Deserializing Json

 

With this post I’m back to my lovely OneNote screen clippings, my last few postings were done on Windows8 and I’d no OneNote installed.

So you want to Deserialize Json in .NET! (C#)

How do you go about it?

There are a few approaches, many poeple are familiar with JSon.NET and using it like this

image

or

image

Some people may have done it the hard way

image

But if you add assembly System.Net.Http.Formatting.dll you’ll get a nice little extension ReadAsAsync<T>
http://msdn.microsoft.com/en-us/library/hh836073(v=vs.108).aspx

image

Enjoy!

ASP WebApi query single entity

 

What’s wrong with this?

 

   1:  public class UsersController : RavenController
   2:  {  
   3:      public User Get(int userId)
   4:      {
   5:          this.AutoSave = false;
   6:          var user = RavenSession.Load<User>(userId);
   7:          if (user == null)
   8:             throw new HttpResponseException("Unable to find user for it " + userId);
   9:          return user;
  10:      }
  11:   
  12:      // GET /api/values
  13:      public IQueryable<User> GetAll()
  14:      {
  15:          this.AutoSave = false;
  16:          return RavenSession.Query<User>();            
  17:      }        
  18:  }

The problem is the variable name used for getting a single user the function would never be called.

E.g. if we put http://localhost:65487/api/users/1 into our browser what will happen is the GetAll gets called!

What we need to call is

   1:  public class UsersController : RavenController
   2:  {  
   3:      public User Get(int id)
   4:      {
   5:          this.AutoSave = false;
   6:          var user = RavenSession.Load<User>(id);
   7:          if (user == null)
   8:              throw new HttpResponseException("Unable to find user for it " + id);
   9:          return user;
  10:      }
  11:   
  12:      // GET /api/values
  13:      public IQueryable<User> GetAll()
  14:      {
  15:          this.AutoSave = false;
  16:          return RavenSession.Query<User>();            
  17:      }        
  18:  }

Now you see that the Get takes a variable name of “id” this is key to getting this work.

 

Note: I’m using IQuerable as this allows me to add some query parameters to my request, e.g.

$filter
A Boolean expression for whether a particular entry should be included in the feed, e.g. Categories?$filter=CategoryName eq 'Produce'. The Query Expression section describes OData expressions.

$orderby
One or more comma-separated expressions with an optional “asc” (the default) or “desc” depending on the order you’d like the values sorted, e.g. Categories?$orderby=CategoryName desc.

$select
Limit the properties on each entry to just those requested, e.g. Categories?$select=CategoryName,Description.

$skip
How many entries you’d like to skip, e.g. Categories?$skip=4.

$top-
Return entries from the top of the feed, e.g. Categories?$top=4

See MSDN for more options.

 

-- Updated Post --

Thanks to James Hancock for pointing this one out for me. This post is a little misleading in that the $select is currently not supported. Please see http://forums.asp.net/t/1771116.aspx/1?OData%20Support for more information on this. The other query string parameters listed above are supported.

Using RavenDb with Mvc WebApi

 

I’m starting this post with a disclaimer. I’m not a RavenDb expect, actually far from it, in fact I’ve only started working with it this evening!

I’m working on a pet project and getting the initial building blocks in place. I read about RavenDB in a recent edition of CODE magazine. The same magazine dealt with some other NoSql databases, e.g. Mongo Db, I’ve had a passing interest in NoSql in the last while so I wanted to get me a piece of the pie, and RavenDB jumped out at me for a few reasons.

  • Written in .NET
  • Scalability over RDBMS
  • RestAPI (although i won’t be using it, my app will have its own REST API using RavenDb managed api underneath)
  • .NET API with Linq querying
  • Automatic indexing
  • Scalability

    Create project

    Fire up visual studio and create an new MVC4 project

    Add the RavenDb package,

    Global.asax.cs

    Do the very same that is indicated on the Raven website, We need a single Document Store in our application.

     protected void Application_Start()
            {
                AreaRegistration.RegisterAllAreas();
                            
                RegisterGlobalFilters(GlobalFilters.Filters);
                RegisterRoutes(RouteTable.Routes);
    
                BundleTable.Bundles.RegisterTemplateBundles();
    
                InitRaven();
            }
    
            private void InitRaven()
            {
                Store = new DocumentStore { ConnectionStringName = "RavenDB" };
                Store.Initialize();
    
                IndexCreation.CreateIndexes(Assembly.GetCallingAssembly(), Store);
    
            }
    
            public static DocumentStore Store;

    Create RavenController

    public abstract class RavenController : ApiController
        {
            public RavenController()
            {
                this.AutoSave = true;
                RavenSession = TickTockBaby.Mvc.WebApiApplication.Store.OpenSession();
            }
    
            public bool AutoSave { get; set; }
    
            public IDocumentSession RavenSession { get; protected set; }
    
            protected override void Dispose(bool disposing)
            {
                if (disposing)
                {
                    if (RavenSession != null)
                    {
                        using (RavenSession)
                        {
                            if (this.AutoSave)
                                RavenSession.SaveChanges();
                            RavenSession.Dispose();
                            RavenSession = null;
                        }
                    }
                }
    
                base.Dispose(disposing);
            } 
        }

    Let me explain what I’ve done here…

    I’ve initialized the session in the constructor, and cleaned it up in dispose, I also SaveChanges by default unless it gets switched off in a derived class.

     

    Derive from RavenController

    public class UsersController : RavenController
        {       
            // GET /api/values
            public IEnumerable<string> Get()
            {
                this.AutoSave = false;
                return RavenSession.Query<User>().Select(u => u.Name);            
            }        
        }

    That’s my initial attempt, hope it helps someone out a little.

    I’ll post my final solution possibly using Ninject DI after I’ve used RavenDb for a while and get a better feel for it.

    Raven Studio


    Check results in browser

    Vs11 Xml

     

    I’m working with an XML document all morning, and for the hell of it I decided to open in VS11.

    Guess what I found, some pretty cool xml/xsd/xslt support

     

    image

    but the biggest feature I found is the following…

    Paste XML as classes! BOOM!!

    image

    image

    Loving VS11…

    Linq DistinctBy

     

    Here is an extension method that I just had to share, TBH I’ve forgotten what I robbed the initial idea from, it wasn’t mine, but it’s something I found that I use over and over.

    The problem is I want to use the Distinct() extension method. However the objects I’m creating don’t override the default equality comparer, nor did I want to create a functor and supply to the overload just for this scenario.

    Lets have a look of what I’m dealing with.

    public class Source
    {
            
        public string Code { get; set; }    
        public string Name { get; set; }        
    }

    Here’s what one would initially try

    // Remove any duplicates
     c.DependingOnSources = c.DependingOnSources.Distinct();

    The problem here is that I don’t use the overload that allows me to specify an equality comparer, and the class itself doesn’t have the default equality comparer.

    So what’s the solution?

    var set = new HashSet<string>();
    c.DependingOnSources = c.DependingOnSources.Where(element => set.Add(element.Name));

     

    It’s a beauty it’s it, and quite simplistic, what I do is create a HashSet of the keys I want o compare, then I use use the Linq Where statement to select all the elements that I can add to the list. If you’re familiar with HashSet you’ll know that for first time we try add an element it will be not exist in the set and it gets added to the set and returns true, because the set.Add returns true.. we satisfy the Func in the Where clause and it gets added to the items that get returned.

     

    Simple ey.. yes true, but it gets better, we can make this a little more generic and leverage an extension method to do the lifting for us.

     

    internal static class LinqExtensions
    {
        public static IEnumerable<TSource> DistinctBy<TSource, TKey>(
                            this IEnumerable<TSource> source, Func<TSource, TKey> selector)
        {
            var set = new HashSet<TKey>();
            return source.Where(element => set.Add(selector(element)));
        }
    }

     

    So now we can call our method like so

    // Remove any duplicates
    c.DependingOnSources = c.DependingOnSources.DistinctBy(k => k.Name);
     
    Neat ey! (another common method is to use GroupBy and Select.)

    Uploading a file in MVC4 C#5 .NET 4.5

     

    Back on the bleeding edge again Hot smile I’m in the early stages of my next killer app and I’m investigating the pros and cons of using the new ASP WebApi.

    One of the features of this so called killer app will be to upload pictures (nothing special I agree). But how would I do this for all the clients I hope to support (WinRT/WP7/Html5/IOS).

    Let me first present the server that will be used for all these clients, I’ll then follow up with what I consider to be the simplest client a html5 browser!

    Server

    So I fired up VS11 and created a new MVC4 application using .net 4.5 / C#  and the WebApi template.

    I then added a controller called FileUploadController.cs

       1:  using System.Collections.Generic;
       2:  using System.Linq;
       3:  using System.Net;
       4:  using System.Net.Http;
       5:  using System.Threading.Tasks;
       6:  using System.Web.Http;
       7:   
       8:  namespace MvcApplication16.Controllers
       9:  {
      10:      public class FileUploadController : ApiController
      11:      {
      12:          public async Task<IEnumerable<string>> PostMultipartStream()
      13:          {
      14:              // Check we're uploading a file
      15:              if (!Request.Content.IsMimeMultipartContent("form-data"))            
      16:                  throw new HttpResponseException(HttpStatusCode.UnsupportedMediaType);
      17:                 
      18:              // Create the stream provider, and tell it sort files in my c:\temp\uploads folder
      19:              var provider = new MultipartFormDataStreamProvider("c:\\temp\\uploads");
      20:   
      21:              // Read using the stream
      22:              var bodyparts = await Request.Content.ReadAsMultipartAsync(provider);            
      23:          
      24:              // Create response.
      25:              return provider.BodyPartFileNames.Select(kv => kv.Value);            
      26:          }
      27:      }
      28:      
      29:  }

    You can see from line 12 that I’ve made this operation async, you’ve really got to admire the simplicity of async/await construct in .net 4.5! In line 22 you can see that the compiler and some state machine magic allow the freeing up of the asp worker thread….. (If you have read my previous posts you may be a little confused now.. didn’t I say that Tasks will use use the same threadpool!?  have a look at this link for someone that pondered the very same concerns )

     

    HTML5 Client

    The client couldn’t have been easier, fist a look at it in the browser

    image

       1:  <!DOCTYPE html>
       2:  <html lang="en">
       3:  <head>
       4:      <meta charset="utf-8" />
       5:      <title>ASP.NET Web API</title>
       6:      <link href="@Url.Content("~/Content/Site.css")" rel="stylesheet" type="text/css" />
       7:      <meta name="viewport" content="width=device-width" />
       8:  </head>
       9:  <body>
      10:      @using (Html.BeginForm("FileUpload", "api", FormMethod.Post, new { enctype = "multipart/form-data" }))
      11:      { 
      12:          <div>Please select some files</div>
      13:          <input name="data" type="file" multiple>
      14:          <input type="submit" />            
      15:      }
      16:  </body>
      17:  </html>

     

    The important part above is using the enctype attribute, in fact line 10 loosely translates to

    <form action="~/api/FileUpload" enctype="multipart/form-data" method="POST">
     

    Don’t believe me? Then try VS11’s awesome new feature – page inspector

    Right click on the html and choose view in page inspector

    image

     

     

    and we’re done! Of course in the real world we’ll use ajax with a few trick re sandbox, but here’s the response in the browser with xml.

    image

    I’ll hopefully follow up with the samples for the client list below when I get to the respective development machines.

    • WinRT (c#/xaml)
    • iPhone (objective c)
    • Android (java)

    Using jQuery UI Autocomplete

     

    Hi all, here’s an example of how to use jQuery UI Autocomplete in ASP MVC3.

    The sample app I will show actually connects to a work related webservice, but you could use any repository you so wish.

    Steps

    Create a MVC3 application

    Add jQuery UI (use nuget)

    image

    image

     

    Create your UX

    I just added the following to my Home/Index.cshtml view

    image

     

    Add a new script to your scripts folder

    image

    here you can see that on the page load, I wrap my input “#uris” and call the jQuery UI auto complete on it.

    I set the source to /Home/GetModels  i.e. the GetModels function on the HomeController.cs

     

    Add the GetModels function (click to enlarge)

    image

    Here you can see that I’m just using a webservice to search for entities called modelUris (just strings) and I return the first 10 matches.

    For testing you could just use.

    return Json(new string[] {“one”, “two”}, JsonRequestBehavior.AllowGet);

     

    Here’s what it looks like

    image

    Async MVC Controllers

     

    I previously wrote a post on MVC async controllers. Now I want to follow up on something that’s more cutting edge, unfortunately I’m one of those people that like nosing about with what new, how it will affect me and how I could leverage it in future etc., Often, I’ll readily admit it’s more bleeding edge than cutting edge (xaml support in Blend5 for example Thumbs down).

    However in this post I want to show you something that you might agree is pretty nice.

    A historical example

    So lets take a look at the app we’re trying to build.

    Client is a simple web form (yes it’s webforms but I’m trying to catch the non MVC microsofties too), the instruments are entered in the text box, fetch button is clicked and the result is output

    image_thumb1

    Now the workflow, for the purpose of this test I won’t be connecting to any database webservice etc, I’ve just added a delay of 10 seconds and and assign LastClose to RIC & " " & New Random().NextDouble()

    image_thumb4

    Here’s the code behind for the non-async button event handler

            protected void Button1_Click(object sender, EventArgs e)
            {
                Contract.Requires<ArgumentException>(!string.IsNullOrWhiteSpace(tbInst1.Text) || !string.IsNullOrWhiteSpace(tbInst2.Text), "Please enter values for instruments");
                // Make the call to the workflow to get the close for each instrument
                try
                {
                    var args = new Dictionary<string, object>();
                    args.Add("RIC", tbInst1.Text);                
                    var res = WorkflowInvoker.Invoke(_getPricesWFDefinition, args);
                    Label1.Text = res["LastClose"].ToString();
     
                    args.Clear();
                    args.Add("RIC", tbInst2.Text);
                    res = WorkflowInvoker.Invoke(_getPricesWFDefinition, args);
                    Label2.Text = res["LastClose"].ToString();
                }
                catch (Exception exp)
                {
                    Trace.Warn(exp.Message);
                }
     
            }

    So as you can see, we’re waiting at least 20 seconds for our page to return, nasty.
    In theory we should be able to bring this down to 10 seconds as we can make the calls to the workflows in parallel.

    Let me show you one way to “incorrectly” achieve this

            private void Option1()
            {
     
                var t1 = Option1TaskCreater(tbInst1, Label1);
                var t2 = Option1TaskCreater(tbInst2, Label2);
     
                Task.WaitAll(t1, t2);
     
            }
     
            private Task Option1TaskCreater(TextBox tb, Label lb)
            {
                var t1 = Task.Factory.StartNew(() =>
                {
                    var args = new Dictionary<string, object>();
                    args.Add("RIC", tb.Text);
                    var res = WorkflowInvoker.Invoke(_getPricesWFDefinition, args);
                    lb.Text = res["LastClose"].ToString();
                });
                return t1;
            } 

    So we’re using the task library to make the two workflow requests async, and results look promising, down to about 10 seconds now… so any problems with doing this?

    Well, tasks use threadpool threads to execute. So, the query will execute on a threadpool thread. To get true asynchronous execution(no worker threads blocked), we need to jump through a few more hoops. For webform people, there’s a very good explanation here. MVC people read on!

    But Why/When use async?

    The response to this question has been discussed many times in both books and magazines. ASP.NET uses threads from a common language runtime (CLR) thread pool to process requests. As long as there are threads available in the thread pool, ASP.NET has no trouble dispatching incoming requests. But once the thread pool becomes saturated-that is, all the threads inside it are busy processing requests and no free threads remain-new requests have to wait for threads to become free. If the jam becomes severe enough and the queue fills to capacity, ASP.NET throws up its hands and responds with a "Server Unavailable" to new requests.

    Often to solve the problem of horizontal scalability more servers are added to the webfarm, however this only provided temporary relief to what in fact is an underlying design problem, it’s not a case of adding more processors(threads) but a case of using the threads more efficiently, as you can see from the diagram below, if you are CPU bound, there is little more you can do but add some more servers.

    image_thumb2

    So what is this telling us? Basically, if your app is I/O bound then you should use parallelism, if requests are computationally cheap to process, then parallelism is probably an unnecessary overhead.

    If the incoming request rate is high, then adding more parallelism will likely yield few benefits and could actually decrease performance, since the incoming rate of work may be high enough to keep the CPUs busy.

    If the incoming request rate is low, then the Web application could benefit from parallelism by using the idle CPU cycles to speed up the processing of an individual request. We can use either PLINQ or TPL (either Parallel loops or the Task class) to parallelize the computation over all the processors. Note that by default, however, the PLINQ implementation in .NET 4 will tie-up one ThreadPool worker per processor for the entire execution of the query. As such, it should only be used in Web applications that see few but expensive requests.

    MVC4

    In MVC4 it becomes even easier that my previous post on AsyncControllers, actually to me it looks quite like the WinRT async calls in .net 4.5 and C#5

    Sample using task support for asynchronous controllers

    You can now write asynchronous action methods as single methods that return an object of type Task or Task<ActionResult>.

    e.g.

    public async Task<ActionResult> Index(string city)
    {    
        var newsService = new NewsService();    
        var sportsService = new SportsService();        
        return View("Common",        
                    new PortalViewModel 
                    {       
                        NewsHeadlines = await newsService.GetHeadlinesAsync(),        
                        SportsScores = await sportsService.GetScoresAsync()    
                    });
    }

    In the previous action method, the calls to newsService.GetHeadlinesAsync andsportsService.GetScoresAsync are called asynchronously and do not block a thread from the thread pool.

    Asynchronous action methods that return Task instances can also support timeouts. To make your action method cancellable, add a parameter of type CancellationToken to the action method signature. The following example shows an asynchronous action method that has a timeout of 2500 milliseconds and that displays a TimedOut view to the client if a timeout occurs.

    [AsyncTimeout(2500)] 
    [HandleError(ExceptionType = typeof(TaskCanceledException), View = "TimedOut")]
    public async Task<ActionResult> Index(string city, CancellationToken cancellationToken) 
    {    
        var newsService = new NewsService();    
        var sportsService = new SportsService();       
        return View("Common",        
            new PortalViewModel 
            {        
                NewsHeadlines = await newsService.GetHeadlinesAsync(cancellationToken),        
                SportsScores = await sportsService.GetScoresAsync(cancellationToken)    
            });
    }
     
     
     

    Conculsion

    MVC4 Makes programming of async controllers even easier.

    Layout in Windows Phone 7

     

    So my wife left me for a hen weekend and I needed something to do with my time.
    Friday night I dedicated to my real work to clear my conscience and then I went to play.

    Windows 8

    I spent a few frustrating hours on Saturday working on a Win8 application to compliment a certain website, frustrating… in so far as the Xaml designer in VS11/Blend on Windows 8 hangs like a good one. Actually at serveral points in time I considered changing my app to html5/js, because, for at least for the search section of the app I could see no blockers. However I want to add some pretty nifty features going forward and I don’t feel like implementing them in javascript.
    I guess I may the possibility of writing them in C++/C# as a library and using this from the UX application if it continues to slow me down. I’ll have to consider cutting my losses soon if it keeps hanging the development environment that’s for sure (the joys of working with not only a Beta application, but a beta OS! Smile )

    WP7

    So for a bit of fresh air I started writing the WP7 app, at least this is more familiar ground to me having written quite a few of them already, and I just took my resource dictionaries from the WinRT app. To start with I just used some sample data in expression blend, dropped on a list box and bound my sample data to it.

    image

    But the layout wasn’t really what I wanted. I’m hoping that that API for the real data may provide me with a list of categories, one wouldn’t really want to have to release a new app every time a new section was added would they.
    So my approach would be just to bind the data to a list for now (it may well turn out to be an ordered list in the API). The problem as you can see above what that I was getting a single row for each item.. not what I wanted.

    Would you believe this was the first time I’ve not wanted this default layout in a WP7 app, so I decided to use the WrapPanel container that I’ve previously used in a WPF app… but alas it doesn’t exist out of the box!

    Silverlight WP7 Toolkit to the rescue.

    A quick Google indicated that the WP7 toolkit had the WrapPanel I was looking for, I fired up the Nuget package manager and added it to my project.

    image

    Items Panel

    One more change was needed in my xaml, I needed to specify where to use this wrap panel.
    This I specified in the ItemsPanelTemplate of the listbox in question.

    image

    The final result!

    image

    Hopefully this helps someone else out.

    Reading a file in Windows 8 html5 js

     

    Hi again, this is my last post were I compare the same WinRT application written in three different ways.

    • C++ / Xaml
    • C# / Xaml
    • JavaScript / html

    My previous post covers c++ and c#, this one covers javascript.

    JavaScript / html

    image

    image

    I have to admit, this really took me by surprise! It was pretty painless. I had it written off before I even tried it, but this task proved somewhat simplistic. I’d one little obstacle trying to use a CDN, but other than that it was trivial.

    So the penny has dropped, the WinRT developer pool is going to be massive! I predict good things.
    If Microsoft play their cards correctly it will be a very successful platform (even more so with the promises of WP8 portability).

    So what didn’t I like about this particular app? Not much really, other that realising I’ve a lot more talent to content with Winking smile

     

    Summary

    So I compared the three different approaches, for the task in question c#/xaml or js/html won hands down.
    C++ was overkill.

    I think each option would have to be considered on an application per application basis.

     

    btw: on a non related note: my wife has just switched on the bedroom networked TV and windows 8 on the laptop here in the sitting room started installing stuff

    image

    I’m sure it’s got to be cool, if only I knew what for Smile

    Recent Tweets

    Note: For Customization and Configuration, CheckOut Recent Tweets Documentation

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