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  • How to create posts in asp.net ..?? [closed]

    - by ntechi
    I am doing my final year project and have decided to make a website in asp.net. For that I'll be using Micrsoft Visual Studio 2008. I'm making a Real ESTATE properties website. I want to know how to create posts in asp.net( like in WORDPRESS) and also when I hit SEARCH it should search for the desired keyword or the searched post. If post is not possible then it should display pages....Please help as I'm a beginner..

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  • Java Certification Exams and Their Move to Pearson VUE

    - by Harold Green
    You may be aware that Oracle recently migrated all Sun-branded certification exams from Prometric to Pearson VUE. Below are answers to some frequently-asked questions that we've been getting recently: What changes to the exams should I be aware of?Only minor changes were made to the exams during the transition to Pearson VUE: Renumbering of all exams to the Oracle exam numbering structure (i.e. 1Z0...). Most exam score reports were enhanced to provide more detailed feedback. Score reports now list every exam objective for which a question (or questions) were answered incorrectly. The previous format provided only section-level performance feedback. For three Java exams, some lengthy (time-consuming) questions were removed & replaced with shorter (less time-consuming) questions. This was done in order to shorten the required exam time (to 150 minutes). Some interactive question types were removed from several Java and Solaris exams (including "matching" and "drag-and-drop" questions). The passing scores (for the exams that were revised) were statistically adjusted to make them equal to their prior passing scores, thus ensuring that the exams maintained the same level of difficulty as before. The exam objectives and the exam questions themselves did not change. Candidates should study the same material and objectives. Are there also new testing practices I should be aware of?Oracle follows a common industry practice of placing occasional un-scored questions on our certification exams. Candidates will not know which questions are unscored. At the time of this blog post, only one of the migrated exams (1Z0-898) contains unscored questions.I started the Master certification path through Prometric, and now I need to complete the requirements through Pearson VUE. Where can I get guidance on this process?Visit our Vendor Transition FAQs to find comprehensive instructions. Oracle has created several specific paths to accommodate candidates who were at at varying stages of completion of their master path when the transition occurred. Make sure to follow the specific path designed for your case, as you will need to know which exam number to select in order to submit/re-submit your requirements. QUICK LINKS Oracle Certification Blog Post: Java, Oracle Solaris, MySQL and Other Former Sun Certification Exams Now Being Delivered At Pearson VUE Oracle Certification Website: Vendor Transition Announcement

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  • How can I evaluate a candidate's knowledge of Html/CSS during an interview?

    - by webnoob
    I am trying to determine some good interview questions to assess the ability of people coming in for a Html/CSS job, however that topic is extremely broad, and I'm not sure what sort of questions I can ask to properly evaluate someone's HTML/CSS knowledge. What sort of questions can I ask to evaluate a candidate's Html/CSS abilities during an interview? Ideally I would like to ask few questions and then give them a real life scenario to combat.

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  • Partner Webinar Series CRM/CX Best Practices - Each Friday - 10am PST

    - by Richard Lefebvre
    A CRM/CX Best Practices Webinar will be led each week by the Oracle CRM/CX Sales Consulting team and focus on Demo best practices and previews Lessons Learned from Sales Cycles Competitive & product/solution positioning information Product updates& progress Replays are available from the webinar's portal. Please see the agenda and webinar details here and join us to learn about a new CX topic each Friday at 10am PT.

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  • What does your University 1st class mean?

    - by Abimaran
    I know, it's highly subjective question, but, I need the opinion. Please don't close this! IMHO and experience, they (the 1st class fellows) have a the resources (tutorials, past papers, etc), courage and the ability to memorize the answers on that. But, there are some talented peoples, who have the real knowledge with the 1st class. Are those peoples really win in the industries? Please don't ask my class :)

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  • Building a Flash Platformer

    - by Jonathan O
    I am basically making a game where the whole game is run in the onEnterFrame method. This is causing a delay in my code that makes debugging and testing difficult. Should programming an entire platformer in this method be efficient enough for me to run hundreds of lines of code? Also, do variables in flash get updated immediately? Are there just lots of threads listening at the same time? Here is the code... stage.addEventListener(Event.ENTER_FRAME, onEnter); function onEnter(e:Event):void { //Jumping if (Yoshi.y > groundBaseLevel) { dy = 0; canJump = true; onGround = true; //This line is not updated in time } if (Key.isDown(Key.UP) && canJump) { dy = -10; canJump = false; onGround = false; //This line is not updated in time } if(!onGround) { dy += gravity; Yoshi.y += dy; } //limit screen boundaries //character movement if (! Yoshi.hitTestObject(Platform)) //no collision detected { if (Key.isDown(Key.RIGHT)) { speed += 4; speed *= friction; Yoshi.x = Yoshi.x + movementIncrement + speed; Yoshi.scaleX = 1; Yoshi.gotoAndStop('Walking'); } else if (Key.isDown(Key.LEFT)) { speed -= 4; speed *= friction; Yoshi.x = Yoshi.x - movementIncrement + speed; Yoshi.scaleX = -1; Yoshi.gotoAndStop('Walking'); } else { speed *= friction; Yoshi.x = Yoshi.x + speed; Yoshi.gotoAndStop('Still'); } } else //bounce back collision detected { if(Yoshi.hitTestPoint(Platform.x - Platform.width/2, Platform.y - Platform.height/2, false)) { trace('collision left'); Yoshi.x -=20; } if(Yoshi.hitTestPoint(Platform.x, Platform.y - Platform.height/2, false)) { trace('collision top'); onGround=true; //This update is not happening in time speed = 0; } } }

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  • Learning how to integrate JavaScript with other languages

    - by beacon
    After learning JavaScript syntax, what are some good resources for learning about integrating JavaScript with other languages (HTML, XML, CSS, PHP) to create real, useful applications? I'm most interested in reading articles or other people's code - not so interested in books. Basically, I'm looking to move from programming puzzle-solvers to programming complex applications and could use some advice.

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  • SQL Solstice

    - by andyleonard
    Introduction My friends in North Carolina have decided to create a new event called SQL Solstice . Details: 18 - 20 Aug 2011 Holiday Inn Brownstone & Conference Center 1707 Hillsborough Street - Raleigh, NC 27605 Toll Free 800-331-7919 18 Aug - A Day of Deep Dives ($259) Day-long presentations delivered by folks with real-world, hands-on experience. Louis Davidson on Database Design Andrew Kelly on Performance Tuning Jessica M. Moss on Reporting Services Ed Wilson on Powershell (me) on SSIS 19...(read more)

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  • Inserting data to database from Android

    - by Angel
    I have to build an application where the requirement is that my clients will send data from their Android device and I have to save that data to a database. I have done the part of coding that inserts data from Android emulator to my XAMPP database on localhost, now I have to implement the real thing. How can I connect the devices where my application will be installed to the XAMPP database I have created so that the data they send can be inserted into it?

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  • Google I/O 2010 - Integrate apps w/ Google Apps Marketplace

    Google I/O 2010 - Integrate apps w/ Google Apps Marketplace Google I/O 2010 - Integrating your app with the Google Apps Marketplace: Navigation, SSO, Data APIs and manifests Enterprise 201 Ryan Boyd, Steve Bazyl In this fast-paced, demo-focused session, you'll learn how to build, integrate, and sell a web app on the Google Apps Marketplace. We'll go end-to-end in 40 minutes with time left for Q&A. For all I/O 2010 sessions, please go to code.google.com From: GoogleDevelopers Views: 5 0 ratings Time: 59:45 More in Science & Technology

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  • Algorithm for approximating sihlouette image as polygon

    - by jack
    I want to be able to analyze a texture in real time and approximate a polygon to represent a silhouette. Imagine a person standing in front of a green screen and I want to approximately trace around their outline and get a 2D polygon as the result. Are there algorithms to do this and are they fast enough to work frame-to-frame in a game? (I have found algorithms to triangulate polygons, but I am having trouble knowing what to search for that describes my goal.)

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  • Microsoft Blacklists Google, Windows 8 Integrated Security

    According to researcher Brian Krebs, millions of surfers were affected by the error which was caused by two of Microsoft's antivirus solutions in the form of Microsoft Security Essentials and the business-related Microsoft Forefront. Both received updates as part of Microsoft's traditional Patch Tuesday on February 14, and those patches are believed to be the cause behind Google's incorrect blacklisting. The false positive alert specifically tagged the search site as being infected with the infamous Blackhole Exploit Kit, which reportedly gives cybercriminals the power to create their own bo...

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  • TDD vs. Productivity

    - by Nairou
    In my current project (a game, in C++), I decided that I would use Test Driven Development 100% during development. In terms of code quality, this has been great. My code has never been so well designed or so bug-free. I don't cringe when viewing code I wrote a year ago at the start of the project, and I have gained a much better sense for how to structure things, not only to be more easily testable, but to be simpler to implement and use. However... it has been a year since I started the project. Granted, I can only work on it in my spare time, but TDD is still slowing me down considerably compared to what I'm used to. I read that the slower development speed gets better over time, and I definitely do think up tests a lot more easily than I used to, but I've been at it for a year now and I'm still working at a snail's pace. Each time I think about the next step that needs work, I have to stop every time and think about how I would write a test for it, to allow me to write the actual code. I'll sometimes get stuck for hours, knowing exactly what code I want to write, but not knowing how to break it down finely enough to fully cover it with tests. Other times, I'll quickly think up a dozen tests, and spend an hour writing tests to cover a tiny piece of real code that would have otherwise taken a few minutes to write. Or, after finishing the 50th test to cover a particular entity in the game and all aspects of it's creation and usage, I look at my to-do list and see the next entity to be coded, and cringe in horror at the thought of writing another 50 similar tests to get it implemented. It's gotten to the point that, looking over the progress of the last year, I'm considering abandoning TDD for the sake of "getting the damn project finished". However, giving up the code quality that came with it is not something I'm looking forward to. I'm afraid that if I stop writing tests, then I'll slip out of the habit of making the code so modular and testable. Am I perhaps doing something wrong to still be so slow at this? Are there alternatives that speed up productivity without completely losing the benefits? TAD? Less test coverage? How do other people survive TDD without killing all productivity and motivation?

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  • Open Source AI Bot interfaces

    - by David Young
    What are some open source AI Bot interfaces? Similar to Pogamut 3 GameBots2004 for custom Unreal Tournament bots or Brood Wars API for Starcraft bots etc. If you could please post one AI bot interface per answer (make sure to provide a link) and give a brief summary as to the content of the blog posts. Please include what type of bot interface structure it is, client/server, server/server, etc e.g. BWAPI is client/server which emulates a real player

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  • Showplan Operator of the Week - Merge Interval

    When Fabiano agreed to undertake the epic task of describing each showplan operator, none of us quite predicted the interesting ways that the series helps to understand how the query optimizer works. With the Merge Interval, Fabiano comes up with some insights about the way that the Query optimizer handles overlapping ranges efficiently. Free trial of SQL Backup™“SQL Backup was able to cut down my backup time significantly AND achieved a 90% compression at the same time!” Joe Cheng. Download a free trial now.

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  • Attunity Oracle CDC Solution for SSIS - Beta

    We in no way work for Attunity but we were asked to test drive a beta version of their Oracle CDC solution for SSIS.  Everybody should know that moving more data than you need to takes too much time and uses resources that may better be employed doing something else.  Change data Capture is a technology that is designed to help you identify only the data that has had something done to it and you can therefore move only what is needed.  Microsoft have implemented this exact functionality into SQL server 2008 and I really like it there.  Attunity though are doing it on Oracle. DISCLAIMER: This is a BETA release and some of the parts are a bit ugly/difficult to work with.  The idea though is definitely right and the product once working does exactly what it says on the tin.  They have always been helpful to me when I have had a problem with the product and if that continues then beta testing pain should be eased somewhat. In due course I am going to be doing some videos around me using the product.  If you use Oracle and SSIS then give it a go. Here is their product description.   Attunity is a Microsoft SQL Server technology partner and the creator of the Microsoft Connectors for Oracle and Teradata, currently available in SQL Server 2008 Enterprise Edition. Attunity released a beta version of the Attunity Oracle-CDC for SSIS, a product that integrates continually changing Oracle data into SSIS, efficiently and in real-time. Attunity designed the product and integrated it into SSIS to create the simple creation of change data capture (CDC) solutions, accelerate implementation time, and reduce resources and costs. They also utilize log-based CDC so the solution has minimal impact on the Oracle source system. You can use the product to implement enterprise-class data replication, synchronization, and real-time business intelligence (BI) and data warehousing projects, quickly and efficiently, leveraging their existing SQL Server investments and resource skills. Attunity architected the product specifically for the Microsoft SSIS developer community and the product is available for both SQL Server 2005 and SQL Server 2008. It offers the following key capabilities: · Log-based, non-intrusive Oracle CDC · Full integration into SSIS and the Business Intelligence Developer Studio · Automatic generation of SSIS packages for CDC as well as full-loads of Oracle data · Filtering of Oracle tables and columns at the source · Monitoring and control of CDC processing Click to learn more and download the beta.

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  • Uninstalling with Ubuntu Software Center doesn't work on Ubuntu 12.04.1 64bit

    - by likethesky
    Not sure if I'm doing something wrong, or if the .deb package I'm installing is broken in some way (I've built it, using NetBeans 7.2), or if indeed this is a bug in Software Center. When I install this particular 32-bit .deb on Ubuntu 10.04 LTS--all updates applied--(where it was built), GDebi shows it and has an 'Uninstall' button next to it. So it works fine to uninstall it there, via the GDebi GUI. However, when I install it on 12.04.1 LTS--all updates applied--it installs fine, but then does not show up in Ubuntu Software Center as available to be uninstalled. No combination of searching finds it. However, I can from the command line, do sudo apt-get purge javafxapplication1 and it finds it and deletes it. The same thing happens when I build a 64-bit .deb and attempt to install it to the same (64-bit AMD) or a different 64-bit Ubuntu 12.04.1 system. So it seems to be isolated to this NetBeans-generated .deb and the 64-bit AMD build (though I haven't tried it on a 32-bit 12.04.1 install yet). These are all on VirtualBox VMs, btw, if that matters. Any way to clean up my Software Center and see if it's something I've done to get it in this state? Could this behavior be due to how this particular .deb has been built? (It doesn't have an 'Installed-Size' control field, so I do get the "Package is of bad quality" warning when I install it--which I do by clicking 'Ignore and install' button.) If you want all the gory details about why this happening--a bug has been reported against NetBeans for this behavior here: http://javafx-jira.kenai.com/browse/RT-25486 (EDIT: Just to be clear, the app installs fine, runs fine, all works as intended--I just can't get that 'bad package' message to go away, and now... I also can't uninstall it via Software Center, but rather, need to use sudo apt-get purge to uninstall it, after it installs.) Thanks for any pointers. I'm happy to report this as a bug against Ubuntu Software Center/Centre too, if that's what it seems to be, just tell me where to do so (a link). I'm a relative Ubuntu, NetBeans, and JavaFX newbie, though a long-time programmer. If I report it as a bug, I'll try it on the 32-bit build of 12.04.1 as well. Also, if I should add any more detail to the bug reported against NetBeans above, let me know--or feel free to add it yourself to the bug report above, if you would like. Thanks again!

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  • IMPORTANT - FY13 OPN Incentive Program VAD Webcast - June 21st @ 4PM GMT

    - by Cinzia Mascanzoni
    Please mark your calendars for the FY13 OPN Incentive Program update webcast on June 21. The objective of this call is to share the updates to the OPN Incentive Program for FY13 with you. Thursday, June 21st @: 4:00 PM GMT : 5PM CET Click here for the details of the webcast. Please plan to call in 5-10 minutes prior to the start to avoid delays. We look forward to your participation on this call.

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  • Is monkeypatching considered good programming practice?

    - by vartec
    I've been under impression, that monkeypatching is more in quick and dirty hack category, rather than standard, good programming practice. While I'd used from time to time to fix minor issues with 3rd party libs, I considered it temporary fix and I'd submit proper patch to the 3rd party project. However, I've seen this technique used as "the normal way" in mainstream projects, for example in Gevent's gevent.monkey module. Has monkeypatching became mainstream, normal, acceptable programming practice? See also: "Monkeypatching For Humans" by Jeff Atwood

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  • schedule compliance and keeping technical supports and resolving issues

    - by imays
    I am an entrepreneur of a small software developer company. The flagship product is developed by myself and my company grew up to 14 people. One of pride is that we've never have to be invested or loaned. The core development team is 5 people. 3 are seniors and 2 are juniors. After the first release, we've received many issues from our customers. Most of them are bug issues, customization needs, usage questions and upgrade requests. The issues from customers are incoming many times everyday, so it takes little time or much time of our developers. Because of our product is a software development kit(SDK) so most of questions can be answered only from our developers. And, for resolving bug issues, developers must be involved. Estimating time to resolve bug is hard. I fully understand it. However, our developers insist they cannot set the any due date of each project because they are busy doing technical supports and bug fixes by issues from customers everyday. Of course, they never do overwork. I suggested them an idea to divide the team into two parts: one for focusing on development by milestones, other for doing technical supports and bug fixes without setting due days. Then we could announce release plan officially. After the finish of release, two parts exchange the role for next milestone. However, they say they "NO, because it is impossible to share knowledge and design document fully." They still say they cannot set the release date and they request me to alter the due date flexibly. They does not fix the due date of each milestone. Fortunately, our company is not loaned and invested so we are not chocked. But I think it is bad idea to keep this situation. I know the story of ant and grasshopper. Our customers are tired of waiting forever of our release date. Companies consume limited time and money. If flexible due date without limit could be acceptable, could they accept flexible salary day? What is the root cause of our problem? All that I want is to fix and achieve precisely due date of each milestone without losing frequent technical supports. I think there must be solution for this situation. Please answer me. Thanks in advance. PS. Our tools and ways of project management are Trello, Mantis-like issue tracker, shared calendar software and scrum(collected cards into series of 'small and high completeness' projects).

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  • Consuming the Amazon S3 service from a Win8 Metro Application

    - by cibrax
    As many of the existing Http APIs for Cloud Services, AWS also provides a set of different platform SDKs for hiding many of complexities present in the APIs. While there is a platform SDK for .NET, which is open source and available in C#, that SDK does not work in Win8 Metro Applications for the changes introduced in WinRT. WinRT offers a complete different set of APIs for doing I/O operations such as doing http calls or using cryptography for signing or encrypting data, two aspects that are absolutely necessary for consuming AWS. All the I/O APIs available as part of WinRT are asynchronous, and uses the TPL model for .NET applications (HTML and JavaScript Metro applications use a model based in promises, which is similar concept).  In the case of S3, the http Authorization header is used for two purposes, authenticating clients and make sure the messages were not altered while they were in transit. For doing that, it uses a signature or hash of the message content and some of the headers using a symmetric key (That's just one of the available mechanisms). Windows Azure for example also uses the same mechanism in many of its APIs. There are three challenges that any developer working for first time in Metro will have to face to consume S3, the new WinRT APIs, the asynchronous nature of them and the complexity introduced for generating the Authorization header. Having said that, I decided to write this post with some of the gotchas I found myself trying to consume this Amazon service. 1. Generating the signature for the Authorization header All the cryptography APIs in WinRT are available under Windows.Security.Cryptography namespace. Many of operations available in these APIs uses the concept of buffers (IBuffer) for representing a chunk of binary data. As you will see in the example below, these buffers are mainly generated with the use of static methods in a WinRT class CryptographicBuffer available as part of the namespace previously mentioned. private string DeriveAuthToken(string resource, string httpMethod, string timestamp) { var stringToSign = string.Format("{0}\n" + "\n" + "\n" + "\n" + "x-amz-date:{1}\n" + "/{2}/", httpMethod, timestamp, resource); var algorithm = MacAlgorithmProvider.OpenAlgorithm("HMAC_SHA1"); var keyMaterial = CryptographicBuffer.CreateFromByteArray(Encoding.UTF8.GetBytes(this.secret)); var hmacKey = algorithm.CreateKey(keyMaterial); var signature = CryptographicEngine.Sign( hmacKey, CryptographicBuffer.CreateFromByteArray(Encoding.UTF8.GetBytes(stringToSign)) ); return CryptographicBuffer.EncodeToBase64String(signature); } .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 algorithm that determines the information or content you need to use for generating the signature is very well described as part of the AWS documentation. In this case, this method is generating a signature required for creating a new bucket. A HmacSha1 hash is computed using a secret or symetric key provided by AWS in the management console. 2. Sending an Http Request to the S3 service WinRT also ships with the System.Net.Http.HttpClient that was first introduced some months ago with ASP.NET Web API. This client provides a rich interface on top the traditional WebHttpRequest class, and also solves some of limitations found in this last one. There are a few things that don't work with a raw WebHttpRequest such as setting the Host header, which is something absolutely required for consuming S3. Also, HttpClient is more friendly for doing unit tests, as it receives a HttpMessageHandler as part of the constructor that can fake to emulate a real http call. This is how the code for consuming the service with HttpClient looks like, public async Task<S3Response> CreateBucket(string name, string region = null, params string[] acl) { var timestamp = string.Format("{0:r}", DateTime.UtcNow); var auth = DeriveAuthToken(name, "PUT", timestamp); var request = new HttpRequestMessage(HttpMethod.Put, "http://s3.amazonaws.com/"); request.Headers.Host = string.Format("{0}.s3.amazonaws.com", name); request.Headers.TryAddWithoutValidation("Authorization", "AWS " + this.key + ":" + auth); request.Headers.Add("x-amz-date", timestamp); var client = new HttpClient(); var response = await client.SendAsync(request); return new S3Response { Succeed = response.StatusCode == HttpStatusCode.OK, Message = (response.Content != null) ? await response.Content.ReadAsStringAsync() : null }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You will notice a few additional things in this code. By default, HttpClient validates the values for some well-know headers, and Authorization is one of them. It won't allow you to set a value with ":" on it, which is something that S3 expects. However, that's not a problem at all, as you can skip the validation by using the TryAddWithoutValidation method. Also, the code is heavily relying on the new async and await keywords to transform all the asynchronous calls into synchronous ones. In case you would want to unit test this code and faking the call to the real S3 service, you should have to modify it to inject a custom HttpMessageHandler into the HttpClient. The following implementation illustrates this concept, In case you would want to unit test this code and faking the call to the real S3 service, you should have to modify it to inject a custom HttpMessageHandler into the HttpClient. The following implementation illustrates this concept, public class FakeHttpMessageHandler : HttpMessageHandler { HttpResponseMessage response; public FakeHttpMessageHandler(HttpResponseMessage response) { this.response = response; } protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) { var tcs = new TaskCompletionSource<HttpResponseMessage>(); tcs.SetResult(response); return tcs.Task; } } .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 use this handler for injecting any response while you are unit testing the code.

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  • Consuming the Amazon S3 service from a Win8 Metro Application

    - by cibrax
    As many of the existing Http APIs for Cloud Services, AWS also provides a set of different platform SDKs for hiding many of complexities present in the APIs. While there is a platform SDK for .NET, which is open source and available in C#, that SDK does not work in Win8 Metro Applications for the changes introduced in WinRT. WinRT offers a complete different set of APIs for doing I/O operations such as doing http calls or using cryptography for signing or encrypting data, two aspects that are absolutely necessary for consuming AWS. All the I/O APIs available as part of WinRT are asynchronous, and uses the TPL model for .NET applications (HTML and JavaScript Metro applications use a model based in promises, which is similar concept).  In the case of S3, the http Authorization header is used for two purposes, authenticating clients and make sure the messages were not altered while they were in transit. For doing that, it uses a signature or hash of the message content and some of the headers using a symmetric key (That's just one of the available mechanisms). Windows Azure for example also uses the same mechanism in many of its APIs. There are three challenges that any developer working for first time in Metro will have to face to consume S3, the new WinRT APIs, the asynchronous nature of them and the complexity introduced for generating the Authorization header. Having said that, I decided to write this post with some of the gotchas I found myself trying to consume this Amazon service. 1. Generating the signature for the Authorization header All the cryptography APIs in WinRT are available under Windows.Security.Cryptography namespace. Many of operations available in these APIs uses the concept of buffers (IBuffer) for representing a chunk of binary data. As you will see in the example below, these buffers are mainly generated with the use of static methods in a WinRT class CryptographicBuffer available as part of the namespace previously mentioned. private string DeriveAuthToken(string resource, string httpMethod, string timestamp) { var stringToSign = string.Format("{0}\n" + "\n" + "\n" + "\n" + "x-amz-date:{1}\n" + "/{2}/", httpMethod, timestamp, resource); var algorithm = MacAlgorithmProvider.OpenAlgorithm("HMAC_SHA1"); var keyMaterial = CryptographicBuffer.CreateFromByteArray(Encoding.UTF8.GetBytes(this.secret)); var hmacKey = algorithm.CreateKey(keyMaterial); var signature = CryptographicEngine.Sign( hmacKey, CryptographicBuffer.CreateFromByteArray(Encoding.UTF8.GetBytes(stringToSign)) ); return CryptographicBuffer.EncodeToBase64String(signature); } .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 algorithm that determines the information or content you need to use for generating the signature is very well described as part of the AWS documentation. In this case, this method is generating a signature required for creating a new bucket. A HmacSha1 hash is computed using a secret or symetric key provided by AWS in the management console. 2. Sending an Http Request to the S3 service WinRT also ships with the System.Net.Http.HttpClient that was first introduced some months ago with ASP.NET Web API. This client provides a rich interface on top the traditional WebHttpRequest class, and also solves some of limitations found in this last one. There are a few things that don't work with a raw WebHttpRequest such as setting the Host header, which is something absolutely required for consuming S3. Also, HttpClient is more friendly for doing unit tests, as it receives a HttpMessageHandler as part of the constructor that can fake to emulate a real http call. This is how the code for consuming the service with HttpClient looks like, public async Task<S3Response> CreateBucket(string name, string region = null, params string[] acl) { var timestamp = string.Format("{0:r}", DateTime.UtcNow); var auth = DeriveAuthToken(name, "PUT", timestamp); var request = new HttpRequestMessage(HttpMethod.Put, "http://s3.amazonaws.com/"); request.Headers.Host = string.Format("{0}.s3.amazonaws.com", name); request.Headers.TryAddWithoutValidation("Authorization", "AWS " + this.key + ":" + auth); request.Headers.Add("x-amz-date", timestamp); var client = new HttpClient(); var response = await client.SendAsync(request); return new S3Response { Succeed = response.StatusCode == HttpStatusCode.OK, Message = (response.Content != null) ? await response.Content.ReadAsStringAsync() : null }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You will notice a few additional things in this code. By default, HttpClient validates the values for some well-know headers, and Authorization is one of them. It won't allow you to set a value with ":" on it, which is something that S3 expects. However, that's not a problem at all, as you can skip the validation by using the TryAddWithoutValidation method. Also, the code is heavily relying on the new async and await keywords to transform all the asynchronous calls into synchronous ones. In case you would want to unit test this code and faking the call to the real S3 service, you should have to modify it to inject a custom HttpMessageHandler into the HttpClient. The following implementation illustrates this concept, In case you would want to unit test this code and faking the call to the real S3 service, you should have to modify it to inject a custom HttpMessageHandler into the HttpClient. The following implementation illustrates this concept, public class FakeHttpMessageHandler : HttpMessageHandler { HttpResponseMessage response; public FakeHttpMessageHandler(HttpResponseMessage response) { this.response = response; } protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) { var tcs = new TaskCompletionSource<HttpResponseMessage>(); tcs.SetResult(response); return tcs.Task; } } .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 use this handler for injecting any response while you are unit testing the code.

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