, the scope chain contains only global object. what is the value of this property in Variable object?

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• Python Multiword Index

  - by Manab Chetia

  index = {'Michael': [['mj.com',1], ['Nine.com',9],['i.com', 34]], / 'Jackson': [['One.com',4],['mj.com', 2],['Nine.com', 10], ['i.com', 45]], / 'Thriller' : [['Seven.com', 7], ['Ten.com',10], ['One.com', 5], ['mj.com',3]} # In this dictionary (index), for eg: 'KEYWORD': # [['THE LINK in which KEYWORD is present,'POSITION # of KEYWORD in the page specified by link']] eg: Michael is present in MJ.com, NINE.com, and i.com at positions 1, 9, 34 of respective pages. Please help me with a python procedure which takes index and KEYWORDS as input. When i enter 'MICHAEL'. The result should be: >>['mj.com', 'nine.com', 'i.com'] When I enter 'MICHAEL JACKSON'. The result should be : >>['mj.com', 'Nine.com'] as 'Michael' and 'Jackson' are present at 'mj.com' and 'nine.com' consecutively i.e. in positions (1,2) & (9,10) respectively. The result should not show 'i.com' even though it contains both KEYWORDS but they are not placed consecutively. When I enter 'MICHAEL JACKSON THRILLER', the result should be ['mj.com'] as the 3 words 'MICHAEL', 'JACKSON', 'THRILLER' are placed consecutively in 'mj.com' ie positions (1, 2, 3) respectively. If I enter 'THRILLER JACKSON' or 'THRILLER FEDERER', the result should be NONE.

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• CoreStore Encryption Error on Mac Lion

  - by Michael

  I am trying to encrypt an external drive using diskutil CoreStorage on Mac Lion 10.7.4. I thought the only requirements were that the drive have GUID partition scheme and Journaled HFS+ file system. I think my drive is configured accordingly but when I type the following command I get an error message back: Michaels-MacBook-Pro:~ Michael$ diskutil cs convert disk2 -passphrase TestPassword Error converting disk to CoreStorage: The given file system is not supported on Core Storage (-69756) Here are the details reported for the drive in question: Michaels-MacBook-Pro:~ Michael$ diskutil list disk2 /dev/disk2 #: TYPE NAME SIZE IDENTIFIER 0: GUID_partition_scheme *500.1 GB disk2 1: EFI 209.7 MB disk2s1 2: Apple_HFS Test1 499.8 GB disk2s2 Michaels-MacBook-Pro:~ Michael$ diskutil list disk2 /dev/disk2 #: TYPE NAME SIZE IDENTIFIER 0: GUID_partition_scheme *500.1 GB disk2 1: EFI 209.7 MB disk2s1 2: Apple_HFS Test1 499.8 GB disk2s2 Michaels-MacBook-Pro:~ Michael$ diskutil info disk2s2 Device Identifier: disk2s2 Device Node: /dev/disk2s2 Part of Whole: disk2 Device / Media Name: Test1 Volume Name: Test1 Escaped with Unicode: Test1 Mounted: Yes Mount Point: /Volumes/Test1 Escaped with Unicode: /Volumes/Test1 File System Personality: Journaled HFS+ Type (Bundle): hfs Name (User Visible): Mac OS Extended (Journaled) Journal: Journal size 40960 KB at offset 0xe8e000 Owners: Disabled Partition Type: Apple_HFS OS Can Be Installed: Yes Media Type: Generic Protocol: FireWire SMART Status: Not Supported Volume UUID: 1024D0B8-1C45-3057-B040-AE5C3841DABF Total Size: 499.8 GB (499763888128 Bytes) (exactly 976101344 512-Byte-Blocks) Volume Free Space: 499.3 GB (499315826688 Bytes) (exactly 975226224 512-Byte-Blocks) Device Block Size: 512 Bytes Read-Only Media: No Read-Only Volume: No Ejectable: Yes Whole: No Internal: No I'm a little concerned that the "Partition Type: Apple_HFS" entry is causing the problem, but I don't know how to change that. I only seem to be able to control the "File System Personality: Journaled HFS+" in Disk Utility. Can anyone shed some light on this for me?

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• SSH and Active Directory authentication

  - by disserman

  Is it possible to set up Linux (and Solaris) SSH server to authenticate users in this way: i.e. user john is a member of the group Project1_Developers in the Active Directory. we have something on the server A (running Linux, the server has an access to the AD via i.e. LDAP) in the SSH server LDAP (or other module) authentication config like root=Project1_Developers,Company_NIX_Admins. when john connects to the server A using his username "john" and domain password, the server checks the john's group in the domain and if the group is "Project1_Developers" or "Company_NIX_Admins", makes him locally as a root with a root privileges. The idea is also to have only a "root" and a system users on the server, without adding user "john" to all servers where John can log in. Any help or the idea how to make the above or something similar to the above? Preferred using AD but any other similar solution is also possible. p.s. please don't open a discussions is it secure to login via ssh as root or not, thanks :)

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• JavaScript Class Patterns Revisited: Endgame

  - by Liam McLennan

  I recently described some of the patterns used to simulate classes (types) in JavaScript. But I missed the best pattern of them all. I described a pattern I called constructor function with a prototype that looks like this: function Person(name, age) { this.name = name; this.age = age; } Person.prototype = { toString: function() { return this.name + " is " + this.age + " years old."; } }; var john = new Person("John Galt", 50); console.log(john.toString()); and I mentioned that the problem with this pattern is that it does not provide any encapsulation, that is, it does not allow private variables. Jan Van Ryswyck recently posted the solution, obvious in hindsight, of wrapping the constructor function in another function, thereby allowing private variables through closure. The above example becomes: var Person = (function() { // private variables go here var name,age; function constructor(n, a) { name = n; age = a; } constructor.prototype = { toString: function() { return name + " is " + age + " years old."; } }; return constructor; })(); var john = new Person("John Galt", 50); console.log(john.toString()); Now we have prototypal inheritance and encapsulation. The important thing to understand is that the constructor, and the toString function both have access to the name and age private variables because they are in an outer scope and they become part of the closure.

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