Silverlight 3 and RIA Services – The advanced things

My last article was about the basics of RIA Services. This article goes about the more advanced things in RIA Services. This article contains a few things that make the usage of RIA Services in more advanced scenario’s possible.

• Complex Types in RIA Services
• RIA Services in a separate class library
• RIA Services and Out of browser mode
• RIA Services on a different host

Using Complex Types in RIA Services

In my other article I just made use just a string as input parameter and a string as output parameter. It’s however very well possible to use custom types instead. There’s hower one prerequisite for those custom types.

• Each Custom Type needs to have one property decorated with a KeyAttribute. This is required for input and output types.

I created a WorldRequest and a WorldResponse which fits nicely in the example for HelloWorld.

public class WorldRequest
{
    [Key]
    public string Name { get; set; }
}

public class WorldResponse
{
    [Key]
    public string Greeting { get; set; }
}

This can be used in the HelloWorldDomainService just like you would do in a normal class.

[EnableClientAccess]
public class HelloWorldDomainService : DomainService
{
    [ServiceOperation]
    public WorldResponse HelloWorld(WorldRequest worldRequest)
    {
        return new WorldResponse { Greeting = string.Format("Hello {0}.", worldRequest.Name) };
    }
}

After compilation those custom types get generated in the Silverlight project as well as we saw in my previous article. The Custom Type is now overloaded from Entity. And has a specific method called GetIdentity. This has something to do with the KeyAttribute that’s required to add to one property inside a custom types. Although this is probably necessary for integration with the Entity Framework it doesn’t make sense in my example.

[DataContract(Namespace="http://schemas.datacontract.org/2004/07/MM.Ria")]
public sealed partial class WorldRequest : Entity
{
    
    private string _name;
    
    [DataMember()]
    [Key()]
    public string Name
    {
        get
        {
            return this._name;
        }
        set
        {
            if ((this._name != value))
            {
                this.ValidateProperty("Name", value);
                this.RaiseDataMemberChanging("Name");
                this._name = value;
                this.RaiseDataMemberChanged("Name");
            }
        }
    }
    
    public override object GetIdentity()
    {
        return this._name;
    }
}

We can now easily use this generated class as we would have done in different scenario’s.

var helloWorld = new HelloWorldDomainContext();
helloWorld.HelloWorldCompleted += HelloWorldHelloWorldCompleted;
helloWorld.HelloWorld(new WorldRequest{Name = "Mark Monster"});

And in the EventHandler we have to cast the ReturnValue property to the WorldResponse type. Again I hope they make InvokeEventArgs a generic type so that we don’t have to cast this ReturnValue and have it return the correct type.

private void HelloWorldHelloWorldCompleted(object sender, InvokeEventArgs e)
{
    Debug.WriteLine((e.ReturnValue as WorldResponse).Greeting);
}

Move code for the RIA Service to a class library

Next thing that came in my mind was the fact what if I want to share my RIA Services with other people? Do they need to have the source or is a different approach possible?

Luckily it’s possible to create class library (standard .NET) add references to a few dlls.

After that just move your RIA Service code in there. This library can now be used in any Web project that’s linked to a Silverlight application. Just add a reference to the new library containing your RIA Service and while building code will get generated in your Silverlight application.

What about using RIA Services in the Out of browser mode?

It just works. I didn’t have to do anything to make the Out of browser version communicate with the RIA Services.

When the host running the RIA Services is different from the url hosting the Silverlight application?

Of course in some scenario’s the RIA Services are hosted on a different location than the Silverlight application itself. Of course you have to remind yourself about cross domain issues, so make sure the host has a clientaccesspolicy.xml or crossdomain.xml file in place.

When we take a closer look into the generated code we’ll find a default constructor and a constructor where you can specify the service URI.

/// <summary>
/// Default constructor.
/// </summary>
public HelloWorldDomainContext() : 
        base(new HttpDomainClient(new Uri("DataService.axd/MM-Ria-HelloWorldDomainService/", System.UriKind.Relative)))
{
}

/// <summary>
/// Constructor used to specify a data service URI.
/// </summary>
/// <param name="serviceUri">
/// The HelloWorldDomainService data service URI.
/// </param>
public HelloWorldDomainContext(Uri serviceUri) : 
        base(new HttpDomainClient(serviceUri))
{
}

We can now make use of the constructor which accepts a serviceUri to connect to the RIA Service that’s running at a different location. The tricky part however is the DataService.axd/MM-Ria-HelloWorldDomainService/ part. Besides DataService.axd it contains also the namespace and type name for the RIA Service, but instead of using dots to separate the namespace parts and the type name dashes are used. But for the easy parts, just copy it from the generated code I would say.

var helloWorld = new HelloWorldDomainContext(new Uri("http://myhostruningsomewhere.com/DataService.axd/MM-Ria-HelloWorldDomainService/", UriKind.Absolute));
helloWorld.HelloWorldCompleted += HelloWorldHelloWorldCompleted;
helloWorld.HelloWorld(new WorldRequest {Name = "Mark Monster"});

Ps. This article is cross posted on: Mark Monster’s blog and Silverlight Help.