In this post I will explore a possibility of talking to a WCF REST Service from a Windows Phone 7 device. This should complete my posts related to consuming and working with data on Windows Phone 7.
I am going to start with creating a WCF REST Service. First of all, I am going to create data using Entity Framework Code First. I am going to re-use classes with my previous posts. I am going to define a handful : Attendee, Session and Session Category. Here is what Attendee class looks like as it will be the class I will use in my services.
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
namespace VSLiveData.EF
{
public class Attendee
{
[Key]
public int AttendeeID { get; set; }
[StringLength(50), Required]
public string FirstName { get; set; }
[StringLength(50), Required]
public string LastName { get; set; }
[StringLength(int.MaxValue)]
public string Notes { get; set; }
public virtual ICollection<Session> Sessions { get; set; }
}
}
Nest step is to define a service. .NET 4 comes with a template for RESTfull WCF Service, and I am going to use it to get a head start on my code. I am going to right click on my solution, and in Add New Item dialog I will select WCF REST Service Applications.
In next step I will rename and update created service. I am going to rename it to JSONDataService. I am going to start with a method that get list of attendees sorted by last name:
using System.Collections.Generic;
using System.Linq;
using System.ServiceModel;
using System.ServiceModel.Activation;
using System.ServiceModel.Web;
using VSLiveData.EF;
namespace WcfRestService
{
[ServiceContract]
[AspNetCompatibilityRequirements(
RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall)]
public class JSONDataService
{
[WebGet(UriTemplate = "/Attendee/List", ResponseFormat = WebMessageFormat.Json)]
public List<Attendee> GetList()
{
using (VSLiveContext context = new VSLiveContext())
{
context.Configuration.LazyLoadingEnabled = false;
context.Configuration.ProxyCreationEnabled = false;
return context.Attendees.ToList();
}
}
A couple of important things to notice here. I am turning off proxy creation. I have to do this, otherwise I will get serialization problems. I am also turning off lazy loading because I do not want to populate navigation properties, plus I will get an exception if I touch that property if my code is outside of using statement. You will see that I specify uri template as well. I want to use meaningful path for it. I also specify JSON format for returned data. Let’s take a look at create method next
[WebInvoke(UriTemplate = "/Attendee/Create", Method = "POST",
ResponseFormat = WebMessageFormat.Json,
RequestFormat = WebMessageFormat.Json)]
public Attendee Create(Attendee attendee)
{
using (VSLiveContext context = new VSLiveContext())
{
context.Attendees.Add(attendee);
context.SaveChanges();
}
return attendee;
}
The code to actually save attendee is pretty easy – I am utilizing entity framework code first API to add new attendee to the collection, save and return new attendee. Entity framework will populate ID for me as part of Save method. I also specify JSON as my format for incoming and outgoing data. The rest of the methods are very similar, so here is entire class:
using System.Collections.Generic;
using System.Linq;
using System.ServiceModel;
using System.ServiceModel.Activation;
using System.ServiceModel.Web;
using VSLiveData.EF;
namespace WcfRestService
{
[ServiceContract]
[AspNetCompatibilityRequirements(
RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall)]
public class JSONDataService
{
[WebGet(UriTemplate = "/Attendee/List", ResponseFormat = WebMessageFormat.Json)]
public List<Attendee> GetList()
{
using (VSLiveContext context = new VSLiveContext())
{
context.Configuration.LazyLoadingEnabled = false;
context.Configuration.ProxyCreationEnabled = false;
return context.Attendees.ToList();
}
}
[WebInvoke(UriTemplate = "/Attendee/Create", Method = "POST",
ResponseFormat = WebMessageFormat.Json,
RequestFormat = WebMessageFormat.Json)]
public Attendee Create(Attendee attendee)
{
using (VSLiveContext context = new VSLiveContext())
{
context.Attendees.Add(attendee);
context.SaveChanges();
}
return attendee;
}
[WebGet(UriTemplate = "/Attendee/Get/{id}",
ResponseFormat = WebMessageFormat.Json)]
public Attendee Get(string id)
{
Attendee attendee = null;
using (VSLiveContext context = new VSLiveContext())
{
context.Configuration.LazyLoadingEnabled = false;
context.Configuration.ProxyCreationEnabled = false;
int attendeeID = int.Parse(id);
attendee = context.Attendees.Where(one => one.AttendeeID == attendeeID).FirstOrDefault();
}
return attendee;
}
[WebInvoke(UriTemplate = "/Attendee/Update", Method = "PUT",
ResponseFormat = WebMessageFormat.Json, RequestFormat = WebMessageFormat.Json)]
public Attendee Update(Attendee attendee)
{
using (VSLiveContext context = new VSLiveContext())
{
context.Attendees.Attach(attendee);
context.Entry(attendee).State = System.Data.EntityState.Modified;
context.SaveChanges();
}
return attendee;
}
[WebInvoke(UriTemplate = "/Attendee/Delete/{id}", Method = "DELETE")]
public void Delete(string id)
{
using (VSLiveContext context = new VSLiveContext())
{
var attendee = new Attendee() { AttendeeID = int.Parse(id) };
context.Attendees.Attach(attendee);
context.Entry(attendee).State = System.Data.EntityState.Deleted;
context.SaveChanges();
}
}
}
}
I have to register routes for my service in Global.asax.cs file:
using System;
using System.ServiceModel.Activation;
using System.Web;
using System.Web.Routing;
namespace WcfRestService
{
public class Global : HttpApplication
{
void Application_Start(object sender, EventArgs e)
{
RegisterRoutes();
}
private void RegisterRoutes()
{
RouteTable.Routes.Add(new ServiceRoute("JSONDataService", new WebServiceHostFactory(), typeof(JSONDataService)));
}
}
}
In my web.config I just need to set my connection string for my data context and specify routing engine
<?xml version="1.0"?>
<configuration>
<connectionStrings>
<add
name="VSLive"
connectionString="Server=.;Database=VSLive;Trusted_Connection=True;"
providerName="System.Data.SqlClient"/>
</connectionStrings>
<system.web>
<compilation debug="true" targetFramework="4.0" />
</system.web>
<system.webServer>
<modules runAllManagedModulesForAllRequests="true">
<add name="UrlRoutingModule" type="System.Web.Routing.UrlRoutingModule, System.Web, Version=4.0.0.0,
Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />
</modules>
</system.webServer>
<system.serviceModel>
<serviceHostingEnvironment aspNetCompatibilityEnabled="true"/>
<standardEndpoints>
<webHttpEndpoint>
<standardEndpoint name="" helpEnabled="true" automaticFormatSelectionEnabled="true"/>
</webHttpEndpoint>
</standardEndpoints>
</system.serviceModel>
Now, it is time to get to windows phone 7 app. Just add new project and select Windows Phone 7 application. The most interesting part is my view model that talks to my WCF service. First of all, I am going to add a property to hold collection of attendees:
public ObservableCollection<Attendee> Items { get; private set; }
Next, I am going to use WebClient to get the data. I could also use HTTPRequest. The difference between the two is that callbacks from WebClient are automatically marshaled to UI thread. Here is how I would get the list of attendees:
/// <summary>
/// Creates and adds a few ItemViewModel objects into the Items collection.
/// </summary>
public void LoadData()
{
WebClient client = new WebClient();
client.OpenReadCompleted += new OpenReadCompletedEventHandler(client_OpenReadCompleted);
client.OpenReadAsync(new Uri(@"http://localhost/WcfRestService/JSONDataService/Attendee/List"));
}
void client_OpenReadCompleted(object sender, OpenReadCompletedEventArgs e)
{
ObservableCollection<Attendee> data = new ObservableCollection<Attendee>();
DataContractJsonSerializer serializer = new DataContractJsonSerializer(typeof(List<Attendee>));
List<Attendee> attendees = (List<Attendee>)serializer.ReadObject(e.Result);
attendees.ForEach(one => Items.Add(one));
}
Let me explain what this code does. I am creating a web client, then I am subscribing to completed event, then I am calling OpenRead. Because of the URL I am using, this call will eventually end up in the method that matches my URL based on UriTemplate attribute for the method:
[WebGet(UriTemplate = "/Attendee/List", ResponseFormat = WebMessageFormat.Json)]
public List<Attendee> GetList()
{
using (VSLiveContext context = new VSLiveContext())
{
context.Configuration.LazyLoadingEnabled = false;
context.Configuration.ProxyCreationEnabled = false;
return context.Attendees.ToList();
}
}
In completed handler for read, I am using DataContractJsonSerializer to de-serialize downloaded data into List of attendees. Then I am adding them to the items collection, which in turn is exposed to UI as following:
<ListBox x:Name="FirstListBox" Margin="0,0,-12,0" ItemsSource="{Binding Items}" >
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Margin="0,0,0,17" Width="432" Height="78">
<TextBlock Text="{Binding FirstName}" TextWrapping="Wrap"
Style="{StaticResource PhoneTextExtraLargeStyle}"/>
<TextBlock Text="{Binding LastName}" TextWrapping="Wrap"
Margin="12,-6,12,0" Style="{StaticResource PhoneTextSubtleStyle}"/>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
Next, Let’s look at the Create (Insert) method, as it demonstrates how to post data to the service.
public void OnSaveAttendee(object parameter)
{
string json = null;
WebClient client = new WebClient();
client.Headers["Content-Type"] = "application/json";
DataContractJsonSerializer serializer = new DataContractJsonSerializer(typeof(Attendee));
using (MemoryStream stream = new MemoryStream())
{
serializer.WriteObject(stream, CurrentAttendee);
stream.Flush();
json = Encoding.UTF8.GetString(stream.ToArray(), 0, (int)stream.Length);
}
client.UploadStringCompleted += new UploadStringCompletedEventHandler(client_UploadStringCompleted);
client.UploadStringAsync(new Uri("http://localhost/WcfRestService/JSONDataService/Attendee/Create"), "POST", json);
}
void client_UploadStringCompleted(object sender, UploadStringCompletedEventArgs e)
{
if (e.Error == null)
{
MessageBox.Show("OK");
}
else
{
MessageBox.Show(e.Error.Message);
}
}
Now, I am reversing the order of operations. I am serializing Attendee instance to Json, then using UTF8 encoding to convert the data to a string. One important part to remember is to set content type on the request to JSON, otherwise you will get 404 Not Found. In completed handler I am just checking for errors. Again, I will end up eventually in my service’s Create method based on URI Template.
You can download entire solution here. You will also notice that even though my classes on the client, such as Attendee:
using System.Collections.Generic;
using System.ComponentModel;
namespace VSLiveData.EF
{
public class Attendee : INotifyPropertyChanged
{
public int AttendeeID { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string Notes { get; set; }
public virtual ICollection<Session> Sessions { get; set; }
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (null != handler)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
}
I am not calling NotifyPropertyChanged anywhere. This is because I am using NotifyPropertyChangedWeaver, which is awesome!
Thanks.