Question: I want to add the ability to see the server exception on the client side. 

If the server got some exception => i want to show some MessageBox on the client side that will show the exception message .. 

How can i do it ?

Answer: 
First of all, you need to enable your WCF service to return detailed error information. This is OFF by default, for security reasons (you don't want to tell your attackers all the details of your system in your error messages...)

For that, you need to create a new or amend an existing service behavior with the `<ServiceDebug>` behavior:

```
<behaviors>
    <serviceBehaviors>
       <behavior name="ServiceWithDetailedErrors">
           <serviceDebug includeExceptionDetailInFaults="true" />
       </behavior>
    </serviceBehaviors>
</behaviors>

```

Secondly, you need to change your `<service>` tag to reference this new service behavior:

```
<service name="YourNamespace.YourServiceClassName"
         behaviorConfiguration="ServiceWithDetailedErrors">
   ......
</service>

```

And third: you need to adapt your SL solution to look at the details of the errors you're getting back now.

And lastly: while this setting is very useful in development and testing, you **should** turn those error details OFF for production - see above, for security reasons.
In addition to the things Marc mentioned you will also want to switch to the HTTP Client Stack in order to avoid the dreaded generic "Not Found" error.

```
bool registerResult = WebRequest.RegisterPrefix("http://", WebRequestCreator.ClientHttp);

```