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  • Ubuntu: Failure to login with multiple video adapters

    - by tsilb
    Forgive my ignorance, for I am a complete linux noob. I have a computer with three video cards and six monitors. Works great on Windows. Trying to get it to run Ubuntu as well. It loads fine when I have it configured to run on one adapter; detects both screens, runs ok. But I want to turn the other 4 monitors on and run the whole thing as one extended desktop (one session, etc). So I downloaded and installed the newest ATI driver for Linux, which seems to work, kinda. I ran this to set up the screens: aticonfig --adapter=all --initial -f Now when I boot, Ubuntu seems to turn on all the screens (3 viewports, each with two cloned displays from what I can tell). When I enter my login info OR move the mouse off the main screen, the screens freeze and the kbd/ms become unresponsive. aticonfig generated xorg.conf included below. Have tried the following: aticonfig -initial -f - works, but only detects the primary adapter and 2 screens aticccle - Tells me I have to reboot after enabling the other cards. Then goes into above described freezing state. aticonfig --adapter=all --initial -f - see above Manually editing xorg.conf file with my limited knowledge - Was able to get two adapters running, but only the second adapter initialized while the primary stopped at the Ubuntu boot screen. Was unable to see the login prompt. Froze after I logged in blindly (was able to hear the login sound). Using generic "radeon" driver instead of ATI Proprietary driver with the above init attempts Toggling xinerama Various combinations of the above Hardware: Intel Core 2 Quad q6600 8GB DDR2 (3x) ATI Radeon HD 4680 5 monitors (21W, 21W, 22W Portrait, 22W Portrait, 19")and an HDTV (26"W, HDMI) in a horizontal arrangement I know next to nothing about Linux/Ubuntu aside from basic filesystem navigation, editing text files, and accessing my local and networked Windows stores and shares. Basically this is the most advanced thing I've had to do. I installed today. Please advise how to make this configuration work. my xorg.conf: Section "ServerLayout" Identifier "Layout0" Screen 0 "aticonfig-Screen[0]-0" 0 0 Screen "aticonfig-Screen[1]-0" RightOf "aticonfig-Screen[0]-0" Screen "aticonfig-Screen[2]-0" RightOf "aticonfig-Screen[1]-0" Option "RenderAccel" "true" Option "AllowGLXWithComposite" "true" EndSection Section "Files" EndSection Section "Module" EndSection Section "ServerFlags" Option "Xinerama" "0" EndSection Section "Monitor" Identifier "aticonfig-Monitor[0]-0" Option "VendorName" "ATI Proprietary Driver" Option "ModelName" "Generic Autodetecting Monitor" Option "DPMS" "true" EndSection Section "Monitor" Identifier "aticonfig-Monitor[1]-0" Option "VendorName" "ATI Proprietary Driver" Option "ModelName" "Generic Autodetecting Monitor" Option "DPMS" "true" EndSection Section "Monitor" Identifier "aticonfig-Monitor[2]-0" Option "VendorName" "ATI Proprietary Driver" Option "ModelName" "Generic Autodetecting Monitor" Option "DPMS" "true" EndSection Section "Device" Identifier "aticonfig-Device[0]-0" Driver "fglrx" BusID "PCI:1:0:0" EndSection Section "Device" Identifier "aticonfig-Device[1]-0" Driver "fglrx" BusID "PCI:3:0:0" EndSection Section "Device" Identifier "aticonfig-Device[2]-0" Driver "fglrx" BusID "PCI:4:0:0" EndSection Section "Screen" Identifier "aticonfig-Screen[0]-0" Device "aticonfig-Device[0]-0" Monitor "aticonfig-Monitor[0]-0" DefaultDepth 24 SubSection "Display" Viewport 0 0 Depth 24 EndSubSection EndSection Section "Screen" Identifier "aticonfig-Screen[1]-0" Device "aticonfig-Device[1]-0" Monitor "aticonfig-Monitor[1]-0" DefaultDepth 24 SubSection "Display" Viewport 0 0 Depth 24 EndSubSection EndSection Section "Screen" Identifier "aticonfig-Screen[2]-0" Device "aticonfig-Device[2]-0" Monitor "aticonfig-Monitor[2]-0" DefaultDepth 24 SubSection "Display" Viewport 0 0 Depth 24 EndSubSection EndSection

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  • OSX: Python packages fail to install, error message "/usr/local/bin: File Exists"

    - by kylehotchkiss
    I keep trying to install django and other python packages, and I keep getting the exact same error message: Installing django-admin.py script to /usr/local/bin error: /usr/local/bin: File exists So I look to make sure that my /usr/local folder is okay. At first glance it appears okay, until I try cd-ing into my bin. It says it can't because it's not a directory. Peculiar, I thought, so then I tried a Anchorage:local khotchkiss$ ls -a -l total 26168 drwxr-xr-x 6 root wheel 204 Dec 26 20:18 . drwxr-xr-x@ 14 root wheel 476 Feb 24 12:54 .. -rwxr-xr-x@ 1 root wheel 13395080 Oct 22 23:04 bin drwxr-xr-x 8 root wheel 272 Dec 26 20:18 git drwxr-xr-x 4 root wheel 136 Dec 18 11:31 include drwxr-xr-x 12 root wheel 408 Dec 18 11:31 lib And haven't a clue of what the 'bin' is, why its so large, and why its preventing me from installing python packages. Any clue?

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  • How to remove package from apt-get autoremove "queue"

    - by Darth
    I just installed Calibre for ebook management via apt-get on Ubuntu 10.04, however I found out that it's one major version behind the current release, so I decided to reinstall it directly from sources. When I uninstalled the packaged version, apt added bunch of dependencies to the autoremove queue, and as I installed newer version of Calibre from sources, it has no knowledge of it being dependent on those packages. Now I basically have all libraries that I want, but they are still in the autoremove queue. The following packages were automatically installed and are no longer required: libqt4-script libqt4-designer libqt4-dbus python-lxml python-cherrypy3 python-encutils libqt4-xmlpatterns libqt4-help python-qt4 python-clientform python-sip python-django python-mechanize libqt4-svg python-django-tagging libphonon4 libqt4-xml libqt4-assistant libqt4-webkit libqt4-scripttools python-beautifulsoup python-pypdf python-dateutil python-cssutils Use 'apt-get autoremove' to remove them. How do I tell apt that I want to keep these packages installed, without reinstalling them manually?

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  • Can I set up a 'Deny from x' that overrides other confs for debugging?

    - by Nick T
    I'm currently working on developing/deploying a Django application on Apache and am often fiddling with the debug settings which alter how Django accepts connections, ignoring or using ALLOWED_HOSTS. If DEBUG is False, it uses them, which is handy to keep up some walls around my construction site. However, the useful info it spits out when True is quite nice. I'm currently just using an SSH tunnel and just allowing localhost when DEBUG is False, but how can I keep everyone out without relying on the aforementioned ALLOWED_HOSTS? Editing the httpd.conf file which is in source control is a bit irritating; I've accidentally committed a few botched configs.

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  • FCGI & recompiling python code without restarting apache.

    - by Zayatzz
    Hello At one hosting company, they used to run python projects with fcgi. They had set it up so that when i changed django.fcgi file, which put django & my project on pythonpath, my project code was instantly recompiled. Because of that a friend set up hosting for our shared project in his server using fastcgi. It has been set up and the python scripts execute as they should, but what we do not know is, how to set it up so that my project would be recompiled when my setup file has been changed. Alan

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  • Bugzilla : No SASL mechanism found

    - by niteshsinha
    I am using Bugzilla on windows 7. I am using the unofficial Bugzilla installer. I followed the steps accordingly and gave valid credentials wherever required. I open Bugzilla and try to create a new account , but i get the following error. Software error: No SASL mechanism found at C:/Program Files/Bugzilla/perl/perl/site/lib/Authen/SASL.pm line 77 at C:/Program Files/Bugzilla/perl/perl/lib/Net/SMTP.pm line 143 i ran checksetup.pl and found that Authen::SASL and SMTP both are available on my machine. The output of checksetup.pl is as follows. * This is Bugzilla 3.6.3 on perl 5.10.1 * Running on Win7 Build 7600 Checking perl modules... Checking for CGI.pm (v3.33) ok: found v3.49 Checking for Digest-SHA (any) ok: found v5.48 Checking for TimeDate (v2.21) ok: found v2.24 Checking for DateTime (v0.28) ok: found v0.53 Checking for DateTime-TimeZone (v0.79) ok: found v1.10 Checking for DBI (v1.41) ok: found v1.609 Checking for Template-Toolkit (v2.22) ok: found v2.22 Checking for Email-Send (v2.16) ok: found v2.198 Checking for Email-MIME (v1.861) ok: found v1.903 Checking for Email-MIME-Encodings (v1.313) ok: found v1.313 Checking for Email-MIME-Modifier (v1.442) ok: found v1.903 Checking for URI (any) ok: found v1.52 Checking available perl DBD modules... Checking for DBD-Pg (v1.45) ok: found v2.16.1 Checking for DBD-mysql (v4.00) ok: found v4.012 Checking for DBD-Oracle (v1.19) not found The following Perl modules are optional: Checking for GD (v1.20) ok: found v2.44 Checking for Chart (v2.1) ok: found v2.4.1 Checking for Template-GD (any) ok: found v1.56 Checking for GDTextUtil (any) ok: found v0.86 Checking for GDGraph (any) ok: found v1.44 Checking for XML-Twig (any) ok: found v3.34 Checking for MIME-tools (v5.406) ok: found v5.427 Checking for libwww-perl (any) ok: found v5.834 Checking for PatchReader (v0.9.4) ok: found v0.9.5 Checking for perl-ldap (any) ok: found v0.39 Checking for Authen-SASL (any) ok: found v2.15 Checking for RadiusPerl (any) ok: found v0.17 Checking for SOAP-Lite (v0.710.06) ok: found v0.710.10 Checking for JSON-RPC (any) ok: found v0.95 Checking for Test-Taint (any) ok: found v1.04 Checking for HTML-Parser (v3.40) ok: found v3.64 Checking for HTML-Scrubber (any) ok: found v0.08 Checking for Email-MIME-Attachment-Stripper (any) ok: found v1.316 Checking for Email-Reply (any) ok: found v1.202 Checking for TheSchwartz (any) not found Checking for Daemon-Generic (any) not found Checking for mod_perl (v1.999022) not found *********************************************************************** * OPTIONAL MODULES * *********************************************************************** * Certain Perl modules are not required by Bugzilla, but by * * installing the latest version you gain access to additional * * features. * * * * The optional modules you do not have installed are listed below, * * with the name of the feature they enable. Below that table are the * * commands to install each module. * *********************************************************************** * MODULE NAME * ENABLES FEATURE(S) * *********************************************************************** * TheSchwartz * Mail Queueing * * Daemon-Generic * Mail Queueing * * mod_perl * mod_perl * *********************************************************************** * Note For Windows Users * *********************************************************************** * In order to install the modules listed below, you first have to run * * the following command as an Administrator: * * * * ppm repo add theory58S http://cpan.uwinnipeg.ca/PPMPackages/10xx/ * * * Then you have to do (also as an Administrator): * * * * ppm repo up theory58S * * * * Do that last command over and over until you see "theory58S" at the * * top of the displayed list. * *********************************************************************** COMMANDS TO INSTALL OPTIONAL MODULES: TheSchwartz: ppm install TheSchwartz Daemon-Generic: ppm install Daemon-Generic mod_perl: ppm install mod_perl Reading ./localconfig... Checking for DBD-mysql (v4.00) ok: found v4.012 Checking for MySQL (v4.1.2) ok: found v5.1.44-community-log Removing existing compiled templates... Precompiling templates...done. Now that you have installed Bugzilla, you should visit the 'Parameters' page (linked in the footer of the Administrator account) to ensure it is set up as you wish - this includes setting the 'urlbase' option to the correct URL. Press any key to continue . . . Please tell me what should i do. Please note: i am running behind a corporate proxy , SSL/TLS is not used internally but i am giving the smtpUser and smtpPass also.

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  • Restart single uWSGI application (when it's in emperor mode)

    - by Oli
    I'm running uWSGI in emperor mode to host a bunch of Django sites based on their individual configs. These are supposed to update when it detects a change in the config file and this largely works when I just touch uwsgi.ini the relevant file. But occasionally I'll mess something up in the Django site and the server won't load. Yeah, yeah, I should be testing better but that's not really the point. When this happens, uWSGI seems to mark the site as dead and stops trying to run it (seems to make sense). Even after I fix the underlying issue, no amount of touching will get that site's uWSGI process up and running. I have to reload the whole uWSGI server (knocking dozens of sites out at once for a few seconds). Is there a way to force uWSGI to just reload one of its sites?

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  • How to set up Nginx as a caching reverse proxy?

    - by Continuation
    I heard recently that Nginx has added caching to its reverse proxy feature. I looked around but couldn't find much info about it. I want to set up Nginx as a caching reverse proxy in front of Apache/Django: to have Nginx proxy requests for some (but not all) dynamic pages to Apache, then cache the generated pages and serve subsequent requests for those pages from cache. Ideally I'd want to invalidate cache in 2 ways: Set an expiration date on the cached item To explicitly invalidate the cached item. E.g. if my Django backend has updated certain data, I'd want to tell Nginx to invalidate the cache of the affected pages Is it possible to set Nginx to do that? How?

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  • Building intranet search

    - by gmkv
    At work, we have lots of information squirreled away in many different sites -- wikis, product docs, ticketing system, etc -- many of which require authentication. I'm very interested in having a single way to search all our various silos, and in my spare time have looked at Nutch, Grub, Django + Haystack, etc. None of these is a complete solution a la Google Mini or Google Search Appliance. Has anybody built a basic intranet search engine out of a mixture of these tools? Would you have recommendations about how to go about it? I like Django, and Haystack seems to be a mildly popular search solution for it, but I'd need to wire up a crawler that can support crawling authenticated sites to it.

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  • Forward Request to Multiple Servers

    - by cactuarz
    We have 2 servers. One is old server and another is the new one. Currently we about doing a migration because the old server is not capable enough to handle everyday requests. The specs are: Old server Ubuntu 10.04 Nginx as Reverse Proxy Apache WSGI Python/Django New Server Ubuntu 10.04 Nginx Gunicorn Python/Django Celery+Redis Our manager asked us to research if the old server can perform multiple forwarding to all incoming request, for example, set Nginx of old server to forward all request to both old and new server. The purpose is to perform unit testing to new server using old server as comparer, see if the new server is ready to take over the role. Please help, if there is an idea, or must install some engine, or what we do is impossible. Many thanks.

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  • How to set up Nginx as a caching reverse proxy?

    - by Continuation
    I heard recently that Nginx has added caching to its reverse proxy feature. I looked around but couldn't find much info about it. I want to set up Nginx as a caching reverse proxy in front of Apache/Django: to have Nginx proxy requests for some (but not all) dynamic pages to Apache, then cache the generated pages and serve subsequent requests for those pages from cache. Ideally I'd want to invalidate cache in 2 ways: Set an expiration date on the cached item To explicitly invalidate the cached item. E.g. if my Django backend has updated certain data, I'd want to tell Nginx to invalidate the cache of the affected pages Is it possible to set Nginx to do that? How?

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  • Using the West Wind Web Toolkit to set up AJAX and REST Services

    - by Rick Strahl
    I frequently get questions about which option to use for creating AJAX and REST backends for ASP.NET applications. There are many solutions out there to do this actually, but when I have a choice - not surprisingly - I fall back to my own tools in the West Wind West Wind Web Toolkit. I've talked a bunch about the 'in-the-box' solutions in the past so for a change in this post I'll talk about the tools that I use in my own and customer applications to handle AJAX and REST based access to service resources using the West Wind West Wind Web Toolkit. Let me preface this by saying that I like things to be easy. Yes flexible is very important as well but not at the expense of over-complexity. The goal I've had with my tools is make it drop dead easy, with good performance while providing the core features that I'm after, which are: Easy AJAX/JSON Callbacks Ability to return any kind of non JSON content (string, stream, byte[], images) Ability to work with both XML and JSON interchangeably for input/output Access endpoints via POST data, RPC JSON calls, GET QueryString values or Routing interface Easy to use generic JavaScript client to make RPC calls (same syntax, just what you need) Ability to create clean URLS with Routing Ability to use standard ASP.NET HTTP Stack for HTTP semantics It's all about options! In this post I'll demonstrate most of these features (except XML) in a few simple and short samples which you can download. So let's take a look and see how you can build an AJAX callback solution with the West Wind Web Toolkit. Installing the Toolkit Assemblies The easiest and leanest way of using the Toolkit in your Web project is to grab it via NuGet: West Wind Web and AJAX Utilities (Westwind.Web) and drop it into the project by right clicking in your Project and choosing Manage NuGet Packages from anywhere in the Project.   When done you end up with your project looking like this: What just happened? Nuget added two assemblies - Westwind.Web and Westwind.Utilities and the client ww.jquery.js library. It also added a couple of references into web.config: The default namespaces so they can be accessed in pages/views and a ScriptCompressionModule that the toolkit optionally uses to compress script resources served from within the assembly (namely ww.jquery.js and optionally jquery.js). Creating a new Service The West Wind Web Toolkit supports several ways of creating and accessing AJAX services, but for this post I'll stick to the lower level approach that works from any plain HTML page or of course MVC, WebForms, WebPages. There's also a WebForms specific control that makes this even easier but I'll leave that for another post. So, to create a new standalone AJAX/REST service we can create a new HttpHandler in the new project either as a pure class based handler or as a generic .ASHX handler. Both work equally well, but generic handlers don't require any web.config configuration so I'll use that here. In the root of the project add a Generic Handler. I'm going to call this one StockService.ashx. Once the handler has been created, edit the code and remove all of the handler body code. Then change the base class to CallbackHandler and add methods that have a [CallbackMethod] attribute. Here's the modified base handler implementation now looks like with an added HelloWorld method: using System; using Westwind.Web; namespace WestWindWebAjax { /// <summary> /// Handler implements CallbackHandler to provide REST/AJAX services /// </summary> public class SampleService : CallbackHandler { [CallbackMethod] public string HelloWorld(string name) { return "Hello " + name + ". Time is: " + DateTime.Now.ToString(); } } } Notice that the class inherits from CallbackHandler and that the HelloWorld service method is marked up with [CallbackMethod]. We're done here. Services Urlbased Syntax Once you compile, the 'service' is live can respond to requests. All CallbackHandlers support input in GET and POST formats, and can return results as JSON or XML. To check our fancy HelloWorld method we can now access the service like this: http://localhost/WestWindWebAjax/StockService.ashx?Method=HelloWorld&name=Rick which produces a default JSON response - in this case a string (wrapped in quotes as it's JSON): (note by default JSON will be downloaded by most browsers not displayed - various options are available to view JSON right in the browser) If I want to return the same data as XML I can tack on a &format=xml at the end of the querystring which produces: <string>Hello Rick. Time is: 11/1/2011 12:11:13 PM</string> Cleaner URLs with Routing Syntax If you want cleaner URLs for each operation you can also configure custom routes on a per URL basis similar to the way that WCF REST does. To do this you need to add a new RouteHandler to your application's startup code in global.asax.cs one for each CallbackHandler based service you create: protected void Application_Start(object sender, EventArgs e) { CallbackHandlerRouteHandler.RegisterRoutes<StockService>(RouteTable.Routes); } With this code in place you can now add RouteUrl properties to any of your service methods. For the HelloWorld method that doesn't make a ton of sense but here is what a routed clean URL might look like in definition: [CallbackMethod(RouteUrl="stocks/HelloWorld/{name}")] public string HelloWorld(string name) { return "Hello " + name + ". Time is: " + DateTime.Now.ToString(); } The same URL I previously used now becomes a bit shorter and more readable with: http://localhost/WestWindWebAjax/HelloWorld/Rick It's an easy way to create cleaner URLs and still get the same functionality. Calling the Service with $.getJSON() Since the result produced is JSON you can now easily consume this data using jQuery's getJSON method. First we need a couple of scripts - jquery.js and ww.jquery.js in the page: <!DOCTYPE html> <html> <head> <link href="Css/Westwind.css" rel="stylesheet" type="text/css" /> <script src="scripts/jquery.min.js" type="text/javascript"></script> <script src="scripts/ww.jquery.min.js" type="text/javascript"></script> </head> <body> Next let's add a small HelloWorld example form (what else) that has a single textbox to type a name, a button and a div tag to receive the result: <fieldset> <legend>Hello World</legend> Please enter a name: <input type="text" name="txtHello" id="txtHello" value="" /> <input type="button" id="btnSayHello" value="Say Hello (POST)" /> <input type="button" id="btnSayHelloGet" value="Say Hello (GET)" /> <div id="divHelloMessage" class="errordisplay" style="display:none;width: 450px;" > </div> </fieldset> Then to call the HelloWorld method a little jQuery is used to hook the document startup and the button click followed by the $.getJSON call to retrieve the data from the server. <script type="text/javascript"> $(document).ready(function () { $("#btnSayHelloGet").click(function () { $.getJSON("SampleService.ashx", { Method: "HelloWorld", name: $("#txtHello").val() }, function (result) { $("#divHelloMessage") .text(result) .fadeIn(1000); }); });</script> .getJSON() expects a full URL to the endpoint of our service, which is the ASHX file. We can either provide a full URL (SampleService.ashx?Method=HelloWorld&name=Rick) or we can just provide the base URL and an object that encodes the query string parameters for us using an object map that has a property that matches each parameter for the server method. We can also use the clean URL routing syntax, but using the object parameter encoding actually is safer as the parameters will get properly encoded by jQuery. The result returned is whatever the result on the server method is - in this case a string. The string is applied to the divHelloMessage element and we're done. Obviously this is a trivial example, but it demonstrates the basics of getting a JSON response back to the browser. AJAX Post Syntax - using ajaxCallMethod() The previous example allows you basic control over the data that you send to the server via querystring parameters. This works OK for simple values like short strings, numbers and boolean values, but doesn't really work if you need to pass something more complex like an object or an array back up to the server. To handle traditional RPC type messaging where the idea is to map server side functions and results to a client side invokation, POST operations can be used. The easiest way to use this functionality is to use ww.jquery.js and the ajaxCallMethod() function. ww.jquery wraps jQuery's AJAX functions and knows implicitly how to call a CallbackServer method with parameters and parse the result. Let's look at another simple example that posts a simple value but returns something more interesting. Let's start with the service method: [CallbackMethod(RouteUrl="stocks/{symbol}")] public StockQuote GetStockQuote(string symbol) { Response.Cache.SetExpires(DateTime.UtcNow.Add(new TimeSpan(0, 2, 0))); StockServer server = new StockServer(); var quote = server.GetStockQuote(symbol); if (quote == null) throw new ApplicationException("Invalid Symbol passed."); return quote; } This sample utilizes a small StockServer helper class (included in the sample) that downloads a stock quote from Yahoo's financial site via plain HTTP GET requests and formats it into a StockQuote object. Lets create a small HTML block that lets us query for the quote and display it: <fieldset> <legend>Single Stock Quote</legend> Please enter a stock symbol: <input type="text" name="txtSymbol" id="txtSymbol" value="msft" /> <input type="button" id="btnStockQuote" value="Get Quote" /> <div id="divStockDisplay" class="errordisplay" style="display:none; width: 450px;"> <div class="label-left">Company:</div> <div id="stockCompany"></div> <div class="label-left">Last Price:</div> <div id="stockLastPrice"></div> <div class="label-left">Quote Time:</div> <div id="stockQuoteTime"></div> </div> </fieldset> The final result looks something like this:   Let's hook up the button handler to fire the request and fill in the data as shown: $("#btnStockQuote").click(function () { ajaxCallMethod("SampleService.ashx", "GetStockQuote", [$("#txtSymbol").val()], function (quote) { $("#divStockDisplay").show().fadeIn(1000); $("#stockCompany").text(quote.Company + " (" + quote.Symbol + ")"); $("#stockLastPrice").text(quote.LastPrice); $("#stockQuoteTime").text(quote.LastQuoteTime.formatDate("MMM dd, HH:mm EST")); }, onPageError); }); So we point at SampleService.ashx and the GetStockQuote method, passing a single parameter of the input symbol value. Then there are two handlers for success and failure callbacks.  The success handler is the interesting part - it receives the stock quote as a result and assigns its values to various 'holes' in the stock display elements. The data that comes back over the wire is JSON and it looks like this: { "Symbol":"MSFT", "Company":"Microsoft Corpora", "OpenPrice":26.11, "LastPrice":26.01, "NetChange":0.02, "LastQuoteTime":"2011-11-03T02:00:00Z", "LastQuoteTimeString":"Nov. 11, 2011 4:20pm" } which is an object representation of the data. JavaScript can evaluate this JSON string back into an object easily and that's the reslut that gets passed to the success function. The quote data is then applied to existing page content by manually selecting items and applying them. There are other ways to do this more elegantly like using templates, but here we're only interested in seeing how the data is returned. The data in the object is typed - LastPrice is a number and QuoteTime is a date. Note about the date value: JavaScript doesn't have a date literal although the JSON embedded ISO string format used above  ("2011-11-03T02:00:00Z") is becoming fairly standard for JSON serializers. However, JSON parsers don't deserialize dates by default and return them by string. This is why the StockQuote actually returns a string value of LastQuoteTimeString for the same date. ajaxMethodCallback always converts dates properly into 'real' dates and the example above uses the real date value along with a .formatDate() data extension (also in ww.jquery.js) to display the raw date properly. Errors and Exceptions So what happens if your code fails? For example if I pass an invalid stock symbol to the GetStockQuote() method you notice that the code does this: if (quote == null) throw new ApplicationException("Invalid Symbol passed."); CallbackHandler automatically pushes the exception message back to the client so it's easy to pick up the error message. Regardless of what kind of error occurs: Server side, client side, protocol errors - any error will fire the failure handler with an error object parameter. The error is returned to the client via a JSON response in the error callback. In the previous examples I called onPageError which is a generic routine in ww.jquery that displays a status message on the bottom of the screen. But of course you can also take over the error handling yourself: $("#btnStockQuote").click(function () { ajaxCallMethod("SampleService.ashx", "GetStockQuote", [$("#txtSymbol").val()], function (quote) { $("#divStockDisplay").fadeIn(1000); $("#stockCompany").text(quote.Company + " (" + quote.Symbol + ")"); $("#stockLastPrice").text(quote.LastPrice); $("#stockQuoteTime").text(quote.LastQuoteTime.formatDate("MMM dd, hh:mmt")); }, function (error, xhr) { $("#divErrorDisplay").text(error.message).fadeIn(1000); }); }); The error object has a isCallbackError, message and  stackTrace properties, the latter of which is only populated when running in Debug mode, and this object is returned for all errors: Client side, transport and server side errors. Regardless of which type of error you get the same object passed (as well as the XHR instance optionally) which makes for a consistent error retrieval mechanism. Specifying HttpVerbs You can also specify HTTP Verbs that are allowed using the AllowedHttpVerbs option on the CallbackMethod attribute: [CallbackMethod(AllowedHttpVerbs=HttpVerbs.GET | HttpVerbs.POST)] public string HelloWorld(string name) { … } If you're building REST style API's this might be useful to force certain request semantics onto the client calling. For the above if call with a non-allowed HttpVerb the request returns a 405 error response along with a JSON (or XML) error object result. The default behavior is to allow all verbs access (HttpVerbs.All). Passing in object Parameters Up to now the parameters I passed were very simple. But what if you need to send something more complex like an object or an array? Let's look at another example now that passes an object from the client to the server. Keeping with the Stock theme here lets add a method called BuyOrder that lets us buy some shares for a stock. Consider the following service method that receives an StockBuyOrder object as a parameter: [CallbackMethod] public string BuyStock(StockBuyOrder buyOrder) { var server = new StockServer(); var quote = server.GetStockQuote(buyOrder.Symbol); if (quote == null) throw new ApplicationException("Invalid or missing stock symbol."); return string.Format("You're buying {0} shares of {1} ({2}) stock at {3} for a total of {4} on {5}.", buyOrder.Quantity, quote.Company, quote.Symbol, quote.LastPrice.ToString("c"), (quote.LastPrice * buyOrder.Quantity).ToString("c"), buyOrder.BuyOn.ToString("MMM d")); } public class StockBuyOrder { public string Symbol { get; set; } public int Quantity { get; set; } public DateTime BuyOn { get; set; } public StockBuyOrder() { BuyOn = DateTime.Now; } } This is a contrived do-nothing example that simply echoes back what was passed in, but it demonstrates how you can pass complex data to a callback method. On the client side we now have a very simple form that captures the three values on a form: <fieldset> <legend>Post a Stock Buy Order</legend> Enter a symbol: <input type="text" name="txtBuySymbol" id="txtBuySymbol" value="GLD" />&nbsp;&nbsp; Qty: <input type="text" name="txtBuyQty" id="txtBuyQty" value="10" style="width: 50px" />&nbsp;&nbsp; Buy on: <input type="text" name="txtBuyOn" id="txtBuyOn" value="<%= DateTime.Now.ToString("d") %>" style="width: 70px;" /> <input type="button" id="btnBuyStock" value="Buy Stock" /> <div id="divStockBuyMessage" class="errordisplay" style="display:none"></div> </fieldset> The completed form and demo then looks something like this:   The client side code that picks up the input values and assigns them to object properties and sends the AJAX request looks like this: $("#btnBuyStock").click(function () { // create an object map that matches StockBuyOrder signature var buyOrder = { Symbol: $("#txtBuySymbol").val(), Quantity: $("#txtBuyQty").val() * 1, // number Entered: new Date() } ajaxCallMethod("SampleService.ashx", "BuyStock", [buyOrder], function (result) { $("#divStockBuyMessage").text(result).fadeIn(1000); }, onPageError); }); The code creates an object and attaches the properties that match the server side object passed to the BuyStock method. Each property that you want to update needs to be included and the type must match (ie. string, number, date in this case). Any missing properties will not be set but also not cause any errors. Pass POST data instead of Objects In the last example I collected a bunch of values from form variables and stuffed them into object variables in JavaScript code. While that works, often times this isn't really helping - I end up converting my types on the client and then doing another conversion on the server. If lots of input controls are on a page and you just want to pick up the values on the server via plain POST variables - that can be done too - and it makes sense especially if you're creating and filling the client side object only to push data to the server. Let's add another method to the server that once again lets us buy a stock. But this time let's not accept a parameter but rather send POST data to the server. Here's the server method receiving POST data: [CallbackMethod] public string BuyStockPost() { StockBuyOrder buyOrder = new StockBuyOrder(); buyOrder.Symbol = Request.Form["txtBuySymbol"]; ; int qty; int.TryParse(Request.Form["txtBuyQuantity"], out qty); buyOrder.Quantity = qty; DateTime time; DateTime.TryParse(Request.Form["txtBuyBuyOn"], out time); buyOrder.BuyOn = time; // Or easier way yet //FormVariableBinder.Unbind(buyOrder,null,"txtBuy"); var server = new StockServer(); var quote = server.GetStockQuote(buyOrder.Symbol); if (quote == null) throw new ApplicationException("Invalid or missing stock symbol."); return string.Format("You're buying {0} shares of {1} ({2}) stock at {3} for a total of {4} on {5}.", buyOrder.Quantity, quote.Company, quote.Symbol, quote.LastPrice.ToString("c"), (quote.LastPrice * buyOrder.Quantity).ToString("c"), buyOrder.BuyOn.ToString("MMM d")); } Clearly we've made this server method take more code than it did with the object parameter. We've basically moved the parameter assignment logic from the client to the server. As a result the client code to call this method is now a bit shorter since there's no client side shuffling of values from the controls to an object. $("#btnBuyStockPost").click(function () { ajaxCallMethod("SampleService.ashx", "BuyStockPost", [], // Note: No parameters - function (result) { $("#divStockBuyMessage").text(result).fadeIn(1000); }, onPageError, // Force all page Form Variables to be posted { postbackMode: "Post" }); }); The client simply calls the BuyStockQuote method and pushes all the form variables from the page up to the server which parses them instead. The feature that makes this work is one of the options you can pass to the ajaxCallMethod() function: { postbackMode: "Post" }); which directs the function to include form variable POST data when making the service call. Other options include PostNoViewState (for WebForms to strip out WebForms crap vars), PostParametersOnly (default), None. If you pass parameters those are always posted to the server except when None is set. The above code can be simplified a bit by using the FormVariableBinder helper, which can unbind form variables directly into an object: FormVariableBinder.Unbind(buyOrder,null,"txtBuy"); which replaces the manual Request.Form[] reading code. It receives the object to unbind into, a string of properties to skip, and an optional prefix which is stripped off form variables to match property names. The component is similar to the MVC model binder but it's independent of MVC. Returning non-JSON Data CallbackHandler also supports returning non-JSON/XML data via special return types. You can return raw non-JSON encoded strings like this: [CallbackMethod(ReturnAsRawString=true,ContentType="text/plain")] public string HelloWorldNoJSON(string name) { return "Hello " + name + ". Time is: " + DateTime.Now.ToString(); } Calling this method results in just a plain string - no JSON encoding with quotes around the result. This can be useful if your server handling code needs to return a string or HTML result that doesn't fit well for a page or other UI component. Any string output can be returned. You can also return binary data. Stream, byte[] and Bitmap/Image results are automatically streamed back to the client. Notice that you should set the ContentType of the request either on the CallbackMethod attribute or using Response.ContentType. This ensures the Web Server knows how to display your binary response. Using a stream response makes it possible to return any of data. Streamed data can be pretty handy to return bitmap data from a method. The following is a method that returns a stock history graph for a particular stock over a provided number of years: [CallbackMethod(ContentType="image/png",RouteUrl="stocks/history/graph/{symbol}/{years}")] public Stream GetStockHistoryGraph(string symbol, int years = 2,int width = 500, int height=350) { if (width == 0) width = 500; if (height == 0) height = 350; StockServer server = new StockServer(); return server.GetStockHistoryGraph(symbol,"Stock History for " + symbol,width,height,years); } I can now hook this up into the JavaScript code when I get a stock quote. At the end of the process I can assign the URL to the service that returns the image into the src property and so force the image to display. Here's the changed code: $("#btnStockQuote").click(function () { var symbol = $("#txtSymbol").val(); ajaxCallMethod("SampleService.ashx", "GetStockQuote", [symbol], function (quote) { $("#divStockDisplay").fadeIn(1000); $("#stockCompany").text(quote.Company + " (" + quote.Symbol + ")"); $("#stockLastPrice").text(quote.LastPrice); $("#stockQuoteTime").text(quote.LastQuoteTime.formatDate("MMM dd, hh:mmt")); // display a stock chart $("#imgStockHistory").attr("src", "stocks/history/graph/" + symbol + "/2"); },onPageError); }); The resulting output then looks like this: The charting code uses the new ASP.NET 4.0 Chart components via code to display a bar chart of the 2 year stock data as part of the StockServer class which you can find in the sample download. The ability to return arbitrary data from a service is useful as you can see - in this case the chart is clearly associated with the service and it's nice that the graph generation can happen off a handler rather than through a page. Images are common resources, but output can also be PDF reports, zip files for downloads etc. which is becoming increasingly more common to be returned from REST endpoints and other applications. Why reinvent? Obviously the examples I've shown here are pretty basic in terms of functionality. But I hope they demonstrate the core features of AJAX callbacks that you need to work through in most applications which is simple: return data, send back data and potentially retrieve data in various formats. While there are other solutions when it comes down to making AJAX callbacks and servicing REST like requests, I like the flexibility my home grown solution provides. Simply put it's still the easiest solution that I've found that addresses my common use cases: AJAX JSON RPC style callbacks Url based access XML and JSON Output from single method endpoint XML and JSON POST support, querystring input, routing parameter mapping UrlEncoded POST data support on callbacks Ability to return stream/raw string data Essentially ability to return ANYTHING from Service and pass anything All these features are available in various solutions but not together in one place. I've been using this code base for over 4 years now in a number of projects both for myself and commercial work and it's served me extremely well. Besides the AJAX functionality CallbackHandler provides, it's also an easy way to create any kind of output endpoint I need to create. Need to create a few simple routines that spit back some data, but don't want to create a Page or View or full blown handler for it? Create a CallbackHandler and add a method or multiple methods and you have your generic endpoints.  It's a quick and easy way to add small code pieces that are pretty efficient as they're running through a pretty small handler implementation. I can have this up and running in a couple of minutes literally without any setup and returning just about any kind of data. Resources Download the Sample NuGet: Westwind Web and AJAX Utilities (Westwind.Web) ajaxCallMethod() Documentation Using the AjaxMethodCallback WebForms Control West Wind Web Toolkit Home Page West Wind Web Toolkit Source Code © Rick Strahl, West Wind Technologies, 2005-2011Posted in ASP.NET  jQuery  AJAX   Tweet (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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  • Failed to get i915 symbols, graphics turbo disabled

    - by Optimus Prime
    I'm getting "Failed to get i915 symbols, graphics turbo disabled" error message after installing following softwares and few updates from Ubuntu. Django, Mysql server 5.5 Mysql benchmark And i have installed few updates for ubuntu. It was showing as Security Updates for Ubuntu. After installing Updates the update manager showed that i should restart the system. On restart i got following error message. " failed to get i915 symbols, graphics turbo disabled". So i tried the work around mentioned here (using the Live CD) ie add intel_ips to the blacklist echo "blacklist intel_ips" /etc/modprobe.d/blacklist.conf add i915 and intel_ips to /etc/modules echo -e "i915/nintel_ips" /etc/modules Now when start the system it freezes at Ubuntu splash screen. I'm using Ubuntu 12.04 LTS, on Dell inspiron N1040. I need to boot the system as i have spend lot of days configuring. Python and Django. Please help EDIT : OK when i restarted the system yesterday it magically turned on. Now i can view my desktop. But one problem, i can't mount any of the drives. It says failed to mount Drive. I'm also frequently getting "Ubuntu System Failure" Error Message.

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  • Game software design

    - by L. De Leo
    I have been working on a simple implementation of a card game in object oriented Python/HTML/Javascript and building on the top of Django. At this point the game is in its final stage of development but, while spotting a big issue about how I was keeping the application state (basically using a global variable), I reached the point that I'm stuck. The thing is that ignoring the design flaw, in a single-threaded environment such as under the Django development server, the game works perfectly. While I tried to design classes cleanly and keep methods short I now have in front of me an issue that has been keeping me busy for the last 2 days and that countless print statements and visual debugging hasn't helped me spot. The reason I think has to do with some side-effects of functions and to solve it I've been wondering if maybe refactoring the code entirely with static classes that keep no state and just passing the state around might be a good option to keep side-effects under control. Or maybe trying to program it in a functional programming style (although I'm not sure Python allows for a purely functional style). I feel that now there's already too many layers that the software (which I plan to make incredibly more complex by adding non trivial features) has already become unmanageable. How would you suggest I re-take control of my code-base that (despite being still only at < 1000 LOC) seems to have taken a life of its own?

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  • how to choose a web framework and javascript library?

    - by Trylks
    I've been procrastinating learning some framework for web apps w/ some library for AJAX, something like django with prototype, or turbogears with mootools, or zeta components with dojo, grok, jquery, symfony... The point is to spend some of my spare time, have "fun" and create cool stuff that hopefully is some useful. I think maybe I wouldn't like something like GWT or pyjamas because I wouldn't like to "get married" with some technology, I want to keep my freedom to add another javascript library, and so on. I didn't decide even the language yet, but I think I'd prefer python. PHP could be fine if there is some framework that is nice enough. Besides that, I don't even know where to start. I don't feel like learning a framework to then realize there is something that I cannot comfortably do, switch to another framework then find that a third framework has something really cool, etc. And the same goes for javascript libraries. So, some guidance would be really appreciated. I don't really know why are so many options available and what do they aim for, I guess some of them focus on some aspects and some on others, but I just want to make cool and nice apps that I can easily maintain, without spending too much time on coding or learning and avoiding the "trapped in the framework" feeling, when doing something is awfully complicated (or even impossible) with compared with the rest of things or doing that same thing on a different framework. I guess in the end I'll go for django and jquery since they are the most widely used options, afaik, but if I was going for the most widely used options I guess I should choose Java or PHP (I don't really like Java for my spare time, but php is not so bad), so I preferred to ask first. I think the question has to consider both, framework and library, since sometimes they are coupled. I think this is the place to ask this kind of things, sorry if not, and thank you.

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  • What benefits can I get upgrading my ASP.NET (Webform) + DAL(EF) + Repository + BLL structure to MVC?

    - by Etienne
    I'm in the process of defining an approach that may best fit our needs for a big web application development. For now, I'm thinking going with an ASP.NET Architecture with a DAL using Entity Framework, a Repository concept to not access DAL directly from BLL and a BLL that call the repository and make every manipulations necessary to prepare data to push in a presentation layer (.aspx files). I don't plan to use ASP.Net controls and prefer to keep things simple and lightweight using plain html, jQuery UI controls and do most of the server calls with jQuery Ajax. Sometimes, when needed, I plan to use handlers (.ashx) to call BLL methods that will return JSON or HTML to client for dynamic stuff. My solution also has a test project that Mock the Repository with in-memory data to not repose on database for testing BLL methods... It may be usefull to add that we will build a big application over this architecture with hundreds of tables and store procedures with a lot of reading and writing to database. My question is, having this architecture in mind, Is there any evident advantages that I can obtain by using an MVC3 project instead of the described architecture base on Webform? Do you see any problem in this architecture that may cause us problem during the next steps of development? I know the MVC pattern for using it in others projects with Django... but the Microsoft MVC implementation look so much more complex and verbose than Django MVC and it's why I'm hesitating (or waiting for a little push?) right now before jumping into it... We are in a real project with deadlines and don't want to slow the development process without any real benefits.

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  • Can not login Dashboard / Unable to find the server at mykeystoneurl

    - by neo0
    I installed Dashboard following this guide: http://wiki.openstack.org/OpenStackDashboard Everything fine, but when I run the server, I can not login with the username and password in DATABASE config in local_settings.py. Here's my config: DATABASES = { 'default': { 'ENGINE': 'django.db.backends.mysql', 'NAME': 'dashboarddb', 'USER': 'nova', 'PASSWORD': 'nova', 'HOST': 'localhost', 'default-character-set': 'utf8' }, } When I run the Dashboard server and enter username + password. It returned this error on browser: Unable to find the server at mykeystoneurl (HTTP 400) And in the command line: DEBUG:openstack_dashboard.settings:Running in debug mode without debug_toolbar. DEBUG:openstack_dashboard.settings:Running in debug mode without debug_toolbar. Validating models... 0 errors found Django version 1.3.1, using settings 'openstack_dashboard.settings' Development server is running at http://0.0.0.0:8888/ Quit the server with CONTROL-C. Request returned failure status. Traceback (most recent call last): File "/home/us/horizon/.venv/src/python-keystoneclient/keystoneclient/client.py", line 121, in request body = json.loads(body) File "/usr/lib/python2.7/json/__init__.py", line 326, in loads return _default_decoder.decode(s) File "/usr/lib/python2.7/json/decoder.py", line 366, in decode obj, end = self.raw_decode(s, idx=_w(s, 0).end()) File "/usr/lib/python2.7/json/decoder.py", line 384, in raw_decode raise ValueError("No JSON object could be decoded") ValueError: No JSON object could be decoded [06/Mar/2012 15:20:03] "POST /auth/login/ HTTP/1.1" 200 3735 I also tried login as "admin" with password is "password" or "secrete" but I didn't work. What's wrong? Thank you!

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  • How to deal with the need to know multiple programming languages? When to stop learning new languages?

    - by Raphael
    I am a relatively young programmer. I am 23 and I have been programming professionally for about 5 years. As most programmers I started with C, learned some x86 assembly for fun and then I found C++ which turned out to be my greatest passion in the programming world. Programming with C and C++ forces you to learn platform specific APIs, libs and frameworks all of each requires constant study and experimentation. After some time I had to move on to Java and C# as the demand on my region is basically for these languages. With these languages I entered the world of web development and then I had to learn javascript. Developing for the .NET Framework was exciting at first but I constantly felt as I was getting tied up by Microsoft (and of course the .NET Framework was driving me away from Linux). For desktop development I could do pretty much everything I did with .NET using C++ with Qt but for web development I had to look for an alternative. Quickly I found Django and then I proceeded to learn Python so I could use Django. Nowadays I am learning iOS development with Objective-C. So far it was pretty much easy to learn all these languages (C++ trained me well) but I am worried that someday I won't be able to keep track of them all. Just to clarify. The only languages I learned cause I had to were C# and Java. All of the others I learned for fun, because I love programming and learning new things. Also I like to keep my skills sharp on desktop, web and mobile development. My question is: How do you keep track of multiple programming languages? (I mean, keep track of changes to these languages and keep your skills sharp) and: Is there such a thing as enough programming languages?

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  • How to choose a server side language / framework

    - by pllee
    I am trying to come up with a list / ranking system on determining which server language to choose for a particular website. Assume that familiarity with a certain language is not important and the implementation can be done in any language. Here are some things that might be important but I am not sure how to rank them : Maintainability. Libraries. For example, Memcached and NoSql support right out the box would be really nice addition to a particular framework. 3rd party SDK's. For example, if I need Paypal on my site they openly provide SDK's for all senarios in Java, PHP and .Net. If I choose Django I would have to rely on 3rd party libraries that are don't support everything and are not officially maintained. Would that be dealbreaker for Django? Performance This one is tricky to put on a generic list because it can be a deal breaker but for many websites performance will not be an issue that the language/framework is responsible for. Cost (hosting, open source). edit - Any reason for the votes to close? I didn't see any duplicates mentioned and the question should not drum up a flame war.

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  • Where does ASP.NET Web API Fit?

    - by Rick Strahl
    With the pending release of ASP.NET MVC 4 and the new ASP.NET Web API, there has been a lot of discussion of where the new Web API technology fits in the ASP.NET Web stack. There are a lot of choices to build HTTP based applications available now on the stack - we've come a long way from when WebForms and Http Handlers/Modules where the only real options. Today we have WebForms, MVC, ASP.NET Web Pages, ASP.NET AJAX, WCF REST and now Web API as well as the core ASP.NET runtime to choose to build HTTP content with. Web API definitely squarely addresses the 'API' aspect - building consumable services - rather than HTML content, but even to that end there are a lot of choices you have today. So where does Web API fit, and when doesn't it? But before we get into that discussion, let's talk about what a Web API is and why we should care. What's a Web API? HTTP 'APIs' (Microsoft's new terminology for a service I guess)  are becoming increasingly more important with the rise of the many devices in use today. Most mobile devices like phones and tablets run Apps that are using data retrieved from the Web over HTTP. Desktop applications are also moving in this direction with more and more online content and synching moving into even traditional desktop applications. The pending Windows 8 release promises an app like platform for both the desktop and other devices, that also emphasizes consuming data from the Cloud. Likewise many Web browser hosted applications these days are relying on rich client functionality to create and manipulate the browser user interface, using AJAX rather than server generated HTML data to load up the user interface with data. These mobile or rich Web applications use their HTTP connection to return data rather than HTML markup in the form of JSON or XML typically. But an API can also serve other kinds of data, like images or other binary files, or even text data and HTML (although that's less common). A Web API is what feeds rich applications with data. ASP.NET Web API aims to service this particular segment of Web development by providing easy semantics to route and handle incoming requests and an easy to use platform to serve HTTP data in just about any content format you choose to create and serve from the server. But .NET already has various HTTP Platforms The .NET stack already includes a number of technologies that provide the ability to create HTTP service back ends, and it has done so since the very beginnings of the .NET platform. From raw HTTP Handlers and Modules in the core ASP.NET runtime, to high level platforms like ASP.NET MVC, Web Forms, ASP.NET AJAX and the WCF REST engine (which technically is not ASP.NET, but can integrate with it), you've always been able to handle just about any kind of HTTP request and response with ASP.NET. The beauty of the raw ASP.NET platform is that it provides you everything you need to build just about any type of HTTP application you can dream up from low level APIs/custom engines to high level HTML generation engine. ASP.NET as a core platform clearly has stood the test of time 10+ years later and all other frameworks like Web API are built on top of this ASP.NET core. However, although it's possible to create Web APIs / Services using any of the existing out of box .NET technologies, none of them have been a really nice fit for building arbitrary HTTP based APIs. Sure, you can use an HttpHandler to create just about anything, but you have to build a lot of plumbing to build something more complex like a comprehensive API that serves a variety of requests, handles multiple output formats and can easily pass data up to the server in a variety of ways. Likewise you can use ASP.NET MVC to handle routing and creating content in various formats fairly easily, but it doesn't provide a great way to automatically negotiate content types and serve various content formats directly (it's possible to do with some plumbing code of your own but not built in). Prior to Web API, Microsoft's main push for HTTP services has been WCF REST, which was always an awkward technology that had a severe personality conflict, not being clear on whether it wanted to be part of WCF or purely a separate technology. In the end it didn't do either WCF compatibility or WCF agnostic pure HTTP operation very well, which made for a very developer-unfriendly environment. Personally I didn't like any of the implementations at the time, so much so that I ended up building my own HTTP service engine (as part of the West Wind Web Toolkit), as have a few other third party tools that provided much better integration and ease of use. With the release of Web API for the first time I feel that I can finally use the tools in the box and not have to worry about creating and maintaining my own toolkit as Web API addresses just about all the features I implemented on my own and much more. ASP.NET Web API provides a better HTTP Experience ASP.NET Web API differentiates itself from the previous Microsoft in-box HTTP service solutions in that it was built from the ground up around the HTTP protocol and its messaging semantics. Unlike WCF REST or ASP.NET AJAX with ASMX, it’s a brand new platform rather than bolted on technology that is supposed to work in the context of an existing framework. The strength of the new ASP.NET Web API is that it combines the best features of the platforms that came before it, to provide a comprehensive and very usable HTTP platform. Because it's based on ASP.NET and borrows a lot of concepts from ASP.NET MVC, Web API should be immediately familiar and comfortable to most ASP.NET developers. Here are some of the features that Web API provides that I like: Strong Support for URL Routing to produce clean URLs using familiar MVC style routing semantics Content Negotiation based on Accept headers for request and response serialization Support for a host of supported output formats including JSON, XML, ATOM Strong default support for REST semantics but they are optional Easily extensible Formatter support to add new input/output types Deep support for more advanced HTTP features via HttpResponseMessage and HttpRequestMessage classes and strongly typed Enums to describe many HTTP operations Convention based design that drives you into doing the right thing for HTTP Services Very extensible, based on MVC like extensibility model of Formatters and Filters Self-hostable in non-Web applications  Testable using testing concepts similar to MVC Web API is meant to handle any kind of HTTP input and produce output and status codes using the full spectrum of HTTP functionality available in a straight forward and flexible manner. Looking at the list above you can see that a lot of functionality is very similar to ASP.NET MVC, so many ASP.NET developers should feel quite comfortable with the concepts of Web API. The Routing and core infrastructure of Web API are very similar to how MVC works providing many of the benefits of MVC, but with focus on HTTP access and manipulation in Controller methods rather than HTML generation in MVC. There’s much improved support for content negotiation based on HTTP Accept headers with the framework capable of detecting automatically what content the client is sending and requesting and serving the appropriate data format in return. This seems like such a little and obvious thing, but it's really important. Today's service backends often are used by multiple clients/applications and being able to choose the right data format for what fits best for the client is very important. While previous solutions were able to accomplish this using a variety of mixed features of WCF and ASP.NET, Web API combines all this functionality into a single robust server side HTTP framework that intrinsically understands the HTTP semantics and subtly drives you in the right direction for most operations. And when you need to customize or do something that is not built in, there are lots of hooks and overrides for most behaviors, and even many low level hook points that allow you to plug in custom functionality with relatively little effort. No Brainers for Web API There are a few scenarios that are a slam dunk for Web API. If your primary focus of an application or even a part of an application is some sort of API then Web API makes great sense. HTTP ServicesIf you're building a comprehensive HTTP API that is to be consumed over the Web, Web API is a perfect fit. You can isolate the logic in Web API and build your application as a service breaking out the logic into controllers as needed. Because the primary interface is the service there's no confusion of what should go where (MVC or API). Perfect fit. Primary AJAX BackendsIf you're building rich client Web applications that are relying heavily on AJAX callbacks to serve its data, Web API is also a slam dunk. Again because much if not most of the business logic will probably end up in your Web API service logic, there's no confusion over where logic should go and there's no duplication. In Single Page Applications (SPA), typically there's very little HTML based logic served other than bringing up a shell UI and then filling the data from the server with AJAX which means the business logic required for data retrieval and data acceptance and validation too lives in the Web API. Perfect fit. Generic HTTP EndpointsAnother good fit are generic HTTP endpoints that to serve data or handle 'utility' type functionality in typical Web applications. If you need to implement an image server, or an upload handler in the past I'd implement that as an HTTP handler. With Web API you now have a well defined place where you can implement these types of generic 'services' in a location that can easily add endpoints (via Controller methods) or separated out as more full featured APIs. Granted this could be done with MVC as well, but Web API seems a clearer and more well defined place to store generic application services. This is one thing I used to do a lot of in my own libraries and Web API addresses this nicely. Great fit. Mixed HTML and AJAX Applications: Not a clear Choice  For all the commonality that Web API and MVC share they are fundamentally different platforms that are independent of each other. A lot of people have asked when does it make sense to use MVC vs. Web API when you're dealing with typical Web application that creates HTML and also uses AJAX functionality for rich functionality. While it's easy to say that all 'service'/AJAX logic should go into a Web API and all HTML related generation into MVC, that can often result in a lot of code duplication. Also MVC supports JSON and XML result data fairly easily as well so there's some confusion where that 'trigger point' is of when you should switch to Web API vs. just implementing functionality as part of MVC controllers. Ultimately there's a tradeoff between isolation of functionality and duplication. A good rule of thumb I think works is that if a large chunk of the application's functionality serves data Web API is a good choice, but if you have a couple of small AJAX requests to serve data to a grid or autocomplete box it'd be overkill to separate out that logic into a separate Web API controller. Web API does add overhead to your application (it's yet another framework that sits on top of core ASP.NET) so it should be worth it .Keep in mind that MVC can generate HTML and JSON/XML and just about any other content easily and that functionality is not going away, so just because you Web API is there it doesn't mean you have to use it. Web API is not a full replacement for MVC obviously either since there's not the same level of support to feed HTML from Web API controllers (although you can host a RazorEngine easily enough if you really want to go that route) so if you're HTML is part of your API or application in general MVC is still a better choice either alone or in combination with Web API. I suspect (and hope) that in the future Web API's functionality will merge even closer with MVC so that you might even be able to mix functionality of both into single Controllers so that you don't have to make any trade offs, but at the moment that's not the case. Some Issues To think about Web API is similar to MVC but not the Same Although Web API looks a lot like MVC it's not the same and some common functionality of MVC behaves differently in Web API. For example, the way single POST variables are handled is different than MVC and doesn't lend itself particularly well to some AJAX scenarios with POST data. Code Duplication I already touched on this in the Mixed HTML and Web API section, but if you build an MVC application that also exposes a Web API it's quite likely that you end up duplicating a bunch of code and - potentially - infrastructure. You may have to create authentication logic both for an HTML application and for the Web API which might need something different altogether. More often than not though the same logic is used, and there's no easy way to share. If you implement an MVC ActionFilter and you want that same functionality in your Web API you'll end up creating the filter twice. AJAX Data or AJAX HTML On a recent post's comments, David made some really good points regarding the commonality of MVC and Web API's and its place. One comment that caught my eye was a little more generic, regarding data services vs. HTML services. David says: I see a lot of merit in the combination of Knockout.js, client side templates and view models, calling Web API for a responsive UI, but sometimes late at night that still leaves me wondering why I would no longer be using some of the nice tooling and features that have evolved in MVC ;-) You know what - I can totally relate to that. On the last Web based mobile app I worked on, we decided to serve HTML partials to the client via AJAX for many (but not all!) things, rather than sending down raw data to inject into the DOM on the client via templating or direct manipulation. While there are definitely more bytes on the wire, with this, the overhead ended up being actually fairly small if you keep the 'data' requests small and atomic. Performance was often made up by the lack of client side rendering of HTML. Server rendered HTML for AJAX templating gives so much better infrastructure support without having to screw around with 20 mismatched client libraries. Especially with MVC and partials it's pretty easy to break out your HTML logic into very small, atomic chunks, so it's actually easy to create small rendering islands that can be used via composition on the server, or via AJAX calls to small, tight partials that return HTML to the client. Although this is often frowned upon as to 'heavy', it worked really well in terms of developer effort as well as providing surprisingly good performance on devices. There's still plenty of jQuery and AJAX logic happening on the client but it's more manageable in small doses rather than trying to do the entire UI composition with JavaScript and/or 'not-quite-there-yet' template engines that are very difficult to debug. This is not an issue directly related to Web API of course, but something to think about especially for AJAX or SPA style applications. Summary Web API is a great new addition to the ASP.NET platform and it addresses a serious need for consolidation of a lot of half-baked HTTP service API technologies that came before it. Web API feels 'right', and hits the right combination of usability and flexibility at least for me and it's a good fit for true API scenarios. However, just because a new platform is available it doesn't meant that other tools or tech that came before it should be discarded or even upgraded to the new platform. There's nothing wrong with continuing to use MVC controller methods to handle API tasks if that's what your app is running now - there's very little to be gained by upgrading to Web API just because. But going forward Web API clearly is the way to go, when building HTTP data interfaces and it's good to see that Microsoft got this one right - it was sorely needed! Resources ASP.NET Web API AspConf Ask the Experts Session (first 5 minutes) © Rick Strahl, West Wind Technologies, 2005-2012Posted in Web Api   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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  • Enterprise Process Maps: A Process Picture worth a Million Words

    - by raul.goycoolea
    p { margin-bottom: 0.08in; }h1 { margin-top: 0.33in; margin-bottom: 0in; color: rgb(54, 95, 145); page-break-inside: avoid; }h1.western { font-family: "Cambria",serif; font-size: 14pt; }h1.cjk { font-family: "DejaVu Sans"; font-size: 14pt; }h1.ctl { font-size: 14pt; } Getting Started with Business Transformations A well-known proverb states that "A picture is worth a thousand words." In relation to Business Process Management (BPM), a credible analyst might have a few questions. What if the picture was taken from some particular angle, like directly overhead? What if it was taken from only an inch away or a mile away? What if the photographer did not focus the camera correctly? Does the value of the picture depend on who is looking at it? Enterprise Process Maps are analogous in this sense of relative value. Every BPM project (holistic BPM kick-off, enterprise system implementation, Service-oriented Architecture, business process transformation, corporate performance management, etc.) should be begin with a clear understanding of the business environment, from the biggest picture representations down to the lowest level required or desired for the particular project type, scope and objectives. The Enterprise Process Map serves as an entry point for the process architecture and is defined: the single highest level of process mapping for an organization. It is constructed and evaluated during the Strategy Phase of the Business Process Management Lifecycle. (see Figure 1) Fig. 1: Business Process Management Lifecycle Many organizations view such maps as visual abstractions, constructed for the single purpose of process categorization. This, in turn, results in a lesser focus on the inherent intricacies of the Enterprise Process view, which are explored in the course of this paper. With the main focus of a large scale process documentation effort usually underlying an ERP or other system implementation, it is common for the work to be driven by the desire to "get to the details," and to the type of modeling that will derive near-term tangible results. For instance, a project in American Pharmaceutical Company X is driven by the Director of IT. With 120+ systems in place, and a lack of standardized processes across the United States, he and the VP of IT have decided to embark on a long-term ERP implementation. At the forethought of both are questions, such as: How does my application architecture map to the business? What are each application's functionalities, and where do the business processes utilize them? Where can we retire legacy systems? Well-developed BPM methodologies prescribe numerous model types to capture such information and allow for thorough analysis in these areas. Process to application maps, Event Driven Process Chains, etc. provide this level of detail and facilitate the completion of such project-specific questions. These models and such analysis are appropriately carried out at a relatively low level of process detail. (see figure 2) Fig. 2: The Level Concept, Generic Process HierarchySome of the questions remaining are ones of documentation longevity, the continuation of BPM practice in the organization, process governance and ownership, process transparency and clarity in business process objectives and strategy. The Level Concept in Brief Figure 2 shows a generic, four-level process hierarchy depicting the breakdown of a "Process Area" into progressively more detailed process classifications. The number of levels and the names of these levels are flexible, and can be fit to the standards of the organization's chosen terminology or any other chosen reference model that makes logical sense for both short and long term process description. It is at Level 1 (in this case the Process Area level), that the Enterprise Process Map is created. This map and its contained objects become the foundation for a top-down approach to subsequent mapping, object relationship development, and analysis of the organization's processes and its supporting infrastructure. Additionally, this picture serves as a communication device, at an executive level, describing the design of the business in its service to a customer. It seems, then, imperative that the process development effort, and this map, start off on the right foot. Figuring out just what that right foot is, however, is critical and trend-setting in an evolving organization. Key Considerations Enterprise Process Maps are usually not as living and breathing as other process maps. Just as it would be an extremely difficult task to change the foundation of the Sears Tower or a city plan for the entire city of Chicago, the Enterprise Process view of an organization usually remains unchanged once developed (unless, of course, an organization is at a stage where it is capable of true, high-level process innovation). Regardless, the Enterprise Process map is a key first step, and one that must be taken in a precise way. What makes this groundwork solid depends on not only the materials used to construct it (process areas), but also the layout plan and knowledge base of what will be built (the entire process architecture). It seems reasonable that care and consideration are required to create this critical high level map... but what are the important factors? Does the process modeler need to worry about how many process areas there are? About who is looking at it? Should he only use the color pink because it's his boss' favorite color? Interestingly, and perhaps surprisingly, these are all valid considerations that may just require a bit of structure. Below are Three Key Factors to consider when building an Enterprise Process Map: Company Strategic Focus Process Categorization: Customer is Core End-to-end versus Functional Processes Company Strategic Focus As mentioned above, the Enterprise Process Map is created during the Strategy Phase of the Business Process Management Lifecycle. From Oracle Business Process Management methodology for business transformation, it is apparent that business processes exist for the purpose of achieving the strategic objectives of an organization. In a prescribed, top-down approach to process development, it must be ensured that each process fulfills its objectives, and in an aggregated manner, drives fulfillment of the strategic objectives of the company, whether for particular business segments or in a broader sense. This is a crucial point, as the strategic messages of the company must therefore resound in its process maps, in particular one that spans the processes of the complete business: the Enterprise Process Map. One simple example from Company X is shown below (see figure 3). Fig. 3: Company X Enterprise Process Map In reviewing Company X's Enterprise Process Map, one can immediately begin to understand the general strategic mindset of the organization. It shows that Company X is focused on its customers, defining 10 of its process areas belonging to customer-focused categories. Additionally, the organization views these end-customer-oriented process areas as part of customer-fulfilling value chains, while support process areas do not provide as much contiguous value. However, by including both support and strategic process categorizations, it becomes apparent that all processes are considered vital to the success of the customer-oriented focus processes. Below is an example from Company Y (see figure 4). Fig. 4: Company Y Enterprise Process Map Company Y, although also a customer-oriented company, sends a differently focused message with its depiction of the Enterprise Process Map. Along the top of the map is the company's product tree, overarching the process areas, which when executed deliver the products themselves. This indicates one strategic objective of excellence in product quality. Additionally, the view represents a less linear value chain, with strong overlaps of the various process areas. Marketing and quality management are seen as a key support processes, as they span the process lifecycle. Often, companies may incorporate graphics, logos and symbols representing customers and suppliers, and other objects to truly send the strategic message to the business. Other times, Enterprise Process Maps may show high level of responsibility to organizational units, or the application types that support the process areas. It is possible that hundreds of formats and focuses can be applied to an Enterprise Process Map. What is of vital importance, however, is which formats and focuses are chosen to truly represent the direction of the company, and serve as a driver for focusing the business on the strategic objectives set forth in that right. Process Categorization: Customer is Core In the previous two examples, processes were grouped using differing categories and techniques. Company X showed one support and three customer process categorizations using encompassing chevron objects; Customer Y achieved a less distinct categorization using a gradual color scheme. Either way, and in general, modeling of the process areas becomes even more valuable and easily understood within the context of business categorization, be it strategic or otherwise. But how one categorizes their processes is typically more complex than simply choosing object shapes and colors. Previously, it was stated that the ideal is a prescribed top-down approach to developing processes, to make certain linkages all the way back up to corporate strategy. But what about external influences? What forces push and pull corporate strategy? Industry maturity, product lifecycle, market profitability, competition, etc. can all drive the critical success factors of a particular business segment, or the company as a whole, in addition to previous corporate strategy. This may seem to be turning into a discussion of theory, but that is far from the case. In fact, in years of recent study and evolution of the way businesses operate, cross-industry and across the globe, one invariable has surfaced with such strength to make it undeniable in the game plan of any strategy fit for survival. That constant is the customer. Many of a company's critical success factors, in any business segment, relate to the customer: customer retention, satisfaction, loyalty, etc. Businesses serve customers, and so do a business's processes, mapped or unmapped. The most effective way to categorize processes is in a manner that visualizes convergence to what is core for a company. It is the value chain, beginning with the customer in mind, and ending with the fulfillment of that customer, that becomes the core or the centerpiece of the Enterprise Process Map. (See figure 5) Fig. 5: Company Z Enterprise Process Map Company Z has what may be viewed as several different perspectives or "cuts" baked into their Enterprise Process Map. It has divided its processes into three main categories (top, middle, and bottom) of Management Processes, the Core Value Chain and Supporting Processes. The Core category begins with Corporate Marketing (which contains the activities of beginning to engage customers) and ends with Customer Service Management. Within the value chain, this company has divided into the focus areas of their two primary business lines, Foods and Beverages. Does this mean that areas, such as Strategy, Information Management or Project Management are not as important as those in the Core category? No! In some cases, though, depending on the organization's understanding of high-level BPM concepts, use of category names, such as "Core," "Management" or "Support," can be a touchy subject. What is important to understand, is that no matter the nomenclature chosen, the Core processes are those that drive directly to customer value, Support processes are those which make the Core processes possible to execute, and Management Processes are those which steer and influence the Core. Some common terms for these three basic categorizations are Core, Customer Fulfillment, Customer Relationship Management, Governing, Controlling, Enabling, Support, etc. End-to-end versus Functional Processes Every high and low level of process: function, task, activity, process/work step (whatever an organization calls it), should add value to the flow of business in an organization. Suppose that within the process "Deliver package," there is a documented task titled "Stop for ice cream." It doesn't take a process expert to deduce the room for improvement. Though stopping for ice cream may create gain for the one person performing it, it likely benefits neither the organization nor, more importantly, the customer. In most cases, "Stop for ice cream" wouldn't make it past the first pass of To-Be process development. What would make the cut, however, would be a flow of tasks that, each having their own value add, build up to greater and greater levels of process objective. In this case, those tasks would combine to achieve a status of "package delivered." Figure 3 shows a simple example: Just as the package can only be delivered (outcome of the process) without first being retrieved, loaded, and the travel destination reached (outcomes of the process steps), some higher level of process "Play Practical Joke" (e.g., main process or process area) cannot be completed until a package is delivered. It seems that isolated or functionally separated processes, such as "Deliver Package" (shown in Figure 6), are necessary, but are always part of a bigger value chain. Each of these individual processes must be analyzed within the context of that value chain in order to ensure successful end-to-end process performance. For example, this company's "Create Joke Package" process could be operating flawlessly and efficiently, but if a joke is never developed, it cannot be created, so the end-to-end process breaks. Fig. 6: End to End Process Construction That being recognized, it is clear that processes must be viewed as end-to-end, customer-to-customer, and in the context of company strategy. But as can also be seen from the previous example, these vital end-to-end processes cannot be built without the functionally oriented building blocks. Without one, the other cannot be had, or at least not in a complete and organized fashion. As it turns out, but not discussed in depth here, the process modeling effort, BPM organizational development, and comprehensive coverage cannot be fully realized without a semi-functional, process-oriented approach. Then, an Enterprise Process Map should be concerned with both views, the building blocks, and access points to the business-critical end-to-end processes, which they construct. Without the functional building blocks, all streams of work needed for any business transformation would be lost mess of process disorganization. End-to-end views are essential for utilization in optimization in context, understanding customer impacts, base-lining all project phases and aligning objectives. Including both views on an Enterprise Process Map allows management to understand the functional orientation of the company's processes, while still providing access to end-to-end processes, which are most valuable to them. (See figures 7 and 8). Fig. 7: Simplified Enterprise Process Map with end-to-end Access Point The above examples show two unique ways to achieve a successful Enterprise Process Map. The first example is a simple map that shows a high level set of process areas and a separate section with the end-to-end processes of concern for the organization. This particular map is filtered to show just one vital end-to-end process for a project-specific focus. Fig. 8: Detailed Enterprise Process Map showing connected Functional Processes The second example shows a more complex arrangement and categorization of functional processes (the names of each process area has been removed). The end-to-end perspective is achieved at this level through the connections (interfaces at lower levels) between these functional process areas. An important point to note is that the organization of these two views of the Enterprise Process Map is dependent, in large part, on the orientation of its audience, and the complexity of the landscape at the highest level. If both are not apparent, the Enterprise Process Map is missing an opportunity to serve as a holistic, high-level view. Conclusion In the world of BPM, and specifically regarding Enterprise Process Maps, a picture can be worth as many words as the thought and effort that is put into it. Enterprise Process Maps alone cannot change an organization, but they serve more purposes than initially meet the eye, and therefore must be designed in a way that enables a BPM mindset, business process understanding and business transformation efforts. Every Enterprise Process Map will and should be different when looking across organizations. Its design will be driven by company strategy, a level of customer focus, and functional versus end-to-end orientations. This high-level description of the considerations of the Enterprise Process Maps is not a prescriptive "how to" guide. However, a company attempting to create one may not have the practical BPM experience to truly explore its options or impacts to the coming work of business process transformation. The biggest takeaway is that process modeling, at all levels, is a science and an art, and art is open to interpretation. It is critical that the modeler of the highest level of process mapping be a cognoscente of the message he is delivering and the factors at hand. Without sufficient focus on the design of the Enterprise Process Map, an entire BPM effort may suffer. For additional information please check: Oracle Business Process Management.

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  • ASP.NET MVC 3: Layouts and Sections with Razor

    - by ScottGu
    This is another in a series of posts I’m doing that cover some of the new ASP.NET MVC 3 features: Introducing Razor (July 2nd) New @model keyword in Razor (Oct 19th) Layouts with Razor (Oct 22nd) Server-Side Comments with Razor (Nov 12th) Razor’s @: and <text> syntax (Dec 15th) Implicit and Explicit code nuggets with Razor (Dec 16th) Layouts and Sections with Razor (Today) In today’s post I’m going to go into more details about how Layout pages work with Razor.  In particular, I’m going to cover how you can have multiple, non-contiguous, replaceable “sections” within a layout file – and enable views based on layouts to optionally “fill in” these different sections at runtime.  The Razor syntax for doing this is clean and concise. I’ll also show how you can dynamically check at runtime whether a particular layout section has been defined, and how you can provide alternate content (or even an alternate layout) in the event that a section isn’t specified within a view template.  This provides a powerful and easy way to customize the UI of your site and make it clean and DRY from an implementation perspective. What are Layouts? You typically want to maintain a consistent look and feel across all of the pages within your web-site/application.  ASP.NET 2.0 introduced the concept of “master pages” which helps enable this when using .aspx based pages or templates.  Razor also supports this concept with a feature called “layouts” – which allow you to define a common site template, and then inherit its look and feel across all the views/pages on your site. I previously discussed the basics of how layout files work with Razor in my ASP.NET MVC 3: Layouts with Razor blog post.  Today’s post will go deeper and discuss how you can define multiple, non-contiguous, replaceable regions within a layout file that you can then optionally “fill in” at runtime. Site Layout Scenario Let’s look at how we can implement a common site layout scenario with ASP.NET MVC 3 and Razor.  Specifically, we’ll implement some site UI where we have a common header and footer on all of our pages.  We’ll also add a “sidebar” section to the right of our common site layout.  On some pages we’ll customize the SideBar to contain content specific to the page it is included on: And on other pages (that do not have custom sidebar content) we will fall back and provide some “default content” to the sidebar: We’ll use ASP.NET MVC 3 and Razor to enable this customization in a nice, clean way.  Below are some step-by-step tutorial instructions on how to build the above site with ASP.NET MVC 3 and Razor. Part 1: Create a New Project with a Layout for the “Body” section We’ll begin by using the “File->New Project” menu command within Visual Studio to create a new ASP.NET MVC 3 Project.  We’ll create the new project using the “Empty” template option: This will create a new project that has no default controllers in it: Creating a HomeController We will then right-click on the “Controllers” folder of our newly created project and choose the “Add->Controller” context menu command.  This will bring up the “Add Controller” dialog: We’ll name the new controller we create “HomeController”.  When we click the “Add” button Visual Studio will add a HomeController class to our project with a default “Index” action method that returns a view: We won’t need to write any Controller logic to implement this sample – so we’ll leave the default code as-is.  Creating a View Template Our next step will be to implement the view template associated with the HomeController’s Index action method.  To implement the view template, we will right-click within the “HomeController.Index()” method and select the “Add View” command to create a view template for our home page: This will bring up the “Add View” dialog within Visual Studio.  We do not need to change any of the default settings within the above dialog (the name of the template was auto-populated to Index because we invoked the “Add View” context menu command within the Index method).  When we click the “Add” Button within the dialog, a Razor-based “Index.cshtml” view template will be added to the \Views\Home\ folder within our project.  Let’s add some simple default static content to it: Notice above how we don’t have an <html> or <body> section defined within our view template.  This is because we are going to rely on a layout template to supply these elements and use it to define the common site layout and structure for our site (ensuring that it is consistent across all pages and URLs within the site).  Customizing our Layout File Let’s open and customize the default “_Layout.cshtml” file that was automatically added to the \Views\Shared folder when we created our new project: The default layout file (shown above) is pretty basic and simply outputs a title (if specified in either the Controller or the View template) and adds links to a stylesheet and jQuery.  The call to “RenderBody()” indicates where the main body content of our Index.cshtml file will merged into the output sent back to the browser. Let’s modify the Layout template to add a common header, footer and sidebar to the site: We’ll then edit the “Site.css” file within the \Content folder of our project and add 4 CSS rules to it: And now when we run the project and browse to the home “/” URL of our project we’ll see a page like below: Notice how the content of the HomeController’s Index view template and the site’s Shared Layout template have been merged together into a single HTML response.  Below is what the HTML sent back from the server looks like: Part 2: Adding a “SideBar” Section Our site so far has a layout template that has only one “section” in it – what we call the main “body” section of the response.  Razor also supports the ability to add additional "named sections” to layout templates as well.  These sections can be defined anywhere in the layout file (including within the <head> section of the HTML), and allow you to output dynamic content to multiple, non-contiguous, regions of the final response. Defining the “SideBar” section in our Layout Let’s update our Layout template to define an additional “SideBar” section of content that will be rendered within the <div id=”sidebar”> region of our HTML.  We can do this by calling the RenderSection(string sectionName, bool required) helper method within our Layout.cshtml file like below:   The first parameter to the “RenderSection()” helper method specifies the name of the section we want to render at that location in the layout template.  The second parameter is optional, and allows us to define whether the section we are rendering is required or not.  If a section is “required”, then Razor will throw an error at runtime if that section is not implemented within a view template that is based on the layout file (which can make it easier to track down content errors).  If a section is not required, then its presence within a view template is optional, and the above RenderSection() code will render nothing at runtime if it isn’t defined. Now that we’ve made the above change to our layout file, let’s hit refresh in our browser and see what our Home page now looks like: Notice how we currently have no content within our SideBar <div> – that is because the Index.cshtml view template doesn’t implement our new “SideBar” section yet. Implementing the “SideBar” Section in our View Template Let’s change our home-page so that it has a SideBar section that outputs some custom content.  We can do that by opening up the Index.cshtml view template, and by adding a new “SiderBar” section to it.  We’ll do this using Razor’s @section SectionName { } syntax: We could have put our SideBar @section declaration anywhere within the view template.  I think it looks cleaner when defined at the top or bottom of the file – but that is simply personal preference.  You can include any content or code you want within @section declarations.  Notice above how I have a C# code nugget that outputs the current time at the bottom of the SideBar section.  I could have also written code that used ASP.NET MVC’s HTML/AJAX helper methods and/or accessed any strongly-typed model objects passed to the Index.cshtml view template. Now that we’ve made the above template changes, when we hit refresh in our browser again we’ll see that our SideBar content – that is specific to the Home Page of our site – is now included in the page response sent back from the server: The SideBar section content has been merged into the proper location of the HTML response : Part 3: Conditionally Detecting if a Layout Section Has Been Implemented Razor provides the ability for you to conditionally check (from within a layout file) whether a section has been defined within a view template, and enables you to output an alternative response in the event that the section has not been defined.  This provides a convenient way to specify default UI for optional layout sections.  Let’s modify our Layout file to take advantage of this capability.  Below we are conditionally checking whether the “SideBar” section has been defined without the view template being rendered (using the IsSectionDefined() method), and if so we render the section.  If the section has not been defined, then we now instead render some default content for the SideBar:  Note: You want to make sure you prefix calls to the RenderSection() helper method with a @ character – which will tell Razor to execute the HelperResult it returns and merge in the section content in the appropriate place of the output.  Notice how we wrote @RenderSection(“SideBar”) above instead of just RenderSection(“SideBar”).  Otherwise you’ll get an error. Above we are simply rendering an inline static string (<p>Default SideBar Content</p>) if the section is not defined.  A real-world site would more likely refactor this default content to be stored within a separate partial template (which we’d render using the Html.RenderPartial() helper method within the else block) or alternatively use the Html.Action() helper method within the else block to encapsulate both the logic and rendering of the default sidebar. When we hit refresh on our home-page, we will still see the same custom SideBar content we had before.  This is because we implemented the SideBar section within our Index.cshtml view template (and so our Layout rendered it): Let’s now implement a “/Home/About” URL for our site by adding a new “About” action method to our HomeController: The About() action method above simply renders a view back to the client when invoked.  We can implement the corresponding view template for this action by right-clicking within the “About()” method and using the “Add View” menu command (like before) to create a new About.cshtml view template.  We’ll implement the About.cshtml view template like below. Notice that we are not defining a “SideBar” section within it: When we browse the /Home/About URL we’ll see the content we supplied above in the main body section of our response, and the default SideBar content will rendered: The layout file determined at runtime that a custom SideBar section wasn’t present in the About.cshtml view template, and instead rendered the default sidebar content. One Last Tweak… Let’s suppose that at a later point we decide that instead of rendering default side-bar content, we just want to hide the side-bar entirely from pages that don’t have any custom sidebar content defined.  We could implement this change simply by making a small modification to our layout so that the sidebar content (and its surrounding HTML chrome) is only rendered if the SideBar section is defined.  The code to do this is below: Razor is flexible enough so that we can make changes like this and not have to modify any of our view templates (nor make change any Controller logic changes) to accommodate this.  We can instead make just this one modification to our Layout file and the rest happens cleanly.  This type of flexibility makes Razor incredibly powerful and productive. Summary Razor’s layout capability enables you to define a common site template, and then inherit its look and feel across all the views/pages on your site. Razor enables you to define multiple, non-contiguous, “sections” within layout templates that can be “filled-in” by view templates.  The @section {} syntax for doing this is clean and concise.  Razor also supports the ability to dynamically check at runtime whether a particular section has been defined, and to provide alternate content (or even an alternate layout) in the event that it isn’t specified.  This provides a powerful and easy way to customize the UI of your site - and make it clean and DRY from an implementation perspective. Hope this helps, Scott P.S. In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

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  • The case of the phantom ADF developer (and other yarns)

    - by Chris Muir
    A few years of ADF experience means I see common mistakes made by different developers, some I regularly make myself.  This post is designed to assist beginners to Oracle JDeveloper Application Development Framework (ADF) avoid a common ADF pitfall, the case of the phantom ADF developer [add Scooby-Doo music here]. ADF Business Components - triggers, default table values and instead of views. Oracle's JDeveloper tutorials help with the A-B-Cs of ADF development, typically built on the nice 'n safe demo schema provided by with the Oracle database such as the HR demo schema. However it's not too long until ADF beginners, having built up some confidence from learning with the tutorials and vanilla demo schemas, start building ADF Business Components based upon their own existing database schema objects.  This is where unexpected problems can sneak in. The crime Developers may encounter a surprising error at runtime when editing a record they just created or updated and committed to the database, based on their own existing tables, namely the error: JBO-25014: Another user has changed the row with primary key oracle.jbo.Key[x] ...where X is the primary key value of the row at hand.  In a production environment with multiple users this error may be legit, one of the other users has updated the row since you queried it.  Yet in a development environment this error is just plain confusing.  If developers are isolated in their own database, creating and editing records they know other users can't possibly be working with, or all the other developers have gone home for the day, how is this error possible? There are no other users?  It must be the phantom ADF developer! [insert dramatic music here] The following picture is what you'll see in the Business Component Browser, and you'll receive a similar error message via an ADF Faces page: A false conclusion What can possibly cause this issue if it isn't our phantom ADF developer?  Doesn't ADF BC implement record locking, locking database records when the row is modified in the ADF middle-tier by a user?  How can our phantom ADF developer even take out a lock if this is the case?  Maybe ADF has a bug, maybe ADF isn't implementing record locking at all?  Shouldn't we see the error "JBO-26030: Failed to lock the record, another user holds the lock" as we attempt to modify the record, why do we see JBO-25014? : Let's verify that ADF is in fact issuing the correct SQL LOCK-FOR-UPDATE statement to the database. First we need to verify ADF's locking strategy.  It is determined by the Application Module's jbo.locking.mode property.  The default (as of JDev 11.1.1.4.0 if memory serves me correct) and recommended value is optimistic, and the other valid value is pessimistic. Next we need a mechanism to check that ADF is issuing the LOCK statements to the database.  We could ask DBAs to monitor locks with OEM, but optimally we'd rather not involve overworked DBAs in this process, so instead we can use the ADF runtime setting –Djbo.debugoutput=console.  At runtime this options turns on instrumentation within the ADF BC layer, which among a lot of extra detail displayed in the log window, will show the actual SQL statement issued to the database, including the LOCK statement we're looking to confirm. Setting our locking mode to pessimistic, opening the Business Components Browser of a JSF page allowing us to edit a record, say the CHARGEABLE field within a BOOKINGS record where BOOKING_NO = 1206, upon editing the record see among others the following log entries: [421] Built select: 'SELECT BOOKING_NO, EVENT_NO, RESOURCE_CODE, CHARGEABLE, MADE_BY, QUANTITY, COST, STATUS, COMMENTS FROM BOOKINGS Bookings'[422] Executing LOCK...SELECT BOOKING_NO, EVENT_NO, RESOURCE_CODE, CHARGEABLE, MADE_BY, QUANTITY, COST, STATUS, COMMENTS FROM BOOKINGS Bookings WHERE BOOKING_NO=:1 FOR UPDATE NOWAIT[423] Where binding param 1: 1206  As can be seen on line 422, in fact a LOCK-FOR-UPDATE is indeed issued to the database.  Later when we commit the record we see: [441] OracleSQLBuilder: SAVEPOINT 'BO_SP'[442] OracleSQLBuilder Executing, Lock 1 DML on: BOOKINGS (Update)[443] UPDATE buf Bookings>#u SQLStmtBufLen: 210, actual=62[444] UPDATE BOOKINGS Bookings SET CHARGEABLE=:1 WHERE BOOKING_NO=:2[445] Update binding param 1: N[446] Where binding param 2: 1206[447] BookingsView1 notify COMMIT ... [448] _LOCAL_VIEW_USAGE_model_Bookings_ResourceTypesView1 notify COMMIT ... [449] EntityCache close prepared statement ....and as a result the changes are saved to the database, and the lock is released. Let's see what happens when we use the optimistic locking mode, this time to change the same BOOKINGS record CHARGEABLE column again.  As soon as we edit the record we see little activity in the logs, nothing to indicate any SQL statement, let alone a LOCK has been taken out on the row. However when we save our records by issuing a commit, the following is recorded in the logs: [509] OracleSQLBuilder: SAVEPOINT 'BO_SP'[510] OracleSQLBuilder Executing doEntitySelect on: BOOKINGS (true)[511] Built select: 'SELECT BOOKING_NO, EVENT_NO, RESOURCE_CODE, CHARGEABLE, MADE_BY, QUANTITY, COST, STATUS, COMMENTS FROM BOOKINGS Bookings'[512] Executing LOCK...SELECT BOOKING_NO, EVENT_NO, RESOURCE_CODE, CHARGEABLE, MADE_BY, QUANTITY, COST, STATUS, COMMENTS FROM BOOKINGS Bookings WHERE BOOKING_NO=:1 FOR UPDATE NOWAIT[513] Where binding param 1: 1205[514] OracleSQLBuilder Executing, Lock 2 DML on: BOOKINGS (Update)[515] UPDATE buf Bookings>#u SQLStmtBufLen: 210, actual=62[516] UPDATE BOOKINGS Bookings SET CHARGEABLE=:1 WHERE BOOKING_NO=:2[517] Update binding param 1: Y[518] Where binding param 2: 1205[519] BookingsView1 notify COMMIT ... [520] _LOCAL_VIEW_USAGE_model_Bookings_ResourceTypesView1 notify COMMIT ... [521] EntityCache close prepared statement Again even though we're seeing the midtier delay the LOCK statement until commit time, it is in fact occurring on line 412, and released as part of the commit issued on line 419.  Therefore with either optimistic or pessimistic locking a lock is indeed issued. Our conclusion at this point must be, unless there's the unlikely cause the LOCK statement is never really hitting the database, or the even less likely cause the database has a bug, then ADF does in fact take out a lock on the record before allowing the current user to update it.  So there's no way our phantom ADF developer could even modify the record if he tried without at least someone receiving a lock error. Hmm, we can only conclude the locking mode is a red herring and not the true cause of our problem.  Who is the phantom? At this point we'll need to conclude that the error message "JBO-25014: Another user has changed" is somehow legit, even though we don't understand yet what's causing it. This leads onto two further questions, how does ADF know another user has changed the row, and what's been changed anyway? To answer the first question, how does ADF know another user has changed the row, the Fusion Guide's section 4.10.11 How to Protect Against Losing Simultaneous Updated Data , that details the Entity Object Change-Indicator property, gives us the answer: At runtime the framework provides automatic "lost update" detection for entity objects to ensure that a user cannot unknowingly modify data that another user has updated and committed in the meantime. Typically, this check is performed by comparing the original values of each persistent entity attribute against the corresponding current column values in the database at the time the underlying row is locked. Before updating a row, the entity object verifies that the row to be updated is still consistent with the current state of the database.  The guide further suggests to make this solution more efficient: You can make the lost update detection more efficient by identifying any attributes of your entity whose values you know will be updated whenever the entity is modified. Typical candidates include a version number column or an updated date column in the row.....To detect whether the row has been modified since the user queried it in the most efficient way, select the Change Indicator option to compare only the change-indicator attribute values. We now know that ADF BC doesn't use the locking mechanism at all to protect the current user against updates, but rather it keeps a copy of the original record fetched, separate to the user changed version of the record, and it compares the original record against the one in the database when the lock is taken out.  If values don't match, be it the default compare-all-columns behaviour, or the more efficient Change Indicator mechanism, ADF BC will throw the JBO-25014 error. This leaves one last question.  Now we know the mechanism under which ADF identifies a changed row, what we don't know is what's changed and who changed it? The real culprit What's changed?  We know the record in the mid-tier has been changed by the user, however ADF doesn't use the changed record in the mid-tier to compare to the database record, but rather a copy of the original record before it was changed.  This leaves us to conclude the database record has changed, but how and by who? There are three potential causes: Database triggers The database trigger among other uses, can be configured to fire PLSQL code on a database table insert, update or delete.  In particular in an insert or update the trigger can override the value assigned to a particular column.  The trigger execution is actioned by the database on behalf of the user initiating the insert or update action. Why this causes the issue specific to our ADF use, is when we insert or update a record in the database via ADF, ADF keeps a copy of the record written to the database.  However the cached record is instantly out of date as the database triggers have modified the record that was actually written to the database.  Thus when we update the record we just inserted or updated for a second time to the database, ADF compares its original copy of the record to that in the database, and it detects the record has been changed – giving us JBO-25014. This is probably the most common cause of this problem. Default values A second reason this issue can occur is another database feature, default column values.  When creating a database table the schema designer can define default values for specific columns.  For example a CREATED_BY column could be set to SYSDATE, or a flag column to Y or N.  Default values are only used by the database when a user inserts a new record and the specific column is assigned NULL.  The database in this case will overwrite the column with the default value. As per the database trigger section, it then becomes apparent why ADF chokes on this feature, though it can only specifically occur in an insert-commit-update-commit scenario, not the update-commit-update-commit scenario. Instead of trigger views I must admit I haven't double checked this scenario but it seems plausible, that of the Oracle database's instead of trigger view (sometimes referred to as instead of views).  A view in the database is based on a query, and dependent on the queries complexity, may support insert, update and delete functionality to a limited degree.  In order to support fully insertable, updateable and deletable views, Oracle introduced the instead of view, that gives the view designer the ability to not only define the view query, but a set of programmatic PLSQL triggers where the developer can define their own logic for inserts, updates and deletes. While this provides the database programmer a very powerful feature, it can cause issues for our ADF application.  On inserting or updating a record in the instead of view, the record and it's data that goes in is not necessarily the data that comes out when ADF compares the records, as the view developer has the option to practically do anything with the incoming data, including throwing it away or pushing it to tables which aren't used by the view underlying query for fetching the data. Readers are at this point reminded that this article is specifically about how the JBO-25014 error occurs in the context of 1 developer on an isolated database.  The article is not considering how the error occurs in a production environment where there are multiple users who can cause this error in a legitimate fashion.  Assuming none of the above features are the cause of the problem, and optimistic locking is turned on (this error is not possible if pessimistic locking is the default mode *and* none of the previous causes are possible), JBO-25014 is quite feasible in a production ADF application if 2 users modify the same record. At this point under project timelines pressure, the obvious fix for developers is to drop both database triggers and default values from the underlying tables.  However we must be careful that these legacy constructs aren't used and assumed to be in place by other legacy systems.  Dropping the database triggers or default value that the existing Oracle Forms  applications assumes and requires to be in place could cause unexpected behaviour and bugs in the Forms application.  Proficient software engineers would recognize such a change may require a partial or full regression test of the existing legacy system, a potentially costly and timely exercise, not ideal. Solving the mystery once and for all Luckily ADF has built in functionality to deal with this issue, though it's not a surprise, as Oracle as the author of ADF also built the database, and are fully aware of the Oracle database's feature set.  At the Entity Object attribute level, the Refresh After Insert and Refresh After Update properties.  Simply selecting these instructs ADF BC after inserting or updating a record to the database, to expect the database to modify the said attributes, and read a copy of the changed attributes back into its cached mid-tier record.  Thus next time the developer modifies the current record, the comparison between the mid-tier record and the database record match, and JBO-25014: Another user has changed" is no longer an issue. [Post edit - as per the comment from Oracle's Steven Davelaar below, as he correctly points out the above solution will not work for instead-of-triggers views as it relies on SQL RETURNING clause which is incompatible with this type of view] Alternatively you can set the Change Indicator on one of the attributes.  This will work as long as the relating column for the attribute in the database itself isn't inadvertently updated.  In turn you're possibly just masking the issue rather than solving it, because if another developer turns the Change Indicator back on the original issue will return.

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  • Adding SQL Cache Dependencies to the Loosely coupled .NET Cache Provider

    - by Rhames
    This post adds SQL Cache Dependency support to the loosely coupled .NET Cache Provider that I described in the previous post (http://geekswithblogs.net/Rhames/archive/2012/09/11/loosely-coupled-.net-cache-provider-using-dependency-injection.aspx). The sample code is available on github at https://github.com/RobinHames/CacheProvider.git. Each time we want to apply a cache dependency to a call to fetch or cache a data item we need to supply an instance of the relevant dependency implementation. This suggests an Abstract Factory will be useful to create cache dependencies as needed. We can then use Dependency Injection to inject the factory into the relevant consumer. Castle Windsor provides a typed factory facility that will be utilised to implement the cache dependency abstract factory (see http://docs.castleproject.org/Windsor.Typed-Factory-Facility-interface-based-factories.ashx). Cache Dependency Interfaces First I created a set of cache dependency interfaces in the domain layer, which can be used to pass a cache dependency into the cache provider. ICacheDependency The ICacheDependency interface is simply an empty interface that is used as a parent for the specific cache dependency interfaces. This will allow us to place a generic constraint on the Cache Dependency Factory, and will give us a type that can be passed into the relevant Cache Provider methods. namespace CacheDiSample.Domain.CacheInterfaces { public interface ICacheDependency { } }   ISqlCacheDependency.cs The ISqlCacheDependency interface provides specific SQL caching details, such as a Sql Command or a database connection and table. It is the concrete implementation of this interface that will be created by the factory in passed into the Cache Provider. using System; using System.Collections.Generic; using System.Linq; using System.Text;   namespace CacheDiSample.Domain.CacheInterfaces { public interface ISqlCacheDependency : ICacheDependency { ISqlCacheDependency Initialise(string databaseConnectionName, string tableName); ISqlCacheDependency Initialise(System.Data.SqlClient.SqlCommand sqlCommand); } } If we want other types of cache dependencies, such as by key or file, interfaces may be created to support these (the sample code includes an IKeyCacheDependency interface). Modifying ICacheProvider to accept Cache Dependencies Next I modified the exisitng ICacheProvider<T> interface so that cache dependencies may be passed into a Fetch method call. I did this by adding two overloads to the existing Fetch methods, which take an IEnumerable<ICacheDependency> parameter (the IEnumerable allows more than one cache dependency to be included). I also added a method to create cache dependencies. This means that the implementation of the Cache Provider will require a dependency on the Cache Dependency Factory. It is pretty much down to personal choice as to whether this approach is taken, or whether the Cache Dependency Factory is injected directly into the repository or other consumer of Cache Provider. I think, because the cache dependency cannot be used without the Cache Provider, placing the dependency on the factory into the Cache Provider implementation is cleaner. ICacheProvider.cs using System; using System.Collections.Generic;   namespace CacheDiSample.Domain.CacheInterfaces { public interface ICacheProvider<T> { T Fetch(string key, Func<T> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry); T Fetch(string key, Func<T> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry, IEnumerable<ICacheDependency> cacheDependencies);   IEnumerable<T> Fetch(string key, Func<IEnumerable<T>> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry); IEnumerable<T> Fetch(string key, Func<IEnumerable<T>> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry, IEnumerable<ICacheDependency> cacheDependencies);   U CreateCacheDependency<U>() where U : ICacheDependency; } }   Cache Dependency Factory Next I created the interface for the Cache Dependency Factory in the domain layer. ICacheDependencyFactory.cs namespace CacheDiSample.Domain.CacheInterfaces { public interface ICacheDependencyFactory { T Create<T>() where T : ICacheDependency;   void Release<T>(T cacheDependency) where T : ICacheDependency; } }   I used the ICacheDependency parent interface as a generic constraint on the create and release methods in the factory interface. Now the interfaces are in place, I moved on to the concrete implementations. ISqlCacheDependency Concrete Implementation The concrete implementation of ISqlCacheDependency will need to provide an instance of System.Web.Caching.SqlCacheDependency to the Cache Provider implementation. Unfortunately this class is sealed, so I cannot simply inherit from this. Instead, I created an interface called IAspNetCacheDependency that will provide a Create method to create an instance of the relevant System.Web.Caching Cache Dependency type. This interface is specific to the ASP.NET implementation of the Cache Provider, so it should be defined in the same layer as the concrete implementation of the Cache Provider (the MVC UI layer in the sample code). IAspNetCacheDependency.cs using System.Web.Caching;   namespace CacheDiSample.CacheProviders { public interface IAspNetCacheDependency { CacheDependency CreateAspNetCacheDependency(); } }   Next, I created the concrete implementation of the ISqlCacheDependency interface. This class also implements the IAspNetCacheDependency interface. This concrete implementation also is defined in the same layer as the Cache Provider implementation. AspNetSqlCacheDependency.cs using System.Web.Caching; using CacheDiSample.Domain.CacheInterfaces;   namespace CacheDiSample.CacheProviders { public class AspNetSqlCacheDependency : ISqlCacheDependency, IAspNetCacheDependency { private string databaseConnectionName;   private string tableName;   private System.Data.SqlClient.SqlCommand sqlCommand;   #region ISqlCacheDependency Members   public ISqlCacheDependency Initialise(string databaseConnectionName, string tableName) { this.databaseConnectionName = databaseConnectionName; this.tableName = tableName; return this; }   public ISqlCacheDependency Initialise(System.Data.SqlClient.SqlCommand sqlCommand) { this.sqlCommand = sqlCommand; return this; }   #endregion   #region IAspNetCacheDependency Members   public System.Web.Caching.CacheDependency CreateAspNetCacheDependency() { if (sqlCommand != null) return new SqlCacheDependency(sqlCommand); else return new SqlCacheDependency(databaseConnectionName, tableName); }   #endregion   } }   ICacheProvider Concrete Implementation The ICacheProvider interface is implemented by the CacheProvider class. This implementation is modified to include the changes to the ICacheProvider interface. First I needed to inject the Cache Dependency Factory into the Cache Provider: private ICacheDependencyFactory cacheDependencyFactory;   public CacheProvider(ICacheDependencyFactory cacheDependencyFactory) { if (cacheDependencyFactory == null) throw new ArgumentNullException("cacheDependencyFactory");   this.cacheDependencyFactory = cacheDependencyFactory; }   Next I implemented the CreateCacheDependency method, which simply passes on the create request to the factory: public U CreateCacheDependency<U>() where U : ICacheDependency { return this.cacheDependencyFactory.Create<U>(); }   The signature of the FetchAndCache helper method was modified to take an additional IEnumerable<ICacheDependency> parameter:   private U FetchAndCache<U>(string key, Func<U> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry, IEnumerable<ICacheDependency> cacheDependencies) and the following code added to create the relevant System.Web.Caching.CacheDependency object for any dependencies and pass them to the HttpContext Cache: CacheDependency aspNetCacheDependencies = null;   if (cacheDependencies != null) { if (cacheDependencies.Count() == 1) // We know that the implementations of ICacheDependency will also implement IAspNetCacheDependency // so we can use a cast here and call the CreateAspNetCacheDependency() method aspNetCacheDependencies = ((IAspNetCacheDependency)cacheDependencies.ElementAt(0)).CreateAspNetCacheDependency(); else if (cacheDependencies.Count() > 1) { AggregateCacheDependency aggregateCacheDependency = new AggregateCacheDependency(); foreach (ICacheDependency cacheDependency in cacheDependencies) { // We know that the implementations of ICacheDependency will also implement IAspNetCacheDependency // so we can use a cast here and call the CreateAspNetCacheDependency() method aggregateCacheDependency.Add(((IAspNetCacheDependency)cacheDependency).CreateAspNetCacheDependency()); } aspNetCacheDependencies = aggregateCacheDependency; } }   HttpContext.Current.Cache.Insert(key, value, aspNetCacheDependencies, absoluteExpiry.Value, relativeExpiry.Value);   The full code listing for the modified CacheProvider class is shown below: using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.Caching; using CacheDiSample.Domain.CacheInterfaces;   namespace CacheDiSample.CacheProviders { public class CacheProvider<T> : ICacheProvider<T> { private ICacheDependencyFactory cacheDependencyFactory;   public CacheProvider(ICacheDependencyFactory cacheDependencyFactory) { if (cacheDependencyFactory == null) throw new ArgumentNullException("cacheDependencyFactory");   this.cacheDependencyFactory = cacheDependencyFactory; }   public T Fetch(string key, Func<T> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry) { return FetchAndCache<T>(key, retrieveData, absoluteExpiry, relativeExpiry, null); }   public T Fetch(string key, Func<T> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry, IEnumerable<ICacheDependency> cacheDependencies) { return FetchAndCache<T>(key, retrieveData, absoluteExpiry, relativeExpiry, cacheDependencies); }   public IEnumerable<T> Fetch(string key, Func<IEnumerable<T>> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry) { return FetchAndCache<IEnumerable<T>>(key, retrieveData, absoluteExpiry, relativeExpiry, null); }   public IEnumerable<T> Fetch(string key, Func<IEnumerable<T>> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry, IEnumerable<ICacheDependency> cacheDependencies) { return FetchAndCache<IEnumerable<T>>(key, retrieveData, absoluteExpiry, relativeExpiry, cacheDependencies); }   public U CreateCacheDependency<U>() where U : ICacheDependency { return this.cacheDependencyFactory.Create<U>(); }   #region Helper Methods   private U FetchAndCache<U>(string key, Func<U> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry, IEnumerable<ICacheDependency> cacheDependencies) { U value; if (!TryGetValue<U>(key, out value)) { value = retrieveData(); if (!absoluteExpiry.HasValue) absoluteExpiry = Cache.NoAbsoluteExpiration;   if (!relativeExpiry.HasValue) relativeExpiry = Cache.NoSlidingExpiration;   CacheDependency aspNetCacheDependencies = null;   if (cacheDependencies != null) { if (cacheDependencies.Count() == 1) // We know that the implementations of ICacheDependency will also implement IAspNetCacheDependency // so we can use a cast here and call the CreateAspNetCacheDependency() method aspNetCacheDependencies = ((IAspNetCacheDependency)cacheDependencies.ElementAt(0)).CreateAspNetCacheDependency(); else if (cacheDependencies.Count() > 1) { AggregateCacheDependency aggregateCacheDependency = new AggregateCacheDependency(); foreach (ICacheDependency cacheDependency in cacheDependencies) { // We know that the implementations of ICacheDependency will also implement IAspNetCacheDependency // so we can use a cast here and call the CreateAspNetCacheDependency() method aggregateCacheDependency.Add( ((IAspNetCacheDependency)cacheDependency).CreateAspNetCacheDependency()); } aspNetCacheDependencies = aggregateCacheDependency; } }   HttpContext.Current.Cache.Insert(key, value, aspNetCacheDependencies, absoluteExpiry.Value, relativeExpiry.Value);   } return value; }   private bool TryGetValue<U>(string key, out U value) { object cachedValue = HttpContext.Current.Cache.Get(key); if (cachedValue == null) { value = default(U); return false; } else { try { value = (U)cachedValue; return true; } catch { value = default(U); return false; } } }   #endregion } }   Wiring up the DI Container Now the implementations for the Cache Dependency are in place, I wired them up in the existing Windsor CacheInstaller. First I needed to register the implementation of the ISqlCacheDependency interface: container.Register( Component.For<ISqlCacheDependency>() .ImplementedBy<AspNetSqlCacheDependency>() .LifestyleTransient());   Next I registered the Cache Dependency Factory. Notice that I have not implemented the ICacheDependencyFactory interface. Castle Windsor will do this for me by using the Type Factory Facility. I do need to bring the Castle.Facilities.TypedFacility namespace into scope: using Castle.Facilities.TypedFactory;   Then I registered the factory: container.AddFacility<TypedFactoryFacility>();   container.Register( Component.For<ICacheDependencyFactory>() .AsFactory()); The full code for the CacheInstaller class is: using Castle.MicroKernel.Registration; using Castle.MicroKernel.SubSystems.Configuration; using Castle.Windsor; using Castle.Facilities.TypedFactory;   using CacheDiSample.Domain.CacheInterfaces; using CacheDiSample.CacheProviders;   namespace CacheDiSample.WindsorInstallers { public class CacheInstaller : IWindsorInstaller { public void Install(IWindsorContainer container, IConfigurationStore store) { container.Register( Component.For(typeof(ICacheProvider<>)) .ImplementedBy(typeof(CacheProvider<>)) .LifestyleTransient());   container.Register( Component.For<ISqlCacheDependency>() .ImplementedBy<AspNetSqlCacheDependency>() .LifestyleTransient());   container.AddFacility<TypedFactoryFacility>();   container.Register( Component.For<ICacheDependencyFactory>() .AsFactory()); } } }   Configuring the ASP.NET SQL Cache Dependency There are a couple of configuration steps required to enable SQL Cache Dependency for the application and database. From the Visual Studio Command Prompt, the following commands should be used to enable the Cache Polling of the relevant database tables: aspnet_regsql -S <servername> -E -d <databasename> –ed aspnet_regsql -S <servername> -E -d CacheSample –et –t <tablename>   (The –t option should be repeated for each table that is to be made available for cache dependencies). Finally the SQL Cache Polling needs to be enabled by adding the following configuration to the <system.web> section of web.config: <caching> <sqlCacheDependency pollTime="10000" enabled="true"> <databases> <add name="BloggingContext" connectionStringName="BloggingContext"/> </databases> </sqlCacheDependency> </caching>   (obviously the name and connection string name should be altered as required). Using a SQL Cache Dependency Now all the coding is complete. To specify a SQL Cache Dependency, I can modify my BlogRepositoryWithCaching decorator class (see the earlier post) as follows: public IList<Blog> GetAll() { var sqlCacheDependency = cacheProvider.CreateCacheDependency<ISqlCacheDependency>() .Initialise("BloggingContext", "Blogs");   ICacheDependency[] cacheDependencies = new ICacheDependency[] { sqlCacheDependency };   string key = string.Format("CacheDiSample.DataAccess.GetAll");   return cacheProvider.Fetch(key, () => { return parentBlogRepository.GetAll(); }, null, null, cacheDependencies) .ToList(); }   This will add a dependency of the “Blogs” table in the database. The data will remain in the cache until the contents of this table change, then the cache item will be invalidated, and the next call to the GetAll() repository method will be routed to the parent repository to refresh the data from the database.

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