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  • Displaying an image on a LED matrix with a Netduino

    - by Bertrand Le Roy
    In the previous post, we’ve been flipping bits manually on three ports of the Netduino to simulate the data, clock and latch pins that a shift register expected. We did all that in order to control one line of a LED matrix and create a simple Knight Rider effect. It was rightly pointed out in the comments that the Netduino has built-in knowledge of the sort of serial protocol that this shift register understands through a feature called SPI. That will of course make our code a whole lot simpler, but it will also make it a whole lot faster: writing to the Netduino ports is actually not that fast, whereas SPI is very, very fast. Unfortunately, the Netduino documentation for SPI is severely lacking. Instead, we’ve been reliably using the documentation for the Fez, another .NET microcontroller. To send data through SPI, we’ll just need  to move a few wires around and update the code. SPI uses pin D11 for writing, pin D12 for reading (which we won’t do) and pin D13 for the clock. The latch pin is a parameter that can be set by the user. This is very close to the wiring we had before (data on D11, clock on D12 and latch on D13). We just have to move the latch from D13 to D10, and the clock from D12 to D13. The code that controls the shift register has slimmed down considerably with that change. Here is the new version, which I invite you to compare with what we had before: public class ShiftRegister74HC595 { protected SPI Spi; public ShiftRegister74HC595(Cpu.Pin latchPin) : this(latchPin, SPI.SPI_module.SPI1) { } public ShiftRegister74HC595(Cpu.Pin latchPin, SPI.SPI_module spiModule) { var spiConfig = new SPI.Configuration( SPI_mod: spiModule, ChipSelect_Port: latchPin, ChipSelect_ActiveState: false, ChipSelect_SetupTime: 0, ChipSelect_HoldTime: 0, Clock_IdleState: false, Clock_Edge: true, Clock_RateKHz: 1000 ); Spi = new SPI(spiConfig); } public void Write(byte buffer) { Spi.Write(new[] {buffer}); } } All we have to do here is configure SPI. The write method couldn’t be any simpler. Everything is now handled in hardware by the Netduino. We set the frequency to 1MHz, which is largely sufficient for what we’ll be doing, but it could potentially go much higher. The shift register addresses the columns of the matrix. The rows are directly wired to ports D0 to D7 of the Netduino. The code writes to only one of those eight lines at a time, which will make it fast enough. The way an image is displayed is that we light the lines one after the other so fast that persistence of vision will give the illusion of a stable image: foreach (var bitmap in matrix.MatrixBitmap) { matrix.OnRow(row, bitmap, true); matrix.OnRow(row, bitmap, false); row++; } Now there is a twist here: we need to run this code as fast as possible in order to display the image with as little flicker as possible, but we’ll eventually have other things to do. In other words, we need the code driving the display to run in the background, except when we want to change what’s being displayed. Fortunately, the .NET Micro Framework supports multithreading. In our implementation, we’ve added an Initialize method that spins a new thread that is tied to the specific instance of the matrix it’s being called on. public LedMatrix Initialize() { DisplayThread = new Thread(() => DoDisplay(this)); DisplayThread.Start(); return this; } I quite like this way to spin a thread. As you may know, there is another, built-in way to contextualize a thread by passing an object into the Start method. For the method to work, the thread must have been constructed with a ParameterizedThreadStart delegate, which takes one parameter of type object. I like to use object as little as possible, so instead I’m constructing a closure with a Lambda, currying it with the current instance. This way, everything remains strongly-typed and there’s no casting to do. Note that this method would extend perfectly to several parameters. Of note as well is the return value of Initialize, a common technique to add some fluency to the API and enabling the matrix to be instantiated and initialized in a single line: using (var matrix = new LedMS88SR74HC595().Initialize()) The “using” in the previous line is because we have implemented IDisposable so that the matrix kills the thread and clears the display when the user code is done with it: public void Dispose() { Clear(); DisplayThread.Abort(); } Thanks to the multi-threaded version of the matrix driver class, we can treat the display as a simple bitmap with a very synchronous programming model: matrix.Set(someimage); while (button.Read()) { Thread.Sleep(10); } Here, the call into Set returns immediately and from the moment the bitmap is set, the background display thread will constantly continue refreshing no matter what happens in the main thread. That enables us to wait or read a button’s port on the main thread knowing that the current image will continue displaying unperturbed and without requiring manual refreshing. We’ve effectively hidden the implementation of the display behind a convenient, synchronous-looking API. Pretty neat, eh? Before I wrap up this post, I want to talk about one small caveat of using SPI rather than driving the shift register directly: when we got to the point where we could actually display images, we noticed that they were a mirror image of what we were sending in. Oh noes! Well, the reason for it is that SPI is sending the bits in a big-endian fashion, in other words backwards. Now sure you could fix that in software by writing some bit-level code to reverse the bits we’re sending in, but there is a far more efficient solution than that. We are doing hardware here, so we can simply reverse the order in which the outputs of the shift register are connected to the columns of the matrix. That’s switching 8 wires around once, as compared to doing bit operations every time we send a line to display. All right, so bringing it all together, here is the code we need to write to display two images in succession, separated by a press on the board’s button: var button = new InputPort(Pins.ONBOARD_SW1, false, Port.ResistorMode.Disabled); using (var matrix = new LedMS88SR74HC595().Initialize()) { // Oh, prototype is so sad! var sad = new byte[] { 0x66, 0x24, 0x00, 0x18, 0x00, 0x3C, 0x42, 0x81 }; DisplayAndWait(sad, matrix, button); // Let's make it smile! var smile = new byte[] { 0x42, 0x18, 0x18, 0x81, 0x7E, 0x3C, 0x18, 0x00 }; DisplayAndWait(smile, matrix, button); } And here is a video of the prototype running: The prototype in action I’ve added an artificial delay between the display of each row of the matrix to clearly show what’s otherwise happening very fast. This way, you can clearly see each of the two images being displayed line by line. Next time, we’ll do no hardware changes, focusing instead on building a nice programming model for the matrix, with sprites, text and hardware scrolling. Fun stuff. By the way, can any of my reader guess where we’re going with all that? The code for this prototype can be downloaded here: http://weblogs.asp.net/blogs/bleroy/Samples/NetduinoLedMatrixDriver.zip

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  • Tulsa SharePoint Interest Group – Meeting Reminder

    - by dmccollough
    Just a quick reminder that the Tulsa SharePoint Interest Group is having it’s monthly meeting this coming Monday April 12th @6:00 PM.   Please come see Corey Roth’s presentation on SharePoint 2010 Business Connectivity Services   We are going to be giving away some GREAT prizes XBox 360 – Halo 3 ODST Telerik Premium Collection ($1,300.00 value) ReSharper ($199.00 value) SQL Sets ($149.00 value) 64 Bit Windows 7 Infragistics NetAdvantage for .NET Platform ($1,195.00 value) You can click here for more information. You can click here to RSVP for the meeting.

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  • Speaking at Microsoft's Duth DevDays

    - by gsusx
    Last week I had the pleasure of presenting two sessions at Microsoft's Dutch DevDays at Den Hague. On Tuesday I presented a sessions about how to implement real world RESTFul services patterns using WCF, WCF Data Services and ASP.NET MVC2. During that session I showed a total of 15 small demos that highlighted how to implement key aspects of RESTful solutions such as Security, LowREST clients, URI modeling, Validation, Error Handling, etc. As part of those demos I used the OAuth implementation created...(read more)

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  • Using delegates in C# (Part 2)

    - by rajbk
    Part 1 of this post can be read here. We are now about to see the different syntaxes for invoking a delegate and some c# syntactic sugar which allows you to code faster. We have the following console application. 1: public delegate double Operation(double x, double y); 2:  3: public class Program 4: { 5: [STAThread] 6: static void Main(string[] args) 7: { 8: Operation op1 = new Operation(Division); 9: double result = op1.Invoke(10, 5); 10: 11: Console.WriteLine(result); 12: Console.ReadLine(); 13: } 14: 15: static double Division(double x, double y) { 16: return x / y; 17: } 18: } Line 1 defines a delegate type called Operation with input parameters (double x, double y) and a return type of double. On Line 8, we create an instance of this delegate and set the target to be a static method called Division (Line 15) On Line 9, we invoke the delegate (one entry in the invocation list). The program outputs 5 when run. The language provides shortcuts for creating a delegate and invoking it (see line 9 and 11). Line 9 is a syntactical shortcut for creating an instance of the Delegate. The C# compiler will infer on its own what the delegate type is and produces intermediate language that creates a new instance of that delegate. Line 11 uses a a syntactical shortcut for invoking the delegate by removing the Invoke method. The compiler sees the line and generates intermediate language which invokes the delegate. When this code is compiled, the generated IL will look exactly like the IL of the compiled code above. 1: public delegate double Operation(double x, double y); 2:  3: public class Program 4: { 5: [STAThread] 6: static void Main(string[] args) 7: { 8: //shortcut constructor syntax 9: Operation op1 = Division; 10: //shortcut invoke syntax 11: double result = op1(10, 2); 12: 13: Console.WriteLine(result); 14: Console.ReadLine(); 15: } 16: 17: static double Division(double x, double y) { 18: return x / y; 19: } 20: } C# 2.0 introduced Anonymous Methods. Anonymous methods avoid the need to create a separate method that contains the same signature as the delegate type. Instead you write the method body in-line. There is an interesting fact about Anonymous methods and closures which won’t be covered here. Use your favorite search engine ;-)We rewrite our code to use anonymous methods (see line 9): 1: public delegate double Operation(double x, double y); 2:  3: public class Program 4: { 5: [STAThread] 6: static void Main(string[] args) 7: { 8: //Anonymous method 9: Operation op1 = delegate(double x, double y) { 10: return x / y; 11: }; 12: double result = op1(10, 2); 13: 14: Console.WriteLine(result); 15: Console.ReadLine(); 16: } 17: 18: static double Division(double x, double y) { 19: return x / y; 20: } 21: } We could rewrite our delegate to be of a generic type like so (see line 2 and line 9). You will see why soon. 1: //Generic delegate 2: public delegate T Operation<T>(T x, T y); 3:  4: public class Program 5: { 6: [STAThread] 7: static void Main(string[] args) 8: { 9: Operation<double> op1 = delegate(double x, double y) { 10: return x / y; 11: }; 12: double result = op1(10, 2); 13: 14: Console.WriteLine(result); 15: Console.ReadLine(); 16: } 17: 18: static double Division(double x, double y) { 19: return x / y; 20: } 21: } The .NET 3.5 framework introduced a whole set of predefined delegates for us including public delegate TResult Func<T1, T2, TResult>(T1 arg1, T2 arg2); Our code can be modified to use this delegate instead of the one we declared. Our delegate declaration has been removed and line 7 has been changed to use the Func delegate type. 1: public class Program 2: { 3: [STAThread] 4: static void Main(string[] args) 5: { 6: //Func is a delegate defined in the .NET 3.5 framework 7: Func<double, double, double> op1 = delegate (double x, double y) { 8: return x / y; 9: }; 10: double result = op1(10, 2); 11: 12: Console.WriteLine(result); 13: Console.ReadLine(); 14: } 15: 16: static double Division(double x, double y) { 17: return x / y; 18: } 19: } .NET 3.5 also introduced lambda expressions. A lambda expression is an anonymous function that can contain expressions and statements, and can be used to create delegates or expression tree types. We change our code to use lambda expressions. 1: public class Program 2: { 3: [STAThread] 4: static void Main(string[] args) 5: { 6: //lambda expression 7: Func<double, double, double> op1 = (x, y) => x / y; 8: double result = op1(10, 2); 9: 10: Console.WriteLine(result); 11: Console.ReadLine(); 12: } 13: 14: static double Division(double x, double y) { 15: return x / y; 16: } 17: } C# 3.0 introduced the keyword var (implicitly typed local variable) where the type of the variable is inferred based on the type of the associated initializer expression. We can rewrite our code to use var as shown below (line 7).  The implicitly typed local variable op1 is inferred to be a delegate of type Func<double, double, double> at compile time. 1: public class Program 2: { 3: [STAThread] 4: static void Main(string[] args) 5: { 6: //implicitly typed local variable 7: var op1 = (x, y) => x / y; 8: double result = op1(10, 2); 9: 10: Console.WriteLine(result); 11: Console.ReadLine(); 12: } 13: 14: static double Division(double x, double y) { 15: return x / y; 16: } 17: } You have seen how we can write code in fewer lines by using a combination of the Func delegate type, implicitly typed local variables and lambda expressions.

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  • EF 4’s PluralizationService Class: A Singularly Impossible Plurality

    - by Ken Cox [MVP]
    Entity Framework’s new 4.0 designer does its best to generate correct plural and singular forms of object names. This magic is done through the PluralizationService Class found in the System.Data.Entity.Design.PluralizationServices namespace and in the System.Data.Entity.Design.dll assembly. [Before you ask… Yes, I’ll post my example page, the service, and the project source code as soon as my ISP makes ASP.NET 4 RTM available. Stay tuned.] Anyone who speaks English is brutally aware of the ridiculous...(read more)

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  • Using MAC Authentication for simple Web API’s consumption

    - by cibrax
    For simple scenarios of Web API consumption where identity delegation is not required, traditional http authentication schemas such as basic, certificates or digest are the most used nowadays. All these schemas rely on sending the caller credentials or some representation of it in every request message as part of the Authorization header, so they are prone to suffer phishing attacks if they are not correctly secured at transport level with https. In addition, most client applications typically authenticate two different things, the caller application and the user consuming the API on behalf of that application. For most cases, the schema is simplified by using a single set of username and password for authenticating both, making necessary to store those credentials temporally somewhere in memory. The true is that you can use two different identities, one for the user running the application, which you might authenticate just once during the first call when the application is initialized, and another identity for the application itself that you use on every call. Some cloud vendors like Windows Azure or Amazon Web Services have adopted an schema to authenticate the caller application based on a Message Authentication Code (MAC) generated with a symmetric algorithm using a key known by the two parties, the caller and the Web API. The caller must include a MAC as part of the Authorization header created from different pieces of information in the request message such as the address, the host, and some other headers. The Web API can authenticate the caller by using the key associated to it and validating the attached MAC in the request message. In that way, no credentials are sent as part of the request message, so there is no way an attacker to intercept the message and get access to those credentials. Anyways, this schema also suffers from some deficiencies that can generate attacks. For example, brute force can be still used to infer the key used for generating the MAC, and impersonate the original caller. This can be mitigated by renewing keys in a relative short period of time. This schema as any other can be complemented with transport security. Eran Rammer, one of the brains behind OAuth, has recently published an specification of a protocol based on MAC for Http authentication called Hawk. The initial version of the spec is available here. A curious fact is that the specification per se does not exist, and the specification itself is the code that Eran initially wrote using node.js. In that implementation, you can associate a key to an user, so once the MAC has been verified on the Web API, the user can be inferred from that key. Also a timestamp is used to avoid replay attacks. As a pet project, I decided to port that code to .NET using ASP.NET Web API, which is available also in github under https://github.com/pcibraro/hawknet Enjoy!.

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  • VS 2010 Debugger Improvements (BreakPoints, DataTips, Import/Export)

    - by ScottGu
    This is the twenty-first in a series of blog posts I’m doing on the VS 2010 and .NET 4 release.  Today’s blog post covers a few of the nice usability improvements coming with the VS 2010 debugger.  The VS 2010 debugger has a ton of great new capabilities.  Features like Intellitrace (aka historical debugging), the new parallel/multithreaded debugging capabilities, and dump debuging support typically get a ton of (well deserved) buzz and attention when people talk about the debugging improvements with this release.  I’ll be doing blog posts in the future that demonstrate how to take advantage of them as well.  With today’s post, though, I thought I’d start off by covering a few small, but nice, debugger usability improvements that were also included with the VS 2010 release, and which I think you’ll find useful. Breakpoint Labels VS 2010 includes new support for better managing debugger breakpoints.  One particularly useful feature is called “Breakpoint Labels” – it enables much better grouping and filtering of breakpoints within a project or across a solution.  With previous releases of Visual Studio you had to manage each debugger breakpoint as a separate item. Managing each breakpoint separately can be a pain with large projects and for cases when you want to maintain “logical groups” of breakpoints that you turn on/off depending on what you are debugging.  Using the new VS 2010 “breakpoint labeling” feature you can now name these “groups” of breakpoints and manage them as a unit. Grouping Multiple Breakpoints Together using a Label Below is a screen-shot of the breakpoints window within Visual Studio 2010.  This lists all of the breakpoints defined within my solution (which in this case is the ASP.NET MVC 2 code base): The first and last breakpoint in the list above breaks into the debugger when a Controller instance is created or released by the ASP.NET MVC Framework. Using VS 2010, I can now select these two breakpoints, right-click, and then select the new “Edit labels…” menu command to give them a common label/name (making them easier to find and manage): Below is the dialog that appears when I select the “Edit labels” command.  We can use it to create a new string label for our breakpoints or select an existing one we have already defined.  In this case we’ll create a new label called “Lifetime Management” to describe what these two breakpoints cover: When we press the OK button our two selected breakpoints will be grouped under the newly created “Lifetime Management” label: Filtering/Sorting Breakpoints by Label We can use the “Search” combobox to quickly filter/sort breakpoints by label.  Below we are only showing those breakpoints with the “Lifetime Management” label: Toggling Breakpoints On/Off by Label We can also toggle sets of breakpoints on/off by label group.  We can simply filter by the label group, do a Ctrl-A to select all the breakpoints, and then enable/disable all of them with a single click: Importing/Exporting Breakpoints VS 2010 now supports importing/exporting breakpoints to XML files – which you can then pass off to another developer, attach to a bug report, or simply re-load later.  To export only a subset of breakpoints, you can filter by a particular label and then click the “Export breakpoint” button in the Breakpoints window: Above I’ve filtered my breakpoint list to only export two particular breakpoints (specific to a bug that I’m chasing down).  I can export these breakpoints to an XML file and then attach it to a bug report or email – which will enable another developer to easily setup the debugger in the correct state to investigate it on a separate machine.  Pinned DataTips Visual Studio 2010 also includes some nice new “DataTip pinning” features that enable you to better see and track variable and expression values when in the debugger.  Simply hover over a variable or expression within the debugger to expose its DataTip (which is a tooltip that displays its value)  – and then click the new “pin” button on it to make the DataTip always visible: You can “pin” any number of DataTips you want onto the screen.  In addition to pinning top-level variables, you can also drill into the sub-properties on variables and pin them as well.  Below I’ve “pinned” three variables: “category”, “Request.RawUrl” and “Request.LogonUserIdentity.Name”.  Note that these last two variable are sub-properties of the “Request” object.   Associating Comments with Pinned DataTips Hovering over a pinned DataTip exposes some additional UI within the debugger: Clicking the comment button at the bottom of this UI expands the DataTip - and allows you to optionally add a comment with it: This makes it really easy to attach and track debugging notes: Pinned DataTips are usable across both Debug Sessions and Visual Studio Sessions Pinned DataTips can be used across multiple debugger sessions.  This means that if you stop the debugger, make a code change, and then recompile and start a new debug session - any pinned DataTips will still be there, along with any comments you associate with them.  Pinned DataTips can also be used across multiple Visual Studio sessions.  This means that if you close your project, shutdown Visual Studio, and then later open the project up again – any pinned DataTips will still be there, along with any comments you associate with them. See the Value from Last Debug Session (Great Code Editor Feature) How many times have you ever stopped the debugger only to go back to your code and say: $#@! – what was the value of that variable again??? One of the nice things about pinned DataTips is that they keep track of their “last value from debug session” – and you can look these values up within the VB/C# code editor even when the debugger is no longer running.  DataTips are by default hidden when you are in the code editor and the debugger isn’t running.  On the left-hand margin of the code editor, though, you’ll find a push-pin for each pinned DataTip that you’ve previously setup: Hovering your mouse over a pinned DataTip will cause it to display on the screen.  Below you can see what happens when I hover over the first pin in the editor - it displays our debug session’s last values for the “Request” object DataTip along with the comment we associated with them: This makes it much easier to keep track of state and conditions as you toggle between code editing mode and debugging mode on your projects. Importing/Exporting Pinned DataTips As I mentioned earlier in this post, pinned DataTips are by default saved across Visual Studio sessions (you don’t need to do anything to enable this). VS 2010 also now supports importing/exporting pinned DataTips to XML files – which you can then pass off to other developers, attach to a bug report, or simply re-load later. Combined with the new support for importing/exporting breakpoints, this makes it much easier for multiple developers to share debugger configurations and collaborate across debug sessions. Summary Visual Studio 2010 includes a bunch of great new debugger features – both big and small.  Today’s post shared some of the nice debugger usability improvements. All of the features above are supported with the Visual Studio 2010 Professional edition (the Pinned DataTip features are also supported in the free Visual Studio 2010 Express Editions)  I’ll be covering some of the “big big” new debugging features like Intellitrace, parallel/multithreaded debugging, and dump file analysis in future blog posts.  Hope this helps, Scott P.S. In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

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  • Visual Studio 2012 RC and Windows 8 Release Review is available for download

    - by Fredrik N
    Today Visual Studio 2012 RC is available for download at:http://www.microsoft.com/visualstudio/11/en-us/downloads#express-win8EF 5, MVC 4, WebApi and much more in the RC release. Widows 8 Release Review!http://blogs.msdn.com/b/b8/archive/2012/05/31/delivering-the-windows-8-release-preview.aspxASP.NET MVC 4 RC for Visual Studio 2010 SP1http://www.microsoft.com/en-us/download/details.aspx?id=29935 Happy coding!!

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  • EF 4 Pluralization Update

    - by Ken Cox [MVP]
    I previously wrote about playing with EF 4’s PluralizationService class . Now that OrcsWeb is running ASP.NET 4, you can play with my little pluralization page and its WCF service online. The source code (such as it is!) can be downloaded from the MSDN Code Gallery here: http://code.msdn.microsoft.com/PluralizationService BTW, one annoyance is that the WDSL still includes the default namespace:  namespace="http://tempuri.org/" I swatted a couple of these instances, but if you know...(read more)

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  • Transposition - the success story of VB6 migration

    - by Visual WebGui
    Since all of you VB developers in the present or past would probably find it hard to believe that the old VB code can be migrated and modernized into the latest .NET based HTML5 without having to rewrite the application I am feeling I need to write another post on our migration solution. Hopefully, after reading this and the previous post you will be able to understand the different approach of our solution which already helps organizations around the world move away from the constraints of VB6 and...(read more)

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  • Academy Webcast: Moving C/S applications to Windows Azure

    - by Visual WebGui
    The Cloud and SaaS models are changing the face of enterprise IT in terms of economics, scalability and accessibility. As I wrote before Visual WebGui Instant CloudMove transforms your Client / Server application code to run natively as .NET on Windows Azure and enables your Azure Client / Server application to have a secured-by-design plain Web or Mobile browser based accessibility. On Tuesday 8 March at 8am (USA Pacific Time) Itzik Spitzen VP of R&D @ Gizmox will present a webcast on Microsoft...(read more)

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  • DNNWorld 2012, The Trailer

    - by Chris Hammond
    Some people in the asp.net community love to hate on DotNetNuke ( see Shaun's latest blog post comments ), that’s fine, the rest of us are off having a good time with it and the community! Check out the trailer for DNNWorld 2012, coming up in Orlando Florida in October (you can register for DNN World at http://dnnworld.dotnetnuke.com ). For those of you who love to hate on DNN, I challenge you to give it another look. A lot has changed with the platform in the past 10 years, most recently in the...(read more)

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  • The QueryExtender web server control

    - by nikolaosk
    In this post I am going to present a hands on example on how to use the QueryExtender web server control. It is built into ASP.Net 4.0 and it is available from the Toolbox in VS 2010.Before we move on with our example let me explain what this control does and why we need it. Its goal is to extend the functionality of the LINQ to Entities and LINQ to SQL datasources.Most of the times when we have data coming out from a datasource we want some sort of filtering. We do achieve that by using a Where...(read more)

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  • DotNetNuke is switching to C#, uh oh

    - by Chris Hammond
    If you didn’t see Shaun’s blog post earlier this week you should give it a good read through . The post announced the fact that starting with Version 6.0 (targeted for Q2 2011) DotNetNuke will no longer be developed/released as a VB.NET Application. All development of the core platform will be in C# (this does not mean that the community modules for the platform will change languages). Most of the feedback I have seen so far has been rather positive, most folks who use DotNetNuke on a regular basis...(read more)

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  • Why you need to learn async in .NET

    - by PSteele
    I had an opportunity to teach a quick class yesterday about what’s new in .NET 4.0.  One of the topics was the TPL (Task Parallel Library) and how it can make async programming easier.  I also stressed that this is the direction Microsoft is going with for C# 5.0 and learning the TPL will greatly benefit their understanding of the new async stuff.  We had a little time left over and I was able to show some code that uses the Async CTP to accomplish some stuff, but it wasn’t a simple demo that you could jump in to and understand so I thought I’d thrown one together and put it in a blog post. The entire solution file with all of the sample projects is located here. A Simple Example Let’s start with a super-simple example (WindowsApplication01 in the solution). I’ve got a form that displays a label and a button.  When the user clicks the button, I want to start displaying the current time for 15 seconds and then stop. What I’d like to write is this: lblTime.ForeColor = Color.Red; for (var x = 0; x < 15; x++) { lblTime.Text = DateTime.Now.ToString("HH:mm:ss"); Thread.Sleep(1000); } lblTime.ForeColor = SystemColors.ControlText; (Note that I also changed the label’s color while counting – not quite an ILM-level effect, but it adds something to the demo!) As I’m sure most of my readers are aware, you can’t write WinForms code this way.  WinForms apps, by default, only have one thread running and it’s main job is to process messages from the windows message pump (for a more thorough explanation, see my Visual Studio Magazine article on multithreading in WinForms).  If you put a Thread.Sleep in the middle of that code, your UI will be locked up and unresponsive for those 15 seconds.  Not a good UX and something that needs to be fixed.  Sure, I could throw an “Application.DoEvents()” in there, but that’s hacky. The Windows Timer Then I think, “I can solve that.  I’ll use the Windows Timer to handle the timing in the background and simply notify me when the time has changed”.  Let’s see how I could accomplish this with a Windows timer (WindowsApplication02 in the solution): public partial class Form1 : Form { private readonly Timer clockTimer; private int counter;   public Form1() { InitializeComponent(); clockTimer = new Timer {Interval = 1000}; clockTimer.Tick += UpdateLabel; }   private void UpdateLabel(object sender, EventArgs e) { lblTime.Text = DateTime.Now.ToString("HH:mm:ss"); counter++; if (counter == 15) { clockTimer.Enabled = false; lblTime.ForeColor = SystemColors.ControlText; } }   private void cmdStart_Click(object sender, EventArgs e) { lblTime.ForeColor = Color.Red; counter = 0; clockTimer.Start(); } } Holy cow – things got pretty complicated here.  I use the timer to fire off a Tick event every second.  Inside there, I can update the label.  Granted, I can’t use a simple for/loop and have to maintain a global counter for the number of iterations.  And my “end” code (when the loop is finished) is now buried inside the bottom of the Tick event (inside an “if” statement).  I do, however, get a responsive application that doesn’t hang or stop repainting while the 15 seconds are ticking away. But doesn’t .NET have something that makes background processing easier? The BackgroundWorker Next I try .NET’s BackgroundWorker component – it’s specifically designed to do processing in a background thread (leaving the UI thread free to process the windows message pump) and allows updates to be performed on the main UI thread (WindowsApplication03 in the solution): public partial class Form1 : Form { private readonly BackgroundWorker worker;   public Form1() { InitializeComponent(); worker = new BackgroundWorker {WorkerReportsProgress = true}; worker.DoWork += StartUpdating; worker.ProgressChanged += UpdateLabel; worker.RunWorkerCompleted += ResetLabelColor; }   private void StartUpdating(object sender, DoWorkEventArgs e) { var workerObject = (BackgroundWorker) sender; for (int x = 0; x < 15; x++) { workerObject.ReportProgress(0); Thread.Sleep(1000); } }   private void UpdateLabel(object sender, ProgressChangedEventArgs e) { lblTime.Text = DateTime.Now.ToString("HH:mm:ss"); }   private void ResetLabelColor(object sender, RunWorkerCompletedEventArgs e) { lblTime.ForeColor = SystemColors.ControlText; }   private void cmdStart_Click(object sender, EventArgs e) { lblTime.ForeColor = Color.Red; worker.RunWorkerAsync(); } } Well, this got a little better (I think).  At least I now have my simple for/next loop back.  Unfortunately, I’m still dealing with event handlers spread throughout my code to co-ordinate all of this stuff in the right order. Time to look into the future. The async way Using the Async CTP, I can go back to much simpler code (WindowsApplication04 in the solution): private async void cmdStart_Click(object sender, EventArgs e) { lblTime.ForeColor = Color.Red; for (var x = 0; x < 15; x++) { lblTime.Text = DateTime.Now.ToString("HH:mm:ss"); await TaskEx.Delay(1000); } lblTime.ForeColor = SystemColors.ControlText; } This code will run just like the Timer or BackgroundWorker versions – fully responsive during the updates – yet is way easier to implement.  In fact, it’s almost a line-for-line copy of the original version of this code.  All of the async plumbing is handled by the compiler and the framework.  My code goes back to representing the “what” of what I want to do, not the “how”. I urge you to download the Async CTP.  All you need is .NET 4.0 and Visual Studio 2010 sp1 – no need to set up a virtual machine with the VS2011 beta (unless, of course, you want to dive right in to the C# 5.0 stuff!).  Starting playing around with this today and see how much easier it will be in the future to write async-enabled applications.

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  • A free standing ASP.NET Pager Web Control

    - by Rick Strahl
    Paging in ASP.NET has been relatively easy with stock controls supporting basic paging functionality. However, recently I built an MVC application and one of the things I ran into was that I HAD TO build manual paging support into a few of my pages. Dealing with list controls and rendering markup is easy enough, but doing paging is a little more involved. I ended up with a small but flexible component that can be dropped anywhere. As it turns out the task of creating a semi-generic Pager control for MVC was fairly easily. Now I’m back to working in Web Forms and thought to myself that the way I created the pager in MVC actually would also work in ASP.NET – in fact quite a bit easier since the whole thing can be conveniently wrapped up into an easily reusable control. A standalone pager would provider easier reuse in various pages and a more consistent pager display regardless of what kind of 'control’ the pager is associated with. Why a Pager Control? At first blush it might sound silly to create a new pager control – after all Web Forms has pretty decent paging support, doesn’t it? Well, sort of. Yes the GridView control has automatic paging built in and the ListView control has the related DataPager control. The built in ASP.NET paging has several issues though: Postback and JavaScript requirements If you look at paging links in ASP.NET they are always postback links with javascript:__doPostback() calls that go back to the server. While that works fine and actually has some benefit like the fact that paging saves changes to the page and post them back, it’s not very SEO friendly. Basically if you use javascript based navigation nosearch engine will follow the paging links which effectively cuts off list content on the first page. The DataPager control does support GET based links via the QueryStringParameter property, but the control is effectively tied to the ListView control (which is the only control that implements IPageableItemContainer). DataSource Controls required for Efficient Data Paging Retrieval The only way you can get paging to work efficiently where only the few records you display on the page are queried for and retrieved from the database you have to use a DataSource control - only the Linq and Entity DataSource controls  support this natively. While you can retrieve this data yourself manually, there’s no way to just assign the page number and render the pager based on this custom subset. Other than that default paging requires a full resultset for ASP.NET to filter the data and display only a subset which can be very resource intensive and wasteful if you’re dealing with largish resultsets (although I’m a firm believer in returning actually usable sets :-}). If you use your own business layer that doesn’t fit an ObjectDataSource you’re SOL. That’s a real shame too because with LINQ based querying it’s real easy to retrieve a subset of data that is just the data you want to display but the native Pager functionality doesn’t support just setting properties to display just the subset AFAIK. DataPager is not Free Standing The DataPager control is the closest thing to a decent Pager implementation that ASP.NET has, but alas it’s not a free standing component – it works off a related control and the only one that it effectively supports from the stock ASP.NET controls is the ListView control. This means you can’t use the same data pager formatting for a grid and a list view or vice versa and you’re always tied to the control. Paging Events In order to handle paging you have to deal with paging events. The events fire at specific time instances in the page pipeline and because of this you often have to handle data binding in a way to work around the paging events or else end up double binding your data sources based on paging. Yuk. Styling The GridView pager is a royal pain to beat into submission for styled rendering. The DataPager control has many more options and template layout and it renders somewhat cleaner, but it too is not exactly easy to get a decent display for. Not a Generic Solution The problem with the ASP.NET controls too is that it’s not generic. GridView, DataGrid use their own internal paging, ListView can use a DataPager and if you want to manually create data layout – well you’re on your own. IOW, depending on what you use you likely have very different looking Paging experiences. So, I figured I’ve struggled with this once too many and finally sat down and built a Pager control. The Pager Control My goal was to create a totally free standing control that has no dependencies on other controls and certainly no requirements for using DataSource controls. The idea is that you should be able to use this pager control without any sort of data requirements at all – you should just be able to set properties and be able to display a pager. The Pager control I ended up with has the following features: Completely free standing Pager control – no control or data dependencies Complete manual control – Pager can render without any data dependency Easy to use: Only need to set PageSize, ActivePage and TotalItems Supports optional filtering of IQueryable for efficient queries and Pager rendering Supports optional full set filtering of IEnumerable<T> and DataTable Page links are plain HTTP GET href Links Control automatically picks up Page links on the URL and assigns them (automatic page detection no page index changing events to hookup) Full CSS Styling support On the downside there’s no templating support for the control so the layout of the pager is relatively fixed. All elements however are stylable and there are options to control the text, and layout options such as whether to display first and last pages and the previous/next buttons and so on. To give you an idea what the pager looks like, here are two differently styled examples (all via CSS):   The markup for these two pagers looks like this: <ww:Pager runat="server" id="ItemPager" PageSize="5" PageLinkCssClass="gridpagerbutton" SelectedPageCssClass="gridpagerbutton-selected" PagesTextCssClass="gridpagertext" CssClass="gridpager" RenderContainerDiv="true" ContainerDivCssClass="gridpagercontainer" MaxPagesToDisplay="6" PagesText="Item Pages:" NextText="next" PreviousText="previous" /> <ww:Pager runat="server" id="ItemPager2" PageSize="5" RenderContainerDiv="true" MaxPagesToDisplay="6" /> The latter example uses default style settings so it there’s not much to set. The first example on the other hand explicitly assigns custom styles and overrides a few of the formatting options. Styling The styling is based on a number of CSS classes of which the the main pager, pagerbutton and pagerbutton-selected classes are the important ones. Other styles like pagerbutton-next/prev/first/last are based on the pagerbutton style. The default styling shown for the red outlined pager looks like this: .pagercontainer { margin: 20px 0; background: whitesmoke; padding: 5px; } .pager { float: right; font-size: 10pt; text-align: left; } .pagerbutton,.pagerbutton-selected,.pagertext { display: block; float: left; text-align: center; border: solid 2px maroon; min-width: 18px; margin-left: 3px; text-decoration: none; padding: 4px; } .pagerbutton-selected { font-size: 130%; font-weight: bold; color: maroon; border-width: 0px; background: khaki; } .pagerbutton-first { margin-right: 12px; } .pagerbutton-last,.pagerbutton-prev { margin-left: 12px; } .pagertext { border: none; margin-left: 30px; font-weight: bold; } .pagerbutton a { text-decoration: none; } .pagerbutton:hover { background-color: maroon; color: cornsilk; } .pagerbutton-prev { background-image: url(images/prev.png); background-position: 2px center; background-repeat: no-repeat; width: 35px; padding-left: 20px; } .pagerbutton-next { background-image: url(images/next.png); background-position: 40px center; background-repeat: no-repeat; width: 35px; padding-right: 20px; margin-right: 0px; } Yup that’s a lot of styling settings although not all of them are required. The key ones are pagerbutton, pager and pager selection. The others (which are implicitly created by the control based on the pagerbutton style) are for custom markup of the ‘special’ buttons. In my apps I tend to have two kinds of pages: Those that are associated with typical ‘grid’ displays that display purely tabular data and those that have a more looser list like layout. The two pagers shown above represent these two views and the pager and gridpager styles in my standard style sheet reflect these two styles. Configuring the Pager with Code Finally lets look at what it takes to hook up the pager. As mentioned in the highlights the Pager control is completely independent of other controls so if you just want to display a pager on its own it’s as simple as dropping the control and assigning the PageSize, ActivePage and either TotalPages or TotalItems. So for this markup: <ww:Pager runat="server" id="ItemPagerManual" PageSize="5" MaxPagesToDisplay="6" /> I can use code as simple as: ItemPagerManual.PageSize = 3; ItemPagerManual.ActivePage = 4;ItemPagerManual.TotalItems = 20; Note that ActivePage is not required - it will automatically use any Page=x query string value and assign it, although you can override it as I did above. TotalItems can be any value that you retrieve from a result set or manually assign as I did above. A more realistic scenario based on a LINQ to SQL IQueryable result is even easier. In this example, I have a UserControl that contains a ListView control that renders IQueryable data. I use a User Control here because there are different views the user can choose from with each view being a different user control. This incidentally also highlights one of the nice features of the pager: Because the pager is independent of the control I can put the pager on the host page instead of into each of the user controls. IOW, there’s only one Pager control, but there are potentially many user controls/listviews that hold the actual display data. The following code demonstrates how to use the Pager with an IQueryable that loads only the records it displays: protected voidPage_Load(objectsender, EventArgs e) {     Category = Request.Params["Category"] ?? string.Empty;     IQueryable<wws_Item> ItemList = ItemRepository.GetItemsByCategory(Category);     // Update the page and filter the list down     ItemList = ItemPager.FilterIQueryable<wws_Item>(ItemList); // Render user control with a list view Control ulItemList = LoadControl("~/usercontrols/" + App.Configuration.ItemListType + ".ascx"); ((IInventoryItemListControl)ulItemList).InventoryItemList = ItemList; phItemList.Controls.Add(ulItemList); // placeholder } The code uses a business object to retrieve Items by category as an IQueryable which means that the result is only an expression tree that hasn’t execute SQL yet and can be further filtered. I then pass this IQueryable to the FilterIQueryable() helper method of the control which does two main things: Filters the IQueryable to retrieve only the data displayed on the active page Sets the Totaltems property and calculates TotalPages on the Pager and that’s it! When the Pager renders it uses those values, plus the PageSize and ActivePage properties to render the Pager. In addition to IQueryable there are also filter methods for IEnumerable<T> and DataTable, but these versions just filter the data by removing rows/items from the entire already retrieved data. Output Generated and Paging Links The output generated creates pager links as plain href links. Here’s what the output looks like: <div id="ItemPager" class="pagercontainer"> <div class="pager"> <span class="pagertext">Pages: </span><a href="http://localhost/WestWindWebStore/itemlist.aspx?Page=1" class="pagerbutton" />1</a> <a href="http://localhost/WestWindWebStore/itemlist.aspx?Page=2" class="pagerbutton" />2</a> <a href="http://localhost/WestWindWebStore/itemlist.aspx?Page=3" class="pagerbutton" />3</a> <span class="pagerbutton-selected">4</span> <a href="http://localhost/WestWindWebStore/itemlist.aspx?Page=5" class="pagerbutton" />5</a> <a href="http://localhost/WestWindWebStore/itemlist.aspx?Page=6" class="pagerbutton" />6</a> <a href="http://localhost/WestWindWebStore/itemlist.aspx?Page=20" class="pagerbutton pagerbutton-last" />20</a>&nbsp;<a href="http://localhost/WestWindWebStore/itemlist.aspx?Page=3" class="pagerbutton pagerbutton-prev" />Prev</a>&nbsp;<a href="http://localhost/WestWindWebStore/itemlist.aspx?Page=5" class="pagerbutton pagerbutton-next" />Next</a></div> <br clear="all" /> </div> </div> The links point back to the current page and simply append a Page= page link into the page. When the page gets reloaded with the new page number the pager automatically detects the page number and automatically assigns the ActivePage property which results in the appropriate page to be displayed. The code shown in the previous section is all that’s needed to handle paging. Note that HTTP GET based paging is different than the Postback paging ASP.NET uses by default. Postback paging preserves modified page content when clicking on pager buttons, but this control will simply load a new page – no page preservation at this time. The advantage of not using Postback paging is that the URLs generated are plain HTML links that a search engine can follow where __doPostback() links are not. Pager with a Grid The pager also works in combination with grid controls so it’s easy to bypass the grid control’s paging features if desired. In the following example I use a gridView control and binds it to a DataTable result which is also filterable by the Pager control. The very basic plain vanilla ASP.NET grid markup looks like this: <div style="width: 600px; margin: 0 auto;padding: 20px; "> <asp:DataGrid runat="server" AutoGenerateColumns="True" ID="gdItems" CssClass="blackborder" style="width: 600px;"> <AlternatingItemStyle CssClass="gridalternate" /> <HeaderStyle CssClass="gridheader" /> </asp:DataGrid> <ww:Pager runat="server" ID="Pager" CssClass="gridpager" ContainerDivCssClass="gridpagercontainer" PageLinkCssClass="gridpagerbutton" SelectedPageCssClass="gridpagerbutton-selected" PageSize="8" RenderContainerDiv="true" MaxPagesToDisplay="6" /> </div> and looks like this when rendered: using custom set of CSS styles. The code behind for this code is also very simple: protected void Page_Load(object sender, EventArgs e) { string category = Request.Params["category"] ?? ""; busItem itemRep = WebStoreFactory.GetItem(); var items = itemRep.GetItemsByCategory(category) .Select(itm => new {Sku = itm.Sku, Description = itm.Description}); // run query into a DataTable for demonstration DataTable dt = itemRep.Converter.ToDataTable(items,"TItems"); // Remove all items not on the current page dt = Pager.FilterDataTable(dt,0); // bind and display gdItems.DataSource = dt; gdItems.DataBind(); } A little contrived I suppose since the list could already be bound from the list of elements, but this is to demonstrate that you can also bind against a DataTable if your business layer returns those. Unfortunately there’s no way to filter a DataReader as it’s a one way forward only reader and the reader is required by the DataSource to perform the bindings.  However, you can still use a DataReader as long as your business logic filters the data prior to rendering and provides a total item count (most likely as a second query). Control Creation The control itself is a pretty brute force ASP.NET control. Nothing clever about this other than some basic rendering logic and some simple calculations and update routines to determine which buttons need to be shown. You can take a look at the full code from the West Wind Web Toolkit’s Repository (note there are a few dependencies). To give you an idea how the control works here is the Render() method: /// <summary> /// overridden to handle custom pager rendering for runtime and design time /// </summary> /// <param name="writer"></param> protected override void Render(HtmlTextWriter writer) { base.Render(writer); if (TotalPages == 0 && TotalItems > 0) TotalPages = CalculateTotalPagesFromTotalItems(); if (DesignMode) TotalPages = 10; // don't render pager if there's only one page if (TotalPages < 2) return; if (RenderContainerDiv) { if (!string.IsNullOrEmpty(ContainerDivCssClass)) writer.AddAttribute("class", ContainerDivCssClass); writer.RenderBeginTag("div"); } // main pager wrapper writer.WriteBeginTag("div"); writer.AddAttribute("id", this.ClientID); if (!string.IsNullOrEmpty(CssClass)) writer.WriteAttribute("class", this.CssClass); writer.Write(HtmlTextWriter.TagRightChar + "\r\n"); // Pages Text writer.WriteBeginTag("span"); if (!string.IsNullOrEmpty(PagesTextCssClass)) writer.WriteAttribute("class", PagesTextCssClass); writer.Write(HtmlTextWriter.TagRightChar); writer.Write(this.PagesText); writer.WriteEndTag("span"); // if the base url is empty use the current URL FixupBaseUrl(); // set _startPage and _endPage ConfigurePagesToRender(); // write out first page link if (ShowFirstAndLastPageLinks && _startPage != 1) { writer.WriteBeginTag("a"); string pageUrl = StringUtils.SetUrlEncodedKey(BaseUrl, QueryStringPageField, (1).ToString()); writer.WriteAttribute("href", pageUrl); if (!string.IsNullOrEmpty(PageLinkCssClass)) writer.WriteAttribute("class", PageLinkCssClass + " " + PageLinkCssClass + "-first"); writer.Write(HtmlTextWriter.SelfClosingTagEnd); writer.Write("1"); writer.WriteEndTag("a"); writer.Write("&nbsp;"); } // write out all the page links for (int i = _startPage; i < _endPage + 1; i++) { if (i == ActivePage) { writer.WriteBeginTag("span"); if (!string.IsNullOrEmpty(SelectedPageCssClass)) writer.WriteAttribute("class", SelectedPageCssClass); writer.Write(HtmlTextWriter.TagRightChar); writer.Write(i.ToString()); writer.WriteEndTag("span"); } else { writer.WriteBeginTag("a"); string pageUrl = StringUtils.SetUrlEncodedKey(BaseUrl, QueryStringPageField, i.ToString()).TrimEnd('&'); writer.WriteAttribute("href", pageUrl); if (!string.IsNullOrEmpty(PageLinkCssClass)) writer.WriteAttribute("class", PageLinkCssClass); writer.Write(HtmlTextWriter.SelfClosingTagEnd); writer.Write(i.ToString()); writer.WriteEndTag("a"); } writer.Write("\r\n"); } // write out last page link if (ShowFirstAndLastPageLinks && _endPage < TotalPages) { writer.WriteBeginTag("a"); string pageUrl = StringUtils.SetUrlEncodedKey(BaseUrl, QueryStringPageField, TotalPages.ToString()); writer.WriteAttribute("href", pageUrl); if (!string.IsNullOrEmpty(PageLinkCssClass)) writer.WriteAttribute("class", PageLinkCssClass + " " + PageLinkCssClass + "-last"); writer.Write(HtmlTextWriter.SelfClosingTagEnd); writer.Write(TotalPages.ToString()); writer.WriteEndTag("a"); } // Previous link if (ShowPreviousNextLinks && !string.IsNullOrEmpty(PreviousText) && ActivePage > 1) { writer.Write("&nbsp;"); writer.WriteBeginTag("a"); string pageUrl = StringUtils.SetUrlEncodedKey(BaseUrl, QueryStringPageField, (ActivePage - 1).ToString()); writer.WriteAttribute("href", pageUrl); if (!string.IsNullOrEmpty(PageLinkCssClass)) writer.WriteAttribute("class", PageLinkCssClass + " " + PageLinkCssClass + "-prev"); writer.Write(HtmlTextWriter.SelfClosingTagEnd); writer.Write(PreviousText); writer.WriteEndTag("a"); } // Next link if (ShowPreviousNextLinks && !string.IsNullOrEmpty(NextText) && ActivePage < TotalPages) { writer.Write("&nbsp;"); writer.WriteBeginTag("a"); string pageUrl = StringUtils.SetUrlEncodedKey(BaseUrl, QueryStringPageField, (ActivePage + 1).ToString()); writer.WriteAttribute("href", pageUrl); if (!string.IsNullOrEmpty(PageLinkCssClass)) writer.WriteAttribute("class", PageLinkCssClass + " " + PageLinkCssClass + "-next"); writer.Write(HtmlTextWriter.SelfClosingTagEnd); writer.Write(NextText); writer.WriteEndTag("a"); } writer.WriteEndTag("div"); if (RenderContainerDiv) { if (RenderContainerDivBreak) writer.Write("<br clear=\"all\" />\r\n"); writer.WriteEndTag("div"); } } As I said pretty much brute force rendering based on the control’s property settings of which there are quite a few: You can also see the pager in the designer above. unfortunately the VS designer (both 2010 and 2008) fails to render the float: left CSS styles properly and starts wrapping after margins are applied in the special buttons. Not a big deal since VS does at least respect the spacing (the floated elements overlay). Then again I’m not using the designer anyway :-}. Filtering Data What makes the Pager easy to use is the filter methods built into the control. While this functionality is clearly not the most politically correct design choice as it violates separation of concerns, it’s very useful for typical pager operation. While I actually have filter methods that do something similar in my business layer, having it exposed on the control makes the control a lot more useful for typical databinding scenarios. Of course these methods are optional – if you have a business layer that can provide filtered page queries for you can use that instead and assign the TotalItems property manually. There are three filter method types available for IQueryable, IEnumerable and for DataTable which tend to be the most common use cases in my apps old and new. The IQueryable version is pretty simple as it can simply rely on on .Skip() and .Take() with LINQ: /// <summary> /// <summary> /// Queries the database for the ActivePage applied manually /// or from the Request["page"] variable. This routine /// figures out and sets TotalPages, ActivePage and /// returns a filtered subset IQueryable that contains /// only the items from the ActivePage. /// </summary> /// <param name="query"></param> /// <param name="activePage"> /// The page you want to display. Sets the ActivePage property when passed. /// Pass 0 or smaller to use ActivePage setting. /// </param> /// <returns></returns> public IQueryable<T> FilterIQueryable<T>(IQueryable<T> query, int activePage) where T : class, new() { ActivePage = activePage < 1 ? ActivePage : activePage; if (ActivePage < 1) ActivePage = 1; TotalItems = query.Count(); if (TotalItems <= PageSize) { ActivePage = 1; TotalPages = 1; return query; } int skip = ActivePage - 1; if (skip > 0) query = query.Skip(skip * PageSize); _TotalPages = CalculateTotalPagesFromTotalItems(); return query.Take(PageSize); } The IEnumerable<T> version simply  converts the IEnumerable to an IQuerable and calls back into this method for filtering. The DataTable version requires a little more work to manually parse and filter records (I didn’t want to add the Linq DataSetExtensions assembly just for this): /// <summary> /// Filters a data table for an ActivePage. /// /// Note: Modifies the data set permanently by remove DataRows /// </summary> /// <param name="dt">Full result DataTable</param> /// <param name="activePage">Page to display. 0 to use ActivePage property </param> /// <returns></returns> public DataTable FilterDataTable(DataTable dt, int activePage) { ActivePage = activePage < 1 ? ActivePage : activePage; if (ActivePage < 1) ActivePage = 1; TotalItems = dt.Rows.Count; if (TotalItems <= PageSize) { ActivePage = 1; TotalPages = 1; return dt; } int skip = ActivePage - 1; if (skip > 0) { for (int i = 0; i < skip * PageSize; i++ ) dt.Rows.RemoveAt(0); } while(dt.Rows.Count > PageSize) dt.Rows.RemoveAt(PageSize); return dt; } Using the Pager Control The pager as it is is a first cut I built a couple of weeks ago and since then have been tweaking a little as part of an internal project I’m working on. I’ve replaced a bunch of pagers on various older pages with this pager without any issues and have what now feels like a more consistent user interface where paging looks and feels the same across different controls. As a bonus I’m only loading the data from the database that I need to display a single page. With the preset class tags applied too adding a pager is now as easy as dropping the control and adding the style sheet for styling to be consistent – no fuss, no muss. Schweet. Hopefully some of you may find this as useful as I have or at least as a baseline to build ontop of… Resources The Pager is part of the West Wind Web & Ajax Toolkit Pager.cs Source Code (some toolkit dependencies) Westwind.css base stylesheet with .pager and .gridpager styles Pager Example Page © Rick Strahl, West Wind Technologies, 2005-2010Posted in ASP.NET  

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  • Conheça a nova Windows Azure

    - by Leniel Macaferi
    Hoje estamos lançando um grande conjunto de melhorias para a Windows Azure. A seguir está um breve resumo de apenas algumas destas melhorias: Novo Portal de Administração e Ferramentas de Linha de Comando O lançamento de hoje vem com um novo portal para a Windows Azure, o qual lhe permitirá gerenciar todos os recursos e serviços oferecidos na Windows Azure de uma forma perfeitamente integrada. O portal é muito rápido e fluido, suporta filtragem e classificação dos dados (o que o torna muito fácil de usar em implantações/instalações de grande porte), funciona em todos os navegadores, e oferece um monte de ótimos e novos recursos - incluindo suporte nativo à VM (máquina virtual), Web site, Storage (armazenamento), e monitoramento de Serviços hospedados na Nuvem. O novo portal é construído em cima de uma API de gerenciamento baseada no modelo REST dentro da Windows Azure - e tudo o que você pode fazer através do portal também pode ser feito através de programação acessando esta Web API. Também estamos lançando hoje ferramentas de linha de comando (que, igualmente ao portal, chamam as APIs de Gerenciamento REST) para tornar ainda ainda mais fácil a criação de scripts e a automatização de suas tarefas de administração. Estamos oferecendo para download um conjunto de ferramentas para o Powershell (Windows) e Bash (Mac e Linux). Como nossos SDKs, o código destas ferramentas está hospedado no GitHub sob uma licença Apache 2. Máquinas Virtuais ( Virtual Machines [ VM ] ) A Windows Azure agora suporta a capacidade de implantar e executar VMs duráveis/permanentes ??na nuvem. Você pode criar facilmente essas VMs usando uma nova Galeria de Imagens embutida no novo Portal da Windows Azure ou, alternativamente, você pode fazer o upload e executar suas próprias imagens VHD customizadas. Máquinas virtuais são duráveis ??(o que significa que qualquer coisa que você instalar dentro delas persistirá entre as reinicializações) e você pode usar qualquer sistema operacional nelas. Nossa galeria de imagens nativa inclui imagens do Windows Server (incluindo o novo Windows Server 2012 RC), bem como imagens do Linux (incluindo Ubuntu, CentOS, e as distribuições SUSE). Depois de criar uma instância de uma VM você pode facilmente usar o Terminal Server ou SSH para acessá-las a fim de configurar e personalizar a máquina virtual da maneira como você quiser (e, opcionalmente, capturar uma snapshot (cópia instantânea da imagem atual) para usar ao criar novas instâncias de VMs). Isto te proporciona a flexibilidade de executar praticamente qualquer carga de trabalho dentro da plataforma Windows Azure.   A novo Portal da Windows Azure fornece um rico conjunto de recursos para o gerenciamento de Máquinas Virtuais - incluindo a capacidade de monitorar e controlar a utilização dos recursos dentro delas.  Nosso novo suporte à Máquinas Virtuais também permite a capacidade de facilmente conectar múltiplos discos nas VMs (os quais você pode então montar e formatar como unidades de disco). Opcionalmente, você pode ativar o suporte à replicação geográfica (geo-replication) para estes discos - o que fará com que a Windows Azure continuamente replique o seu armazenamento em um data center secundário (criando um backup), localizado a pelo menos 640 quilômetros de distância do seu data-center principal. Nós usamos o mesmo formato VHD que é suportado com a virtualização do Windows hoje (o qual nós lançamos como uma especificação aberta), de modo a permitir que você facilmente migre cargas de trabalho existentes que você já tenha virtualizado na Windows Azure.  Também tornamos fácil fazer o download de VHDs da Windows Azure, o que também oferece a flexibilidade para facilmente migrar cargas de trabalho das VMs baseadas na nuvem para um ambiente local. Tudo o que você precisa fazer é baixar o arquivo VHD e inicializá-lo localmente - nenhuma etapa de importação/exportação é necessária. Web Sites A Windows Azure agora suporta a capacidade de rapidamente e facilmente implantar web-sites ASP.NET, Node.js e PHP em um ambiente na nuvem altamente escalável que te permite começar pequeno (e de maneira gratuita) de modo que você possa em seguida, adaptar/escalar sua aplicação de acordo com o crescimento do seu tráfego. Você pode criar um novo web site na Azure e tê-lo pronto para implantação em menos de 10 segundos: O novo Portal da Windows Azure oferece suporte integrado para a administração de Web sites, incluindo a capacidade de monitorar e acompanhar a utilização dos recursos em tempo real: Você pode fazer o deploy (implantação) para web-sites em segundos usando FTP, Git, TFS e Web Deploy. Também estamos lançando atualizações para as ferramentas do Visual Studio e da Web Matrix que permitem aos desenvolvedores uma fácil instalação das aplicações ASP.NET nesta nova oferta. O suporte de publicação do VS e da Web Matrix inclui a capacidade de implantar bancos de dados SQL como parte da implantação do site - bem como a capacidade de realizar a atualização incremental do esquema do banco de dados com uma implantação realizada posteriormente. Você pode integrar a publicação de aplicações web com o controle de código fonte ao selecionar os links "Set up TFS publishing" (Configurar publicação TFS) ou "Set up Git publishing" (Configurar publicação Git) que estão presentes no dashboard de um web-site: Ao fazer isso, você habilitará a integração com o nosso novo serviço online TFS (que permite um fluxo de trabalho do TFS completo - incluindo um build elástico e suporte a testes), ou você pode criar um repositório Git e referenciá-lo como um remote para executar implantações automáticas. Uma vez que você executar uma implantação usando TFS ou Git, a tab/guia de implantações/instalações irá acompanhar as implantações que você fizer, e permitirá que você selecione uma implantação mais antiga (ou mais recente) para que você possa rapidamente voltar o seu site para um estado anterior do seu código. Isso proporciona uma experiência de fluxo de trabalho muito poderosa.   A Windows Azure agora permite que você implante até 10 web-sites em um ambiente de hospedagem gratuito e compartilhado entre múltiplos usuários e bancos de dados (onde um site que você implantar será um dos vários sites rodando em um conjunto compartilhado de recursos do servidor). Isso te fornece uma maneira fácil para começar a desenvolver projetos sem nenhum custo envolvido. Você pode, opcionalmente, fazer o upgrade do seus sites para que os mesmos sejam executados em um "modo reservado" que os isola, de modo que você seja o único cliente dentro de uma máquina virtual: E você pode adaptar elasticamente a quantidade de recursos que os seus sites utilizam - o que te permite por exemplo aumentar a capacidade da sua instância reservada/particular de acordo com o aumento do seu tráfego: A Windows Azure controla automaticamente o balanceamento de carga do tráfego entre as instâncias das VMs, e você tem as mesmas opções de implantação super rápidas (FTP, Git, TFS e Web Deploy), independentemente de quantas instâncias reservadas você usar. Com a Windows Azure você paga por capacidade de processamento por hora - o que te permite dimensionar para cima e para baixo seus recursos para atender apenas o que você precisa. Serviços da Nuvem (Cloud Services) e Cache Distribuído (Distributed Caching) A Windows Azure também suporta a capacidade de construir serviços que rodam na nuvem que suportam ricas arquiteturas multicamadas, gerenciamento automatizado de aplicações, e que podem ser adaptados para implantações extremamente grandes. Anteriormente nós nos referíamos a esta capacidade como "serviços hospedados" - com o lançamento desta semana estamos agora rebatizando esta capacidade como "serviços da nuvem". Nós também estamos permitindo um monte de novos recursos com eles. Cache Distribuído Um dos novos recursos muito legais que estão sendo habilitados com os serviços da nuvem é uma nova capacidade de cache distribuído que te permite usar e configurar um cache distribuído de baixa latência, armazenado na memória (in-memory) dentro de suas aplicações. Esse cache é isolado para uso apenas por suas aplicações, e não possui limites de corte. Esse cache pode crescer e diminuir dinamicamente e elasticamente (sem que você tenha que reimplantar a sua aplicação ou fazer alterações no código), e suporta toda a riqueza da API do Servidor de Cache AppFabric (incluindo regiões, alta disponibilidade, notificações, cache local e muito mais). Além de suportar a API do Servidor de Cache AppFabric, esta nova capacidade de cache pode agora também suportar o protocolo Memcached - o que te permite apontar código escrito para o Memcached para o cache distribuído (sem que alterações de código sejam necessárias). O novo cache distribuído pode ser configurado para ser executado em uma de duas maneiras: 1) Utilizando uma abordagem de cache co-localizado (co-located). Nesta opção você aloca um percentual de memória dos seus roles web e worker existentes para que o mesmo seja usado ??pelo cache, e então o cache junta a memória em um grande cache distribuído.  Qualquer dado colocado no cache por uma instância do role pode ser acessado por outras instâncias do role em sua aplicação - independentemente de os dados cacheados estarem armazenados neste ou em outro role. O grande benefício da opção de cache "co-localizado" é que ele é gratuito (você não precisa pagar nada para ativá-lo) e ele te permite usar o que poderia ser de outra forma memória não utilizada dentro das VMs da sua aplicação. 2) Alternativamente, você pode adicionar "cache worker roles" no seu serviço na nuvem que são utilizados unicamente para o cache. Estes também serão unidos em um grande anel de cache distribuído que outros roles dentro da sua aplicação podem acessar. Você pode usar esses roles para cachear dezenas ou centenas de GBs de dados na memória de forma extramente eficaz - e o cache pode ser aumentado ou diminuído elasticamente durante o tempo de execução dentro da sua aplicação: Novos SDKs e Ferramentas de Suporte Nós atualizamos todos os SDKs (kits para desenvolvimento de software) da Windows Azure com o lançamento de hoje para incluir novos recursos e capacidades. Nossos SDKs estão agora disponíveis em vários idiomas, e todo o código fonte deles está publicado sob uma licença Apache 2 e é mantido em repositórios no GitHub. O SDK .NET para Azure tem em particular um monte de grandes melhorias com o lançamento de hoje, e agora inclui suporte para ferramentas, tanto para o VS 2010 quanto para o VS 2012 RC. Estamos agora também entregando downloads do SDK para Windows, Mac e Linux nos idiomas que são oferecidos em todos esses sistemas - de modo a permitir que os desenvolvedores possam criar aplicações Windows Azure usando qualquer sistema operacional durante o desenvolvimento. Muito, Muito Mais O resumo acima é apenas uma pequena lista de algumas das melhorias que estão sendo entregues de uma forma preliminar ou definitiva hoje - há muito mais incluído no lançamento de hoje. Dentre estas melhorias posso citar novas capacidades para Virtual Private Networking (Redes Privadas Virtuais), novo runtime do Service Bus e respectivas ferramentas de suporte, o preview público dos novos Azure Media Services, novos Data Centers, upgrade significante para o hardware de armazenamento e rede, SQL Reporting Services, novos recursos de Identidade, suporte para mais de 40 novos países e territórios, e muito, muito mais. Você pode aprender mais sobre a Windows Azure e se cadastrar para experimentá-la gratuitamente em http://windowsazure.com.  Você também pode assistir a uma apresentação ao vivo que estarei realizando às 1pm PDT (17:00Hs de Brasília), hoje 7 de Junho (hoje mais tarde), onde eu vou passar por todos os novos recursos. Estaremos abrindo as novas funcionalidades as quais me referi acima para uso público poucas horas após o término da apresentação. Nós estamos realmente animados para ver as grandes aplicações que você construirá com estes novos recursos. Espero que ajude, - Scott   Texto traduzido do post original por Leniel Macaferi.

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