MVC WebAPI returning 500 error with no information

Question

I've been having this problem for several days (now fixed and solution noted for anyone that comes across this issue and is pulling their hair out).

After my latest round of code changes to my Silverlight application which uses MVC4 WebAPI for data, I was having a problem with one of my HttpGet Actions which was returning IQueryable<oneofmyclasses>. Using Fiddler2 to watch the request, I could see I was getting an internal server error (500), with no body text to explain why. I received no errors thrown in my Action.

Check 1: I verified that my Action was indeed getting to the return collection.AsQueryable(); line with no errors. It was

Check 2: I verified that my data was serializing to JSON with no errors using this code (g is my collection):

var json = new JsonMediaTypeFormatter();
            json.SerializerSettings.PreserveReferencesHandling = PreserveReferencesHandling.Objects;
            ObjectContent<IEnumerable<Model.MenuGroup>> responseContent = new ObjectContent<IEnumerable<Model.MenuGroup>>(g, json); 
            MemoryStream ms = new MemoryStream();

            responseContent.CopyToAsync(ms).Wait();
            ms.Position = 0;
            var sr = new StreamReader(ms);
            var str = sr.ReadToEnd();

This also worked. I also tested it using XML formatter even though I was pretty sure it only ever used JSON (can't be too careful).

Check 3: Enabled .Net Framework debugging. This time when the error occured (in HttpApplication.cs) VS 2012 caught it.

My error:

Despite having marked the property with these attributes,

[XmlIgnore]
[IgnoreDataMember]
[JsonIgnore]

the .Net Source was calling a get on one of my properties. The catch, it was a write-only property. I simply added

get { return null; }

and the problem was solved.

I probably should have just done Check 3 first, but my previous experience with this error has shown it to usually be an error trying to serialize my objects, which was why I had a bit of a head scratcher when they did serialize properly and the error persisted.

Answer 1

How I solved it:

Enabled .Net Framework debugging. Tools -> Options -> Debugging -> Check 'Enable .NET Framework source stepping'

This time when the error occured (in HttpApplication.cs) VS 2012 caught it.