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• Organization &amp; Architecture UNISA Studies &ndash; Chap 6

  - by MarkPearl

  Learning Outcomes Discuss the physical characteristics of magnetic disks Describe how data is organized and accessed on a magnetic disk Discuss the parameters that play a role in the performance of magnetic disks Describe different optical memory devices Magnetic Disk The way data is stored on and retried from magnetic disks Data is recorded on and later retrieved form the disk via a conducting coil named the head (in many systems there are two heads) The writ mechanism exploits the fact that electricity flowing through a coil produces a magnetic field. Electric pulses are sent to the write head, and the resulting magnetic patterns are recorded on the surface below with different patterns for positive and negative currents The physical characteristics of a magnetic disk   Summarize from book   The factors that play a role in the performance of a disk Seek time – the time it takes to position the head at the track Rotational delay / latency – the time it takes for the beginning of the sector to reach the head Access time – the sum of the seek time and rotational delay Transfer time – the time it takes to transfer data RAID The rate of improvement in secondary storage performance has been considerably less than the rate for processors and main memory. Thus secondary storage has become a bit of a bottleneck. RAID works on the concept that if one disk can be pushed so far, additional gains in performance are to be had by using multiple parallel components. Points to note about RAID… RAID is a set of physical disk drives viewed by the operating system as a single logical drive Data is distributed across the physical drives of an array in a scheme known as striping Redundant disk capacity is used to store parity information, which guarantees data recoverability in case of a disk failure (not supported by RAID 0 or RAID 1) Interesting to note that the increase in the number of drives, increases the probability of failure. To compensate for this decreased reliability RAID makes use of stored parity information that enables the recovery of data lost due to a disk failure.   The RAID scheme consists of 7 levels…   Category Level Description Disks Required Data Availability Large I/O Data Transfer Capacity Small I/O Request Rate Striping 0 Non Redundant N Lower than single disk Very high Very high for both read and write Mirroring 1 Mirrored 2N Higher than RAID 2 – 5 but lower than RAID 6 Higher than single disk Up to twice that of a signle disk for read Parallel Access 2 Redundant via Hamming Code N + m Much higher than single disk Highest of all listed alternatives Approximately twice that of a single disk Parallel Access 3 Bit interleaved parity N + 1 Much higher than single disk Highest of all listed alternatives Approximately twice that of a single disk Independent Access 4 Block interleaved parity N + 1 Much higher than single disk Similar to RAID 0 for read, significantly lower than single disk for write Similar to RAID 0 for read, significantly lower than single disk for write Independent Access 5 Block interleaved parity N + 1 Much higher than single disk Similar to RAID 0 for read, lower than single disk for write Similar to RAID 0 for read, generally  lower than single disk for write Independent Access 6 Block interleaved parity N + 2 Highest of all listed alternatives Similar to RAID 0 for read; lower than RAID 5 for write Similar to RAID 0 for read, significantly lower than RAID 5  for write   Read page 215 – 221 for detailed explanation on RAID levels Optical Memory There are a variety of optical-disk systems available. Read through the table on page 222 – 223 Some of the devices include… CD CD-ROM CD-R CD-RW DVD DVD-R DVD-RW Blue-Ray DVD Magnetic Tape Most modern systems use serial recording – data is lade out as a sequence of bits along each track. The typical recording used in serial is referred to as serpentine recording. In this technique when data is being recorded, the first set of bits is recorded along the whole length of the tape. When the end of the tape is reached the heads are repostioned to record a new track, and the tape is again recorded on its whole length, this time in the opposite direction. That process continued back and forth until the tape is full. To increase speed, the read-write head is capable of reading and writing a number of adjacent tracks simultaneously. Data is still recorded serially along individual tracks, but blocks in sequence are stored on adjacent tracks as suggested. A tape drive is a sequential access device. Magnetic tape was the first kind of secondary memory. It is still widely used as the lowest-cost, slowest speed member of the memory hierarchy.

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• links worth clicking&hellip;

  - by Chris Williams

  Scanning my Twitter feed almost always proves to be fruitful when looking for cool/interesting links to share. Here are a few of the highlights: I read this blog post from Justin Angel today, pretty interesting stuff: Windows Phone 7 – Unlocked ROMs  Looks like there’s a lot of good stuff floating just under the surface in the latest build of the WP7 Emulator. (Courtesy of @JustinAngel) Next up is this video titled Game Design Tutorials: From Seconds to Hours of Gameplay. If you’re into Indie Game Development, or just like watching videos… this one is pretty short at 5 minutes, but contains some good information about increasing the duration of fun gameplay in your game. (Courtesy of @Kei_tchan) If you are a Firefly (or Castle, or Dr. Horrible’s Singalong Blog) fan, check out this Facebook campaign to get Nathan Fillion to host SNL: http://tinyurl.com/2dh5m67  It worked for Betty White, so why not, right? (Courtesy of @DGalloway42)

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• Save password in WCF adapter binding file

  - by Edmund Zhao

  Binding file for WCF Adapter doesn't save the password no matter it is generated by "Add Generated Items..." wizard in Visual Studio or "Export Bindings..." in administration console. It is by design dut to the consideration of security, but it is very annoying especially when you import bindings which contain multiple WCF send ports. The way to aviod retyping password everytime after an import is to edit the binding file before import. Here is what needs to be done. 1. Find the following string:     &lt;Password vt="1" /&gt; "&lt;" means "<", "&gt;" means ">", "vt" means "Variable Type", variable type 1 is "NULL", so the above string can be translated to "<Password/>" 2. Replace it with:     &lt;Password vt="8"&gt;MyPassword&lt;/Password&gt;    variable type 8 is "string", the above string can be transalted to "<Password>MyPassword</Password>"   Binding file uses a lot of character entity references for XML character encoding purpose. For a list of the special charactor entiy references, you can check from here. ...Edmund Zhao

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• Great User Group if based near Gloucester + Links from Entity Framework 4.0 session

  - by Eric Nelson

  I had a really fun evening doing “my final” EF 4.0 session last night (26th May 2010) at GL.NET based out of Gloucester (although secretly I made it into a IronRuby and Windows Azure session). They are a great crowd and Jimmy makes for a fantastic host + it is a very nice venue (Symantec offices in Gloucester, lots of parking, good room etc) + free pizza + free SWAG + trip to pub afterwards (the topics were very varied!). What more could you ask for? The next session is June 16th and will be on multi-tenanted ASP.NET MVC and comes highly recommended. Links from my session: Entity Framework 4 Resources http://bit.ly/ef4resources Entity Framework Team Blog http://blogs.msdn.com/adonet Entity Framework Design Blog http://blogs.msdn.com/efdesign/ The must have LINQPad http://www.linqpad.net Entity Framework Profile http://efprof.com/  IronRuby info on my blog http://geekswithblogs.net/iupdateable/category/10076.aspx

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• Developing for 2005 using VS2008!

  - by Vincent Grondin

  I joined a fairly large project recently and it has a particularity… Once finished, everything has to be sent to the client under VS2005 using VB.Net and can target either framework 2.0 or 3.0… A long time ago, the decision to use VS2008 and to target framework 3.0 was taken but people knew they would need to establish a few rules to ensure that each dev would use VS2008 as if it was VS2005… Why is that so? Well simply because the compiler in VS2005 is different from the compiler inside VS2008…  I thought it might be a good idea to note the things that you cannot use in VS2008 if you plan on going back to VS2005. Who knows, this might save someone the headache of going over all their code to fix errors… -        Do not use LinQ keywords (from, in, select, orderby…).   -        Do not use LinQ standard operators under the form of extension methods.   -        Do not use type inference (in VB.Net you can switch it OFF in each project properties). o   This means you cannot use XML Literals.   -        Do not use nullable types under the following declarative form:    Dim myInt as Integer? But using:   Dim myInt as Nullable(Of Integer)     is perfectly fine.   -        Do not test nullable types with     Is Nothing    use    myInt.HasValue     instead.   -        Do not use Lambda expressions (there is no Lambda statements in VB9) so you cannot use the keyword “Function”.   -        Pay attention not to use relaxed delegates because this one is easy to miss in VS2008   -        Do not use Object Initializers   -        Do not use the “ternary If operator” … not the IIf method but this one     If(confition, truepart, falsepart).   As a side note, I talked about not using LinQ keyword nor the extension methods but, this doesn’t mean not to use LinQ in this scenario. LinQ is perfectly accessible from inside VS2005. All you need to do is reference System.Core, use namespace System.Linq and use class “Enumerable” as a helper class… This is one of the many classes containing various methods that VS2008 sees as extensions. The trick is you can use them too! Simply remember that the first parameter of the method is the object you want to query on and then pass in the other parameters needed… That’s pretty much all I see but I could have missed a few… If you know other things that are specific to the VS2008 compiler and which do not work under VS2005, feel free to leave a comment and I’ll modify my list accordingly (and notify our team here…) ! Happy coding all!

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• Using LINQ to Twitter OAuth with Windows 8

  - by Joe Mayo

  In previous posts, I explained how to use LINQ to Twitter with Windows 8, but the example was a Twitter Search, which didn’t require authentication. Much of the Twitter API requires authentication, so this post will explain how you can perform OAuth authentication with LINQ to Twitter in a Windows 8 Metro-style application. Getting Started I have earlier posts on how to create a Windows 8 app and add pages, so I’ll assume it isn’t necessary to repeat here. One difference is that I’m using Visual Studio 2012 RC and some of the terminology and/or library code might be slightly different.  Here are steps to get started: Create a new Windows metro style app, selecting the Blank App project template. Create a new Basic Page and name it OAuth.xaml.  Note: You’ll receive a prompt window for adding files and you should click Yes because those files are necessary for this demo. Add a new Basic Page named TweetPage.xaml. Open App.xaml.cs and change !rootFrame.Navigate(typeof(MainPage)) to !rootFrame.Navigate(typeof(TweetPage)). Now that the project is set up you’ll see the reason why authentication is required by setting up the TweetPage. Setting Up to Tweet a Status In this section, I’ll show you how to set up the XAML and code-behind for a tweet.  The tweet logic will check to see if the user is authenticated before performing the tweet. To tweet, I put a TextBox and Button on the XAML page. The following code omits most of the page, concentrating primarily on the elements of interest in this post: <StackPanel Grid.Row="1"> <TextBox Name="TweetTextBox" Margin="15" /> <Button Name="TweetButton" Content="Tweet" Click="TweetButton_Click" Margin="15,0" /> </StackPanel> Given the UI above, the user types the message they want to tweet, and taps Tweet. This invokes TweetButton_Click, which checks to see if the user is authenticated.  If the user is not authenticated, the app navigates to the OAuth page.  If they are authenticated, LINQ to Twitter does an UpdateStatus to post the user’s tweet.  Here’s the TweetButton_Click implementation: void TweetButton_Click(object sender, RoutedEventArgs e) { PinAuthorizer auth = null; if (SuspensionManager.SessionState.ContainsKey("Authorizer")) { auth = SuspensionManager.SessionState["Authorizer"] as PinAuthorizer; } if (auth == null || !auth.IsAuthorized) { Frame.Navigate(typeof(OAuthPage)); return; } var twitterCtx = new TwitterContext(auth); Status tweet = twitterCtx.UpdateStatus(TweetTextBox.Text); new MessageDialog(tweet.Text, "Successful Tweet").ShowAsync(); } For authentication, this app uses PinAuthorizer, one of several authorizers available in the LINQ to Twitter library. I’ll explain how PinAuthorizer works in the next section. What’s important here is that LINQ to Twitter needs an authorizer to post a Tweet. The code above checks to see if a valid authorizer is available. To do this, it uses the SuspensionManager class, which is part of the code generated earlier when creating OAuthPage.xaml. The SessionState property is a Dictionary<string, object> and I’m using the Authorizer key to store the PinAuthorizer.  If the user previously authorized during this session, the code reads the PinAuthorizer instance from SessionState and assigns it to the auth variable. If the user is authorized, auth would not be null and IsAuthorized would be true. Otherwise, the app navigates the user to OAuthPage.xaml, which I’ll discuss in more depth in the next section. When the user is authorized, the code passes the authorizer, auth, to the TwitterContext constructor. LINQ to Twitter uses the auth instance to build OAuth signatures for each interaction with Twitter.  You no longer need to write any more code to make this happen. The code above accepts the tweet just posted in the Status instance, tweet, and displays a message with the text to confirm success to the user. You can pull the PinAuthorizer instance from SessionState, instantiate your TwitterContext, and use it as you need. Just remember to make sure you have a valid authorizer, like the code above. As shown earlier, the code navigates to OAuthPage.xaml when a valid authorizer isn’t available. The next section shows how to perform the authorization upon arrival at OAuthPage.xaml. Doing the OAuth Dance This section shows how to authenticate with LINQ to Twitter’s built-in OAuth support. From the user perspective, they must be navigated to the Twitter authentication page, add credentials, be navigated to a Pin number page, and then enter that Pin in the Windows 8 application. The following XAML shows the relevant elements that the user will interact with during this process. <StackPanel Grid.Row="2"> <WebView x:Name="OAuthWebBrowser" HorizontalAlignment="Left" Height="400" Margin="15" VerticalAlignment="Top" Width="700" /> <TextBlock Text="Please perform OAuth process (above), enter Pin (below) when ready, and tap Authenticate:" Margin="15,15,15,5" /> <TextBox Name="PinTextBox" Margin="15,0,15,15" Width="432" HorizontalAlignment="Left" IsEnabled="False" /> <Button Name="AuthenticatePinButton" Content="Authenticate" Margin="15" IsEnabled="False" Click="AuthenticatePinButton_Click" /> </StackPanel> The WebView in the code above is what allows the user to see the Twitter authentication page. The TextBox is for entering the Pin, and the Button invokes code that will take the Pin and allow LINQ to Twitter to complete the authentication process. As you can see, there are several steps to OAuth authentication, but LINQ to Twitter tries to minimize the amount of code you have to write. The two important parts of the code to make this happen are the part that starts the authentication process and the part that completes the authentication process. The following code, from OAuthPage.xaml.cs, shows a couple events that are instrumental in making this process happen: public OAuthPage() { this.InitializeComponent(); this.Loaded += OAuthPage_Loaded; OAuthWebBrowser.LoadCompleted += OAuthWebBrowser_LoadCompleted; } The OAuthWebBrowser_LoadCompleted event handler enables UI controls when the browser is done loading – notice that the TextBox and Button in the previous XAML have their IsEnabled attributes set to False. When the Page.Loaded event is invoked, the OAuthPage_Loaded handler starts the OAuth process, shown here: void OAuthPage_Loaded(object sender, RoutedEventArgs e) { auth = new PinAuthorizer { Credentials = new InMemoryCredentials { ConsumerKey = "", ConsumerSecret = "" }, UseCompression = true, GoToTwitterAuthorization = pageLink => Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () => OAuthWebBrowser.Navigate(new Uri(pageLink, UriKind.Absolute))) }; auth.BeginAuthorize(resp => Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () => { switch (resp.Status) { case TwitterErrorStatus.Success: break; case TwitterErrorStatus.RequestProcessingException: case TwitterErrorStatus.TwitterApiError: new MessageDialog(resp.Error.ToString(), resp.Message).ShowAsync(); break; } })); } The PinAuthorizer, auth, a field of this class instantiated in the code above, assigns keys to the Credentials property. These are credentials that come from registering an application with Twitter, explained in the LINQ to Twitter documentation, Securing Your Applications. Notice how I use Dispatcher.RunAsync to marshal the web browser navigation back onto the UI thread. Internally, LINQ to Twitter invokes the lambda expression assigned to GoToTwitterAuthorization when starting the OAuth process.  In this case, we want the WebView control to navigate to the Twitter authentication page, which is defined with a default URL in LINQ to Twitter and passed to the GoToTwitterAuthorization lambda as pageLink. Then you need to start the authorization process by calling BeginAuthorize. This starts the OAuth dance, running asynchronously.  LINQ to Twitter invokes the callback assigned to the BeginAuthorize parameter, allowing you to take whatever action you need, based on the Status of the response, resp. As mentioned earlier, this is where the user performs the authentication process, enters the Pin, and clicks authenticate. The handler for authenticate completes the process and saves the authorizer for subsequent use by the application, as shown below: void AuthenticatePinButton_Click(object sender, RoutedEventArgs e) { auth.CompleteAuthorize( PinTextBox.Text, completeResp => Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () => { switch (completeResp.Status) { case TwitterErrorStatus.Success: SuspensionManager.SessionState["Authorizer"] = auth; Frame.Navigate(typeof(TweetPage)); break; case TwitterErrorStatus.RequestProcessingException: case TwitterErrorStatus.TwitterApiError: new MessageDialog(completeResp.Error.ToString(), completeResp.Message).ShowAsync(); break; } })); } The PinAuthorizer CompleteAuthorize method takes two parameters: Pin and callback. The Pin is from what the user entered in the TextBox prior to clicking the Authenticate button that invoked this method. The callback handles the response from completing the OAuth process. The completeResp holds information about the results of the operation, indicated by a Status property of type TwitterErrorStatus. On success, the code assigns auth to SessionState. You might remember SessionState from the previous description of TweetPage – this is where the valid authorizer comes from. After saving the authorizer, the code navigates the user back to TweetPage, where they can type in a message, click the Tweet button, and observe that they have successfully tweeted. Summary You’ve seen how to get started with using LINQ to Twitter in a Metro-style application. The generated code contained a SuspensionManager class with way to manage information across multiple pages via its SessionState property. You also saw how LINQ to Twitter performs authorization in two steps of starting the process and completing the process when the user provides a Pin number. Remember to marshal callback thread back onto the UI – you saw earlier how to use Dispatcher.RunAsync to accomplish this. There were a few steps in the process, but LINQ to Twitter did minimize the amount of code you needed to write to make it happen. You can download the MetroOAuthDemo.zip sample on the LINQ to Twitter Samples Page.   @JoeMayo

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• The Iron Bird Approach

  - by David Paquette

  It turns out that designing software is not so different than designing commercial aircraft.  I just finished watching a video that talked about the approach that Bombardier is taking in designing the new C Series aircraft.  I was struck by the similarities to agile approaches to software design.  In the video, Bombardier describes how they are using an Iron Bird to work through a number of design questions in advance of ever having a version of the aircraft that can ever be flown.  The Iron Bird is a life size replica of the plane.  Based on the name, I would assume the plane is built in a very heavy material that could never fly.  Using this replica, Bombardier is able to valid certain assumptions such as the length of each wire in the electric system.  They are also able to confirm that some parts are working properly (like the rudders).  They even go as far as to have a complete replica of the cockpit.  This allows Bombardier to put pilots in the cockpit to run through simulated take-off and landing sequences. The basic tenant of the approach seems to be Validate your design early with working prototypes Get feedback from users early, well in advance of finishing the end product   In software development, we tend to think of ourselves as special.  I often tell people that it is difficult to draw comparisons to building items in the physical world (“Building software is nothing like building a sky scraper”).  After watching this video, I am wondering if designing/building software is actually a lot like designing/building commercial aircraft.   Watch the video here (http://www.theglobeandmail.com/report-on-business/video/video-selling-the-c-series/article4400616/)

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• Recursion in the form of a Recursive Func&lt;T, T&gt;

  - by ToStringTheory

  I gotta admit, I am kind of surprised that I didn’t realize I could do this sooner.  I recently had a problem which required a recursive function call to come up with the answer.  After some time messing around with a recursive method, and creating an API that I was not happy with, I was able to create an API that I enjoy, and seems intuitive. Introduction To bring it to a simple example, consider the summation to n: A mathematically identical formula is: In a .NET function, this can be represented by a function: Func<int, int> summation = x => x*(x+1)/2 Calling summation with an input integer will yield the summation to that number: var sum10 = summation(4); //sum10 would be equal to 10 But what if I wanted to get a second level summation…  First some to n, and then use that argument as the input to the same function, to find the second level summation: So as an easy example, calculate the summation to 3, which yields 6.  Then calculate the summation to 6 which yields 21. Represented as a mathematical formula - So what if I wanted to represent this as .NET functions.  I can always do: //using the summation formula from above var sum3 = summation(3); //sets sum3 to 6 var sum3_2 = summation(sum3); //sets sum3 to 21 I could always create a while loop to perform the calculations too: Func<int, int> summation = x => x*(x+1)/2; //for the interests of a smaller example, using shorthand int sumResultTo = 3; int level = 2; while(level-- > 0) { sumResultTo = summation(sumResultTo); } //sumResultTo is equal to 21 now. Or express it as a for-loop, method calls, etc…  I really didn’t like any of the options that I tried.  Then it dawned on me – since I was using a Func<T, T> anyways, why not use the Func’s output from one call as the input as another directly. Some Code So, I decided that I wanted a recursion class.  Something that I would be generic and reusable in case I ever wanted to do something like this again. It is limited to only the Func<T1, T2> level of Func, and T1 must be the same as T2. The first thing in this class is a private field for the function: private readonly Func<T, T> _functionToRecurse; So, I since I want the function to be unchangeable, I have defined it as readonly.  Therefore my constructor looks like: public Recursion(Func<T, T> functionToRecurse) { if (functionToRecurse == null) { throw new ArgumentNullException("functionToRecurse", "The function to recurse can not be null"); } _functionToRecurse = functionToRecurse; } Simple enough.  If you have any questions, feel free to post them in the comments, and I will be sure to answer them. Next, I want enough. If be able to get the result of a function dependent on how many levels of recursion: private Func<T, T> GetXLevel(int level) { if (level < 1) { throw new ArgumentOutOfRangeException("level", level, "The level of recursion must be greater than 0"); } if (level == 1) return _functionToRecurse; return _GetXLevel(level - 1, _functionToRecurse); } So, if you pass in 1 for the level, you get just the Func<T,T> back.  If you say that you want to go deeper down the rabbit hole, it calls a method which accepts the level it is at, and the function which it needs to use to recurse further: private Func<T, T> _GetXLevel(int level, Func<T, T> prevFunc) { if (level == 1) return y => prevFunc(_functionToRecurse(y)); return _GetXLevel(level - 1, y => prevFunc(_functionToRecurse(y))); } That is really all that is needed for this class. If I exposed the GetXLevel function publicly, I could use that to get the function for a level, and pass in the argument..  But I wanted something better.  So, I used the ‘this’ array operator for the class: public Func<T,T> this[int level] { get { if (level < 1) { throw new ArgumentOutOfRangeException("level", level, "The level of recursion must be greater than 0"); } return this.GetXLevel(level); } } So, using the same example above of finding the second recursion of the summation of 3: var summator = new Recursion<int>(x => (x * (x + 1)) / 2); var sum_3_level2 = summator[2](3); //yields 21 You can even find just store the delegate to the second level summation, and use it multiple times: var summator = new Recursion<int>(x => (x * (x + 1)) / 2); var sum_level2 = summator[2]; var sum_3_level2 = sum_level2(3); //yields 21 var sum_4_level2 = sum_level2(4); //yields 55 var sum_5_level2 = sum_level2(5); //yields 120 Full Code Don’t think I was just going to hold off on the full file together and make you do the hard work…  Copy this into a new class file: public class Recursion<T> { private readonly Func<T, T> _functionToRecurse; public Recursion(Func<T, T> functionToRecurse) { if (functionToRecurse == null) { throw new ArgumentNullException("functionToRecurse", "The function to recurse can not be null"); } _functionToRecurse = functionToRecurse; } public Func<T,T> this[int level] { get { if (level < 1) { throw new ArgumentOutOfRangeException("level", level, "The level of recursion must be greater than 0"); } return this.GetXLevel(level); } } private Func<T, T> GetXLevel(int level) { if (level < 1) { throw new ArgumentOutOfRangeException("level", level, "The level of recursion must be greater than 0"); } if (level == 1) return _functionToRecurse; return _GetXLevel(level - 1, _functionToRecurse); } private Func<T, T> _GetXLevel(int level, Func<T, T> prevFunc) { if (level == 1) return y => prevFunc(_functionToRecurse(y)); return _GetXLevel(level - 1, y => prevFunc(_functionToRecurse(y))); } } Conclusion The great thing about this class, is that it can be used with any function with same input/output parameters.  I strived to find an implementation that I found clean and useful, and I finally settled on this.  If you have feedback – good or bad, I would love to hear it!

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• Sneaky Javascript For Loop Bug

  - by Liam McLennan

  Javascript allows you to declare variables simply by assigning a value to an identify, in the same style as ruby: myVar = "some text"; Good javascript developers know that this is a bad idea because undeclared variables are assigned to the global object, usually window, making myVar globally visible. So the above code is equivalent to: window.myVar = "some text"; What I did not realise is that this applies to for loop initialisation as well. for (i = 0; i < myArray.length; i += 1) { } // is equivalent to for (window.i = 0; window.i < myArray.length; window.i += 1) { } Combine this with function calls nested inside of the for loops and you get some very strange behaviour, as the value of i is modified simultaneously by code in different scopes. The moral of the story is to ALWAYS declare javascript variables with the var keyword, even when intialising a for loop. for (var i = 0; i < myArray.length; i += 1) { }

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• Why is NDA so hard to understand?

  - by Dave Campbell

  Maybe this concept is simpler for me because of all the jobs I've been on over the years requiring security clearances. I've signed quite a few NDA forms. Some for big companies, some for small, but the meaning of "NDA" remains constant: Non-Disclosure Agreement. To me, that takes no further explanation, but apparently it's confusing to some people, and I don't understand how you can be confused. The papers I signed with the U.S. Army in 1970 read "10 years and $10,000" for a violation... can't imagine what it's up to now, but THAT is a strict NDA :) So those things I've been told, I cannot talk about, period. Even if the entire world knows about them, I cannot speak about them until the information goes off NDA. An example was a Silverlight release a while back. It might have been Silverlight 3, I don't remember. Everyone was anxiously awaiting the release so they could post their material. Of course the entire world knew it was coming out and imminently so. Some enterprising folks had even found the bits on a server before the official announcement. So then the situation became: everyone knew about it, some were even coding with it and blogging about it and yet we couldn't talk about it. Scott Guthrie's posting about it opened the flood gates and then it went off NDA, but up until that moment, we were locked. Sitting out on the edge you're uninstalling and re-installing all the time and you get frustrated when things that used to work don't, but hey... those bits were still warm when you got 'em, and that's the fun. But that fun comes at a price, and the price is the NDA. Awkward yes, confusing no... See you at MIX10, and Stay in the 'Light! MIX10

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• Windows Azure Interop

  - by kaleidoscope

  How Windows Azure Platform is an open cloud platform. What makes it interoperable? The Windows Azure platform supports popular standards and protocols including SOAP, REST, and XML. Developers can use their preferred programming frameworks including .NET, and PHP, now. Tools such as Eclipse have been created for PHP developers for building Windows Azure applications. Now external endpoints (inbound traffic) have been enabled to worker a role, which enables applications that receive internet traffic that aren’t running under IIS. Windows Azure interoperable with Java At PDC 09, solution accelerator for Tomcat is delivered. Tomcat is an open source software implementation of the Java Servlet and JavaServer Pages technologies. The Windows Azure solution accelerator leverages a PDC09 feature that enable arbitrary processes to bind to inbound service endpoints. Windows Azure interoperable with PHP The Windows Azure tools for Eclipse extension builds upon the PHP Development Toolkit (PDT) and integrates Web Tools Platform (WTP) to provide a complete toolkit for Windows Azure web application development. For more details please refer to the link: http://www.microsoft.com/windowsazure/faq/   Rituraj

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• Register now for the UK Windows Azure Self-paced Interactive Learning Course starting May 10th

  - by Eric Nelson

  [Suggested twitter tag #selfpacedazure] We (myself and David Gristwood) have been working in the UK to create a fantastic opportunity to get yourself up to speed on the Windows Azure Platform over a 6 week period starting May 10th – without ever needing to leave the comfort of your home/office.  The course is derived from the internal training Microsoft gives on Azure which is both fun and challenging in equal parts – and we felt was just too good to keep to ourselves! We will be releasing more details nearer the date but hopefully the following is enough to convince you to register and … recommend it to a colleague or three :-) What we have produced is the “Microsoft Azure Self-paced Learning Course”. This is a free, interactive, self-paced, technical training course covering the Windows Azure platform – Windows Azure, SQL Azure and the Azure AppFabric. The course takes place over a six week period finishing on June 18th. During the course you will work from your own home or workplace, and get involved via interactive Live Meetings session, watch on-line videos, work through hands-on labs and research and complete weekly coursework assignments. The mentors and other attendees on the course will help you in your research and learning, and there are weekly Live Meetings where you can raise questions and interact with them. This is a technical course, aimed at programmers, system designers, and architects who want a solid understanding of the Microsoft Windows Azure platform, hence a prerequisite for this course is at least six months programming in the .NET framework and Visual Studio. Check out the full details of the event or go straight to registration.   The course outline is: Week 1 - Windows Azure Platform Week 2 - Windows Azure Storage Week 3 - Windows Azure Deep Dive and Codename "Dallas" Week 4 - SQL Azure Week 5 - Windows Azure Platform AppFabric Access Control Week 6 - Windows Azure Platform AppFabric Service Bus If you have any questions about the course and its suitability, please email [email protected].

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• Parallel Computing in .Net 4.0

  - by kaleidoscope

  Technorati Tags: Ram,Parallel Computing in .Net 4.0 Parallel computing is the simultaneous use of multiple compute resources to solve a computational problem: To be run using multiple CPUs A problem is broken into discrete parts that can be solved concurrently Each part is further broken down to a series of instructions Instructions from each part execute simultaneously on different CPUs Parallel Extensions in .NET 4.0 provides a set of libraries and tools to achieve the above mentioned objectives. This supports two paradigms of parallel computing Data Parallelism – This refers to dividing the data across multiple processors for parallel execution.e.g we are processing an array of 1000 elements we can distribute the data between two processors say 500 each. This is supported by the Parallel LINQ (PLINQ) in .NET 4.0 Task Parallelism – This breaks down the program into multiple tasks which can be parallelized and are executed on different processors. This is supported by Task Parallel Library (TPL) in .NET 4.0 A high level view is shown below:

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• Silverlight Cream for January 15, 2011 -- #1028

  - by Dave Campbell

  Note to #1024 Swag Winners: I'm sending emails to the vendors Sunday night, thanks for your patience (a few of you have not contacted me yet) In this Issue: Ezequiel Jadib, Daniel Egan(-2-), Page Brooks, Jason Zander, Andrej Tozon, Marlon Grech, Jonathan van de Veen, Walt Ritscher, Jesse Liberty, Jeremy Likness, Sacha Barber, William E. Burrows, and WindowsPhoneGeek. Above the Fold: Silverlight: "Building a Radar Control in Silverlight - Part 1" Page Brooks WP7: "Tutorial: Dynamic Tile Push Notification for Windows Phone 7" Jason Zander Training: "WP7 Unleashed Session I–Hands on Labs" Daniel Egan From SilverlightCream.com: Silverlight Rough Cut Editor SP1 Released Ezequiel Jadib has an announcement about the Rough Cut Editor SP1 release, and he walks you through the content, installation and a bit of the initial use. WP7 Unleashed Session I–Hands on Labs Daniel Egan posted Part 1 of 3 of a new WP7 HOL ... video online and material to download... get 'em while they're hot! WP7 Saving to Media Library Daniel Egan has another post up as well on saving an image to the media library... not the update from Tim Heuer... all good info Building a Radar Control in Silverlight - Part 1 This freakin' cool post from Page Brooks is the first one of a series on building a 'Radar Control' in Silverlight ... seriously, go to the bottom and run the demo... I pretty much guarantee you'll take the next link which is download the code... don't forget to read the article too! Tutorial: Dynamic Tile Push Notification for Windows Phone 7 Jason Zander has a nice-looking tutorial up on dynamic tile notifications... good diagrams and discussion and plenty of code. Reactive.buffering.from event. Andrej Tozon is continuing his Reactive Extensions posts with this one on buffering: BufferWithTime and BufferWIthCount ... good stuff, good write-up, and the start of a WP7 game? MEFedMVVM with PRISM 4 Marlon Grech combines his MEFedMVVM with Prism 4, and says it was easy... check out the post and the code. Adventures while building a Silverlight Enterprise application part #40 Jonathan van de Veen has a discussion up about things you need to pay attention to as your project gets close to first deployment... lots of good information to think about Silverlight or not. Customize Windows 7 Preview pane for XAML files Walt Ritscher has a (very easy) XAML extension for Windows 7 that allows previewing of XAML files in an explorer window... as our UK friends say "Brilliant!" Entity Framework Code-First, oData & Windows Phone Client From the never-ending stream of posts that is Jesse Liberty comes this one on EF Code-First... so Jesse's describing Code-First and OData all wrapped up about a WP7 app Sterling Silverlight and Windows Phone 7 Database Triggers and Auto-Identity Sterling and Database Triggers sitting in a tree... woot for WP7 from Jeremy Likness... provides database solutions including Validation, Data-specific concerns such as 'last modified', and post-save processing ... all good, Jeremy! A Look At Fluent APIs Sacha Barber has a great post up that isn't necessarily Silverlight, but is it? ... we've been hearing a lot about Fluent APIs... read on to see what the buzz is. Windows Phone 7 - Part 3 - Final Application William E. Burrows has Part 3 of his WP7 tutorial series up... this one completing the Golf Handicap app by giving the user the ability to manage scores. User Control vs Custom Control in Silverlight for WP7 WindowsPhoneGeek has a great diagram and description-filled post up on User Controls and Custom Controls in WP7... good external links too. 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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• Managing .NET Deployment Configuration With Rake

  - by Liam McLennan

  Rake is a ruby internal DSL for build scripting. With (or without) the help of albacore rake makes an excellent build scripting tool for .NET projects. The albacore documentation does a good job of explaining how to build solutions with rake but there is nothing to assist with another common build task – updating configuration files. The following ruby script provides some helper methods for performing common configuration changes that are required as part of a build process.  class ConfigTasks def self.set_app_setting(config_file, key, value) ovsd_element = config_file.root.elements['appSettings'].get_elements("add[@key='#{key}']")[0] ovsd_element.attributes['value'] = value end def self.set_connection_string(config_file, name, connection_string) conn_string_element = config_file.root.elements['connectionStrings'].get_elements("add[@name='#{name}']")[0] conn_string_element.attributes['connectionString'] = connection_string end def self.set_debug_compilation(config_file, debug_compilation) compilation_element = config_file.root.elements['system.web'].get_elements("compilation")[0] compilation_element.attributes['debug'] = false end private def self.write_xml_to_file(xml_document, file) File.open(file, 'w') do |config_file| formatter = REXML::Formatters::Default.new formatter.write(xml_document, config_file) end end end To use, require the file and call the class methods, passing the configuration file name and any other parameters. require 'config_tasks' ConfigTasks.set_app_setting 'web.config', 'enableCache', 'false'

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• FREE Technical Training on Windows Server 2012 Virtualization / Hyper-V / Private Cloud

  - by KeithMayer

  Microsoft Learning partnered with the Microsoft Server and Tools team and Developer and Platform Evangelism (DPE) to deliver the “Windows Server 2012 Jump Start: Preparing for the Datacenter Evolution” on June 20-21, 2012. Thanks to an amazing product and a phenomenal team effort, this event shattered two Jump Start records with 2,064 attendees from 103 different countries and extremely positive event feedback! We are excited to announce the release of the HD-quality video recordings available on TechNet Videos now!For complete details: http://aka.ms/TrainWS12JSIf I can help with any other learning topics, please feel free to connect with me and let me know!HTH,Keith http://keithmayer.com | Twitter: @KeithMayer | LinkedIn: http://linkedin.com/in/KeithM

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• Clear list of recent repositories in Git Extensions

  - by Marko Apfel

  Orphaned and wrong specified repositories in the recent list are annoying. Straightaway I does not found an option to clean this entries. And also not the persistence place for that. So it was time for Process Explorer. The storage happens under: HKEY_CURRENT_USER\Software\GitExtensions\GitExtensions\1.0.0.0 in the string value “history” You could edit the content of the string value or delete it – than during restarting Git Extensions the string value will be created with a default skeleton.

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• Best Practices on Building SharePoint 2010 Web Parts with Visual Studio 2010

  - by Jim Duffy

  In this Channel 9 interview, my good friend Beth Massi recently sat down with Boris Scholl, a Program Manager on the Visual Studio Team building tools for SharePoint development, to discuss the best practices for building SharePoint web parts with Visual Studio 2010. SharePoint developers upgrading to Visual Studio 2010 might want to check this out. Have a day. :-|

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• How To: Get the DISTINCT rows in a DataTable or DataView

  - by Rodney Vinyard

  How To: Get the DISTINCT rows in a DataTable or DataView http://devpinoy.org/blogs/keithrull/archive/2008/02/07/how-to-get-the-distinct-rows-in-a-datatable-or-dataview.aspx

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• .NET Code Evolution

  - by Alois Kraus

  Originally posted on: http://geekswithblogs.net/akraus1/archive/2013/07/24/153504.aspxAt my day job I do look at a lot of code written by other people. Most of the code is quite good and some is even a masterpiece. And there is also code which makes you think WTF… oh it was written by me. Hm not so bad after all. There are many excuses reasons for bad code. Most often it is time pressure followed by not enough ambition (who cares) or insufficient training. Normally I do care about code quality quite a lot which makes me a (perceived) slow worker who does write many tests and refines the code quite a lot because of the design deficiencies. Most of the deficiencies I do find by putting my design under stress while checking for invariants. It does also help a lot to step into the code with a debugger (sometimes also Windbg). I do this much more often when my tests are red. That way I do get a much better understanding what my code really does and not what I think it should be doing. This time I do want to show you how code can evolve over the years with different .NET Framework versions. Once there was  time where .NET 1.1 was new and many C++ programmers did switch over to get rid of not initialized pointers and memory leaks. There were also nice new data structures available such as the Hashtable which is fast lookup table with O(1) time complexity. All was good and much code was written since then. At 2005 a new version of the .NET Framework did arrive which did bring many new things like generics and new data structures. The “old” fashioned way of Hashtable were coming to an end and everyone used the new Dictionary<xx,xx> type instead which was type safe and faster because the object to type conversion (aka boxing) was no longer necessary. I think 95% of all Hashtables and dictionaries use string as key. Often it is convenient to ignore casing to make it easy to look up values which the user did enter. An often followed route is to convert the string to upper case before putting it into the Hashtable. Hashtable Table = new Hashtable(); void Add(string key, string value) { Table.Add(key.ToUpper(), value); } This is valid and working code but it has problems. First we can pass to the Hashtable a custom IEqualityComparer to do the string matching case insensitive. Second we can switch over to the now also old Dictionary type to become a little faster and we can keep the the original keys (not upper cased) in the dictionary. Dictionary<string, string> DictTable = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase); void AddDict(string key, string value) { DictTable.Add(key, value); } Many people do not user the other ctors of Dictionary because they do shy away from the overhead of writing their own comparer. They do not know that .NET has for strings already predefined comparers at hand which you can directly use. Today in the many core area we do use threads all over the place. Sometimes things break in subtle ways but most of the time it is sufficient to place a lock around the offender. Threading has become so mainstream that it may sound weird that in the year 2000 some guy got a huge incentive for the idea to reduce the time to process calibration data from 12 hours to 6 hours by using two threads on a dual core machine. Threading does make it easy to become faster at the expense of correctness. Correct and scalable multithreading can be arbitrarily hard to achieve depending on the problem you are trying to solve. Lets suppose we want to process millions of items with two threads and count the processed items processed by all threads. A typical beginners code might look like this: int Counter; void IJustLearnedToUseThreads() { var t1 = new Thread(ThreadWorkMethod); t1.Start(); var t2 = new Thread(ThreadWorkMethod); t2.Start(); t1.Join(); t2.Join(); if (Counter != 2 * Increments) throw new Exception("Hmm " + Counter + " != " + 2 * Increments); } const int Increments = 10 * 1000 * 1000; void ThreadWorkMethod() { for (int i = 0; i < Increments; i++) { Counter++; } } It does throw an exception with the message e.g. “Hmm 10.222.287 != 20.000.000” and does never finish. The code does fail because the assumption that Counter++ is an atomic operation is wrong. The ++ operator is just a shortcut for Counter = Counter + 1 This does involve reading the counter from a memory location into the CPU, incrementing value on the CPU and writing the new value back to the memory location. When we do look at the generated assembly code we will see only inc dword ptr [ecx+10h] which is only one instruction. Yes it is one instruction but it is not atomic. All modern CPUs have several layers of caches (L1,L2,L3) which try to hide the fact how slow actual main memory accesses are. Since cache is just another word for redundant copy it can happen that one CPU does read a value from main memory into the cache, modifies it and write it back to the main memory. The problem is that at least the L1 cache is not shared between CPUs so it can happen that one CPU does make changes to values which did change in meantime in the main memory. From the exception you can see we did increment the value 20 million times but half of the changes were lost because we did overwrite the already changed value from the other thread. This is a very common case and people do learn to protect their  data with proper locking.   void Intermediate() { var time = Stopwatch.StartNew(); Action acc = ThreadWorkMethod_Intermediate; var ar1 = acc.BeginInvoke(null, null); var ar2 = acc.BeginInvoke(null, null); ar1.AsyncWaitHandle.WaitOne(); ar2.AsyncWaitHandle.WaitOne(); if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Intermediate did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Intermediate() { for (int i = 0; i < Increments; i++) { lock (this) { Counter++; } } } This is better and does use the .NET Threadpool to get rid of manual thread management. It does give the expected result but it can result in deadlocks because you do lock on this. This is in general a bad idea since it can lead to deadlocks when other threads use your class instance as lock object. It is therefore recommended to create a private object as lock object to ensure that nobody else can lock your lock object. When you read more about threading you will read about lock free algorithms. They are nice and can improve performance quite a lot but you need to pay close attention to the CLR memory model. It does make quite weak guarantees in general but it can still work because your CPU architecture does give you more invariants than the CLR memory model. For a simple counter there is an easy lock free alternative present with the Interlocked class in .NET. As a general rule you should not try to write lock free algos since most likely you will fail to get it right on all CPU architectures. void Experienced() { var time = Stopwatch.StartNew(); Task t1 = Task.Factory.StartNew(ThreadWorkMethod_Experienced); Task t2 = Task.Factory.StartNew(ThreadWorkMethod_Experienced); t1.Wait(); t2.Wait(); if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Experienced did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Experienced() { for (int i = 0; i < Increments; i++) { Interlocked.Increment(ref Counter); } } Since time does move forward we do not use threads explicitly anymore but the much nicer Task abstraction which was introduced with .NET 4 at 2010. It is educational to look at the generated assembly code. The Interlocked.Increment method must be called which does wondrous things right? Lets see: lock inc dword ptr [eax] The first thing to note that there is no method call at all. Why? Because the JIT compiler does know very well about CPU intrinsic functions. Atomic operations which do lock the memory bus to prevent other processors to read stale values are such things. Second: This is the same increment call prefixed with a lock instruction. The only reason for the existence of the Interlocked class is that the JIT compiler can compile it to the matching CPU intrinsic functions which can not only increment by one but can also do an add, exchange and a combined compare and exchange operation. But be warned that the correct usage of its methods can be tricky. If you try to be clever and look a the generated IL code and try to reason about its efficiency you will fail. Only the generated machine code counts. Is this the best code we can write? Perhaps. It is nice and clean. But can we make it any faster? Lets see how good we are doing currently. Level Time in s IJustLearnedToUseThreads Flawed Code Intermediate 1,5 (lock) Experienced 0,3 (Interlocked.Increment) Master 0,1 (1,0 for int[2]) That lock free thing is really a nice thing. But if you read more about CPU cache, cache coherency, false sharing you can do even better. int[] Counters = new int[12]; // Cache line size is 64 bytes on my machine with an 8 way associative cache try for yourself e.g. 64 on more modern CPUs void Master() { var time = Stopwatch.StartNew(); Task t1 = Task.Factory.StartNew(ThreadWorkMethod_Master, 0); Task t2 = Task.Factory.StartNew(ThreadWorkMethod_Master, Counters.Length - 1); t1.Wait(); t2.Wait(); Counter = Counters[0] + Counters[Counters.Length - 1]; if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Master did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Master(object number) { int index = (int) number; for (int i = 0; i < Increments; i++) { Counters[index]++; } } The key insight here is to use for each core its own value. But if you simply use simply an integer array of two items, one for each core and add the items at the end you will be much slower than the lock free version (factor 3). Each CPU core has its own cache line size which is something in the range of 16-256 bytes. When you do access a value from one location the CPU does not only fetch one value from main memory but a complete cache line (e.g. 16 bytes). This means that you do not pay for the next 15 bytes when you access them. This can lead to dramatic performance improvements and non obvious code which is faster although it does have many more memory reads than another algorithm. So what have we done here? We have started with correct code but it was lacking knowledge how to use the .NET Base Class Libraries optimally. Then we did try to get fancy and used threads for the first time and failed. Our next try was better but it still had non obvious issues (lock object exposed to the outside). Knowledge has increased further and we have found a lock free version of our counter which is a nice and clean way which is a perfectly valid solution. The last example is only here to show you how you can get most out of threading by paying close attention to your used data structures and CPU cache coherency. Although we are working in a virtual execution environment in a high level language with automatic memory management it does pay off to know the details down to the assembly level. Only if you continue to learn and to dig deeper you can come up with solutions no one else was even considering. I have studied particle physics which does help at the digging deeper part. Have you ever tried to solve Quantum Chromodynamics equations? Compared to that the rest must be easy ;-). Although I am no longer working in the Science field I take pride in discovering non obvious things. This can be a very hard to find bug or a new way to restructure data to make something 10 times faster. Now I need to get some sleep ….

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• AppHarbor - Azure Done Right AKA Heroku for .NET

  - by Robz / Fervent Coder

  Easy and Instant deployments and instant scale for .NET? Awhile back a few of us were looking at Ruby Gems as the answer to package management for .NET. The gems platform supported the concept of DLLs as packages although some changes would have needed to happen to have long term use for the entire community. From that we formed a partnership with some folks at Microsoft to make v2 into something that would meet wider adoption across the community, which people now call NuGet. So now we have the concept of package management. What comes next? Heroku Instant deployments and instant scaling. Stupid simple API. This is Heroku. It doesn’t sound like much, but when you think of how fast you can go from an idea to having someone else tinker with it, you can start to see its power. In literally seconds you can be looking at your rails application deployed and online. Then when you are ready to scale, you can do that. This is power. Some may call this “cloud-computing” or PaaS (Platform as a Service). I first ran into Heroku back in July when I met Nick of RubyGems.org. At the time there was no alternative in the .NET-o-sphere. I don’t count Windows Azure, mostly because it is not simple and I don’t believe there is a free version. Heroku itself would not lend itself well to .NET due to the nature of platforms and each language’s specific needs (solution stack).  So I tucked the idea in the back of my head and moved on. AppHarbor Enters The Scene I’m not sure when I first heard about AppHarbor as a possible .NET version of Heroku. It may have been in November, but I didn’t actually try it until January. I was instantly hooked. AppHarbor is awesome! It still has a ways to go to be considered Heroku for .NET, but it already has a growing community. I created a video series (at the bottom of this post) that really highlights how fast you can get a product onto the web and really shows the power and simplicity of AppHarbor. Deploying is as simple as a git/hg push to appharbor. From there they build your code, run any unit tests you have and deploy it if everything succeeds. The screen on the right shows a simple and elegant UI to getting things done. The folks at AppHarbor graciously gave me a limited number of invites to hand out. If you are itching to try AppHarbor then navigate to: https://appharbor.com/account/new?inviteCode=ferventcoder  After playing with it, send feedback if you want more features. Go vote up two features I want that will make it more like Heroku. Disclaimer: I am in no way affiliated with AppHarbor and have not received any funds or favors from anyone at AppHarbor. I just think it is awesome and I want others to know about it. From Zero To Deployed in 15 Minutes (Or Less) Now I have a challenge for you. I created a video series showing how fast I could go from nothing to a deployed application. It could have been from Zero to Deployed in Less than 5 minutes, but I wanted to show you the tools a little more and give you an opportunity to beat my time. And that’s the challenge. Beat my time and show it in a video response. The video series is below (at least one of the videos has to be watched on YouTube). The person with the best time by March 15th @ 11:59PM CST will receive a prize. Ground rules: .NET Application with a valid database connection Start from Zero Deployed with AppHarbor or an alternative A timer displayed in the video that runs during the entire process Video response published on YouTube or acceptable alternative Video(s) must be published by March 15th at 11:59PM CST. Either post the link here as a comment or on YouTube as a response (also by 11:59PM CST March 15th) From Zero To Deployed In 15 Minutes (Or Less) Part 1 From Zero To Deployed In 15 Minutes (Or Less) Part 2 From Zero To Deployed In 15 Minutes (Or Less) Part 3

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• AccelerometerInput XNA GameComponent

  - by Michael B. McLaughlin

  Bad accelerometer controls kill otherwise good games. I decided to try to do something about it. So I create an XNA GameComponent called AccelerometerInput. It’s still a beta project but you are welcome to try it, use it, modify it, etc. I’m releasing under the terms of the Microsoft Public License. Important info: First, it only supports tilt-style controls currently. I have not implemented motion-style controls yet (and make no promises as to when I might find time to do so). Second, I commented it heavily so that you can (hopefully) understand what it is doing. Please read the comments and examine the sample game for a usage overview. There are configurable parameters which I encourage you to make use of (both by modifying the default values where your testing shows it to be appropriate and also by implementing a calibration mechanism in your game that lets the user adjust those configurable values based on his or her own circumstances). Third, even with this code, accelerometer controls are still a fairly advanced topic area; you will likely find nothing but disappointment if you simply plunk this into some project without testing it on a device (or preferably on several devices). Fourth, if you do try this code and find that something doesn’t work as expected on your phone, please let me know as I want to improve it and can only do so with your help. Let me know what phone model it is, what you tried doing, what you expected, and what result you had instead. I may or may not be able to incorporate it into the code, but I can let others know at the very least so that they can make appropriate modifications to their games (I’m hopeful that all phones are reasonably similar in their workings and require, at most, a slight calibration change, but I simply don’t know). Fifth, although I’ll do my best to answer any questions you may have about it, I’m very busy with a number of things currently so it might take a little while. Please look through the code and examine the comments and sample game first before asking any questions. It’s likely that the answer is in there. If not, or if you just aren’t really sure, ask away. Sixth, there are differences between a portrait-mode game and a landscape mode game (specifically in the appropriate default tilt adjustment for toward the user/away from the user calculations). This is documented and the default is set for landscape. If you use this for a portrait game, make the appropriate change (look for the TODO: comment in AccelerometerInput.cs). Seventh, no provision whatsoever is made for disabling screen locking. It is up to you to implement that and to take appropriate measures to detect when the user has been idle for too long and timeout the game. That code is very game-specific. If you have questions about such matters, consult the relevant MSDN documentation and, if you still have questions, visit the App Hub forums and ask there. I answer questions there a lot and so I may even stumble across your question and answer it. But that’s a much better forum than the comments section here for questions of that sort so I would appreciate it if you asked idle detection-related questions there (or on some other suitable site that you may be more familiar and comfortable with). Eighth, this is an XNA GameComponent intended for XNA-based games on WP7. A sufficiently knowledgeable Silverlight developer should have no problem adapting it for use in a Silverlight game or app. I may create a Silverlight version at some point myself. Right now I do not have the time, unfortunately. Ok. Without further ado: http://www.bobtacoindustries.com/developers/utils/AccelerometerInput.zip Have a great St. Patrick’s Day!

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• The Linux Foundation Video

  - by EmbeddedInsider

  They say “Free is the freedom, to sell whatever you want, to whoever you want, and however you want” Linux Video on YouTube Curious this is in Flash.  Is Flash Free?

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• Take advantage of the stimulus plan by hiring someone!

  - by Randy Walker

  In case you didn’t know, businesses can take advantage of the stimulus package by hiring an unemployed worker.  The Hiring Incentives to Restore Employment (HIRE) Act can pay the business portion of the Social Security taxes as well as give you a $1000 general business tax credit. If you’re unemployed, make sure and mention this to a potential employee! You can find out more information from here on Intuit’s website.  http://www.qbenews.com/QB_Payroll/1003_qbpb/landing_01.html

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• Attaching a Command to the WP7 Application Bar.

  - by mbcrump

  One of the biggest problems that I’ve seen with people creating WP7 applications is how do you bind the application bar to a Relay Command. If your using MVVM then this is particular important. Let’s examine the code that one might add to start with.  <phone:PhoneApplicationPage.ApplicationBar> <shell:ApplicationBar IsVisible="True" IsMenuEnabled="True"> <shell:ApplicationBarIconButton x:Name="appbar_button1" IconUri="/icons/appbar.questionmark.rest.png" Text="About"> <i:Interaction.Triggers> <i:EventTrigger EventName="Click"> <GalaSoft_MvvmLight_Command:EventToCommand Command="{Binding DisplayAbout, Mode=OneWay}" /> </i:EventTrigger> </i:Interaction.Triggers> </shell:ApplicationBarIconButton> <shell:ApplicationBar.MenuItems> <shell:ApplicationBarMenuItem x:Name="menuItem1" Text="MenuItem 1"></shell:ApplicationBarMenuItem> <shell:ApplicationBarMenuItem x:Name="menuItem2" Text="MenuItem 2"></shell:ApplicationBarMenuItem> </shell:ApplicationBar.MenuItems> </shell:ApplicationBar> </phone:PhoneApplicationPage.ApplicationBar> Everything looks right. But we quickly notice that we have a squiggly line under our Interaction.Triggers. The problem is that the object is not a FrameworkObject. This same code would have worked perfect if this were a normal button. OK. Point has been proved. Let’s make the ApplicationBar support Commands. So, go ahead and create a new project using MVVM Light. If you want to check out the source and work along side this tutorial then click here.  7 Easy Steps to have binding on the Application Bar using MVVM Light (I might add that you don’t have to use MVVM Light to get this functionality, I just prefer it.) 1) Download MVVM Light if you don’t already have it and install the project templates. It is available at http://mvvmlight.codeplex.com/. 2) Click File-New Project and navigate to Silverlight for Windows Phone. Make sure you use the MVVM Light (WP7) Template. 3) Now that we have our project setup and ready to go let’s download a wrapper created by Nicolas Humann here, it is called Phone7.Fx. After you download it then extract it somewhere that you can find it. This wrapper will make our application bar/menu item bindable. 4) Right click References inside your WP7 project and add the .dll file to your project. 5) In your MainPage.xaml you will need to add the proper namespace to it. Don’t forget to build your project afterwards. xmlns:Preview="clr-namespace:Phone7.Fx.Preview;assembly=Phone7.Fx.Preview" 6) Now you can add the BindableAppBar to your MainPage.xaml with a few lines of code.  <Preview:BindableApplicationBar x:Name="AppBar" BarOpacity="1.0" > <Preview:BindableApplicationBarIconButton Command="{Binding DisplayAbout}" IconUri="/icons/appbar.questionmark.rest.png" Text="About" /> <Preview:BindableApplicationBar.MenuItems> <Preview:BindableApplicationBarMenuItem Text="Settings" Command="{Binding InputBox}" /> </Preview:BindableApplicationBar.MenuItems> </Preview:BindableApplicationBar> So your final MainPage.xaml will look similar to this: NOTE: The AppBar will be located inside of the Grid using this wrapper.   <!--LayoutRoot contains the root grid where all other page content is placed--> <Grid x:Name="LayoutRoot" Background="Transparent"> <Grid.RowDefinitions> <RowDefinition Height="Auto" /> <RowDefinition Height="*" /> </Grid.RowDefinitions> <!--TitlePanel contains the name of the application and page title--> <StackPanel x:Name="TitlePanel" Grid.Row="0" Margin="24,24,0,12"> <TextBlock x:Name="ApplicationTitle" Text="{Binding ApplicationTitle}" Style="{StaticResource PhoneTextNormalStyle}" /> <TextBlock x:Name="PageTitle" Text="{Binding PageName}" Margin="-3,-8,0,0" Style="{StaticResource PhoneTextTitle1Style}" /> </StackPanel> <!--ContentPanel - place additional content here--> <Grid x:Name="ContentGrid" Grid.Row="1"> <TextBlock Text="{Binding Welcome}" Style="{StaticResource PhoneTextNormalStyle}" HorizontalAlignment="Center" VerticalAlignment="Center" FontSize="40" /> </Grid> <Preview:BindableApplicationBar x:Name="AppBar" BarOpacity="1.0" > <Preview:BindableApplicationBarIconButton Command="{Binding DisplayAbout}" IconUri="/icons/appbar.questionmark.rest.png" Text="About" /> <Preview:BindableApplicationBar.MenuItems> <Preview:BindableApplicationBarMenuItem Text="Settings" Command="{Binding InputBox}" /> </Preview:BindableApplicationBar.MenuItems> </Preview:BindableApplicationBar> </Grid> 7) Let’s go ahead and create the RelayCommands and write them up to a MessageBox by editing our MainViewModel.cs file. public class MainViewModel : ViewModelBase { public string ApplicationTitle { get { return "MVVM LIGHT"; } } public string PageName { get { return "My page:"; } } public string Welcome { get { return "Welcome to MVVM Light"; } } public RelayCommand DisplayAbout { get; private set; } public RelayCommand InputBox { get; private set; } /// <summary> /// Initializes a new instance of the MainViewModel class. /// </summary> public MainViewModel() { if (IsInDesignMode) { // Code runs in Blend --> create design time data. } else { DisplayAbout = new RelayCommand(() => { MessageBox.Show("About box called!"); }); InputBox = new RelayCommand(() => { MessageBox.Show("settings button called"); }); } } If you run the project now you should get something similar to this (notice the AppBar at the bottom):  Now if you hit the question mark then you will get the following MessageBox: The MenuItem works as well so for Settings: As you can see, its pretty easy to add a Command to the ApplicationBar/MenuItem. If you want to look through the full source code then click here.   Subscribe to my feed

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