How to make custom WCF error handler return JSON response with non-OK http code?

Question

I\'m implementing a RESTful web service using WCF and the WebHttpBinding. Currently I\'m working on the error handling logic, implementing a custom error handler (IErrorHand

Answer 1

Here's the solution I came up with:

Catching exceptions from WCF Web Services

Basically, you get your web service to set a OutgoingWebResponseContext variable, and return null as the result (yes, really !)

    public List<string> GetAllCustomerNames()
    {
        //  Get a list of unique Customer names.
        //
        try 
        {
            //  As an example, let's throw an exception, for our Angular to display..
            throw new Exception("Oh heck, something went wrong !");

            NorthwindDataContext dc = new NorthwindDataContext();
            var results = (from cust in dc.Customers select cust.CompanyName).Distinct().OrderBy(s => s).ToList();

            return results;
        }  
        catch (Exception ex)
        {
            OutgoingWebResponseContext response = WebOperationContext.Current.OutgoingResponse;
            response.StatusCode = System.Net.HttpStatusCode.Forbidden;
            response.StatusDescription = ex.Message;
            return null;
        }
}

Then, you get your caller to look out for errors, then check if a "statusText" value was returned.

Here's how I did it in Angular:

$http.get('http://localhost:15021/Service1.svc/getAllCustomerNames')
    .then(function (data) {
        //  We successfully loaded the list of Customer names.
        $scope.ListOfCustomerNames = data.GetAllCustomerNamesResult;

    }, function (errorResponse) {

        //  The WCF Web Service returned an error

        var HTTPErrorNumber = errorResponse.status;
        var HTTPErrorStatusText = errorResponse.statusText;

        alert("An error occurred whilst fetching Customer Names\r\nHTTP status code: " + HTTPErrorNumber + "\r\nError: " + HTTPErrorStatusText);

    });

And here's what my Angular code displayed in IE:

Cool, hey ?

Completely generic, and no need to add Success or ErrorMessage fields to the [DataContract] data which your services are returning.

Answer 2

In the latest version of WCF (As of 11/2011) there's a better way of doing this using WebFaultException. You can use it as follows in your service catch blocks:

throw new WebFaultException<ServiceErrorDetail>(new ServiceErrorDetail(ex), HttpStatusCode.SeeOther);


[DataContract]
    public class ServiceErrorDetail
    {
        public ServiceErrorDetail(Exception ex)
        {
            Error = ex.Message;
            Detail = ex.Source;
        }
        [DataMember]
        public String Error { get; set; }
        [DataMember]
        public String Detail { get; set; }
    }