R – Simpler Explanation of How to Make Call WCF Service without Adding Service Ref

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In Understanding WCF Services in Silverlight 2, the author, David Betz, explains how to call a web service without adding a service reference in the client application. I have a couple of weeks experience with WCF, so the article was over my head. In particular, although the author gave a lot of code snippets, but does not say what goes where. In the article, he provides two different code snippets for the web.config file, but does not clarify what's going on.

Looking at the source code there are four projects and two web.config files.

So far, I have been using the standard Silverlight project configuration of one project for the web service and one for the Silverlight client.

Firstly, does the procedure described in the article work with the standard two project configuration? I would think it would.

Secondly, does anyone know of a simpler example? I am very interested in this, but would like to either see source code in the default two project setup which is generated when a new Silverlight project is made, or find a step by step description of how to do this (eg, add a class called xxx.cs and add this code…, open web.config and add these lines…)

Many thanks
Mike Thomas

Best Answer

First, a little philosophy...

If you are a consumer of a WCF service that you did not write, adding a service reference to your client is really the only mechanism you have to enable interaction with that WCF service. Otherwise, you have no way of knowing what the service contract looks like, much less its data and message contracts.

However, if you are in control of both the client and the WCF service itself, adding a service reference to the client is a nice convenience, but I've recently been convinced not to use it. For one, it becomes a nuisance after the first few times you change your contract to remember to update your service reference. And in my case, I have several different C# projects that are consuming the WCF service, so I have to remember to update each one of them. Second, creating a service reference duplicates the contract definitions that are already defined in your WCF service. It is important to understand the implications of this.

Let's say your WCF defines the following type.

[DataContract]
public class Person
{
    [DataMember] public string FirstName {get; set;}
    [DataMember] public string LastName {get; set;}
}

When you add a service reference to your client, the metadata associated with this class is retrieved through the metadata exchange (MEX) endpoint, and an exact replica of this class is created on the client side that your client "compiles" against. So your WCF service has a definition of the Person class, and so does your client, but they are two different, distinct class definitions.

Given this, it would make more sense to abstract the Person class into a separate assembly that is then shared between the WCF service and the client. The added benefit is that when you change the contract definitions within this shared assembly, you no longer have to update the service reference within the client because it is already referencing the shared assembly. Does that make sense?

Now to your question. Personally, I've only used WCF within C# projects, not Silverlight. However, I do not think things are radically different. Given that, I would suggest that you watch the Extreme WCF video at dnrTV. It gives a step-by-step guide for how to bypass the service reference feature.

Hope this helps.

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