How do i call WCF services in Silverlight? - silverlight

Question

Can anybody tell me why is this not working. I have created a WCF service which returns a list of customers from Northwind database.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.Text;
using System.ServiceModel.Activation;
namespace WCFSilverlight.Web
{
// NOTE: You can use the "Rename" command on the "Refactor" menu to change the class name "Customers" in code, svc and config file together.
[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
public class Customers : ICustomers
{
IEnumerable<Customer> ICustomers.GetAllCustomers()
{
NorthwindEntities objNorthwindEntities = new NorthwindEntities();
var query = from cust in objNorthwindEntities.Customers
select cust;
return query.ToList();
}
}
}
And this is my App.xaml.cs code fragment :-
private void Application_Startup(object sender, StartupEventArgs e)
{
this.RootVisual = new MainPage();
CustomersClient objCustomersClient = new CustomersClient();
objCustomersClient.GetAllCustomersCompleted += new EventHandler<GetAllCustomersCompletedEventArgs>(client_GetNameCompleted);
objCustomersClient.GetAllCustomersAsync();
}
void client_GetNameCompleted(object sender, GetAllCustomersCompletedEventArgs e)
{
MessageBox.Show(e.Result.ToString());
}
If I am not wrong the methods in Silverlight are called asynchronously. So I have added a event handler to handle it and then called the method to retrieve customers. But I don't get anything in Messagebox. Further when I try to keep a breakpoint on client_GetNameCompleted, it never executes. But if I keep it in Application_Startup it does execute. What can be the problem?
Also explain me am I doing it correct? I've seen one example where one person directly defines the function using some strange symbols like =>.
EDIT 1:- Kindly also explain me what is e.UserState in e. What does it contain and what can I possibly do with it?
EDIT 2 :- :- I get this error http://img178.imageshack.us/img178/9070/53923202.jpg
The WCF service is working perfectly i have tested the link query. So there is no problem with Sql Server connection or WCF. Something is wrong with my client only.
This is my ServiceReference.ClientConfig :-
<configuration>
<system.serviceModel>
<bindings>
<basicHttpBinding>
<binding name="BasicHttpBinding_ICustomers" maxBufferSize="2147483647"
maxReceivedMessageSize="2147483647">
<security mode="None" />
</binding>
</basicHttpBinding>
</bindings>
<client>
<endpoint address="http://localhost:50622/Customers.svc" binding="basicHttpBinding"
bindingConfiguration="BasicHttpBinding_ICustomers" contract="CustomerServ.ICustomers"
name="BasicHttpBinding_ICustomers" />
</client>
</system.serviceModel>
</configuration>
Can you now tell me what is wrong?
Thanks in advance :)
Update :- I read in google you need to set serialization mode to unidirectional. But where do i set this? What do i write where?

Answer 1

You are correct, All network calls in Silverlight are done asynchronously.
The => syntax you mention is shorthand for defining a delegate method, its called a lambda. (see below)
You should be able to set a break-point in the Completed event handler, if not try restarting Visual Studio (I've seen it act strangly before).
e.UserState will have a reference to whatever object you put in the UserState variable for the async call (note the extra overload).
Code:
objCustomersClient.GetAllCustomersCompleted = delegate(object Sender, GetAllCustomersCompletedEventArgs e)
{
MessageBox.Show(e.Result.ToString());
};
// is the same as
objCustomersClient.GetAllCustomersCompleted += new EventHandler<GetAllCustomersCompletedEventArgs>(client_GetNameCompleted);
void client_GetNameCompleted(object sender, GetAllCustomersCompletedEventArgs e)
{
MessageBox.Show(e.Result.ToString());
}
// which is same as
objCustomersClient.GetAllCustomersCompleted += (sender, e) => { MessageBox.Show(e.Result.ToString()); };