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  • Is prefixing Windows Forms control names with their type OK?

    - by name
    I have seen many responses that say that prefixing variables with their type is bad, since C# is statically typed and we have Intellisense, but I find that prefixing the names of the controls is useful because I don't need to remember the name of the controls or switch to the designer frequently. For example: btnLoad // Button tbFilePath // TextBox tvFileSystem // TreeView Is this considered bad? If it is, what's the alternative?

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  • Why can't your switch statement data type be long Java?

    - by Fostah
    Here's an excerpt from Sun's Java tutorials: A switch works with the byte, short, char, and int primitive data types. It also works with enumerated types (discussed in Classes and Inheritance) and a few special classes that "wrap" certain primitive types: Character, Byte, Short, and Integer (discussed in Simple Data Objects ). There must be a good reason why the long primitive data type is not allowed. Anyone know what it is?

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  • How can I check the network connection type using the Windows API?

    - by Jufkey
    How can I programmatically retrieve the current connection type (eg. LAN or Direct connection)? InternetGetConnectedState() isn't very reliable. For instance, I'm connected to a wireless network, but ConTypeRet is 18, which is INTERNET_CONNECTION_LAN & INTERNET_RAS_INSTALLED. Isn't there any way to make sure that ConTypeRet is either INTERNET_CONNECTION_LAN or INTERNET_CONNECTION_MODEM?

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  • How to use another type of EditingControl in a single .NET 3.5 DataGridView column ?

    - by too
    Is this possible to have two (or more) different kinds of cells to be displayed interchangeably in single column of C# .Net 3.5 WinForms DataGridView? I know one column has specified single EditingControl type, yet I think grid is flexible enough to do some tricks, I may think of only: Adding as many invisible columns to grid as required types of cells and on CellBeginEdit somehow exchange current cell with other column's cell Creating custom column and custom cell with possibility of changing EditingControl for single cell Which approach is better, is there any other solution, are there any examples ?

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  • How to insert item which type is QString to a ComboBox in Qt?

    - by Hanny
    I have an item which type is QString: for example: QString name="Name" the question is: How can I put this name variable into a combobox? I've read the Qt 4.6.2 docs but still cant figure out how to do that. Please dont refer me back to that Qt 4.6.2 docs again.. Please help me ASAP!! this is really urgent! thank you very much!! :)

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  • How can I define a constructor in an open generic type?

    - by Cort
    I am trying to create on open generic type that has a constructor to be used by derived types, but I either don't know how to do it or it is not possible -- not sure which. public struct DataType<T> : IDataType { private T myValue; private TypeState myState; private DataType<T>(T initialValue, TypeState state) { myValue = initialValue; myState = state; } } Any help much appreciated! Cort

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  • Haskell: list of elements with class restriction

    - by user1760586
    here's my question: this works perfectly: type Asdf = [Integer] type ListOfAsdf = [Asdf] Now I want to do the same but with the Integral class restriction: type Asdf2 a = (Integral a) => [a] type ListOfAsdf2 = (Integral a) => [Asdf2 a] I got this error: Illegal polymorphic or qualified type: Asdf2 a Perhaps you intended to use -XImpredicativeTypes In the type synonym declaration for `ListOfAsdf2' I have tried a lot of things but I am still not able to create a type with a class restriction as described above. Thanks in advance!!! =) Dak

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  • Select Elements in nested Divs using JQuery

    - by PIKP
    I have the following html markup inside a Div named item and I want to select all the elements (inside nested divs) and clear the values. As shown in following given Jquery I have managed to access elements in each Div by using.children().each(). But the the problem is .children().each()goes one level down at a time from the parent div, so I have repeated the same code block with multiple .children() to access the elements inside nested Divs, can anyone suggest me a method to do this without repeating the code for N number of nested divs . html markup <div class="item"> <input type="hidden" value="1234" name="testVal"> <div class="form-group" id="c1"> <div class="controls "> <input type="text" value="Results" name="s1" maxlength="255" id="id2"> </div> </div> <div class="form-group" id="id4"> <input type="text" value="Results" name="s12" maxlength="255" id="id225"> <div class="form-group" id="id41"> <input type="text" value="Results" name="s12" maxlength="255" id="5"> <div class="form-group" id="id42"> <input type="text" value="Results" name="s12" maxlength="255" id="5"> <div class="form-group" id="id43"> <input type="text" value="Results" name="s12" maxlength="255" id="id224"> </div> </div> </div> </div> </div> My Qjuery script var row = $(".item:first").clone(false).get(0); $(row).children().each(function () { updateElementIndex(this, prefix, formCount); if ($(this).attr('type') == 'text') { $(this).val(''); } if ($(this).attr('type') == 'hidden' && ($(this).attr('name') != 'csrfmiddlewaretoken')) { $(this).val(''); } if ($(this).attr('type') == 'file') { $(this).val(''); } if ($(this).attr('type') == 'checkbox') { $(this).attr('checked', false); } $(this).remove('a'); }); // Relabel or rename all the relevant bits $(row).children().children().each(function () { updateElementIndex(this, prefix, formCount) if ($(this).attr('type') == 'text') { $(this).val(''); } if ($(this).attr('type') == 'hidden' && ($(this).attr('name') != 'csrfmiddlewaretoken')) { $(this).val(''); } if ($(this).attr('type') == 'file') { $(this).val(''); } if ($(this).attr('type') == 'checkbox') { $(this).attr('checked', false); } $(this).remove('a'); });

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  • Restrict type of method parameter with two or more class names?

    - by Kirzilla
    Hello, We can restrict type of method parameters; for example, we should say that function parameter should be an instance of object described in class with name "Some Class". function some_function(Some_Class $object) { } Is there any php native posibilities to restrict method parameter with two or more classes? For examle, "Some Class" or "Some Class2" or "Some Class3". Or maybe there is any way to restrict method parameter with classes which implements interface with name "Some_Interface"? Thank you.

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  • Android which type of feed is faster for rendering?

    - by ppshein
    Currently, I've developed android news application for my client. In this project, I've used JSON feed for content sync but I feel rendering JSON feed in android is a bit slow. Perhaps, due to my coding or something else. Now want to try XML feed instead of JSON. Thus please let me know which type of feed (between XML and JSon.. but let me know any good feed any other else) is faster for rendering in Android?

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  • How can i filter the files based on type?

    - by user369218
    I need to list out the names of the files based on given type.Is there any tool to do that or is there any source code so that i can get the list of the files with given extension. example:If ".txt" is given then the output must contain list of all the text files in a specific directory.

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  • Handling Trailing Delimiters in HL7 Messages

    - by Thomas Canter
    Applies to: BizTalk Server 2006 with the HL7 1.3 Accelerator Outline of the problem Trailing Delimiters are empty values at the end of an object in a HL7 ER7 formatted message. Examples: Empty Field NTE|P| NTE|P|| Empty component ORC|1|725^ Empty Subcomponent ORC|1|||||27& Empty repeat OBR|1||||||||027~ Trailing delimiters indicate the following object exists and is empty, which is quite different from null, null is an explicit value indicated by a pair of double quotes -> "". The BizTalk HL7 Accelerator by default does not allow trailing delimiters. There are three methods to allow trailing delimiters. NOTE: All Schemas always allow trailing delimiters in the MSH Segment Using party identifiers MSH3.1 – Receive/inbound processing, using this value as a party allows you to configure the system to allow inbound trailing delimiters. MSH5.1 – Send/outbound processing, using this value as a party allows you to configure the system to allow outbound trailing delimiters. Generally, if you allow inbound trailing delimiters, unless you are willing to programmatically remove all trailing delimiters, then you need to configure the send to allow trailing delimiters. Add the appropriate parties to the BizTalk Parties list from these two fields in your message stream. Open the BizTalk HL7 Configuration tool and for each party check the "Allow trailing delimiters (separators)" check box on the Validation tab. Disadvantage – Each MSH3.1 and MSH5.1 value must be represented in the parties list and configured. Advantage – granular control over system behavior for each inbound/outbound system. Using instance properties of a pipeline used in a send port or receive location. Open the BizTalk Server Administration console locate the send port or receive location that contains the BTAHL72XReceivePipeline or BTAHL72XSendPipeline pipeline. Open the properties To the right of the pipeline selected locate the […] ellipses button In the property list, locate the "TrailingDelimiterAllowed" property and set it to True. Advantage – All messages through a particular Send Port or Receive Location will allow trailing delimiters. Disadvantage – Must configure each Send Port or Receive Location. No granular control over which remote parties will send or receive messages with trailing delimiters. Using a custom pipeline that uses a pre-configured BTA HL7 Pipeline component. Use Visual Studio to construct a custom receive and send pipeline using the appropriate assembler or dissasembler. Set the component property to "TrailingDelimitersAllowed" to True Compile and deploy the custom pipeline Use the custom pipeline instead of the standard pipeline for all HL7 message processing Advantage – All messages using the custom pipeline will automatically allow trailing delimiters. Disadvantage – Requires custom coding and development to create and deploy the custom pipeline. No granular control over which remote parties will send or receive messages with trailing delimiters. What does a Trailing Delimiter do to the XML Schema? Allowing trailing delimiters does not have the impact often expected in the actual XML Schema.The Schema reproduces the message with no data loss.Thus, the message when represented in XML must contain the extra fields, in order to reproduce the outbound message.Thus, a trialing delimiter results in an empty XML field.Trailing Delmiters are not stripped from the inbound message. Example:<PID_21>44172</PID_21><PID_21>9257</PID_21> -> the original maximum number of repeats<PID_21></PID_21> -> The empty repeated field Allowing trailing delimiters not remove the trailing delimiters from the message, it simply suppresses the check that will cause the message to fail parse with trailing delimiters. When can you not fix the problem by enabling trailing delimiters Each object in a message must have a location in the target BTAHL7 schema for its content to reside.If you have more objects in the message than are contained at that location, then enabling trailing delimiters will not resolve the problem. The schema must be extended to accommodate the empty message content.Examples: Extra Field NTE|P||||Only 4 fields in NTE Segment, the 4th field exists, but is empty. Extra component PID|1|1523|47^^^^^^^Only 5 components in a CX data type, the 5th component exists, but is empty Extra subcomponent ORC|1|||||27&&Only 2 subcomponents in a CQ data type, the 3rd subcomponent is empty, but exists. Extra Repeat PID|1||||||||||||||||||||4419~5217~Only 2 repeats allowed for the field "Mother's identifier", the repeat is empty, but exists. In each of these cases, you must locate the failing object and extend the type to allow an additional object of that type. FieldAdd a field of ST to the end of the segment with a suitable name in the segments_nnn.xsd Component Create a new Custom CX data type (i.e. CX_XtraComp) in the datatypes_nnn.xsd and add a new component to the custom CX data type. Update the field in the segments_nnn.xsd file to use the custom data type instead of the standard datatype. Subcomponent Create a new Custom CQ data type that accepts an additional TS value at the end of the data type. Create a custom TQ data type that uses the new custom CQ data type as the first subcomponent. Modify the ORC segment to use the new CQ data type at ORC.7 instead of the standard CQ data type. RepeatModify the Field definition for PID.21 in the segments_nnn.xsd to allow more repeats in the field.

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  • HTML5 and Visual Studio 2010

    - by Harish Ranganathan
    All of us work with Visual Studio (or the free Visual Web Developer Express Edition) for developing web applications targeting ASP.NET / ASP.NET MVC or Silverlight etc.,  Over the years, Visual Studio has grown to a great extent.  From being a simple limited functionality tool in VS.NET 2002 to the multi-faceted, MEF driven Visual Studio 2010, it has come a long way.  And as much as Visual Studio supports rapid web development by generating HTML mark up, it also added intellisense for some of the HTML specifications that one has otherwise monotonously type every time.  Ex.- In Visual Studio 2010, one can just type the angular bracket “<” and then the first keyword “h” or “x” for html or xhtml respectively and then press tab twice and it would render the entire markup required for XHTML or HTML 1.0/1.1 strict/transitional and the fully qualified W3C URL. The same holds good for specifying HTML type declaration.  Now, the difference between HTML and XHTML has been discussed in detail already, though, if you are interested to know, you can read it from http://www.w3schools.com/xhtml/xhtml_html.asp But, the industry trend or the buzz around is HTML5.  With browsers like IE9 Beta, Google Chrome, Firefox 4 etc., supporting HTML5 standards big time, everyone wants to start developing HTML5 based websites. VS developers (like me) often get the question around when would VS start supporting HTML5.  VS 2010 was released last year and HTML5 is still specifications under development.  Clearly, with the timelines we started developing Visual Studio (way back in 2008), HTML5 specs were almost non-existent.  Even today, the HTML5 body recommends not to fully depend on the entire mark up set as they are still under development specs and might change in the future. However, with Visual Studio 2010 SP1 beta, there is quite a bit of support for HTML5 based web development.  In fact, one of my colleagues pointed out that SP1 beta’s major enhancement is its ability to support HTML5 tags and even add server mode to them. Lets look at the existing validation schema available in Visual Studio (Tools – Options – Validation) This is before installing Visual Studio 2010 SP1 Beta.  Clearly, the validation options are restricted to HTML 4.01 and XHTML 1.1 transitional and below. Also, lets consider using some of the new HTML5 input type elements.  (I found out this, just today from my friend, also an, ASP.NET team member) <input type=”email”> is one of the new input type elements according to the HTML5 specification.  Now, this works well if you type it as is  in Visual Studio and the page renders without any issue (since the default behaviour is, if there is an “undefined” type specified to input tag, it would fall back on the default mode, which is text. The moment you add <input type=”email” runat=”server” >, you get an error Naturally you don’t get intellisense support as well for these new tags.  Once you install Visual Studio 2010 Service Pack 1 Beta from here (it takes a while so you need to be patient for the installation to complete), you will start getting additional Validation templates for HTML5, as below:- Once you set this, you can start using HTML5 elements in your web page without getting errors/warnings.  Look at the screen shot below, for the new “video” tag which is showing up in intellisense (video is a part of the new HTML5 specifications)     note that, you still need to hook up the <!DOCTYPE html /> on the top manually as it doesn’t change automatically  (from the default XHTML 1.0 strict) when you create a new page. Also, the new input type tags in HTML5 are also supported One, can also use the <asp:TextBox type=”email” which would in turn generate the <input type=”email”> markup when the page is rendered.  In fact, as of SP1 beta, this is the only way to put the new input type tags with the runat=”server” attribute (otherwise you will get the parser error mentioned above.  This issue would be fixed by the final release of SP1 beta) Going further, there may be more support for having server tags for some of the common HTML5 elements, but this is work in progress currently. So, other than not having runat=”server” support for the new HTML5  input tags, you can pretty much build and target HTML5 websites with Visual Studio 2010 SP1 Beta, today.  For those who are running Visual Studio 2008, you also have the “HTML5 intellisense for Visual Studio 2010 and 2008” available for download, from http://visualstudiogallery.msdn.microsoft.com/d771cbc8-d60a-40b0-a1d8-f19fc393127d/ Note that, if you are running Visual Studio 2010, the recommended approach is to install the SP1 beta which would be the way forward for HTML5 support in Visual Studio. Of course, you need to test these on a browser supporting HTML5 such as IE9 Beta or Chrome or FireFox 4.  You can download IE9 Beta from here You can also follow the Visual Web Developer Team Blog for more updates on the stuff they are building. Cheers !!!

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  • Using Event Driven Programming in games, when is it beneficial?

    - by Arthur Wulf White
    I am learning ActionScript 3 and I see the Event flow adheres to the W3C recommendations. From what I learned events can only be captured by the dispatcher unless, the listener capturing the event is a DisplayObject on stage and a parent of the object firing the event. You can capture the events in the capture(before) or bubbling(after) phase depending on Listner and Event setup you use. Does this system lend itself well for game programming? When is this system useful? Could you give an example of a case where using events is a lot better than going without them? Are they somehow better for performance in games? Please do not mention events you must use to get a game running, like Event.ENTER_FRAME Or events that are required to get input from the user like, KeyboardEvent.KEY_DOWN and MouseEvent.CLICK. I am asking if there is any use in firing events that have nothing to do with user input, frame rendering and the likes(that are necessary). I am referring to cases where objects are communicating. Is this used to avoid storing a collection of objects that are on the stage? Thanks Here is some code I wrote as an example of event behavior in ActionScript 3, enjoy. package regression { import flash.display.Shape; import flash.display.Sprite; import flash.events.Event; import flash.events.EventDispatcher; import flash.events.KeyboardEvent; import flash.events.MouseEvent; import flash.events.EventPhase; /** * ... * @author ... */ public class Check_event_listening_1 extends Sprite { public const EVENT_DANCE : String = "dance"; public const EVENT_PLAY : String = "play"; public const EVENT_YELL : String = "yell"; private var baby : Shape = new Shape(); private var mom : Sprite = new Sprite(); private var stranger : EventDispatcher = new EventDispatcher(); public function Check_event_listening_1() { if (stage) init(); else addEventListener(Event.ADDED_TO_STAGE, init); } private function init(e:Event = null):void { trace("test begun"); addChild(mom); mom.addChild(baby); stage.addEventListener(EVENT_YELL, onEvent); this.addEventListener(EVENT_YELL, onEvent); mom.addEventListener(EVENT_YELL, onEvent); baby.addEventListener(EVENT_YELL, onEvent); stranger.addEventListener(EVENT_YELL, onEvent); trace("\nTest1 - Stranger yells with no bubbling"); stranger.dispatchEvent(new Event(EVENT_YELL, false)); trace("\nTest2 - Stranger yells with bubbling"); stranger.dispatchEvent(new Event(EVENT_YELL, true)); stage.addEventListener(EVENT_PLAY, onEvent); this.addEventListener(EVENT_PLAY, onEvent); mom.addEventListener(EVENT_PLAY, onEvent); baby.addEventListener(EVENT_PLAY, onEvent); stranger.addEventListener(EVENT_PLAY, onEvent); trace("\nTest3 - baby plays with no bubbling"); baby.dispatchEvent(new Event(EVENT_PLAY, false)); trace("\nTest4 - baby plays with bubbling"); baby.dispatchEvent(new Event(EVENT_PLAY, true)); trace("\nTest5 - baby plays with bubbling but is not a child of mom"); mom.removeChild(baby); baby.dispatchEvent(new Event(EVENT_PLAY, true)); mom.addChild(baby); stage.addEventListener(EVENT_DANCE, onEvent, true); this.addEventListener(EVENT_DANCE, onEvent, true); mom.addEventListener(EVENT_DANCE, onEvent, true); baby.addEventListener(EVENT_DANCE, onEvent); trace("\nTest6 - Mom dances without bubbling - everyone is listening during capture phase(not target and bubble phase)"); mom.dispatchEvent(new Event(EVENT_DANCE, false)); trace("\nTest7 - Mom dances with bubbling - everyone is listening during capture phase(not target and bubble phase)"); mom.dispatchEvent(new Event(EVENT_DANCE, true)); } private function onEvent(e : Event):void { trace("Event was captured"); trace("\nTYPE : ", e.type, "\nTARGET : ", objToName(e.target), "\nCURRENT TARGET : ", objToName(e.currentTarget), "\nPHASE : ", phaseToString(e.eventPhase)); } private function phaseToString(phase : int):String { switch(phase) { case EventPhase.AT_TARGET : return "TARGET"; case EventPhase.BUBBLING_PHASE : return "BUBBLING"; case EventPhase.CAPTURING_PHASE : return "CAPTURE"; default: return "UNKNOWN"; } } private function objToName(obj : Object):String { if (obj == stage) return "STAGE"; else if (obj == this) return "MAIN"; else if (obj == mom) return "Mom"; else if (obj == baby) return "Baby"; else if (obj == stranger) return "Stranger"; else return "Unknown" } } } /*result : test begun Test1 - Stranger yells with no bubbling Event was captured TYPE : yell TARGET : Stranger CURRENT TARGET : Stranger PHASE : TARGET Test2 - Stranger yells with bubbling Event was captured TYPE : yell TARGET : Stranger CURRENT TARGET : Stranger PHASE : TARGET Test3 - baby plays with no bubbling Event was captured TYPE : play TARGET : Baby CURRENT TARGET : Baby PHASE : TARGET Test4 - baby plays with bubbling Event was captured TYPE : play TARGET : Baby CURRENT TARGET : Baby PHASE : TARGET Event was captured TYPE : play TARGET : Baby CURRENT TARGET : Mom PHASE : BUBBLING Event was captured TYPE : play TARGET : Baby CURRENT TARGET : MAIN PHASE : BUBBLING Event was captured TYPE : play TARGET : Baby CURRENT TARGET : STAGE PHASE : BUBBLING Test5 - baby plays with bubbling but is not a child of mom Event was captured TYPE : play TARGET : Baby CURRENT TARGET : Baby PHASE : TARGET Test6 - Mom dances without bubbling - everyone is listening during capture phase(not target and bubble phase) Event was captured TYPE : dance TARGET : Mom CURRENT TARGET : STAGE PHASE : CAPTURE Event was captured TYPE : dance TARGET : Mom CURRENT TARGET : MAIN PHASE : CAPTURE Test7 - Mom dances with bubbling - everyone is listening during capture phase(not target and bubble phase) Event was captured TYPE : dance TARGET : Mom CURRENT TARGET : STAGE PHASE : CAPTURE Event was captured TYPE : dance TARGET : Mom CURRENT TARGET : MAIN PHASE : CAPTURE */

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  • Introduction to the ASP.NET Web API

    - by Stephen.Walther
    I am a huge fan of Ajax. If you want to create a great experience for the users of your website – regardless of whether you are building an ASP.NET MVC or an ASP.NET Web Forms site — then you need to use Ajax. Otherwise, you are just being cruel to your customers. We use Ajax extensively in several of the ASP.NET applications that my company, Superexpert.com, builds. We expose data from the server as JSON and use jQuery to retrieve and update that data from the browser. One challenge, when building an ASP.NET website, is deciding on which technology to use to expose JSON data from the server. For example, how do you expose a list of products from the server as JSON so you can retrieve the list of products with jQuery? You have a number of options (too many options) including ASMX Web services, WCF Web Services, ASHX Generic Handlers, WCF Data Services, and MVC controller actions. Fortunately, the world has just been simplified. With the release of ASP.NET 4 Beta, Microsoft has introduced a new technology for exposing JSON from the server named the ASP.NET Web API. You can use the ASP.NET Web API with both ASP.NET MVC and ASP.NET Web Forms applications. The goal of this blog post is to provide you with a brief overview of the features of the new ASP.NET Web API. You learn how to use the ASP.NET Web API to retrieve, insert, update, and delete database records with jQuery. We also discuss how you can perform form validation when using the Web API and use OData when using the Web API. Creating an ASP.NET Web API Controller The ASP.NET Web API exposes JSON data through a new type of controller called an API controller. You can add an API controller to an existing ASP.NET MVC 4 project through the standard Add Controller dialog box. Right-click your Controllers folder and select Add, Controller. In the dialog box, name your controller MovieController and select the Empty API controller template: A brand new API controller looks like this: using System; using System.Collections.Generic; using System.Linq; using System.Net.Http; using System.Web.Http; namespace MyWebAPIApp.Controllers { public class MovieController : ApiController { } } An API controller, unlike a standard MVC controller, derives from the base ApiController class instead of the base Controller class. Using jQuery to Retrieve, Insert, Update, and Delete Data Let’s create an Ajaxified Movie Database application. We’ll retrieve, insert, update, and delete movies using jQuery with the MovieController which we just created. Our Movie model class looks like this: namespace MyWebAPIApp.Models { public class Movie { public int Id { get; set; } public string Title { get; set; } public string Director { get; set; } } } Our application will consist of a single HTML page named Movies.html. We’ll place all of our jQuery code in the Movies.html page. Getting a Single Record with the ASP.NET Web API To support retrieving a single movie from the server, we need to add a Get method to our API controller: using System; using System.Collections.Generic; using System.Linq; using System.Net; using System.Net.Http; using System.Web.Http; using MyWebAPIApp.Models; namespace MyWebAPIApp.Controllers { public class MovieController : ApiController { public Movie GetMovie(int id) { // Return movie by id if (id == 1) { return new Movie { Id = 1, Title = "Star Wars", Director = "Lucas" }; } // Otherwise, movie was not found throw new HttpResponseException(HttpStatusCode.NotFound); } } } In the code above, the GetMovie() method accepts the Id of a movie. If the Id has the value 1 then the method returns the movie Star Wars. Otherwise, the method throws an exception and returns 404 Not Found HTTP status code. After building your project, you can invoke the MovieController.GetMovie() method by entering the following URL in your web browser address bar: http://localhost:[port]/api/movie/1 (You’ll need to enter the correct randomly generated port). In the URL api/movie/1, the first “api” segment indicates that this is a Web API route. The “movie” segment indicates that the MovieController should be invoked. You do not specify the name of the action. Instead, the HTTP method used to make the request – GET, POST, PUT, DELETE — is used to identify the action to invoke. The ASP.NET Web API uses different routing conventions than normal ASP.NET MVC controllers. When you make an HTTP GET request then any API controller method with a name that starts with “GET” is invoked. So, we could have called our API controller action GetPopcorn() instead of GetMovie() and it would still be invoked by the URL api/movie/1. The default route for the Web API is defined in the Global.asax file and it looks like this: routes.MapHttpRoute( name: "DefaultApi", routeTemplate: "api/{controller}/{id}", defaults: new { id = RouteParameter.Optional } ); We can invoke our GetMovie() controller action with the jQuery code in the following HTML page: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Get Movie</title> </head> <body> <div> Title: <span id="title"></span> </div> <div> Director: <span id="director"></span> </div> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> getMovie(1, function (movie) { $("#title").html(movie.Title); $("#director").html(movie.Director); }); function getMovie(id, callback) { $.ajax({ url: "/api/Movie", data: { id: id }, type: "GET", contentType: "application/json;charset=utf-8", statusCode: { 200: function (movie) { callback(movie); }, 404: function () { alert("Not Found!"); } } }); } </script> </body> </html> In the code above, the jQuery $.ajax() method is used to invoke the GetMovie() method. Notice that the Ajax call handles two HTTP response codes. When the GetMove() method successfully returns a movie, the method returns a 200 status code. In that case, the details of the movie are displayed in the HTML page. Otherwise, if the movie is not found, the GetMovie() method returns a 404 status code. In that case, the page simply displays an alert box indicating that the movie was not found (hopefully, you would implement something more graceful in an actual application). You can use your browser’s Developer Tools to see what is going on in the background when you open the HTML page (hit F12 in the most recent version of most browsers). For example, you can use the Network tab in Google Chrome to see the Ajax request which invokes the GetMovie() method: Getting a Set of Records with the ASP.NET Web API Let’s modify our Movie API controller so that it returns a collection of movies. The following Movie controller has a new ListMovies() method which returns a (hard-coded) collection of movies: using System; using System.Collections.Generic; using System.Linq; using System.Net; using System.Net.Http; using System.Web.Http; using MyWebAPIApp.Models; namespace MyWebAPIApp.Controllers { public class MovieController : ApiController { public IEnumerable<Movie> ListMovies() { return new List<Movie> { new Movie {Id=1, Title="Star Wars", Director="Lucas"}, new Movie {Id=1, Title="King Kong", Director="Jackson"}, new Movie {Id=1, Title="Memento", Director="Nolan"} }; } } } Because we named our action ListMovies(), the default Web API route will never match it. Therefore, we need to add the following custom route to our Global.asax file (at the top of the RegisterRoutes() method): routes.MapHttpRoute( name: "ActionApi", routeTemplate: "api/{controller}/{action}/{id}", defaults: new { id = RouteParameter.Optional } ); This route enables us to invoke the ListMovies() method with the URL /api/movie/listmovies. Now that we have exposed our collection of movies from the server, we can retrieve and display the list of movies using jQuery in our HTML page: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>List Movies</title> </head> <body> <div id="movies"></div> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> listMovies(function (movies) { var strMovies=""; $.each(movies, function (index, movie) { strMovies += "<div>" + movie.Title + "</div>"; }); $("#movies").html(strMovies); }); function listMovies(callback) { $.ajax({ url: "/api/Movie/ListMovies", data: {}, type: "GET", contentType: "application/json;charset=utf-8", }).then(function(movies){ callback(movies); }); } </script> </body> </html>     Inserting a Record with the ASP.NET Web API Now let’s modify our Movie API controller so it supports creating new records: public HttpResponseMessage<Movie> PostMovie(Movie movieToCreate) { // Add movieToCreate to the database and update primary key movieToCreate.Id = 23; // Build a response that contains the location of the new movie var response = new HttpResponseMessage<Movie>(movieToCreate, HttpStatusCode.Created); var relativePath = "/api/movie/" + movieToCreate.Id; response.Headers.Location = new Uri(Request.RequestUri, relativePath); return response; } The PostMovie() method in the code above accepts a movieToCreate parameter. We don’t actually store the new movie anywhere. In real life, you will want to call a service method to store the new movie in a database. When you create a new resource, such as a new movie, you should return the location of the new resource. In the code above, the URL where the new movie can be retrieved is assigned to the Location header returned in the PostMovie() response. Because the name of our method starts with “Post”, we don’t need to create a custom route. The PostMovie() method can be invoked with the URL /Movie/PostMovie – just as long as the method is invoked within the context of a HTTP POST request. The following HTML page invokes the PostMovie() method. <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Create Movie</title> </head> <body> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> var movieToCreate = { title: "The Hobbit", director: "Jackson" }; createMovie(movieToCreate, function (newMovie) { alert("New movie created with an Id of " + newMovie.Id); }); function createMovie(movieToCreate, callback) { $.ajax({ url: "/api/Movie", data: JSON.stringify( movieToCreate ), type: "POST", contentType: "application/json;charset=utf-8", statusCode: { 201: function (newMovie) { callback(newMovie); } } }); } </script> </body> </html> This page creates a new movie (the Hobbit) by calling the createMovie() method. The page simply displays the Id of the new movie: The HTTP Post operation is performed with the following call to the jQuery $.ajax() method: $.ajax({ url: "/api/Movie", data: JSON.stringify( movieToCreate ), type: "POST", contentType: "application/json;charset=utf-8", statusCode: { 201: function (newMovie) { callback(newMovie); } } }); Notice that the type of Ajax request is a POST request. This is required to match the PostMovie() method. Notice, furthermore, that the new movie is converted into JSON using JSON.stringify(). The JSON.stringify() method takes a JavaScript object and converts it into a JSON string. Finally, notice that success is represented with a 201 status code. The HttpStatusCode.Created value returned from the PostMovie() method returns a 201 status code. Updating a Record with the ASP.NET Web API Here’s how we can modify the Movie API controller to support updating an existing record. In this case, we need to create a PUT method to handle an HTTP PUT request: public void PutMovie(Movie movieToUpdate) { if (movieToUpdate.Id == 1) { // Update the movie in the database return; } // If you can't find the movie to update throw new HttpResponseException(HttpStatusCode.NotFound); } Unlike our PostMovie() method, the PutMovie() method does not return a result. The action either updates the database or, if the movie cannot be found, returns an HTTP Status code of 404. The following HTML page illustrates how you can invoke the PutMovie() method: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Put Movie</title> </head> <body> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> var movieToUpdate = { id: 1, title: "The Hobbit", director: "Jackson" }; updateMovie(movieToUpdate, function () { alert("Movie updated!"); }); function updateMovie(movieToUpdate, callback) { $.ajax({ url: "/api/Movie", data: JSON.stringify(movieToUpdate), type: "PUT", contentType: "application/json;charset=utf-8", statusCode: { 200: function () { callback(); }, 404: function () { alert("Movie not found!"); } } }); } </script> </body> </html> Deleting a Record with the ASP.NET Web API Here’s the code for deleting a movie: public HttpResponseMessage DeleteMovie(int id) { // Delete the movie from the database // Return status code return new HttpResponseMessage(HttpStatusCode.NoContent); } This method simply deletes the movie (well, not really, but pretend that it does) and returns a No Content status code (204). The following page illustrates how you can invoke the DeleteMovie() action: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Delete Movie</title> </head> <body> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> deleteMovie(1, function () { alert("Movie deleted!"); }); function deleteMovie(id, callback) { $.ajax({ url: "/api/Movie", data: JSON.stringify({id:id}), type: "DELETE", contentType: "application/json;charset=utf-8", statusCode: { 204: function () { callback(); } } }); } </script> </body> </html> Performing Validation How do you perform form validation when using the ASP.NET Web API? Because validation in ASP.NET MVC is driven by the Default Model Binder, and because the Web API uses the Default Model Binder, you get validation for free. Let’s modify our Movie class so it includes some of the standard validation attributes: using System.ComponentModel.DataAnnotations; namespace MyWebAPIApp.Models { public class Movie { public int Id { get; set; } [Required(ErrorMessage="Title is required!")] [StringLength(5, ErrorMessage="Title cannot be more than 5 characters!")] public string Title { get; set; } [Required(ErrorMessage="Director is required!")] public string Director { get; set; } } } In the code above, the Required validation attribute is used to make both the Title and Director properties required. The StringLength attribute is used to require the length of the movie title to be no more than 5 characters. Now let’s modify our PostMovie() action to validate a movie before adding the movie to the database: public HttpResponseMessage PostMovie(Movie movieToCreate) { // Validate movie if (!ModelState.IsValid) { var errors = new JsonArray(); foreach (var prop in ModelState.Values) { if (prop.Errors.Any()) { errors.Add(prop.Errors.First().ErrorMessage); } } return new HttpResponseMessage<JsonValue>(errors, HttpStatusCode.BadRequest); } // Add movieToCreate to the database and update primary key movieToCreate.Id = 23; // Build a response that contains the location of the new movie var response = new HttpResponseMessage<Movie>(movieToCreate, HttpStatusCode.Created); var relativePath = "/api/movie/" + movieToCreate.Id; response.Headers.Location = new Uri(Request.RequestUri, relativePath); return response; } If ModelState.IsValid has the value false then the errors in model state are copied to a new JSON array. Each property – such as the Title and Director property — can have multiple errors. In the code above, only the first error message is copied over. The JSON array is returned with a Bad Request status code (400 status code). The following HTML page illustrates how you can invoke our modified PostMovie() action and display any error messages: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Create Movie</title> </head> <body> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> var movieToCreate = { title: "The Hobbit", director: "" }; createMovie(movieToCreate, function (newMovie) { alert("New movie created with an Id of " + newMovie.Id); }, function (errors) { var strErrors = ""; $.each(errors, function(index, err) { strErrors += "*" + err + "\n"; }); alert(strErrors); } ); function createMovie(movieToCreate, success, fail) { $.ajax({ url: "/api/Movie", data: JSON.stringify(movieToCreate), type: "POST", contentType: "application/json;charset=utf-8", statusCode: { 201: function (newMovie) { success(newMovie); }, 400: function (xhr) { var errors = JSON.parse(xhr.responseText); fail(errors); } } }); } </script> </body> </html> The createMovie() function performs an Ajax request and handles either a 201 or a 400 status code from the response. If a 201 status code is returned then there were no validation errors and the new movie was created. If, on the other hand, a 400 status code is returned then there was a validation error. The validation errors are retrieved from the XmlHttpRequest responseText property. The error messages are displayed in an alert: (Please don’t use JavaScript alert dialogs to display validation errors, I just did it this way out of pure laziness) This validation code in our PostMovie() method is pretty generic. There is nothing specific about this code to the PostMovie() method. In the following video, Jon Galloway demonstrates how to create a global Validation filter which can be used with any API controller action: http://www.asp.net/web-api/overview/web-api-routing-and-actions/video-custom-validation His validation filter looks like this: using System.Json; using System.Linq; using System.Net; using System.Net.Http; using System.Web.Http.Controllers; using System.Web.Http.Filters; namespace MyWebAPIApp.Filters { public class ValidationActionFilter:ActionFilterAttribute { public override void OnActionExecuting(HttpActionContext actionContext) { var modelState = actionContext.ModelState; if (!modelState.IsValid) { dynamic errors = new JsonObject(); foreach (var key in modelState.Keys) { var state = modelState[key]; if (state.Errors.Any()) { errors[key] = state.Errors.First().ErrorMessage; } } actionContext.Response = new HttpResponseMessage<JsonValue>(errors, HttpStatusCode.BadRequest); } } } } And you can register the validation filter in the Application_Start() method in the Global.asax file like this: GlobalConfiguration.Configuration.Filters.Add(new ValidationActionFilter()); After you register the Validation filter, validation error messages are returned from any API controller action method automatically when validation fails. You don’t need to add any special logic to any of your API controller actions to take advantage of the filter. Querying using OData The OData protocol is an open protocol created by Microsoft which enables you to perform queries over the web. The official website for OData is located here: http://odata.org For example, here are some of the query options which you can use with OData: · $orderby – Enables you to retrieve results in a certain order. · $top – Enables you to retrieve a certain number of results. · $skip – Enables you to skip over a certain number of results (use with $top for paging). · $filter – Enables you to filter the results returned. The ASP.NET Web API supports a subset of the OData protocol. You can use all of the query options listed above when interacting with an API controller. The only requirement is that the API controller action returns its data as IQueryable. For example, the following Movie controller has an action named GetMovies() which returns an IQueryable of movies: public IQueryable<Movie> GetMovies() { return new List<Movie> { new Movie {Id=1, Title="Star Wars", Director="Lucas"}, new Movie {Id=2, Title="King Kong", Director="Jackson"}, new Movie {Id=3, Title="Willow", Director="Lucas"}, new Movie {Id=4, Title="Shrek", Director="Smith"}, new Movie {Id=5, Title="Memento", Director="Nolan"} }.AsQueryable(); } If you enter the following URL in your browser: /api/movie?$top=2&$orderby=Title Then you will limit the movies returned to the top 2 in order of the movie Title. You will get the following results: By using the $top option in combination with the $skip option, you can enable client-side paging. For example, you can use $top and $skip to page through thousands of products, 10 products at a time. The $filter query option is very powerful. You can use this option to filter the results from a query. Here are some examples: Return every movie directed by Lucas: /api/movie?$filter=Director eq ‘Lucas’ Return every movie which has a title which starts with ‘S’: /api/movie?$filter=startswith(Title,’S') Return every movie which has an Id greater than 2: /api/movie?$filter=Id gt 2 The complete documentation for the $filter option is located here: http://www.odata.org/developers/protocols/uri-conventions#FilterSystemQueryOption Summary The goal of this blog entry was to provide you with an overview of the new ASP.NET Web API introduced with the Beta release of ASP.NET 4. In this post, I discussed how you can retrieve, insert, update, and delete data by using jQuery with the Web API. I also discussed how you can use the standard validation attributes with the Web API. You learned how to return validation error messages to the client and display the error messages using jQuery. Finally, we briefly discussed how the ASP.NET Web API supports the OData protocol. For example, you learned how to filter records returned from an API controller action by using the $filter query option. I’m excited about the new Web API. This is a feature which I expect to use with almost every ASP.NET application which I build in the future.

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  • Introduction to the ASP.NET Web API

    - by Stephen.Walther
    I am a huge fan of Ajax. If you want to create a great experience for the users of your website – regardless of whether you are building an ASP.NET MVC or an ASP.NET Web Forms site — then you need to use Ajax. Otherwise, you are just being cruel to your customers. We use Ajax extensively in several of the ASP.NET applications that my company, Superexpert.com, builds. We expose data from the server as JSON and use jQuery to retrieve and update that data from the browser. One challenge, when building an ASP.NET website, is deciding on which technology to use to expose JSON data from the server. For example, how do you expose a list of products from the server as JSON so you can retrieve the list of products with jQuery? You have a number of options (too many options) including ASMX Web services, WCF Web Services, ASHX Generic Handlers, WCF Data Services, and MVC controller actions. Fortunately, the world has just been simplified. With the release of ASP.NET 4 Beta, Microsoft has introduced a new technology for exposing JSON from the server named the ASP.NET Web API. You can use the ASP.NET Web API with both ASP.NET MVC and ASP.NET Web Forms applications. The goal of this blog post is to provide you with a brief overview of the features of the new ASP.NET Web API. You learn how to use the ASP.NET Web API to retrieve, insert, update, and delete database records with jQuery. We also discuss how you can perform form validation when using the Web API and use OData when using the Web API. Creating an ASP.NET Web API Controller The ASP.NET Web API exposes JSON data through a new type of controller called an API controller. You can add an API controller to an existing ASP.NET MVC 4 project through the standard Add Controller dialog box. Right-click your Controllers folder and select Add, Controller. In the dialog box, name your controller MovieController and select the Empty API controller template: A brand new API controller looks like this: using System; using System.Collections.Generic; using System.Linq; using System.Net.Http; using System.Web.Http; namespace MyWebAPIApp.Controllers { public class MovieController : ApiController { } } An API controller, unlike a standard MVC controller, derives from the base ApiController class instead of the base Controller class. Using jQuery to Retrieve, Insert, Update, and Delete Data Let’s create an Ajaxified Movie Database application. We’ll retrieve, insert, update, and delete movies using jQuery with the MovieController which we just created. Our Movie model class looks like this: namespace MyWebAPIApp.Models { public class Movie { public int Id { get; set; } public string Title { get; set; } public string Director { get; set; } } } Our application will consist of a single HTML page named Movies.html. We’ll place all of our jQuery code in the Movies.html page. Getting a Single Record with the ASP.NET Web API To support retrieving a single movie from the server, we need to add a Get method to our API controller: using System; using System.Collections.Generic; using System.Linq; using System.Net; using System.Net.Http; using System.Web.Http; using MyWebAPIApp.Models; namespace MyWebAPIApp.Controllers { public class MovieController : ApiController { public Movie GetMovie(int id) { // Return movie by id if (id == 1) { return new Movie { Id = 1, Title = "Star Wars", Director = "Lucas" }; } // Otherwise, movie was not found throw new HttpResponseException(HttpStatusCode.NotFound); } } } In the code above, the GetMovie() method accepts the Id of a movie. If the Id has the value 1 then the method returns the movie Star Wars. Otherwise, the method throws an exception and returns 404 Not Found HTTP status code. After building your project, you can invoke the MovieController.GetMovie() method by entering the following URL in your web browser address bar: http://localhost:[port]/api/movie/1 (You’ll need to enter the correct randomly generated port). In the URL api/movie/1, the first “api” segment indicates that this is a Web API route. The “movie” segment indicates that the MovieController should be invoked. You do not specify the name of the action. Instead, the HTTP method used to make the request – GET, POST, PUT, DELETE — is used to identify the action to invoke. The ASP.NET Web API uses different routing conventions than normal ASP.NET MVC controllers. When you make an HTTP GET request then any API controller method with a name that starts with “GET” is invoked. So, we could have called our API controller action GetPopcorn() instead of GetMovie() and it would still be invoked by the URL api/movie/1. The default route for the Web API is defined in the Global.asax file and it looks like this: routes.MapHttpRoute( name: "DefaultApi", routeTemplate: "api/{controller}/{id}", defaults: new { id = RouteParameter.Optional } ); We can invoke our GetMovie() controller action with the jQuery code in the following HTML page: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Get Movie</title> </head> <body> <div> Title: <span id="title"></span> </div> <div> Director: <span id="director"></span> </div> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> getMovie(1, function (movie) { $("#title").html(movie.Title); $("#director").html(movie.Director); }); function getMovie(id, callback) { $.ajax({ url: "/api/Movie", data: { id: id }, type: "GET", contentType: "application/json;charset=utf-8", statusCode: { 200: function (movie) { callback(movie); }, 404: function () { alert("Not Found!"); } } }); } </script> </body> </html> In the code above, the jQuery $.ajax() method is used to invoke the GetMovie() method. Notice that the Ajax call handles two HTTP response codes. When the GetMove() method successfully returns a movie, the method returns a 200 status code. In that case, the details of the movie are displayed in the HTML page. Otherwise, if the movie is not found, the GetMovie() method returns a 404 status code. In that case, the page simply displays an alert box indicating that the movie was not found (hopefully, you would implement something more graceful in an actual application). You can use your browser’s Developer Tools to see what is going on in the background when you open the HTML page (hit F12 in the most recent version of most browsers). For example, you can use the Network tab in Google Chrome to see the Ajax request which invokes the GetMovie() method: Getting a Set of Records with the ASP.NET Web API Let’s modify our Movie API controller so that it returns a collection of movies. The following Movie controller has a new ListMovies() method which returns a (hard-coded) collection of movies: using System; using System.Collections.Generic; using System.Linq; using System.Net; using System.Net.Http; using System.Web.Http; using MyWebAPIApp.Models; namespace MyWebAPIApp.Controllers { public class MovieController : ApiController { public IEnumerable<Movie> ListMovies() { return new List<Movie> { new Movie {Id=1, Title="Star Wars", Director="Lucas"}, new Movie {Id=1, Title="King Kong", Director="Jackson"}, new Movie {Id=1, Title="Memento", Director="Nolan"} }; } } } Because we named our action ListMovies(), the default Web API route will never match it. Therefore, we need to add the following custom route to our Global.asax file (at the top of the RegisterRoutes() method): routes.MapHttpRoute( name: "ActionApi", routeTemplate: "api/{controller}/{action}/{id}", defaults: new { id = RouteParameter.Optional } ); This route enables us to invoke the ListMovies() method with the URL /api/movie/listmovies. Now that we have exposed our collection of movies from the server, we can retrieve and display the list of movies using jQuery in our HTML page: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>List Movies</title> </head> <body> <div id="movies"></div> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> listMovies(function (movies) { var strMovies=""; $.each(movies, function (index, movie) { strMovies += "<div>" + movie.Title + "</div>"; }); $("#movies").html(strMovies); }); function listMovies(callback) { $.ajax({ url: "/api/Movie/ListMovies", data: {}, type: "GET", contentType: "application/json;charset=utf-8", }).then(function(movies){ callback(movies); }); } </script> </body> </html>     Inserting a Record with the ASP.NET Web API Now let’s modify our Movie API controller so it supports creating new records: public HttpResponseMessage<Movie> PostMovie(Movie movieToCreate) { // Add movieToCreate to the database and update primary key movieToCreate.Id = 23; // Build a response that contains the location of the new movie var response = new HttpResponseMessage<Movie>(movieToCreate, HttpStatusCode.Created); var relativePath = "/api/movie/" + movieToCreate.Id; response.Headers.Location = new Uri(Request.RequestUri, relativePath); return response; } The PostMovie() method in the code above accepts a movieToCreate parameter. We don’t actually store the new movie anywhere. In real life, you will want to call a service method to store the new movie in a database. When you create a new resource, such as a new movie, you should return the location of the new resource. In the code above, the URL where the new movie can be retrieved is assigned to the Location header returned in the PostMovie() response. Because the name of our method starts with “Post”, we don’t need to create a custom route. The PostMovie() method can be invoked with the URL /Movie/PostMovie – just as long as the method is invoked within the context of a HTTP POST request. The following HTML page invokes the PostMovie() method. <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Create Movie</title> </head> <body> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> var movieToCreate = { title: "The Hobbit", director: "Jackson" }; createMovie(movieToCreate, function (newMovie) { alert("New movie created with an Id of " + newMovie.Id); }); function createMovie(movieToCreate, callback) { $.ajax({ url: "/api/Movie", data: JSON.stringify( movieToCreate ), type: "POST", contentType: "application/json;charset=utf-8", statusCode: { 201: function (newMovie) { callback(newMovie); } } }); } </script> </body> </html> This page creates a new movie (the Hobbit) by calling the createMovie() method. The page simply displays the Id of the new movie: The HTTP Post operation is performed with the following call to the jQuery $.ajax() method: $.ajax({ url: "/api/Movie", data: JSON.stringify( movieToCreate ), type: "POST", contentType: "application/json;charset=utf-8", statusCode: { 201: function (newMovie) { callback(newMovie); } } }); Notice that the type of Ajax request is a POST request. This is required to match the PostMovie() method. Notice, furthermore, that the new movie is converted into JSON using JSON.stringify(). The JSON.stringify() method takes a JavaScript object and converts it into a JSON string. Finally, notice that success is represented with a 201 status code. The HttpStatusCode.Created value returned from the PostMovie() method returns a 201 status code. Updating a Record with the ASP.NET Web API Here’s how we can modify the Movie API controller to support updating an existing record. In this case, we need to create a PUT method to handle an HTTP PUT request: public void PutMovie(Movie movieToUpdate) { if (movieToUpdate.Id == 1) { // Update the movie in the database return; } // If you can't find the movie to update throw new HttpResponseException(HttpStatusCode.NotFound); } Unlike our PostMovie() method, the PutMovie() method does not return a result. The action either updates the database or, if the movie cannot be found, returns an HTTP Status code of 404. The following HTML page illustrates how you can invoke the PutMovie() method: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Put Movie</title> </head> <body> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> var movieToUpdate = { id: 1, title: "The Hobbit", director: "Jackson" }; updateMovie(movieToUpdate, function () { alert("Movie updated!"); }); function updateMovie(movieToUpdate, callback) { $.ajax({ url: "/api/Movie", data: JSON.stringify(movieToUpdate), type: "PUT", contentType: "application/json;charset=utf-8", statusCode: { 200: function () { callback(); }, 404: function () { alert("Movie not found!"); } } }); } </script> </body> </html> Deleting a Record with the ASP.NET Web API Here’s the code for deleting a movie: public HttpResponseMessage DeleteMovie(int id) { // Delete the movie from the database // Return status code return new HttpResponseMessage(HttpStatusCode.NoContent); } This method simply deletes the movie (well, not really, but pretend that it does) and returns a No Content status code (204). The following page illustrates how you can invoke the DeleteMovie() action: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Delete Movie</title> </head> <body> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> deleteMovie(1, function () { alert("Movie deleted!"); }); function deleteMovie(id, callback) { $.ajax({ url: "/api/Movie", data: JSON.stringify({id:id}), type: "DELETE", contentType: "application/json;charset=utf-8", statusCode: { 204: function () { callback(); } } }); } </script> </body> </html> Performing Validation How do you perform form validation when using the ASP.NET Web API? Because validation in ASP.NET MVC is driven by the Default Model Binder, and because the Web API uses the Default Model Binder, you get validation for free. Let’s modify our Movie class so it includes some of the standard validation attributes: using System.ComponentModel.DataAnnotations; namespace MyWebAPIApp.Models { public class Movie { public int Id { get; set; } [Required(ErrorMessage="Title is required!")] [StringLength(5, ErrorMessage="Title cannot be more than 5 characters!")] public string Title { get; set; } [Required(ErrorMessage="Director is required!")] public string Director { get; set; } } } In the code above, the Required validation attribute is used to make both the Title and Director properties required. The StringLength attribute is used to require the length of the movie title to be no more than 5 characters. Now let’s modify our PostMovie() action to validate a movie before adding the movie to the database: public HttpResponseMessage PostMovie(Movie movieToCreate) { // Validate movie if (!ModelState.IsValid) { var errors = new JsonArray(); foreach (var prop in ModelState.Values) { if (prop.Errors.Any()) { errors.Add(prop.Errors.First().ErrorMessage); } } return new HttpResponseMessage<JsonValue>(errors, HttpStatusCode.BadRequest); } // Add movieToCreate to the database and update primary key movieToCreate.Id = 23; // Build a response that contains the location of the new movie var response = new HttpResponseMessage<Movie>(movieToCreate, HttpStatusCode.Created); var relativePath = "/api/movie/" + movieToCreate.Id; response.Headers.Location = new Uri(Request.RequestUri, relativePath); return response; } If ModelState.IsValid has the value false then the errors in model state are copied to a new JSON array. Each property – such as the Title and Director property — can have multiple errors. In the code above, only the first error message is copied over. The JSON array is returned with a Bad Request status code (400 status code). The following HTML page illustrates how you can invoke our modified PostMovie() action and display any error messages: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Create Movie</title> </head> <body> <script type="text/javascript" src="Scripts/jquery-1.6.2.min.js"></script> <script type="text/javascript"> var movieToCreate = { title: "The Hobbit", director: "" }; createMovie(movieToCreate, function (newMovie) { alert("New movie created with an Id of " + newMovie.Id); }, function (errors) { var strErrors = ""; $.each(errors, function(index, err) { strErrors += "*" + err + "n"; }); alert(strErrors); } ); function createMovie(movieToCreate, success, fail) { $.ajax({ url: "/api/Movie", data: JSON.stringify(movieToCreate), type: "POST", contentType: "application/json;charset=utf-8", statusCode: { 201: function (newMovie) { success(newMovie); }, 400: function (xhr) { var errors = JSON.parse(xhr.responseText); fail(errors); } } }); } </script> </body> </html> The createMovie() function performs an Ajax request and handles either a 201 or a 400 status code from the response. If a 201 status code is returned then there were no validation errors and the new movie was created. If, on the other hand, a 400 status code is returned then there was a validation error. The validation errors are retrieved from the XmlHttpRequest responseText property. The error messages are displayed in an alert: (Please don’t use JavaScript alert dialogs to display validation errors, I just did it this way out of pure laziness) This validation code in our PostMovie() method is pretty generic. There is nothing specific about this code to the PostMovie() method. In the following video, Jon Galloway demonstrates how to create a global Validation filter which can be used with any API controller action: http://www.asp.net/web-api/overview/web-api-routing-and-actions/video-custom-validation His validation filter looks like this: using System.Json; using System.Linq; using System.Net; using System.Net.Http; using System.Web.Http.Controllers; using System.Web.Http.Filters; namespace MyWebAPIApp.Filters { public class ValidationActionFilter:ActionFilterAttribute { public override void OnActionExecuting(HttpActionContext actionContext) { var modelState = actionContext.ModelState; if (!modelState.IsValid) { dynamic errors = new JsonObject(); foreach (var key in modelState.Keys) { var state = modelState[key]; if (state.Errors.Any()) { errors[key] = state.Errors.First().ErrorMessage; } } actionContext.Response = new HttpResponseMessage<JsonValue>(errors, HttpStatusCode.BadRequest); } } } } And you can register the validation filter in the Application_Start() method in the Global.asax file like this: GlobalConfiguration.Configuration.Filters.Add(new ValidationActionFilter()); After you register the Validation filter, validation error messages are returned from any API controller action method automatically when validation fails. You don’t need to add any special logic to any of your API controller actions to take advantage of the filter. Querying using OData The OData protocol is an open protocol created by Microsoft which enables you to perform queries over the web. The official website for OData is located here: http://odata.org For example, here are some of the query options which you can use with OData: · $orderby – Enables you to retrieve results in a certain order. · $top – Enables you to retrieve a certain number of results. · $skip – Enables you to skip over a certain number of results (use with $top for paging). · $filter – Enables you to filter the results returned. The ASP.NET Web API supports a subset of the OData protocol. You can use all of the query options listed above when interacting with an API controller. The only requirement is that the API controller action returns its data as IQueryable. For example, the following Movie controller has an action named GetMovies() which returns an IQueryable of movies: public IQueryable<Movie> GetMovies() { return new List<Movie> { new Movie {Id=1, Title="Star Wars", Director="Lucas"}, new Movie {Id=2, Title="King Kong", Director="Jackson"}, new Movie {Id=3, Title="Willow", Director="Lucas"}, new Movie {Id=4, Title="Shrek", Director="Smith"}, new Movie {Id=5, Title="Memento", Director="Nolan"} }.AsQueryable(); } If you enter the following URL in your browser: /api/movie?$top=2&$orderby=Title Then you will limit the movies returned to the top 2 in order of the movie Title. You will get the following results: By using the $top option in combination with the $skip option, you can enable client-side paging. For example, you can use $top and $skip to page through thousands of products, 10 products at a time. The $filter query option is very powerful. You can use this option to filter the results from a query. Here are some examples: Return every movie directed by Lucas: /api/movie?$filter=Director eq ‘Lucas’ Return every movie which has a title which starts with ‘S’: /api/movie?$filter=startswith(Title,’S') Return every movie which has an Id greater than 2: /api/movie?$filter=Id gt 2 The complete documentation for the $filter option is located here: http://www.odata.org/developers/protocols/uri-conventions#FilterSystemQueryOption Summary The goal of this blog entry was to provide you with an overview of the new ASP.NET Web API introduced with the Beta release of ASP.NET 4. In this post, I discussed how you can retrieve, insert, update, and delete data by using jQuery with the Web API. I also discussed how you can use the standard validation attributes with the Web API. You learned how to return validation error messages to the client and display the error messages using jQuery. Finally, we briefly discussed how the ASP.NET Web API supports the OData protocol. For example, you learned how to filter records returned from an API controller action by using the $filter query option. I’m excited about the new Web API. This is a feature which I expect to use with almost every ASP.NET application which I build in the future.

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