david alt - Page 15 - Developer IT

What is prefered to use in alt text "&" or "&" for screenreader users?

- by metal-gear-solid

Services & Prodcuts or Services & Prodcuts

how to give alt text to link if we use csssprites ?

I made a css menu with css sprites but the problem is with sprite we don't use inline image we use in background only so if images are disabled in browser then nothing will show . any solution for this ? For example : See this menu and turn off images : http://line25.com/wp-content/uploads/2009/css-menu/demo/demo.html

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Silverlight Cream for December 11, 2010 -- #1007

- by Dave Campbell

In this Issue: Mike Wolf, Colin Eberhardt, Mike Snow(-2-, -3-), David Kelley(-2-, -3-), Jesse Liberty(-2-), Erik Mork, Jeff Blankenburg, Laurent Duveau, and Jeremy Likness(-2-). Above the Fold: Silverlight: "The definitive guide to Notification Window in Silverlight 4" Laurent Duveau WP7: "Making the MS Adcontrol REALLY work on phone 7" David Kelley Silverlight 5: "Silverlight 5: In the Trenches" Mike Wolf From SilverlightCream.com: Silverlight 5: In the Trenches How many people can discuss Silverlight 5 'In the Trenches' ... apparently Mike Wolf can, and that's just what he's done in the post to whet your whistle (do people say that any more?) for when we can all get our hands on the bits. Visiblox, Visifire, DynamicDataDisplay – Charting Performance Comparison Colin Eberhardt responds to reader requests, and revisits his Charting Performance after also some discussion with David Anson about the Silverlight Toolkit. This time including Dynamic Data Display which is quite impressive in the ratings... check out the post and the code. Win7 Mobile Back Arrow Key Interception The simple fact is heavy bloggers rise, like Cream, to the top of my list, and I've been missing some goodness from Mike Snow... he's blogging WP7 stuff now... first up of the 'missed' ones is this one on intercepting the Back Arrow Key. Animating the Color of an Object Switching back to Silverlight in general, Mike Snow's next post is on Animating color of an object, such as text foreground. Tombstoning on the Win7 Mobile Platform And now back to WP7, Mike Snow is discussing Tombstoning... discussing the various aspects of it, and some code to use, if you haven't gotten your head around this one yet. What I tell Designers to give me... Integrating and Digital Zen David Kelley has a post up describing what he needs from designers to get his job done... I heard him discussing this at the Firestarter, and didn't realize he had written it up... these 8 items are things learned by doing, and should be discussed with your designers. Making the MS Adcontrol REALLY work on phone 7 David Kelley also has a post up discussing how to really get the Ad control working on WP7 apps... since I've seen lots of posts about this, having a definitive explanation from someone that's doing it is a good thing. Performance Optimization on Phone 7 In a break from his norm of discussing UX, David Kelley is talking about performance on WP7 devices in this post. Windows Phone From Scratch #10 – Visual State Part 2 When I saw Jesse Liberty's latest post, I realized I had missed his Part 2 of VSM for WP7 ... don't you miss it... this completes the good stuff from number 9 :) Windows Phone From Scratch #11 – Behaviors Jesse Liberty's latest Windows Phone from Scratch is up... and he's talking about Behaviors this time out... more of an overview or introduction to behaviors, but all good Show 112: Scott Guthrie on Silverlight 5 Erik Mork's latest Sparkling Client podcast is up and he was able to get some time with Scott Guthrie at the Firestarter. What I Learned in WP7 – Issue #1 Jeff Blankenburg decided to do another series, only this one isn't promised as every day... it's "What I Learned in WP7" ... and the first is up... good interesting bits found surrounding the WP7 device. The definitive guide to Notification Window in Silverlight 4 Laurent Duveau has a great post up that will have you doing Silverlight 'toast' notifications in no time... good descriptions and source. Lessons Learned in Personal Web Page Part 1: Dynamic XAML Jeremy Likness has rebuilt his personal website in Silverlight and is sharing some of that experience on his blog. This first post discusses the dynamic content. He used Jounce, of course, and included the Silverlight Navigation Framework, and... you can download all the source Lessons Learned in Personal Web Page Part 2: Enter the Matrix Jeremy Likness's second post about building his website is all about the 'Matrix' page ... pretty cool stuff... check it out... I think it looks great 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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Visual Studio 2010 Productivity Tips and Tricks-Part 2: Key Shortcuts

- by ToStringTheory

Ask anyone that knows me, and they will confirm that I hate the mouse. This isn’t because I deny affection to objects that don’t look like their mammalian-named self, but rather for a much more simple and not-insane reason: I have terrible eyesight. Introduction Thanks to a degenerative eye disease known as Choroideremia, I have learned to rely more on the keyboard which I can feel digital/static positions of keys relative to my fingers, than the much more analog/random position of the mouse. Now, I would like to share some of the keyboard shortcuts with you now, as I believe that they not only increase my productivity, but yours as well once you know them (if you don’t already of course)... I share one of my biggest tips for productivity in the conclusion at the end. Visual Studio Key Shortcuts Global Editor Shortcuts These are shortcuts that are available from almost any application running in Windows, however are many times forgotten. Shortcut Action Visual Studio 2010 Functionality Ctrl + X Cut This shortcut works without a selection. If nothing is selected, the entire line that the caret is on is cut from the editor. Ctrl + C Copy This shortcut works without a selection. If nothing is selected, the entire line that the caret is on is copied from the editor. Ctrl + V Paste If you copied an entire line by the method above, the data is pasted in the line above the current caret line. Ctrl + Shift + V Next Clipboard Element Cut/Copy multiple things, and then hit this combo repeatedly to switch to the next clipboard item when pasting. Ctrl + Backspace Delete Previous Will delete the previous word from the editor directly before the caret. If anything is selected, will just delete that. Ctrl + Del Delete Next Word Will delete the next word/space from the editor directly after the caret. If anything is selected, will just delete that. Shift + Del Delete Focused Line Will delete the line from the editor that the caret is on. If something is selected, will just delete that. Ctrl + ? or Ctrl + ? Left/Right by Word This will move the caret left or right by word or special character boundary. Holding Shift will also select the word. Ctrl + F Quick Find Either the Quick Find panel, or the search bar if you have the Productivity Power Tools installed. Ctrl + Shift + F Find in Solution Opens up the 'Find in Files' window, allowing you to search your solution, as well as using regex for pattern matching. F2 Rename File... While not debugging, selecting a file in the solution explorer\navigator and pressing F2 allows you to rename the selected file. Global Application Shortcuts These are shortcuts that are available from almost any application running in Windows, however are many times forgotten... Again... Shortcut Action Visual Studio 2010 Functionality Ctrl + N New File dialog Opens up the 'New File' dialog to add a new file to the current directory in the Solution\Project. Ctrl + O Open File dialog Opens up the 'Open File' dialog to open a file in the editor, not necessarily in the solution. Ctrl + S Save File dialog Saves the currently focused editor tab back to your HDD/SSD. Ctrl + Shift + S Save All... Quickly save all open/edited documents back to your disk. Ctrl + Tab Switch Panel\Tab Tapping this combo switches between tabs quickly. Holding down Ctrl when hitting tab will bring up a chooser window. Building Shortcuts These are shortcuts that are focused on building and running a solution. These are not usable when the IDE is in Debug mode, as the shortcut changes by context. Shortcut Action Visual Studio 2010 Functionality Ctrl + Shift + B Build Solution Starts a build process on the solution according to the current build configuration manager settings. Ctrl + Break Cancel a Building Solution Will cancel a build operation currently in progress. Good for long running builds when you think of one last change. F5 Start Debugging Will build the solution if needed and launch debugging according to the current configuration manager settings. Ctrl + F5 Start Without Debugger Will build the solution if needed and launch the startup project without attaching a debugger. Debugging Shortcuts These are shortcuts that are used when debugging a solution. Shortcut Action Visual Studio 2010 Functionality F5 Continue Execution Continues execution of code until the next breakpoint. Ctrl + Alt + Break Pause Execution Pauses the program execution. Shift + F5 Stop Debugging Stops the current debugging session. NOTE: Web apps will still continue processing after stopping the debugger. Keep this in mind if working on code such as credit card processing. Ctrl + Shift + F5 Restart Debugging Stops the current debugging session and restarts the debugging session from the beginning. F9 Place Breakpoint Toggles/Places a breakpoint in the editor on the current line. Set a breakpoint in condensed code by highlighting the statement first. F10 Step Over Statement When debugging, executes all code in methods/properties on the current line until the next line. F11 Step Into Statement When debugging, steps into a method call so you can walk through the code executed there (if available). Ctrl + Alt + I Immediate Window Open the Immediate Window to execute commands when execution is paused. Navigation Shortcuts These are shortcuts that are used for navigating in the IDE or editor panel. Shortcut Action Visual Studio 2010 Functionality F4 Properties Panel Opens the properties panel for the selected item in the editor/designer/solution navigator (context driven). F12 Go to Definition Press F12 with the caret on a member to navigate to its declaration. With the Productivity tools, Ctrl + Click works too. Ctrl + K Ctrl + T View Call Hierarchy View the call hierarchy of the member the caret is on. Great for going through n-tier solutions and interface implementations! Ctrl + Alt + B Breakpoint Window View the breakpoint window to manage breakpoints and their advanced options. Allows easy toggling of breakpoints. Ctrl + Alt + L Solution Navigator Open the solution explorer panel. Ctrl + Alt + O Output Window View the output window to see build\general output from Visual Studio. Ctrl + Alt + Enter Live Web Preview Only available with the Web Essential plugin. Launches the auto-updating Preview panel. Testing Shortcuts These are shortcuts that are used for running tests in the IDE. Please note, Visual Studio 2010 is all about context. If your caret is within a test method when you use one of these combinations, the combination will apply to that test. If your caret is within a test class, it will apply to that class. If the caret is outside of a test class, it will apply to all tests. Shortcut Action Visual Studio 2010 Functionality Ctrl + R T Run Test(s) Run all tests in the current context without a debugger attached. Breakpoints will not be stopped on. Ctrl + R Ctrl + T Run Test(s) (Debug) Run all tests in the current context with a debugger attached. This allows you to use breakpoints. Substitute A for T from the preceding combos to run/debug ALL tests in the current context. Substitute Y for T from the preceding combos to run/debug ALL impacted/covering tests for a method in the current context. Advanced Editor Shortcuts These are shortcuts that are used for more advanced editing in the editor window. Shortcut Action Visual Studio 2010 Functionality Shift + Alt + ? Shift + Alt + ? Multiline caret up/down Use this combo to edit multiple lines at once. Not too many uses for it, but once in a blue moon one comes along. Ctrl + Alt + Enter Insert Line Above Inserts a blank line above the line the caret is currently on. No need to be at end or start of line, so no cutting off words/code. Ctrl + K Ctrl + C Comment Selection Comments the current selection out of compilation. Ctrl + K Ctrl + U Uncomment Selection Uncomments the current selection into compilation. Ctrl + K Ctrl + D Format Document Automatically formats the document into a structured layout. Lines up nodes or code into columns intelligently. Alt + ? Alt + ? Code line up/down *Use this combo to move a line of code up or down quickly. Great for small rearrangements of code. *Requires the Productivity Power pack from Microsoft. Conclusion This list is by no means meant to be exhaustive, but these are the shortcuts I use regularly every hour/minute of the day. There are still 100s more in Visual Studio that you can discover through the configuration window, or by tooltips. Something that I started doing months ago seems to have interest in my office.. In my last post, I talked about how I hated a cluttered UI. One of the ways that I aimed to resolve that was by systematically cleaning up the toolbars week by week. First day, I removed ALL icons that I already knew shortcuts to, or would never use them (Undo in a toolbar?!). Then, every week from that point on, I make it a point to remove an icon/two from the toolbar and make an effort to remember its key combination. I gain extra space in the toolbar area, AND become more productive at the same time! I hope that you found this article interesting or at least somewhat informative.. Maybe a shortcut or two you didn't know. I know some of them seem trivial, but I often see people going to the edit menu for Copy/Paste... Thought a refresher might be helpful!

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Whenever I hold alt/option and move my mouse, Mac OS X resizes my window... how do I stop that?

- by Justin Searls

I've been using Mac OS X for maybe 6 years now, and I have no idea what's causing this. Maybe someone else has this experience and can help me out. Symptom: while holding the alt/option key, if I move my mouse the current window starts resizing, anchored at the top left (it behaves exactly as if I had clicked-and-dragged the lower-right icon on the window). Anyone have an idea of what I may have installed that caused this? Or how to make it stop?

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ASP.NET Web API Exception Handling

- by Fredrik N

When I talk about exceptions in my product team I often talk about two kind of exceptions, business and critical exceptions. Business exceptions are exceptions thrown based on “business rules”, for example if you aren’t allowed to do a purchase. Business exceptions in most case aren’t important to log into a log file, they can directly be shown to the user. An example of a business exception could be "DeniedToPurchaseException”, or some validation exceptions such as “FirstNameIsMissingException” etc. Critical Exceptions are all other kind of exceptions such as the SQL server is down etc. Those kind of exception message need to be logged and should not reach the user, because they can contain information that can be harmful if it reach out to wrong kind of users. I often distinguish business exceptions from critical exceptions by creating a base class called BusinessException, then in my error handling code I catch on the type BusinessException and all other exceptions will be handled as critical exceptions. This blog post will be about different ways to handle exceptions and how Business and Critical Exceptions could be handled. Web API and Exceptions the basics When an exception is thrown in a ApiController a response message will be returned with a status code set to 500 and a response formatted by the formatters based on the “Accept” or “Content-Type” HTTP header, for example JSON or XML. Here is an example: public IEnumerable<string> Get() { throw new ApplicationException("Error!!!!!"); return new string[] { "value1", "value2" }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The response message will be: HTTP/1.1 500 Internal Server Error Content-Length: 860 Content-Type: application/json; charset=utf-8 { "ExceptionType":"System.ApplicationException","Message":"Error!!!!!","StackTrace":" at ..."} .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The stack trace will be returned to the client, this is because of making it easier to debug. Be careful so you don’t leak out some sensitive information to the client. So as long as you are developing your API, this is not harmful. In a production environment it can be better to log exceptions and return a user friendly exception instead of the original exception. There is a specific exception shipped with ASP.NET Web API that will not use the formatters based on the “Accept” or “Content-Type” HTTP header, it is the exception is the HttpResponseException class. Here is an example where the HttpReponseExcetpion is used: // GET api/values [ExceptionHandling] public IEnumerable<string> Get() { throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError)); return new string[] { "value1", "value2" }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The response will not contain any content, only header information and the status code based on the HttpStatusCode passed as an argument to the HttpResponseMessage. Because the HttpResponsException takes a HttpResponseMessage as an argument, we can give the response a content: public IEnumerable<string> Get() { throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent("My Error Message"), ReasonPhrase = "Critical Exception" }); return new string[] { "value1", "value2" }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The code above will have the following response: HTTP/1.1 500 Critical Exception Content-Length: 5 Content-Type: text/plain; charset=utf-8 My Error Message .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The Content property of the HttpResponseMessage doesn’t need to be just plain text, it can also be other formats, for example JSON, XML etc. By using the HttpResponseException we can for example catch an exception and throw a user friendly exception instead: public IEnumerable<string> Get() { try { DoSomething(); return new string[] { "value1", "value2" }; } catch (Exception e) { throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent("An error occurred, please try again or contact the administrator."), ReasonPhrase = "Critical Exception" }); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Adding a try catch to every ApiController methods will only end in duplication of code, by using a custom ExceptionFilterAttribute or our own custom ApiController base class we can reduce code duplicationof code and also have a more general exception handler for our ApiControllers . By creating a custom ApiController’s and override the ExecuteAsync method, we can add a try catch around the base.ExecuteAsync method, but I prefer to skip the creation of a own custom ApiController, better to use a solution that require few files to be modified. The ExceptionFilterAttribute has a OnException method that we can override and add our exception handling. Here is an example: using System; using System.Diagnostics; using System.Net; using System.Net.Http; using System.Web.Http; using System.Web.Http.Filters; public class ExceptionHandlingAttribute : ExceptionFilterAttribute { public override void OnException(HttpActionExecutedContext context) { if (context.Exception is BusinessException) { throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent(context.Exception.Message), ReasonPhrase = "Exception" }); } //Log Critical errors Debug.WriteLine(context.Exception); throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent("An error occurred, please try again or contact the administrator."), ReasonPhrase = "Critical Exception" }); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Note: Something to have in mind is that the ExceptionFilterAttribute will be ignored if the ApiController action method throws a HttpResponseException. The code above will always make sure a HttpResponseExceptions will be returned, it will also make sure the critical exceptions will show a more user friendly message. The OnException method can also be used to log exceptions. By using a ExceptionFilterAttribute the Get() method in the previous example can now look like this: public IEnumerable<string> Get() { DoSomething(); return new string[] { "value1", "value2" }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } To use the an ExceptionFilterAttribute, we can for example add the ExceptionFilterAttribute to our ApiControllers methods or to the ApiController class definition, or register it globally for all ApiControllers. You can read more about is here. Note: If something goes wrong in the ExceptionFilterAttribute and an exception is thrown that is not of type HttpResponseException, a formatted exception will be thrown with stack trace etc to the client. How about using a custom IHttpActionInvoker? We can create our own IHTTPActionInvoker and add Exception handling to the invoker. The IHttpActionInvoker will be used to invoke the ApiController’s ExecuteAsync method. Here is an example where the default IHttpActionInvoker, ApiControllerActionInvoker, is used to add exception handling: public class MyApiControllerActionInvoker : ApiControllerActionInvoker { public override Task<HttpResponseMessage> InvokeActionAsync(HttpActionContext actionContext, System.Threading.CancellationToken cancellationToken) { var result = base.InvokeActionAsync(actionContext, cancellationToken); if (result.Exception != null && result.Exception.GetBaseException() != null) { var baseException = result.Exception.GetBaseException(); if (baseException is BusinessException) { return Task.Run<HttpResponseMessage>(() => new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent(baseException.Message), ReasonPhrase = "Error" }); } else { //Log critical error Debug.WriteLine(baseException); return Task.Run<HttpResponseMessage>(() => new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent(baseException.Message), ReasonPhrase = "Critical Error" }); } } return result; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You can register the IHttpActionInvoker with your own IoC to resolve the MyApiContollerActionInvoker, or add it in the Global.asax: GlobalConfiguration.Configuration.Services.Remove(typeof(IHttpActionInvoker), GlobalConfiguration.Configuration.Services.GetActionInvoker()); GlobalConfiguration.Configuration.Services.Add(typeof(IHttpActionInvoker), new MyApiControllerActionInvoker()); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } How about using a Message Handler for Exception Handling? By creating a custom Message Handler, we can handle error after the ApiController and the ExceptionFilterAttribute is invoked and in that way create a global exception handler, BUT, the only thing we can take a look at is the HttpResponseMessage, we can’t add a try catch around the Message Handler’s SendAsync method. The last Message Handler that will be used in the Wep API pipe-line is the HttpControllerDispatcher and this Message Handler is added to the HttpServer in an early stage. The HttpControllerDispatcher will use the IHttpActionInvoker to invoke the ApiController method. The HttpControllerDipatcher has a try catch that will turn ALL exceptions into a HttpResponseMessage, so that is the reason why a try catch around the SendAsync in a custom Message Handler want help us. If we create our own Host for the Wep API we could create our own custom HttpControllerDispatcher and add or exception handler to that class, but that would be little tricky but is possible. We can in a Message Handler take a look at the HttpResponseMessage’s IsSuccessStatusCode property to see if the request has failed and if we throw the HttpResponseException in our ApiControllers, we could use the HttpResponseException and give it a Reason Phrase and use that to identify business exceptions or critical exceptions. I wouldn’t add an exception handler into a Message Handler, instead I should use the ExceptionFilterAttribute and register it globally for all ApiControllers. BUT, now to another interesting issue. What will happen if we have a Message Handler that throws an exception? Those exceptions will not be catch and handled by the ExceptionFilterAttribute. I found a bug in my previews blog post about “Log message Request and Response in ASP.NET WebAPI” in the MessageHandler I use to log incoming and outgoing messages. Here is the code from my blog before I fixed the bug: public abstract class MessageHandler : DelegatingHandler { protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) { var corrId = string.Format("{0}{1}", DateTime.Now.Ticks, Thread.CurrentThread.ManagedThreadId); var requestInfo = string.Format("{0} {1}", request.Method, request.RequestUri); var requestMessage = await request.Content.ReadAsByteArrayAsync(); await IncommingMessageAsync(corrId, requestInfo, requestMessage); var response = await base.SendAsync(request, cancellationToken); var responseMessage = await response.Content.ReadAsByteArrayAsync(); await OutgoingMessageAsync(corrId, requestInfo, responseMessage); return response; } protected abstract Task IncommingMessageAsync(string correlationId, string requestInfo, byte[] message); protected abstract Task OutgoingMessageAsync(string correlationId, string requestInfo, byte[] message); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } If a ApiController throws a HttpResponseException, the Content property of the HttpResponseMessage from the SendAsync will be NULL. So a null reference exception is thrown within the MessageHandler. The yellow screen of death will be returned to the client, and the content is HTML and the Http status code is 500. The bug in the MessageHandler was solved by adding a check against the HttpResponseMessage’s IsSuccessStatusCode property: public abstract class MessageHandler : DelegatingHandler { protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) { var corrId = string.Format("{0}{1}", DateTime.Now.Ticks, Thread.CurrentThread.ManagedThreadId); var requestInfo = string.Format("{0} {1}", request.Method, request.RequestUri); var requestMessage = await request.Content.ReadAsByteArrayAsync(); await IncommingMessageAsync(corrId, requestInfo, requestMessage); var response = await base.SendAsync(request, cancellationToken); byte[] responseMessage; if (response.IsSuccessStatusCode) responseMessage = await response.Content.ReadAsByteArrayAsync(); else responseMessage = Encoding.UTF8.GetBytes(response.ReasonPhrase); await OutgoingMessageAsync(corrId, requestInfo, responseMessage); return response; } protected abstract Task IncommingMessageAsync(string correlationId, string requestInfo, byte[] message); protected abstract Task OutgoingMessageAsync(string correlationId, string requestInfo, byte[] message); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } If we don’t handle the exceptions that can occur in a custom Message Handler, we can have a hard time to find the problem causing the exception. The savior in this case is the Global.asax’s Application_Error: protected void Application_Error() { var exception = Server.GetLastError(); Debug.WriteLine(exception); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } I would recommend you to add the Application_Error to the Global.asax and log all exceptions to make sure all kind of exception is handled. Summary There are different ways we could add Exception Handling to the Wep API, we can use a custom ApiController, ExceptionFilterAttribute, IHttpActionInvoker or Message Handler. The ExceptionFilterAttribute would be a good place to add a global exception handling, require very few modification, just register it globally for all ApiControllers, even the IHttpActionInvoker can be used to minimize the modifications of files. Adding the Application_Error to the global.asax is a good way to catch all unhandled exception that can occur, for example exception thrown in a Message Handler. If you want to know when I have posted a blog post, you can follow me on twitter @fredrikn

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Use Extension method to write cleaner code

- by Fredrik N

This blog post will show you step by step to refactoring some code to be more readable (at least what I think). Patrik Löwnedahl gave me some of the ideas when we where talking about making code much cleaner. The following is an simple application that will have a list of movies (Normal and Transfer). The task of the application is to calculate the total sum of each movie and also display the price of each movie. class Program { enum MovieType { Normal, Transfer } static void Main(string[] args) { var movies = GetMovies(); int totalPriceOfNormalMovie = 0; int totalPriceOfTransferMovie = 0; foreach (var movie in movies) { if (movie == MovieType.Normal) { totalPriceOfNormalMovie += 2; Console.WriteLine("$2"); } else if (movie == MovieType.Transfer) { totalPriceOfTransferMovie += 3; Console.WriteLine("$3"); } } } private static IEnumerable<MovieType> GetMovies() { return new List<MovieType>() { MovieType.Normal, MovieType.Transfer, MovieType.Normal }; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } In the code above I’m using an enum, a good way to add types (isn’t it ;)). I also use one foreach loop to calculate the price, the loop has a condition statement to check what kind of movie is added to the list of movies. I want to reuse the foreach only to increase performance and let it do two things (isn’t that smart of me?! ;)). First of all I can admit, I’m not a big fan of enum. Enum often results in ugly condition statements and can be hard to maintain (if a new type is added we need to check all the code in our app to see if we use the enum somewhere else). I don’t often care about pre-optimizations when it comes to write code (of course I have performance in mind). I rather prefer to use two foreach to let them do one things instead of two. So based on what I don’t like and Martin Fowler’s Refactoring catalog, I’m going to refactoring this code to what I will call a more elegant and cleaner code. First of all I’m going to use Split Loop to make sure the foreach will do one thing not two, it will results in two foreach (Don’t care about performance here, if the results will results in bad performance, you can refactoring later, but computers are so fast to day, so iterating through a list is not often so time consuming.) Note: The foreach actually do four things, will come to is later. var movies = GetMovies(); int totalPriceOfNormalMovie = 0; int totalPriceOfTransferMovie = 0; foreach (var movie in movies) { if (movie == MovieType.Normal) { totalPriceOfNormalMovie += 2; Console.WriteLine("$2"); } } foreach (var movie in movies) { if (movie == MovieType.Transfer) { totalPriceOfTransferMovie += 3; Console.WriteLine("$3"); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } To remove the condition statement we can use the Where extension method added to the IEnumerable<T> and is located in the System.Linq namespace: foreach (var movie in movies.Where( m => m == MovieType.Normal)) { totalPriceOfNormalMovie += 2; Console.WriteLine("$2"); } foreach (var movie in movies.Where( m => m == MovieType.Transfer)) { totalPriceOfTransferMovie += 3; Console.WriteLine("$3"); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The above code will still do two things, calculate the total price, and display the price of the movie. I will not take care of it at the moment, instead I will focus on the enum and try to remove them. One way to remove enum is by using the Replace Conditional with Polymorphism. So I will create two classes, one base class called Movie, and one called MovieTransfer. The Movie class will have a property called Price, the Movie will now hold the price: public class Movie { public virtual int Price { get { return 2; } } } public class MovieTransfer : Movie { public override int Price { get { return 3; } } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The following code has no enum and will use the new Movie classes instead: class Program { static void Main(string[] args) { var movies = GetMovies(); int totalPriceOfNormalMovie = 0; int totalPriceOfTransferMovie = 0; foreach (var movie in movies.Where( m => m is Movie)) { totalPriceOfNormalMovie += movie.Price; Console.WriteLine(movie.Price); } foreach (var movie in movies.Where( m => m is MovieTransfer)) { totalPriceOfTransferMovie += movie.Price; Console.WriteLine(movie.Price); } } private static IEnumerable<Movie> GetMovies() { return new List<Movie>() { new Movie(), new MovieTransfer(), new Movie() }; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } If you take a look at the foreach now, you can see it still actually do two things, calculate the price and display the price. We can do some more refactoring here by using the Sum extension method to calculate the total price of the movies: static void Main(string[] args) { var movies = GetMovies(); int totalPriceOfNormalMovie = movies.Where(m => m is Movie) .Sum(m => m.Price); int totalPriceOfTransferMovie = movies.Where(m => m is MovieTransfer) .Sum(m => m.Price); foreach (var movie in movies.Where( m => m is Movie)) Console.WriteLine(movie.Price); foreach (var movie in movies.Where( m => m is MovieTransfer)) Console.WriteLine(movie.Price); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Now when the Movie object will hold the price, there is no need to use two separate foreach to display the price of the movies in the list, so we can use only one instead: foreach (var movie in movies) Console.WriteLine(movie.Price); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } If we want to increase the Maintainability index we can use the Extract Method to move the Sum of the prices into two separate methods. The name of the method will explain what we are doing: static void Main(string[] args) { var movies = GetMovies(); int totalPriceOfMovie = TotalPriceOfMovie(movies); int totalPriceOfTransferMovie = TotalPriceOfMovieTransfer(movies); foreach (var movie in movies) Console.WriteLine(movie.Price); } private static int TotalPriceOfMovieTransfer(IEnumerable<Movie> movies) { return movies.Where(m => m is MovieTransfer) .Sum(m => m.Price); } private static int TotalPriceOfMovie(IEnumerable<Movie> movies) { return movies.Where(m => m is Movie) .Sum(m => m.Price); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Now to the last thing, I love the ForEach method of the List<T>, but the IEnumerable<T> doesn’t have it, so I created my own ForEach extension, here is the code of the ForEach extension method: public static class LoopExtensions { public static void ForEach<T>(this IEnumerable<T> values, Action<T> action) { Contract.Requires(values != null); Contract.Requires(action != null); foreach (var v in values) action(v); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } I will now replace the foreach by using this ForEach method: static void Main(string[] args) { var movies = GetMovies(); int totalPriceOfMovie = TotalPriceOfMovie(movies); int totalPriceOfTransferMovie = TotalPriceOfMovieTransfer(movies); movies.ForEach(m => Console.WriteLine(m.Price)); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The ForEach on the movies will now display the price of the movie, but maybe we want to display the name of the movie etc, so we can use Extract Method by moving the lamdba expression into a method instead, and let the method explains what we are displaying: movies.ForEach(DisplayMovieInfo); private static void DisplayMovieInfo(Movie movie) { Console.WriteLine(movie.Price); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Now the refactoring is done! Here is the complete code: class Program { static void Main(string[] args) { var movies = GetMovies(); int totalPriceOfMovie = TotalPriceOfMovie(movies); int totalPriceOfTransferMovie = TotalPriceOfMovieTransfer(movies); movies.ForEach(DisplayMovieInfo); } private static void DisplayMovieInfo(Movie movie) { Console.WriteLine(movie.Price); } private static int TotalPriceOfMovieTransfer(IEnumerable<Movie> movies) { return movies.Where(m => m is MovieTransfer) .Sum(m => m.Price); } private static int TotalPriceOfMovie(IEnumerable<Movie> movies) { return movies.Where(m => m is Movie) .Sum(m => m.Price); } private static IEnumerable<Movie> GetMovies() { return new List<Movie>() { new Movie(), new MovieTransfer(), new Movie() }; } } public class Movie { public virtual int Price { get { return 2; } } } public class MovieTransfer : Movie { public override int Price { get { return 3; } } } pulbic static class LoopExtensions { public static void ForEach<T>(this IEnumerable<T> values, Action<T> action) { Contract.Requires(values != null); Contract.Requires(action != null); foreach (var v in values) action(v); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } I think the new code is much cleaner than the first one, and I love the ForEach extension on the IEnumerable<T>, I can use it for different kind of things, for example: movies.Where(m => m is Movie) .ForEach(DoSomething); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } By using the Where and ForEach extension method, some if statements can be removed and will make the code much cleaner. But the beauty is in the eye of the beholder. What would you have done different, what do you think will make the first example in the blog post look much cleaner than my results, comments are welcome! If you want to know when I will publish a new blog post, you can follow me on twitter: http://www.twitter.com/fredrikn

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What can I do about rsync of large files killing my laptop's wifi connection

- by David Dean

When I run a rsync to backup my home folder over the network like so: rsync -avhz --progress --delete /home/dbdean/ [email protected]:/home/backups/david/ I seem to have problems with my quite large .VirtualBox/HardDisks/Windows XP.vdi file. Occasionally the wifi will silently fail (the transfer stops, and any other network access is broken). If I reconnect the wifi to my network before the transfer times out, it happily keeps going (and other network access is back), but I can't just leave it unattended most of the time, as I have to keep an eye on it. I'm guessing this is probably a bug in the wireless card related to a particularly high sustained volume of network usage, but I'm not really sure where to start with diagnosing this problem so that I can provide a good bug report. Or it could be something else, I guess. Any help would be appreciated. My network card is an Atheros Communications Inc. AR9285, as lspci -k shows: 43:00.0 Network controller: Atheros Communications Inc. AR9285 Wireless Network Adapter (PCI-Express) (rev 01) Subsystem: Hewlett-Packard Company Device 3040 Kernel driver in use: ath9k Kernel modules: ath9k

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Populate struct values with function argument

- by adohertyd

I am working on a program and part of it requires me to create a struct called DETAILS with the fields name, age, and height. I want to populate the record with data using a function argument. When I run my code I get compiler errors. I have put the errors in comment form beside the lines it is returned for but I can't fix them. Really could do with some help here guys thanks so much. Here is my code: #include <cstdlib> #include <iostream> #include <iomanip> using namespace std; const int LEN=100; struct DETAILS { char name[LEN]; int age; double height; }; person fillperson(struct DETAILS, char[LEN], int, double); int main() { struct person David; fillperson(David, "David Greene", 38, 180.0); //deprecated conversion from string constant to char * [-Wwrite-Strings] } person fillperson(struct DETAILS, char[LEN] name, int age, double height) //expected , or ... before 'name' { cin>>David.name>>name; cin>>David.age>>age; cin>>David.height>>height; cout<<"Done"<<endl; }

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Silverlight Cream for April 20, 2010 -- #842

- by Dave Campbell

In this Issue: Zoltan Arvai, Svetla Stoycheva, Alexey Zakharov, Chris Rouw, David Anson(-2-), Bill Reiss, John Papa and Adam Kinney, Chris Klug, CorrinaB, and Mike Snow. Shoutouts: Pete Brown interviewed David Kelley at MIX10: Pete at MIX10: David Kelley on the Prototype WPF and Silverlight Retail Experience Pete Brown also interviewed Emil Stoychev at MIX10: Pete at MIX10: Emil Stoychev on the CompletIT Silverlight Site SilverlightShow has a MIX10 Review by SilverlightShow Live Reporter Cigdem Patlak SilverlightShow also has an Interview with SilverlightShow Article Author Andrej Tozon From SilverlightCream.com: Implementing Push Notifications in Windows Phone 7 Zoltan Arvai has a post up on SilverlightShow discussing Push Notification on WP7 ... what it is, and how to use it. Completit.com - the challenges behind building a corporate website in Silverlight Svetla Stoycheva shows off the new CompleteIT corporate website which is pretty darn cool... and disucusses some of the challenges and solutions Introducing to Halcyone - Silverlight Application Framework: Silverlight Rest Extensions Alexey Zakharov has a tutorial up on a Silverlight application framework he's working on called Halcyone which is available on CodePlex Using the Tag Property during Silverlight Binding Chris Rouw details his SL3 to SL4 conversion and some issues he had, and how he was able to resolve a binding problem using the tag property. Using ContextMenu to implement SplitButton and MenuButton for Silverlight (or WPF) David Anson has a cool discussion up of using the ContextMenu code he put up previously to build a Split button, and includes all the code as usual. Silverlight/WPF Data Visualization Development Release 4 and Windows Phone 7 Charting sample! David Anson updated his Data Visualization because of the new releases, and this time he's including WP7... charting in WP7... ! Space Rocks game step 10: More fun with rocks In episode 10, Bill Reiss shows how to deal with multiple asteroids and all the interaction. Silverlight Training Course (Silverlight 4) Get your serious Silverlight 4 Mojo on with a new SL4 Training kit on Channel 9 ... buncha folks, spearheaded (it looks like) by John Papa and Adam Kinney... Plug-ins and composite applications in Silverlight – pt 3 Chris Klug is back with part 3 of his series on extensions and plug-in loading. So far he's covered a roll-your-own concept and MEF, now he digs into Prism. Transitions, Animations, and Effects with Blend - Part One How cool to have CorrinaB speak at your User Group meeting! ... She did just that in Portland, and instead of simply dropping a deck and some code in her blog, she's giving the run-down on her presentation... always good stuff, Corrina! Tip of the Day #110 – Using Static Resources in Class Libraries Mike Snow's latest tip is about how to create and use a Resource Dictionary. 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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Unable to change keyboard shortcut

- by balor123

I'm running Ubuntu 10.10 with KDE. I'm trying to setup my desktops with shortcuts alt+1 for desktop 1 and alt+2 for desktop 2 etc. The problem is that Page Settings refuses to change to the desired shortcut and gives no message as to why. When I press the alt key I see "Alt+" appear in the the box but when I add 1 it reverts back to "Input". Why won't KDE let me change the keyboard shortcut and what can I do to solve the problem?

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The Oracle Graduate Experience...A Graduates Perspective by Angelie Tierney

- by david.talamelli

[Note: Angelie has just recently joined Oracle in Australia in our 2011 Graduate Program. Last week I shared my thoughts on our 2011 Graduate Program, this week Angelie took some time to share her thoughts of our Graduate Program. The notes below are Angelie's overview from her experience with us starting with our first contact last year - David Talamelli] How does the 1 year program work? It consists of 3 weeks of training, followed by 2 rotations in 2 different Lines of Business (LoB's). The first rotation goes for 4 months, while your 2nd rotation goes for 7, when you are placed into your final LoB for the program. The interview process: After sorting through the many advertised graduate jobs, submitting so many resumes and studying at the same time, it can all be pretty stressful. Then there is the interview process. David called me on a Sunday afternoon and I spoke to him for about 30 minutes in a mini sort of phone interview. I was worried that working at Oracle would require extensive technical experience, but David stressed that even the less technical, and more business-minded person could, and did, work at Oracle. I was then asked if I would like to attend a group interview in the next weeks, to which I said of course! The first interview was a day long, consisting of a brief introduction, a group interview where we worked on a business plan with a group of other potential graduates and were marked by 3 Oracle employees, on our ability to work together and presentation. After lunch, we then had a short individual interview each, and that was the end of the first round. I received a call a few weeks later, and was asked to come into a second interview, at which I also jumped at the opportunity. This was an interview based purely on your individual abilities and would help to determine which Line of Business you would go to, should you land a graduate position. So how did I cope throughout the interview stages? I believe the best tool to prepare for the interview, was to research Oracle and its culture and to see if I thought I could fit into that. I personally found out about Oracle, its partners as well as competitors and along the way, even found out about their part (or Larry Ellison's specifically) in the Iron Man 2 movie. Armed with some Oracle information and lots of enthusiasm, I approached the Oracle Graduate Interview process. Why did I apply for an Oracle graduate position? I studied a Bachelor of Business/Bachelor of Science in IT, and wanted to be able to use both my degrees, while have the ability to work internationally in the future. Coming straight from university, I wasn't sure exactly what I wanted to do in terms of my career. With the program, you are rotated across various lines of business, to not only expose you to different parts of the business, but to also help you to figure out what you want to achieve out of your career. As a result, I thought Oracle was the perfect fit. So what can an Oracle ANZ Graduate expect? First things first, you can expect to line up for your visitor pass. Really. Next you enter a room full of unknown faces, graduates just like you, and then you realise you're in this with 18 other people, going through the same thing as you. 3 weeks later you leave with many memories, colleagues you can call your friends, and a video of your presentation. Vanessa, the Graduate Manager, will also take lots of photos and keep you (well) fed. Well that's not all you leave with, you are also equipped with a wealth of knowledge and contacts within Oracle, both that will help you throughout your career there. What training is involved? We started our Oracle experience with 3 weeks of training, consisting of employee orientation, extensive product training, presentations on the various lines of business (LoB's), followed by sales and presentation training. While there was potential for an information overload, maybe even death by Powerpoint, we were able to have access to the presentations for future reference, which was very helpful. This period also allowed us to start networking, not only with the graduates, but with the managers who presented to us, as well as through the monthly chinwag, HR celebrations and even with the sharing of tea facilities. We also had a team bonding day when we recorded a "commercial" within groups, and learned how to play an Irish drum. Overall, the training period helped us to learn about Oracle, as well as ourselves, and to prepare us for our transition into our rotations. Where to now? I'm now into my 2nd week of my first graduate rotation. It has been exciting to finally get out into the work environment and utilise that knowledge we gained from training. My manager has been a great mentor, extremely knowledgeable, and it has been good being able to participate in meetings, conference calls and make a contribution towards the business. And while we aren't necessarily working directly with the other graduates, they are still reachable via email, Pidgin and lunch and they are important as a resource and support, after all, they are going through a similar experience to you. While it is only the beginning, there is a lot more to learn and a lot more to experience along the way, especially because, as we learned during training, at Oracle, the only constant is change.

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How to avoid double divide in loop?

- by ignaty

Thank you for your help. My code looks like: var CatItems = ""; for(var x=0; x < data.PRODUCTS.length; x++) { if (x % 3 === 0) CatItems += '<li class="jcarousel-item jcarousel-item-horizontal jcarousel-item-'+[x]+' jcarousel-item-'+[x]+'-horizontal jcarousel-item-placeholder jcarousel-item-placeholder-horizontal">'; CatItems += '<div><a class="large_image" href="#"><img src="'+ data.PRODUCTS[x].product_img +'" alt="' + data.PRODUCTS[x].product_name +'"></a><h3 class="geo_17_darkbrown">' + data.PRODUCTS[x].product_name +'</h3>'; if ( data.PRODUCTS[x].product_onsale==1 ) { CatItems += '<img alt="sale" src="assets/images/sale.gif" class="sale"><span class="geo_17_red_linethr">£'+ data.PRODUCTS[x].product_retailprice +'</span>  <span class="price geo_17_darkbrown">£'+ data.PRODUCTS[x].product_webprice +'</span>'; } else { CatItems += '<span class="price geo_17_darkbrown">£'+ data.PRODUCTS[x].product_webprice +'</span>'; } if ( data.PRODUCTS[x].product_COLOURS ) { CatItems += '<span class="colour">'; for(var y=0; y < data.PRODUCTS[x].product_COLOURS.length; y++) { CatItems += '<span><a href="'+ data.PRODUCTS[x].product_COLOURS[y].colours_large +'"><img src="'+ data.PRODUCTS[x].product_COLOURS[y].colours_thumb +'" alt="'+ data.PRODUCTS[x].product_COLOURS[y].colour_name +'" /></a></span>'; } CatItems += '</span>'; } CatItems += '</div>'; if (x % 3 === 2) CatItems += '</li>'; } and it generates this: <div class="carousel_00 jcarousel-container jcarousel-container-horizontal" style="position: relative; display: block;"> <div class="jcarousel-clip jcarousel-clip-horizontal" style="overflow: hidden; position: relative;"> <ul class="jcarousel-list jcarousel-list-horizontal" style="overflow: hidden; position: relative; top: 0px; left: 0px; margin: 0px; padding: 0px; width: 7890px;"> <li class="jcarousel-item jcarousel-item-horizontal jcarousel-item-0 jcarousel-item-0-horizontal jcarousel-item-placeholder jcarousel-item-placeholder-horizontal"> <div> <a href="#" class="large_image"> <img alt="Elena Top" src="assets/images/dress1.gif"></a> <h3 class="geo_17_darkbrown">Elena Top</h3> <img class="sale" src="assets/images/sale.gif" alt="sale"> <span class="geo_17_red_linethr">£120 </span>   <span class="price geo_17_darkbrown">£100 </span> <span class="colour"> <span> <a href="assets/images/colour.gif"> <img alt="Black" src="assets/images/black.gif"></a> </span> <span> <a href="assets/images/colour.gif"> <img alt="Brown" src="assets/images/brown.gif"></a> </span> <span> <a href="assets/images/colour.gif"> <img alt="Purple" src="assets/images/purple.gif"></a> </span> </span> </div> <div> <a href="#" class="large_image"> <img alt="Rachel Dress" src="assets/images/dress2.gif"></a> <h3 class="geo_17_darkbrown">Rachel Dress</h3> <span class="price geo_17_darkbrown">£120 </span> </div> <div> <a href="#" class="large_image"> <img alt="Elena Top" src="assets/images/dress3.gif"></a> <h3 class="geo_17_darkbrown">Elena Top</h3> <span class="price geo_17_darkbrown">£120 </span> </div> </li> <li class="jcarousel-item jcarousel-item-horizontal jcarousel-item-1 jcarousel-item-1-horizontal jcarousel-item-placeholder jcarousel-item-placeholder-horizontal" style="float: left; list-style: none outside none;" jcarouselindex="1"> </li> <li class="jcarousel-item jcarousel-item-horizontal jcarousel-item-3 jcarousel-item-3-horizontal jcarousel-item-placeholder jcarousel-item-placeholder-horizontal"> <div> <a href="#" class="large_image"> <img alt="Elena Top" src="assets/images/dress1.gif"></a> <h3 class="geo_17_darkbrown">Elena Top</h3> <span class="price geo_17_darkbrown">£120 </span> </div> <div> <a href="#" class="large_image"> <img alt="Elena Top" src="assets/images/dress2.gif"></a> <h3 class="geo_17_darkbrown">Elena Top</h3> <span class="price geo_17_darkbrown">£120 </span> </div> <div> <a href="#" class="large_image"> <img alt="Elena Top" src="assets/images/dress3.gif"></a> <h3 class="geo_17_darkbrown">Elena Top</h3> <span class="price geo_17_darkbrown">£120 </span> </div> </li> <li class="jcarousel-item jcarousel-item-horizontal jcarousel-item-6 jcarousel-item-6-horizontal jcarousel-item-placeholder jcarousel-item-placeholder-horizontal"> <div> <a href="#" class="large_image"> <img alt="Elena Top" src="assets/images/dress3.gif"></a> <h3 class="geo_17_darkbrown">Elena Top</h3> <span class="price geo_17_darkbrown">£120 </span> </div> <div> <a href="#" class="large_image"> <img alt="Elena Top" src="assets/images/dress3.gif"></a> <h3 class="geo_17_darkbrown">Elena Top</h3> <span class="price geo_17_darkbrown">£120 </span> </div> </li> </ul> </div> <div class="jcarousel-prev jcarousel-prev-horizontal jcarousel-prev-disabled jcarousel-prev-disabled-horizontal" style="display: block;" disabled="true"> </div> <div class="jcarousel-next jcarousel-next-horizontal" style="display: block;" disabled="false"> </div> <div class="jcarousel-control geo_10_darkbrown_capital"> 7 products    <a href="#">1</a> <a href="#">2</a> <a href="#">3</a> <a href="#">4</a> <a href="#">5</a> <a href="#">6</a> <a href="#" class="last">7</a> </div> </div> It works like it should, put every 3 div's in li. but I have another problem with divide. It divide "x" inside the loop. For example in JS: <li class="jcarousel-item jcarousel-item-horizontal jcarousel-item-'+[x]+' jcarousel-item-'+[x]+'-horizontal jcarousel-item-placeholder jcarousel-item-placeholder-horizontal"> And HTML out is: <li class="jcarousel-item jcarousel-item-horizontal jcarousel-item-0 jcarousel-item-0-horizontal jcarousel-item-placeholder jcarousel-item-placeholder-horizontal"></li> then <li class="jcarousel-item jcarousel-item-horizontal jcarousel-item-3 jcarousel-item-3-horizontal jcarousel-item-placeholder jcarousel-item-placeholder-horizontal"></li> then <li class="jcarousel-item jcarousel-item-horizontal jcarousel-item-6 jcarousel-item-6-horizontal jcarousel-item-placeholder jcarousel-item-placeholder-horizontal"></li> etc... What I need is that count goes as 0-1-2-3-4-5-etc, but with divide it goes 0-3-6-etc and jCarousel insert blank li's 1-2, 4-5, 7-8. How I can avoid "x" divide inside the loop? Tnak you!

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CSS: series of floated elements without wrapping but rather scrolling horizontally

- by tybro0103

I'm working on a album viewer. At the top I want a horizontal container of all the image thumbnails. Right now all the thumbnails are wrapped in a div with float:left. I'm trying to figure out how to keep these thumbnails from wrapping to the next line when there are too many, but rather stay all in one horizontal row and use the scrollbar. Here's my code: (I don't want to use tables) <style type="text/css"> div { overflow:hidden; } #frame { width:600px; padding:8px; border:1px solid black; } #thumbnails_container { height:75px; border:1px solid black; padding:4px; overflow-x:scroll; } .thumbnail { border:1px solid black; margin-right:4px; width:100px; height:75px; float:left; } .thumbnail img { width:100px; height:75px; } #current_image_container img { width:600px; } </style> <div id="frame"> <div id="thumbnails_container"> <div class="thumbnail"><img src="http://www.blueridgexotics.com/images/glry-pixie-bob-kittens.jpg" alt="foo" /></div> <div class="thumbnail"><img src="http://www.blueridgexotics.com/images/PB-KitJan08-1.jpg" alt="foo" /></div> <div class="thumbnail"><img src="http://www.blueridgexotics.com/images/PB-KitJan08-3.jpg" alt="foo" /></div> <div class="thumbnail"><img src="http://www.blueridgexotics.com/images/PB-Jan08.jpg" alt="foo" /></div> <div class="thumbnail"><img src="http://www.blueridgexotics.com/images/gallery3.jpg" alt="foo" /></div> <div class="thumbnail"><img src="http://www.blueridgexotics.com/images/gallery4.jpg" alt="foo" /></div> <div class="thumbnail"><img src="http://www.blueridgexotics.com/Gallery-Pics/kitten3.jpg" alt="foo" /></div> <div class="thumbnail"><img src="http://www.blueridgexotics.com/Gallery-Pics/kitten1.jpg" alt="foo" /></div> </div> <div id="current_image_container"> <img src="http://www.whitetailrun.com/Pixiebobs/PBkittenpics/shani-kits/Cats0031a.jpg" alt="foo" /> </div> </div>

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Help with manipulating child/parent elements with jQuery

- by Mohammad

Currently I have this JQuery script var img = $(this); img.wrap('<div class="photo"></div>'); img.parent().append("<p>" + img.attr("alt") + "</p>"); which successfully turns the following: <img src="photo.jpg" alt="caption"> into this <div class="photo"> <img src="photos.jpg" alt="caption"/> <p>caption</p> </div> All is well unless the image has a link as a parent; <a href="#"><img since I want it to be correct html (I'm fussy) improving the resulting outcome bellow would be satisfactory <a href="#"> <div class="photo"> <img src="photos.jpg" alt="caption"/> <p>caption</p> </div> </a> to this: <div class="photo"> <a href="#"> <img src="photos.jpg" alt="caption"/> </a> <p><a href="#">caption</a></p> </div> </a> This is my jQuery script so far (which doesn't work bc I'm a noob) aha if(img.parent('a')){ var targetLink = img.parent('a').attr('href').val(); img.parent('a').wrap('<div class="photo"></div>'); img.parent('div').append('<p><a href="'+targetLink+'">' + img.attr("alt") + '</p></a>'); }else{ img.wrap('<div class="photo"></div>'); img.parent().append("<p>" + img.attr("alt") + "</p>"); }; Any advice, or help will be greatly appreciated : ) Thank You! Update *Answer* (works but looks sloppy) I'm editing it atm; if(img.parent('a').length){ var targetLink = img.parent().attr('href'); img.parent().wrap('<div class="photo"></div>'); var divTarget = img.parent('a').parent('div'); divTarget.append('<p><a href="'+targetLink+'">' + img.attr("alt") + '</p></a>'); }else{ img.wrap('<div class="photo"></div>'); img.parent().append("<p>" + img.attr("alt") + "</p>"); };

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PHP else/if statements

- by V Neal

I've written the following PHP statement but everytime i try to combine it into an else/if, it breaks. Can someone please advise? I'm new to PHP and am getting a tad stuck. Thanks :) <?php if (is_page( 19 ) ) {?> <div class="imageSlider"><img src="<?php echo bloginfo('template_directory');?>/Images/mainImages/innerPage-Image.jpg" alt="" /><img src="<?php echo bloginfo('template_directory');?>/Images/mainImages/innerPage-Image2.jpg" alt="" /><img src="<?php echo bloginfo('template_directory');?>/Images/mainImages/innerPage-Image3.jpg" alt="" /></div> <?php }?> <?php if (is_page( 23 ) ) {?> <div class="imageSlider"><img src="<?php echo bloginfo('template_directory');?>/Images/mainImages/innerPage-Image.jpg" alt="" /><img src="<?php echo bloginfo('template_directory');?>/Images/mainImages/innerPage-Image.jpg" alt="" /><img src="<?php echo bloginfo('template_directory');?>/Images/mainImages/innerPage-Image.jpg" alt="" /></div> } <?php }?>

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DISABLING KEYS IN WINDOWS

- by BEENA

how to disable ctrl+alt+del,alt+F4,ALT+TAB,WINDOWS USING JAVASCRIPT FOR WINDOWS?

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os x 10.4 Old, deleted user mail account problems

- by Chris

Hello- A while back I tried to add a user 'david' as a mail user on my OS X 10.4 server using dscl (I only had terminal access at the time, no ability to use workgroup manager). I could never get this account to work properly, so I deleted it. dscl . -list /Users no longer shows 'david' as an entry. I have since gained access via Workgroup Manager, and I am trying to re-create the 'david' account. Workgroup manager creates the account fine, along with an email account, which I can then log into via IMAP ('login david password' returns 'OK user logged in'). However, this mail account does not have an inbox, and I can not create one thru a mail client, IMAP or cyradm (they all say 'system I/O error'). When I re-delete this user, I can't find any record of him in any of the mail spool locations. Creating a user with any other name works fine (Inbox, mail access, everything). Any ideas on how I can get this user up and running again? -Chris P.S. - to create this user in the first place, I used dscl . create, then dscl . append /Users/david "some XML I found on the 'net" to add email privileges, if this helps...

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Have you ever used kon-boot?

- by Ctrl Alt D-1337

Has anyone here ever used kon-boot? I guess it may work because of the few blog posts about it but I feel kinda concerned and am interested at hearing experiences from anyone who have used multiple times with no side effects. I am slightly worried for any direct memory altering it tries to do. I am also worried if this will do its job fine to hide the fact it puts in a low level trojan or if the author planned to do anything like that in a future release as it looks like closed source from the site. Also I don't intend to gain illegal access but I find these sort of things very useful for my box of live discs I take every where, just in case. OT: Other question that me be of interest to readers here

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#TechEd 2010

- by T

It has been another fantastic year for TechEd North America. I always love my time here. First, I have to give a huge thank you to Ineta for giving me the opportunity to work the Ineta booth and BOF’s (birds of a feather). I can not even begin to list how many fantastic leaders in the .Net space and Developers from all over I have met through Ineta at this event. It has been truly amazing and great fun!! New Orlean’s has been awesome. The night life is hoppin’. In addition to enjoying a few (too many??) of the local hurricanes in New Orleans, I have hung out with some of the coolest people Deepesh Mohnani, David Poll, Viresh, Alan Stephens, Shawn Wildermuth, Greg Leonardo, Doug Seven, Chris Willams, David Carley and some of our southcentral hero’s Jeffery Palermo, Todd Anglin, Shawn Weisfeld, Randy Walker, The midnight DBA’s, Zeeshan Hirani, Dennis Bottjer just to name a few. A big thanks to Microsoft and everyone that has helped to put TechEd together. I have loved hanging out with people from the Silverlight and Expression Teams and have learned a ton. I am ramped up and ready to take all that knowledge back to my co-workers and my community. I can not wait to see you all again next year in Atlanta!!! Here are video links to some of my fav sessions: Using MVVM Design Pattern with VS 2010 XAML Designer – Rockford Lhotka Effective RIA: Tips and Tricks for Building Effective Rich Internet Applications – Deepesh Mohani Taking Microsoft Silverlight 4 Applications Beyond the Browser – David Poll Jump into Silvelright! and become immediately effective – Tim Huckaby Prototyping Rich Microsoft Silverlight 4 Applications with MS Expression Blend + SketchFlow – David Carley Tales from the Trenches: Building a Real-World Microsoft Silvelright Line-of-Business Application – Dan Wahlin

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Oracle 'In Touch' PartnerCast – Neues von der Oracle OpenWorld

- by Alliances & Channels Redaktion

Kurz nach den vielen interessanten Ankündigungen auf der Oracle OpenWorld sind alle Oracle EMEA Partner herzlich eingeladen, an dem „In Touch“-Partnerwebcast mit David Callaghan, Senior Vice President EMEA Alliances and Channels, und seinen Studiogästen teilzunehmen. Am Dienstag, 29. Oktober, um 11:30 Uhr MEZ informiert Sie David Callaghan über die neuesten Entwicklungen rund um die Oracle Cloud und Oracle Hardware. Er wird die Key Partner Wins aus dem ersten Quartal vorstellen sowie Ihre Fragen an seine Studiogäste weiterleiten. Live im Studio dabei ist Will O'Brien, Vice President Alliances & Channels, UK & Irland, der über die Highlights der Oracle OpenWorld berichtet und die Relevanz von Storage für das Software Business erläutert. David Callaghan wird Will O’Brien zu seiner neuen Rolle interviewen und ihn nach seinen obersten Prioritäten für FY14 befragen. Markus Reischl, Senior Director und Sales Leader EMEA Strategic Alliances, stellt die Updates in Business Intelligence vor und berichtet darüber, wie diese das gesamte Oracle Portfolio beeinflussen und welche Chancen dies für die Partner bringt. Registrieren Sie sich hier für den Webcast. Über Fragen an die Studiogäste freut sich David Callaghan. Kontaktieren Sie ihn über Twitter mit dem Hashtag #DCpickme oder per E-Mail [email protected]. Mehr Informationen über diesen sowie frühere Webcasts on-demand finden Sie hier auf der neuen Website.

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Oracle 'In Touch' PartnerCast – Neues von der Oracle OpenWorld

- by Alliances & Channels Redaktion

Kurz nach den vielen interessanten Ankündigungen auf der Oracle OpenWorld sind alle Oracle EMEA Partner herzlich eingeladen, an dem „In Touch“-Partnerwebcast mit David Callaghan, Senior Vice President EMEA Alliances and Channels, und seinen Studiogästen teilzunehmen. Am Dienstag, 29. Oktober, um 11:30 Uhr MEZ informiert Sie David Callaghan über die neuesten Entwicklungen rund um die Oracle Cloud und Oracle Hardware. Er wird die Key Partner Wins aus dem ersten Quartal vorstellen sowie Ihre Fragen an seine Studiogäste weiterleiten. Live im Studio dabei ist Will O'Brien, Vice President Alliances & Channels, UK & Irland, der über die Highlights der Oracle OpenWorld berichtet und die Relevanz von Storage für das Software Business erläutert. David Callaghan wird Will O’Brien zu seiner neuen Rolle interviewen und ihn nach seinen obersten Prioritäten für FY14 befragen. Markus Reischl, Senior Director und Sales Leader EMEA Strategic Alliances, stellt die Updates in Business Intelligence vor und berichtet darüber, wie diese das gesamte Oracle Portfolio beeinflussen und welche Chancen dies für die Partner bringt. Registrieren Sie sich hier für den Webcast. Über Fragen an die Studiogäste freut sich David Callaghan. Kontaktieren Sie ihn über Twitter mit dem Hashtag #DCpickme oder per E-Mail [email protected]. Mehr Informationen über diesen sowie frühere Webcasts on-demand finden Sie hier auf der neuen Website.

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I finished my #TechEd 2010, may I have another??

- by T

It has been another fantastic year for TechEd North America. I always love my time here. First, I have to give a huge thank you to Ineta for giving me the opportunity to work the Ineta booth and BOF’s (birds of a feather). I can not even begin to list how many fantastic leaders in the .Net space and Developers from all over I have met through Ineta at this event. It has been truly amazing and great fun!! New Orlean’s has been awesome. The night life is hoppin’. In addition to enjoying a few (too many??) of the local hurricanes in New Orleans, I have hung out with some of the coolest people Deepesh Mohnani, David Poll, Viresh, Alan Stephens, Shawn Wildermuth, Greg Leonardo, Doug Seven, Chris Willams, David Carley and some of our southcentral hero’s Jeffery Palermo, Todd Anglin, Shawn Weisfeld, Randy Walker, The midnight DBA’s, Zeeshan Hirani, Dennis Bottjer just to name a few. A big thanks to Microsoft and everyone that has helped to put TechEd together. I have loved hanging out with people from the Silverlight and Expression Teams and have learned a ton. I am ramped up and ready to take all that knowledge back to my co-workers and my community. I can not wait to see you all again next year in Atlanta!!! Here are video links to some of my fav sessions: Using MVVM Design Pattern with VS 2010 XAML Designer – Rockford Lhotka Effective RIA: Tips and Tricks for Building Effective Rich Internet Applications – Deepesh Mohani Taking Microsoft Silverlight 4 Applications Beyond the Browser – David Poll Jump into Silvelright! and become immediately effective – Tim Huckaby Prototyping Rich Microsoft Silverlight 4 Applications with MS Expression Blend + SketchFlow – David Carley Tales from the Trenches: Building a Real-World Microsoft Silvelright Line-of-Business Application – Dan Wahlin

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TestDriven.Net 3.0 – All Systems Go

- by Jamie Cansdale

I’m pleased to announce that TestDriven.Net 3.0 is now available. Finally! I know many of you will already be using the Beta and RC versions, but if you look at the release notes you’ll see there’s been many refinements since then, so I highly recommend you install the RTM version. Here is a quick summary of a few new features: Visual Studio 2010 supports targeting multiple versions of the .NET framework (multi-targeting). This means you can easily upgrade your Visual Studio 2005/2008 solutions without necessarily converting them to use .NET 4.0. TestDriven.Net will execute your tests using the .NET version your test project is targeting (see ‘Properties > Application > Target framework’). There is now first class support for MSTest when using Visual Studio 2008 & 2010. Previous versions of TestDriven.Net had support for a limited number of MSTest attributes. This version supports virtually all MSTest unit testing related attributes, including support for deployment item and data driven test attributes. You should also find this test runner is quick. ;) There is a new ‘Go To Test/Code’ command on the code context menu. You can think of this as Ctrl-Tab for test driven developers; it will quickly flip back and forth between your tests and code under test. I recommend assigning a keyboard shortcut to the ‘TestDriven.NET.GoToTestOrCode’ command. NCover can now be used for code coverage on .NET 4.0. This is only officially supported since NCover 3.2 (your mileage may vary if you’re using the 1.5.8 version). Rather than clutter the ‘Output’ window, ignored or skipped tests will be placed on the ‘Task List’. You can double-click on these items to navigate to the offending test (or assign a keyboard shortcut to ‘View.NextTask’). If you’re using a Team, Premium or Ultimate edition of Visual Studio 2005-2010, a new ‘Test With > Performance’ command will be available. This command will perform instrumented performance profiling on your target code. A particular focus of this version has been to make it more keyboard friendly. Here’s a list of commands you will probably want to assign keyboard shortcuts to: Name Default What I use TestDriven.NET.RunTests Run tests in context Alt + T TestDriven.NET.RerunTests Repeat test run Alt + R TestDriven.NET.GoToTestOrCode Flip between tests and code Alt + G TestDriven.NET.Debugger Run tests with debugger Alt + D View.Output Show the ‘Output’ window Ctrl+ Alt + O Edit.BreakLine Edit code in stack trace Enter View.NextError Jump to next failed test Ctrl + Shift + F12 View.NextTask Jump to next skipped test Alt + S By default the ‘Output’ window will automatically activate when there is test output or a failed test (this is an option). The cursor will be positioned on the stack trace of the last failed test, ready for you to hit ‘Enter’ to jump to the fail point or ‘Esc’ to return to your source (assuming your ‘Output’ window is set to auto-hide). If your ‘Output’ window isn’t set to auto-hide, you’ll need to hit ‘Ctrl + Alt + O’ then ‘Enter’. Alternatively you can use ‘Ctrl + Shift + F12’ (View.NextError) to navigate between all failed tests. For more frequent updates or to give feedback, you can find me on twitter here. I hope you enjoy this version. Let me know how you get on. :)

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Design by Contract with Microsoft .Net Code Contract

- by Fredrik N

I have done some talks on different events and summits about Defensive Programming and Design by Contract, last time was at Cornerstone’s Developer Summit 2010. Next time will be at SweNug (Sweden .Net User Group). I decided to write a blog post about of some stuffs I was talking about. Users are a terrible thing! Protect your self from them ”Human users have a gift for doing the worst possible thing at the worst possible time.” – Michael T. Nygard, Release It! The kind of users Michael T. Nygard are talking about is the users of a system. We also have users that uses our code, the users I’m going to focus on is the users of our code. Me and you and another developers. “Any fool can write code that a computer can understand. Good programmers write code that humans can understand.” – Martin Fowler Good programmers also writes code that humans know how to use, good programmers also make sure software behave in a predictable manner despise inputs or user actions. Design by Contract Design by Contract (DbC) is a way for us to make a contract between us (the code writer) and the users of our code. It’s about “If you give me this, I promise to give you this”. It’s not about business validations, that is something completely different that should be part of the domain model. DbC is to make sure the users of our code uses it in a correct way, and that we can rely on the contract and write code in a way where we know that the users will follow the contract. It will make it much easier for us to write code with a contract specified. Something like the following code is something we may see often: public void DoSomething(Object value) { value.DoIKnowThatICanDoThis(); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Where “value” can be uses directly or passed to other methods and later be used. What some of us can easily forget here is that the “value” can be “null”. We will probably not passing a null value, but someone else that uses our code maybe will do it. I think most of you (including me) have passed “null” into a method because you don’t know if the argument need to be specified to a valid value etc. I bet most of you also have got the “Null reference exception”. Sometimes this “Null reference exception” can be hard and take time to fix, because we need to search among our code to see where the “null” value was passed in etc. Wouldn’t it be much better if we can as early as possible specify that the value can’t not be null, so the users of our code also know it when the users starts to use our code, and before run time execution of the code? This is where DbC comes into the picture. We can use DbC to specify what we need, and by doing so we can rely on the contract when we write our code. So the code above can actually use the DoIKnowThatICanDoThis() method on the value object without being worried that the “value” can be null. The contract between the users of the code and us writing the code, says that the “value” can’t be null. Pre- and Postconditions When working with DbC we are specifying pre- and postconditions. Precondition is a condition that should be met before a query or command is executed. An example of a precondition is: “The Value argument of the method can’t be null”, and we make sure the “value” isn’t null before the method is called. Postcondition is a condition that should be met when a command or query is completed, a postcondition will make sure the result is correct. An example of a postconditon is “The method will return a list with at least 1 item”. Commands an Quires When using DbC, we need to know what a Command and a Query is, because some principles that can be good to follow are based on commands and queries. A Command is something that will not return anything, like the SQL’s CREATE, UPDATE and DELETE. There are two kinds of Commands when using DbC, the Creation commands (for example a Constructor), and Others. Others can for example be a Command to add a value to a list, remove or update a value etc. //Creation commands public Stack(int size) //Other commands public void Push(object value); public void Remove(); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } A Query, is something that will return something, for example an Attribute, Property or a Function, like the SQL’s SELECT. There are two kinds of Queries, the Basic Queries (Quires that aren’t based on another queries), and the Derived Queries, queries that is based on another queries. Here is an example of queries of a Stack: //Basic Queries public int Count; public object this[int index] { get; } //Derived Queries //Is related to Count Query public bool IsEmpty() { return Count == 0; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } To understand about some principles that are good to follow when using DbC, we need to know about the Commands and different Queries. The 6 Principles When working with DbC, it’s advisable to follow some principles to make it easier to define and use contracts. The following DbC principles are: Separate commands and queries. Separate basic queries from derived queries. For each derived query, write a postcondition that specifies what result will be returned, in terms of one or more basic queries. For each command, write a postcondition that specifies the value of every basic query. For every query and command, decide on a suitable precondition. Write invariants to define unchanging properties of objects. Before I will write about each of them I want you to now that I’m going to use .Net 4.0 Code Contract. I will in the rest of the post uses a simple Stack (Yes I know, .Net already have a Stack class) to give you the basic understanding about using DbC. A Stack is a data structure where the first item in, will be the first item out. Here is a basic implementation of a Stack where not contract is specified yet: public class Stack { private object[] _array; //Basic Queries public uint Count; public object this[uint index] { get { return _array[index]; } set { _array[index] = value; } } //Derived Queries //Is related to Count Query public bool IsEmpty() { return Count == 0; } //Is related to Count and this[] Query public object Top() { return this[Count]; } //Creation commands public Stack(uint size) { Count = 0; _array = new object[size]; } //Other commands public void Push(object value) { this[++Count] = value; } public void Remove() { this[Count] = null; Count--; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Note: The Stack is implemented in a way to demonstrate the use of Code Contract in a simple way, the implementation may not look like how you would implement it, so don’t think this is the perfect Stack implementation, only used for demonstration. Before I will go deeper into the principles I will simply mention how we can use the .Net Code Contract. I mention before about pre- and postcondition, is about “Require” something and to “Ensure” something. When using Code Contract, we will use a static class called “Contract” and is located in he “System.Diagnostics.Contracts” namespace. The contract must be specified at the top or our member statement block. To specify a precondition with Code Contract we uses the Contract.Requires method, and to specify a postcondition, we uses the Contract.Ensure method. Here is an example where both a pre- and postcondition are used: public object Top() { Contract.Requires(Count > 0, "Stack is empty"); Contract.Ensures(Contract.Result<object>() == this[Count]); return this[Count]; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The contract above requires that the Count is greater than 0, if not we can’t get the item at the Top of a Stack. We also Ensures that the results (By using the Contract.Result method, we can specify a postcondition that will check if the value returned from a method is correct) of the Top query is equal to this[Count]. 1. Separate Commands and Queries When working with DbC, it’s important to separate Command and Quires. A method should either be a command that performs an Action, or returning information to the caller, not both. By asking a question the answer shouldn’t be changed. The following is an example of a Command and a Query of a Stack: public void Push(object value) public object Top() .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The Push is a command and will not return anything, just add a value to the Stack, the Top is a query to get the item at the top of the stack. 2. Separate basic queries from derived queries There are two different kinds of queries, the basic queries that doesn’t rely on another queries, and derived queries that uses a basic query. The “Separate basic queries from derived queries” principle is about about that derived queries can be specified in terms of basic queries. So this principles is more about recognizing that a query is a derived query or a basic query. It will then make is much easier to follow the other principles. The following code shows a basic query and a derived query: //Basic Queries public uint Count; //Derived Queries //Is related to Count Query public bool IsEmpty() { return Count == 0; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } We can see that IsEmpty will use the Count query, and that makes the IsEmpty a Derived query. 3. For each derived query, write a postcondition that specifies what result will be returned, in terms of one or more basic queries. When the derived query is recognize we can follow the 3ed principle. For each derived query, we can create a postcondition that specifies what result our derived query will return in terms of one or more basic queries. Remember that DbC is about contracts between the users of the code and us writing the code. So we can’t use demand that the users will pass in a valid value, we must also ensure that we will give the users what the users wants, when the user is following our contract. The IsEmpty query of the Stack will use a Count query and that will make the IsEmpty a Derived query, so we should now write a postcondition that specified what results will be returned, in terms of using a basic query and in this case the Count query, //Basic Queries public uint Count; //Derived Queries public bool IsEmpty() { Contract.Ensures(Contract.Result<bool>() == (Count == 0)); return Count == 0; } The Contract.Ensures is used to create a postcondition. The above code will make sure that the results of the IsEmpty (by using the Contract.Result to get the result of the IsEmpty method) is correct, that will say that the IsEmpty will be either true or false based on Count is equal to 0 or not. The postcondition are using a basic query, so the IsEmpty is now following the 3ed principle. We also have another Derived Query, the Top query, it will also need a postcondition and it uses all basic queries. The Result of the Top method must be the same value as the this[] query returns. //Basic Queries public uint Count; public object this[uint index] { get { return _array[index]; } set { _array[index] = value; } } //Derived Queries //Is related to Count and this[] Query public object Top() { Contract.Ensures(Contract.Result<object>() == this[Count]); return this[Count]; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } 4. For each command, write a postcondition that specifies the value of every basic query. For each command we will create a postconditon that specifies the value of basic queries. If we look at the Stack implementation we will have three Commands, one Creation command, the Constructor, and two others commands, Push and Remove. Those commands need a postcondition and they should include basic query to follow the 4th principle. //Creation commands public Stack(uint size) { Contract.Ensures(Count == 0); Count = 0; _array = new object[size]; } //Other commands public void Push(object value) { Contract.Ensures(Count == Contract.OldValue<uint>(Count) + 1); Contract.Ensures(this[Count] == value); this[++Count] = value; } public void Remove() { Contract.Ensures(Count == Contract.OldValue<uint>(Count) - 1); this[Count] = null; Count--; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } As you can see the Create command will Ensures that Count will be 0 when the Stack is created, when a Stack is created there shouldn’t be any items in the stack. The Push command will take a value and put it into the Stack, when an item is pushed into the Stack, the Count need to be increased to know the number of items added to the Stack, and we must also make sure the item is really added to the Stack. The postconditon of the Push method will make sure the that old value of the Count (by using the Contract.OldValue we can get the value a Query has before the method is called) plus 1 will be equal to the Count query, this is the way we can ensure that the Push will increase the Count with one. We also make sure the this[] query will now contain the item we pushed into the Stack. The Remove method must make sure the Count is decreased by one when the top item is removed from the Stack. The Commands is now following the 4th principle, where each command now have a postcondition that used the value of basic queries. Note: The principle says every basic Query, the Remove only used one Query the Count, it’s because this command can’t use the this[] query because an item is removed, so the only way to make sure an item is removed is to just use the Count query, so the Remove will still follow the principle. 5. For every query and command, decide on a suitable precondition. We have now focused only on postcondition, now time for some preconditons. The 5th principle is about deciding a suitable preconditon for every query and command. If we starts to look at one of our basic queries (will not go through all Queries and commands here, just some of them) the this[] query, we can’t pass an index that is lower then 1 (.Net arrays and list are zero based, but not the stack in this blog post ;)) and the index can’t be lesser than the number of items in the stack. So here we will need a preconditon. public object this[uint index] { get { Contract.Requires(index >= 1); Contract.Requires(index <= Count); return _array[index]; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Think about the Contract as an documentation about how to use the code in a correct way, so if the contract could be specified elsewhere (not part of the method body), we could simply write “return _array[index]” and there is no need to check if index is greater or lesser than Count, because that is specified in a “contract”. The implementation of Code Contract, requires that the contract is specified in the code. As a developer I would rather have this contract elsewhere (Like Spec#) or implemented in a way Eiffel uses it as part of the language. Now when we have looked at one Query, we can also look at one command, the Remove command (You can see the whole implementation of the Stack at the end of this blog post, where precondition is added to more queries and commands then what I’m going to show in this section). We can only Remove an item if the Count is greater than 0. So we can write a precondition that will require that Count must be greater than 0. public void Remove() { Contract.Requires(Count > 0); Contract.Ensures(Count == Contract.OldValue<uint>(Count) - 1); this[Count] = null; Count--; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } 6. Write invariants to define unchanging properties of objects. The last principle is about making sure the object are feeling great! This is done by using invariants. When using Code Contract we can specify invariants by adding a method with the attribute ContractInvariantMethod, the method must be private or public and can only contains calls to Contract.Invariant. To make sure the Stack feels great, the Stack must have 0 or more items, the Count can’t never be a negative value to make sure each command and queries can be used of the Stack. Here is our invariant for the Stack object: [ContractInvariantMethod] private void ObjectInvariant() { Contract.Invariant(Count >= 0); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Note: The ObjectInvariant method will be called every time after a Query or Commands is called. Here is the full example using Code Contract: public class Stack { private object[] _array; //Basic Queries public uint Count; public object this[uint index] { get { Contract.Requires(index >= 1); Contract.Requires(index <= Count); return _array[index]; } set { Contract.Requires(index >= 1); Contract.Requires(index <= Count); _array[index] = value; } } //Derived Queries //Is related to Count Query public bool IsEmpty() { Contract.Ensures(Contract.Result<bool>() == (Count == 0)); return Count == 0; } //Is related to Count and this[] Query public object Top() { Contract.Requires(Count > 0, "Stack is empty"); Contract.Ensures(Contract.Result<object>() == this[Count]); return this[Count]; } //Creation commands public Stack(uint size) { Contract.Requires(size > 0); Contract.Ensures(Count == 0); Count = 0; _array = new object[size]; } //Other commands public void Push(object value) { Contract.Requires(value != null); Contract.Ensures(Count == Contract.OldValue<uint>(Count) + 1); Contract.Ensures(this[Count] == value); this[++Count] = value; } public void Remove() { Contract.Requires(Count > 0); Contract.Ensures(Count == Contract.OldValue<uint>(Count) - 1); this[Count] = null; Count--; } [ContractInvariantMethod] private void ObjectInvariant() { Contract.Invariant(Count >= 0); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Summary By using Design By Contract we can make sure the users are using our code in a correct way, and we must also make sure the users will get the expected results when they uses our code. This can be done by specifying contracts. To make it easy to use Design By Contract, some principles may be good to follow like the separation of commands an queries. With .Net 4.0 we can use the Code Contract feature to specify contracts.

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