I am working with Entity Framework as model in a REST service, using the CollectionService<T> and i found a little issue in the behavior of Linq to Entities,this is well know but i hope a change in .Net 4.0

Currently Linq to Entities not supports projections that returns types with parameterized constructors, by instance for a method that return a IEnumerable<KeyValuePair<string, Course>> i wanna make

   1:  .Select(c => new KeyValuePair<string, CustomType>(c.StringProperty, c))

This projection for me is pretty natural, but thrown the next error: “Only parameterless constructors and initializers are supported in LINQ to Entities”

My workaround (model is an instance of my Entity Framework ObjectContext)

   1:  protected override IEnumerable<KeyValuePair<string, Course>> OnGetItems()

   2:          {

   3:                        

   4:              List<Course> Course = model.Courses.Select(c => new Course() { Code = c.Code, Description = c.Description, Name = c.Name, OpenDate = c.OpenDate }).ToList();

   5:              Dictionary<string, Course> returnCourse = new Dictionary<string, Course>();

   6:              Course.ForEach((Course item) =>

   7:              {

   8:                  returnCourse.Add(item.Code, item);

   9:              });

  10:   

  11:              return returnCourse;

  12:   

  13:   

  14:          }

See you

Yesterday working in a demo about WCF-REST Starter Kit (http://www.asp.net/downloads/starter-kits/wcf-rest/) i had a little issue to make a query to a XML Structure that includes a xml namespace (aka xmlns), the trick is very simple to get the value from each element in the structure, you should pass the XName in Elements method including the XNamespace

This is my XML structure

<ItemInfoList xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
- <ItemInfo>
  <EditLink>http://localhost:17673/Services/Courses.svc/S02</EditLink> 
- <Item xmlns:a="http://schemas.datacontract.org/2004/07/DotNetUniversity">
  <a:Code>S02</a:Code> 
  <a:Description>La Transferencia de Estado Representacional (Representational State Transfer) o REST es una técnica de arquitectura software para sistemas hipermedia distribuidos como la World Wide Web. El término se originó en el año 2000, en una tesis doctoral sobre la web escrita por Roy Fielding, uno de los principales autores de la especificación del protocolo HTTP y ha pasado a ser ampliamente utilizado por la comunidad de desarrollo.</a:Description> 
  <a:Name>REST</a:Name> 
  <a:OpenDate i:nil="true" /> 
  </Item>
  </ItemInfo>
- <ItemInfo>
  <EditLink>http://localhost:17673/Services/Courses.svc/S01</EditLink> 
- <Item xmlns:a="http://schemas.datacontract.org/2004/07/DotNetUniversity">
  <a:Code>S01</a:Code> 
  <a:Description>La Arquitectura Orientada a Servicios (en inglés Service Oriented Architecture), es un concepto de arquitectura de software que define la utilización de servicios para dar soporte a los requisitos del negocio.</a:Description> 
  <a:Name>SOA</a:Name> 
  <a:OpenDate i:nil="true" /> 
  </Item>
  </ItemInfo>
  </ItemInfoList>

My custom collection

   1:  private ObservableCollection<CourseViewModel> courses = new ObservableCollection<CourseViewModel>();

This is the code to query this structure and populate a collection of a custom entities, BTW i’m using Silverlight 3 with MVVM approach

   1:  public void LoadCatalog()

   2:          {

   3:              courses.Clear();

   4:              WebClient client = new WebClient();

   5:              client.DownloadStringCompleted += (source, args) =>

   6:              {

   7:                  if (args.Error == null)

   8:                  {

   9:                      IEnumerable<XElement> coursesXml = XElement.Load(new StringReader(args.Result)).Descendants("ItemInfo");

  10:                      foreach (var item in coursesXml.Descendants("Item"))

  11:                      {

  12:                          XNamespace ns = "http://schemas.datacontract.org/2004/07/DotNetUniversity";

  13:   

  14:                          bool hasOpenDate = !String.IsNullOrEmpty(item.Element(ns + "OpenDate").Value);

  15:                          DateTime openDate = default(DateTime);

  16:                          if (hasOpenDate)

  17:                          {

  18:                              DateTime.TryParse(item.Element(ns + "OpenDate").Value, out openDate);

  19:                          }

  20:   

  21:                          courses.Add(

  22:                              new CourseViewModel(

  23:                                  new Course()

  24:                                  {

  25:                                      Name = item.Element(ns + "Name").Value,

  26:                                      Code = item.Element(ns + "Code").Value,

  27:                                      Description = item.Element(ns + "Description").Value,

  28:                                      OpenDate = openDate,

  29:                                      OpenDateSpecified = hasOpenDate

  30:                                  }));

  31:                      }

  32:                  }

  33:              };

  34:              client.DownloadStringAsync(new Uri("http://localhost:17673/Services/Courses.svc/"));

  35:          }

See you

Internet Explorer 8 exposes new ways for deliver features from our sites directly to our users. In this session we learn to use the new features of IE8 such as accelerators, web slices and search providers and how to integrate it with our sites

Internet Explorer 8 expone nuevas formas de entregar la funcionalidad que su sitio ofrece directamente a sus usuarios. Venga a esta sesión para aprender cómo usar nuestras nuevas actividades, Web slices y mucho más e integrarlas con nuestros sitios

Webcast Link

http://www.mslatam.com/latam/mediacenter/wcdetail.aspx?EventID=1032422247&p=&a=&k=&f=&t=

See you

Is really simple know if any type implements an interface in the traditional way we can use the “is” keyword to know if the class instance implements the interface, by instance

Interface

Class that implements the interface

Interface validation

But if are we working with an instance of Type class, not exists a built-in method to determinate if the type implements the interface

A simple way to get this is extend the Type class using the Extensions Method feature, we can write something like this

In this manner we can make this validation when works with an instance of Type class

See you

Well on my last post, i talk about changes on controls in #Silverlight3, while i tried to use a demo about Navigation and Styles, Corrina and her team had developed 7 additional application templates, for the community to consume and they’ve put them up on the Expression Community Gallery for download:

Aurora

Frosted Cinnamon Toast

Lime Shocker

Pinky

Retro

Sky Line

Subdued

All templates are terrific and very easy to use only change the reference to the resource in the styles.xaml code file. But if we want work with all templates and load them, based on some policy or the user preference, in the same way that custom styles on ASP.Net? The easy way is get the template from the application host (ASP.Net), and pass it to Silverlight using the init parameters

Copy the styles.xaml files that you want use to the Assets folder in your project, rename each one of the files with a descriptive name, after define the logic for set the current theme in the Application Host (ASP.Net)

   1:  using System;

   2:  using System.Collections.Generic;

   3:  using System.Linq;

   4:  using System.Web;

   5:  using System.Web.UI;

   6:  using System.Web.UI.WebControls;

   7:   

   8:  namespace UIOne.Web

   9:  {

  10:    public partial class _Default : System.Web.UI.Page

  11:    {

  12:      protected void Page_Load(object sender, EventArgs e)

  13:      {

  14:          //Some sort of policy or user preference for get the current Theme

  15:          string applicationTheme = "Frosted.xaml";

  16:          this.Silverlight1.InitParameters = String.Format("applicationTheme={0}", applicationTheme);

  17:      }

  18:    }

  19:  }

Get the parameter in Silverlight code and rewrite the constructor of the Main class to receive one parameter

   1:    private void Application_Startup(object sender, StartupEventArgs e)

   2:          {

   3:              string applicationTheme = e.InitParams["applicationTheme"];

   4:              this.RootVisual = new MainPage(applicationTheme);

   5:          }

In the constructor of the Main class, get the resource file using the GetResourceStream method, create a StreamReader within the result and load the read content using the Load method from the XamlReader class

   1:   public MainPage(string applicationTheme)

   2:          {

   3:              string resurceUri = String.Concat("<<assembly>>;component/Assets/", applicationTheme);

   4:              StreamResourceInfo resourceInfo =

   5:                  App.GetResourceStream(new Uri(resurceUri, UriKind.Relative));

   6:              StreamReader resourceReader = new StreamReader(resourceInfo.Stream);

   7:              string xaml = resourceReader.ReadToEnd();

   8:              ResourceDictionary resourceTheme =

   9:                  XamlReader.Load(xaml) as ResourceDictionary;

  10:              App.Current.Resources.MergedDictionaries.Add(resourceTheme);

  11:   

  12:              InitializeComponent();

  13:          }

Now test the project, modifying the value for applicationTheme variable

See you

Symbolic Lagrangian formulations of the equations of motion of tree structured constrained mechanical systems have the potential to be both more efficient and more numerically robust than formulations which use nonlinear kinematic constraint equations.

D* is a program for efficiently computing symbolic derivatives, derive a simple recursive factorization of the Lagrangian equations of motion which, along with our extended implementation of the D* symbolic differentiation algorithm, yields empirically measured O(n) inverse dynamics and O(n3) forward dynamics.

More: http://research.microsoft.com/en-us/downloads/4714703d-782c-4e37-830d-0e3b7662f743/default.aspx

See you

A few weeks ago Microsoft’s Kerberos team participated in the Kerberos Interop Workshop organized by the MIT Kerberos Consortium, being hosted here at the Microsoft campus here in Redmond. I had a chance to spend some time with the Microsoft folks (Michiko Short, Jeremy Viegas, Larry Zhu and Yi Zeng from the Microsoft’s Kerberos team) who participated in the event to discuss what happened. We thought it would be interesting to share a quick summary.

This sort of interoperability workshop is an effort to gather developers together in a single location, to actually plug them into a network environment together and help each other work through the interoperability challenges associated with their current development efforts. In attendance were representatives from Cornell University, Centrify, Microsoft, MIT, Safe Mashups, and Sun Microsystems.

More: http://blogs.msdn.com/interoperability/archive/2009/05/27/kerberos-interoperability-testing-workshop-hosted-by-microsoft.aspx

See you