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Programming WCF Services by Juval Lowy

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Error-Handling Extensions

WCF enables developers to customize the default exception reporting and propagation, and even provide for a hook for custom logging. This extensibility is applied per channel dispatcher, although you are more than likely to simply utilize it across all dispatchers.

To install your own error-handling extension, you need to provide the dispatchers with an implementation of the IErrorHandler interface defined as:

public interface IErrorHandler
{
   bool HandleError(Exception error);
   void ProvideFault(Exception error,MessageVersion version,ref Message fault);
}

Any party can provide this implementation, but typically it will be provided either by the service itself or by the host. In fact, you can have multiple error-handling extensions chained together. You will see later in this section just how to install the extensions.

Providing a Fault

The ProvideFault( ) method of the extension object is called immediately after any exception is thrown by the service or any object on the call chain down from a service operation. WCF calls ProvideFault( ) before returning control to the client and before terminating the session (if present) and before disposing of the service instance (if required). Because ProvideFault( ) is called on the incoming call thread while the client it still blocked waiting for the operation to complete, you should avoid lengthy execution inside ProvideFault( ).

Using ProvideFault( )

ProvideFault( ) is called regardless of the type of exception ...

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