Custom WebFaultException on WCF Rest Serialization Failure?

Question

With an object like this:

    [DataContract]
    public class SampleItem
    {              
        private int _id;

        [DataMember(IsRequired = true)]
        public int Id
        {
            get { return _id; }
            set { _id = value; }
        }

        private string _stringValue;

        [DataMember()]
        public string StringValue
        {
            get { return _stringValue; }
            set { _stringValue = value; }
        }

And a REST call like this:

        [WebInvoke(UriTemplate = "", Method = "POST")]        
        public SampleItem Create(SampleItem instance)
        {
            if (instance == null)
                throw new WebFaultException<string>("The SampleItem returned wasn't correctly formatted.",
                                                    HttpStatusCode.BadRequest);               

            return instance;
        }        

If I call it with an invalid SampleItem, say something without an ID like this:

<SampleItem xmlns="http://schemas.datacontract.org/2004/07/UserWebServices" xmlns:i="http://www.w3.org/2001/XMLSchema-instance"&gt;&lt;StringValue&gt;SingleItem&lt;/StringValue&gt;&lt;/SampleItem&gt;

Then the server gives me a 400 (correct) back with no useful error info (all I get is this: The server encountered an error processing the request. See server logs for more details). Ideally I want it to say something like ID is required.

How do I intercept the place where this error is being generated and throw my own WebFaultException?

Answer 1

Check out the WebProtocolException from the REST Start Kit. You can then send back a custom error message in your exception like this:

catch (Exception ex)
        {
            throw new WebProtocolException(HttpStatusCode.InternalServerError, "Unexpected Error.", new ServiceFault { ExceptionDetail = "Your custom error message here" }, null);
        }