将IEnumerable从Web API控制器发送到angular js

Question

I'm trying to send a IEnumerable from a web api controller to a AngularJs controller. The code I was using was

Web Api:

readonly InventoryEntities _db = new InventoryEntities();

public IEnumerable<FDVOEligibilityRequest> Get()
{
   return _db.FDVOEligibilityRequests.AsEnumerable();
}

AngularJS:

//get all customer information
$http.get("/api/Customer/").success(function (data) {
        $scope.requests = data;
        $scope.loading = false;
    })
    .error(function () {
        $scope.error = "An Error has occured while loading posts!";
        $scope.loading = false;
    });

This worked fine, but now I'm using linq to include related tables and it doesn't work. The angularJs code is the same. What am I doing wrong?

readonly InventoryEntities _db = new InventoryEntities();

public IEnumerable<FDVOEligibilityRequest> Get()
{
    return _db.FDVOEligibilityRequests
        .Include("FDVOEligibilityRequestMandatoryField")
        .Include("FDVOEligibilityRequestDCCField").AsEnumerable();
}

I do get the data I want in the controller, but when i try to send it back to angular, I get a 500 (Internal Server Error) angular.js:10722

This is what FDVOEligibilityRequest looks like in the new Web Api controller

public partial class FDVOEligibilityRequest
{
    public int Id { get; set; }
    public string TestName { get; set; }
    public string GroupName { get; set; }
    public int MandatoryFieldsID { get; set; }
    public int DCCFieldsID { get; set; }
    public virtual FDVOEligibilityRequestMandatoryField FDVOEligibilityRequestMandatoryField { get; set; }
    public virtual FDVOEligibilityRequestDCCField FDVOEligibilityRequestDCCField { get; set; }
}

Answer 1

If it's 500 and happens after you successfully make a return from your action then it can be an exception during serialization.

I would suggest to check that there are no circular references between FDVOEligibilityRequest and FDVOEligibilityRequestMandatoryField/FDVOEligibilityRequestDCCField.

Or try to diagnose it using code from here :

string Serialize<T>(MediaTypeFormatter formatter, T value)
{
    // Create a dummy HTTP Content.
    Stream stream = new MemoryStream();
    var content = new StreamContent(stream);
    /// Serialize the object.
    formatter.WriteToStreamAsync(typeof(T), value, stream, content, null).Wait();
    // Read the serialized string.
    stream.Position = 0;
    return content.ReadAsStringAsync().Result;
}

try {
    var val = _db.FDVOEligibilityRequests
        .Include("FDVOEligibilityRequestMandatoryField")
        .Include("FDVOEligibilityRequestDCCField").AsEnumerable();
    var str = Serialize(new JsonMediaTypeFormatter(), val);
}
catch (Exception x) 
{ // break point here
}

ps: the common suggestion in this case is to use DTOs instead of EF objects with something like Automapper .