Jquery ajax() handling WCF errors?

Question

How to handle errors/exceptions returned by WCF servicer (REsTful) in Jquery ajax()method?

Assuming I have includeExceptionDetailInFaults="true" turned on and I use

error: function(XMLHttpRequest, textStatus, errorThrown) {
        alert(XMLHttpRequest.responseText);
 }

only thing I get back is an HTML string (HTML page) with error buried deep inside it;;

I want to display errors like

Service not found (HTTP 400 and 500 errrors)
.net exceptions thrown by WCF to the client page (javascript)

How can I do that?

Drew Marsh · Accepted Answer · 2012-11-08 23:23:15Z

4

includeExceptionDetailsInFaults is more of a debugging tool for unhanded exceptions than a way to actually deliver errors to the client. These kinds of errors would normally be 500 internal server errors whose details should not be leaked out to the client any way. For a REST service the way to generically deliver these details to the caller by default is to return them as text/HTML.

However, if you are trying to return logical errors out of your service you should be conjuring up instances of WebFaultException<T> where T can be a simple string message or, if you want something more complex, can be a class which will get serialized into a structured format according to whatever serialized is configured for your service endpoint. You are also able to set the response status code during the construction of the WebFaultException<T>.

If you wanted generic handling of all unhandled exceptions to return a structured content type representation and status code you would need to write your own IErrorHandler and do the translation of the unhanded exception type to a WebFaultException<T> in your ProvideFault implementation.

edited Nov 8, 2012 at 23:23

answered May 12, 2011 at 14:58

Drew Marsh

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4 Comments

Cshah Over a year ago

Any practicle example of IErrorHandler with Jquery ajax() method?

Drew Marsh Over a year ago

IErrorHandler has no strong ties to any specific client library. You make a decision on what "shape" you want the error details object to be that you return to the client and then you can read that in the jQuery failure handler. For example, the simplest thing to do would be to make IErrorHandler::Provide fault just return WebFaultException<string> where you simply put the exception.ToString() into it with 400 bad request. Then in jQuery you would just show what what returned by reading XHR's responseText property.

Alex Nolasco Over a year ago

WebFaultException is in 4.0 only isn't it?

Drew Marsh Over a year ago

@AlexanderN - yes, that's correct. Pre-4.0 you have to roll this solution yourself with a custom Exception subclass that a custom IErrorHandler can watch for -OR- set your own failed HTTP status/body in try/catches within your own methods which is... yuck. :)

Hari Pachuveetil · Accepted Answer · 2011-05-12 14:31:22Z

0

I haven't tried this specifically with a request to the WCF, but this works for calls to WebMethod within an ASP.NET aspx page:

            error: function(e) {
                var errorObject = JSON.parse(e.responseText);
                if (errorObject.ExceptionType === 'MyNamespace.MyException') {
                   //do stuff for MyException
                }
                else {
                    //do regular exception handling
                }
            }

answered May 12, 2011 at 14:31

Hari Pachuveetil

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