I am trying to do a simple JSON return but I am having issues I have the following below.
public JsonResult GetEventData()
{
var data = Event.Find(x => x.ID != 0);
return Json(data);
}
I get a HTTP 500 with the exception as shown in the title of this question. I also tried
var data = Event.All().ToList()
That gave the same problem.
Is this a bug or my implementation?
It seems that there are circular references in your object hierarchy which is not supported by the JSON serializer. Do you need all the columns? You could pick up only the properties you need in the view:
return Json(new
{
PropertyINeed1 = data.PropertyINeed1,
PropertyINeed2 = data.PropertyINeed2
});
This will make your JSON object lighter and easier to understand. If you have many properties, AutoMapper could be used to automatically map between DTO objects and View objects.
I had the same problem and solved by using Newtonsoft.Json;
var list = JsonConvert.SerializeObject(model,
Formatting.None,
new JsonSerializerSettings() {
ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore
});
return Content(list, "application/json");
This actually happens because the complex objects are what makes the resulting json object fails.
And it fails because when the object is mapped it maps the children, which maps their parents, making a circular reference to occur. Json would take infinite time to serialize it, so it prevents the problem with the exception.
Entity Framework mapping also produces the same behavior, and the solution is to discard all unwanted properties.
Just expliciting the final answer, the whole code would be:
public JsonResult getJson()
{
DataContext db = new DataContext ();
return this.Json(
new {
Result = (from obj in db.Things select new {Id = obj.Id, Name = obj.Name})
}
, JsonRequestBehavior.AllowGet
);
}
It could also be the following in case you don't want the objects inside a Result property:
public JsonResult getJson()
{
DataContext db = new DataContext ();
return this.Json(
(from obj in db.Things select new {Id = obj.Id, Name = obj.Name})
, JsonRequestBehavior.AllowGet
);
}
To sum things up, there are 4 solutions to this:
Solution 1: turn off ProxyCreation for the DBContext and restore it in the end.
private DBEntities db = new DBEntities();//dbcontext
public ActionResult Index()
{
bool proxyCreation = db.Configuration.ProxyCreationEnabled;
try
{
//set ProxyCreation to false
db.Configuration.ProxyCreationEnabled = false;
var data = db.Products.ToList();
return Json(data, JsonRequestBehavior.AllowGet);
}
catch (Exception ex)
{
Response.StatusCode = (int)HttpStatusCode.BadRequest;
return Json(ex.Message);
}
finally
{
//restore ProxyCreation to its original state
db.Configuration.ProxyCreationEnabled = proxyCreation;
}
}
Solution 2: Using JsonConvert by Setting ReferenceLoopHandling to ignore on the serializer settings.
//using using Newtonsoft.Json;
private DBEntities db = new DBEntities();//dbcontext
public ActionResult Index()
{
try
{
var data = db.Products.ToList();
JsonSerializerSettings jss = new JsonSerializerSettings { ReferenceLoopHandling = ReferenceLoopHandling.Ignore };
var result = JsonConvert.SerializeObject(data, Formatting.Indented, jss);
return Json(result, JsonRequestBehavior.AllowGet);
}
catch (Exception ex)
{
Response.StatusCode = (int)HttpStatusCode.BadRequest;
return Json(ex.Message);
}
}
Following two solutions are the same, but using a model is better because it's strong typed.
Solution 3: return a Model which includes the needed properties only.
private DBEntities db = new DBEntities();//dbcontext
public class ProductModel
{
public int Product_ID { get; set;}
public string Product_Name { get; set;}
public double Product_Price { get; set;}
}
public ActionResult Index()
{
try
{
var data = db.Products.Select(p => new ProductModel
{
Product_ID = p.Product_ID,
Product_Name = p.Product_Name,
Product_Price = p.Product_Price
}).ToList();
return Json(data, JsonRequestBehavior.AllowGet);
}
catch (Exception ex)
{
Response.StatusCode = (int)HttpStatusCode.BadRequest;
return Json(ex.Message);
}
}
Solution 4: return a new dynamic object which includes the needed properties only.
private DBEntities db = new DBEntities();//dbcontext
public ActionResult Index()
{
try
{
var data = db.Products.Select(p => new
{
Product_ID = p.Product_ID,
Product_Name = p.Product_Name,
Product_Price = p.Product_Price
}).ToList();
return Json(data, JsonRequestBehavior.AllowGet);
}
catch (Exception ex)
{
Response.StatusCode = (int)HttpStatusCode.BadRequest;
return Json(ex.Message);
}
}
JSON, like xml and various other formats, is a tree-based serialization format. It won't love you if you have circular references in your objects, as the "tree" would be:
root B => child A => parent B => child A => parent B => ...
There are often ways of disabling navigation along a certain path; for example, with XmlSerializer you might mark the parent property as XmlIgnore. I don't know if this is possible with the json serializer in question, nor whether DatabaseColumn has suitable markers (very unlikely, as it would need to reference every serialization API)
add [JsonIgnore] to virtuals properties in your model.
Using Newtonsoft.Json: In your Global.asax Application_Start method add this line:
GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;
Its because of the new DbContext T4 template that is used for generating the EntityFramework entities. In order to be able to perform the change tracking, this templates uses the Proxy pattern, by wrapping your nice POCOs with them. This then causes the issues when serializing with the JavaScriptSerializer.
So then the 2 solutions are:
Either you just serialize and return the properties you need on the client
You may switch off the automatic generation of proxies by setting it on the context's configuration
context.Configuration.ProxyCreationEnabled = false;
Very well explained in the below article.
http://juristr.com/blog/2011/08/javascriptserializer-circular-reference/
Provided answers are good, but I think they can be improved by adding an "architectural" perspective.
Investigation
MVC's Controller.Json function is doing the job, but it is very poor at providing a relevant error in this case. By using Newtonsoft.Json.JsonConvert.SerializeObject, the error specifies exactly what is the property that is triggering the circular reference. This is particularly useful when serializing more complex object hierarchies.
Proper architecture
One should never try to serialize data models (e.g. EF models), as ORM's navigation properties is the road to perdition when it comes to serialization. Data flow should be the following:
Database -> data models -> service models -> JSON string
Service models can be obtained from data models using auto mappers (e.g. Automapper). While this does not guarantee lack of circular references, proper design should do it: service models should contain exactly what the service consumer requires (i.e. the properties).
In those rare cases, when the client requests a hierarchy involving the same object type on different levels, the service can create a linear structure with parent->child relationship (using just identifiers, not references).
Modern applications tend to avoid loading complex data structures at once and service models should be slim. E.g.:
access an event - only header data (identifier, name, date etc.) is loaded -> service model (JSON) containing only header data
managed attendees list - access a popup and lazy load the list -> service model (JSON) containing only the list of attendees
Avoid converting the table object directly. If relations are set between other tables, it might throw this error.
Rather, you can create a model class, assign values to the class object and then serialize it.
I'm Using the fix, Because Using Knockout in MVC5 views.
On action
return Json(ModelHelper.GetJsonModel<Core_User>(viewModel));
function
public static TEntity GetJsonModel<TEntity>(TEntity Entity) where TEntity : class
{
TEntity Entity_ = Activator.CreateInstance(typeof(TEntity)) as TEntity;
foreach (var item in Entity.GetType().GetProperties())
{
if (item.PropertyType.ToString().IndexOf("Generic.ICollection") == -1 && item.PropertyType.ToString().IndexOf("SaymenCore.DAL.") == -1)
item.SetValue(Entity_, Entity.GetPropValue(item.Name));
}
return Entity_;
}
You can notice the properties that cause the circular reference. Then you can do something like:
private Object DeCircular(Object object)
{
// Set properties that cause the circular reference to null
return object
}
//first: Create a class as your view model
public class EventViewModel
{
public int Id{get;set}
public string Property1{get;set;}
public string Property2{get;set;}
}
//then from your method
[HttpGet]
public async Task<ActionResult> GetEvent()
{
var events = await db.Event.Find(x => x.ID != 0);
List<EventViewModel> model = events.Select(event => new EventViewModel(){
Id = event.Id,
Property1 = event.Property1,
Property1 = event.Property2
}).ToList();
return Json(new{ data = model }, JsonRequestBehavior.AllowGet);
}
An easier alternative to solve this problem is to return an string, and format that string to json with JavaScriptSerializer.
public string GetEntityInJson()
{
JavaScriptSerializer j = new JavaScriptSerializer();
var entityList = dataContext.Entitites.Select(x => new { ID = x.ID, AnotherAttribute = x.AnotherAttribute });
return j.Serialize(entityList );
}
It is important the "Select" part, which choose the properties you want in your view. Some object have a reference for the parent. If you do not choose the attributes, the circular reference may appear, if you just take the tables as a whole.
Do not do this:
public string GetEntityInJson()
{
JavaScriptSerializer j = new JavaScriptSerializer();
var entityList = dataContext.Entitites.toList();
return j.Serialize(entityList );
}
Do this instead if you don't want the whole table:
public string GetEntityInJson()
{
JavaScriptSerializer j = new JavaScriptSerializer();
var entityList = dataContext.Entitites.Select(x => new { ID = x.ID, AnotherAttribute = x.AnotherAttribute });
return j.Serialize(entityList );
}
This helps render a view with less data, just with the attributes you need, and makes your web run faster.
I am new to Unit Testing and am trying to create some Xunit tests for my Web API Controller's POST method.
Here is my Controller's POST method:
[HttpPost("")]
public async Task<IActionResult> CreateArea([FromBody] AreaForCreationDto area)
{
// Check that the 'area' object parameter can be de-serialised to a AreaForCreationDto.
if (area == null)
{
var message = "Could not de-serialise the request body to an AreaForCreationDto object";
_logger.LogError(message);
// Return an error 400.
return BadRequest(message);
}
/*
* ModelState.IsValid is determined by the attributes associated with the
* Data Annotations on the properties of the ViewModel.
*/
if (!ModelState.IsValid)
{
// Return a response with a Status Code 422.
return new UnprocessableEntityObjectResult(ModelState);
};
// Map a AreaForCreationDto object to a Area entity.
var areaEntityToAdd = _mapper.Map<Area>(area);
// Call the repository to add the new Area entity to the DbContext.
_areaRepository.AddArea(areaEntityToAdd);
// Save the new Area entity, added to the DbContext, to the SQL database.
if (await _areaRepository.SaveChangesAsync())
{
// Note: AutoMapper maps the values of the properties from the areaEntityToAdd
// to a new areaToReturn object.
// This ensures that we don't expose our Area entity to the web browser.
var areaToReturn = _mapper.Map<AreaDto>(areaEntityToAdd);
// Return a 201 'created' response along with the location URL in the
// response Header.
return CreatedAtRoute("GetArea",
new { id = areaToReturn.Id },
areaToReturn);
}
else {
// The save failed.
var message = $"Could not save new Area {areaEntityToAdd.Id} to the database.";
_logger.LogWarning(message);
throw new Exception(message);
};
}
The first Unit Test I have written is intended to ensure that on sending a POST request, with an object which can be de-serialised into an AreaForCreation object, the function returns a 201 CreatedAtRouteResult along with the new Area which has been created.
Here is the Xunit test:
[Fact]
public void ReturnAreaForCreateArea()
{
//Arrange
var _mockAreaRepository = new Mock<IAreaRepository>();
_mockAreaRepository
.Setup(x => x.AddArea(testArea));
var _mockMapper = new Mock<IMapper>();
_mockMapper
.Setup(_ => _.Map<Area>(It.IsAny<AreaForCreationDto>()))
.Returns(testArea);
var _mockLogger = new Mock<ILogger<AreasController>>();
var _sut = new AreasController(_mockAreaRepository.Object, _mockLogger.Object, _mockMapper.Object);
// Act
var result = _sut.CreateArea(testAreaForCreationDto);
// Assert
Assert.NotNull(result);
var objectResult = Assert.IsType<CreatedAtRouteResult>(result);
var model = Assert.IsAssignableFrom<AreaDto>(objectResult.Value);
var areaDescription = model.Description;
Assert.Equal("Test Area For Creation", areaDescription);
}
I am getting an exception thrown when the unit test tries to Assert.IsType<CreatedAtRouteResult>(result). Debugging revealed that the Controller was failing to save to the repository. My AreaRepository has the following AddArea function which does not return a value so I assume that my _mockAreaRepository does not require a Return condition set (could be wrong here).
Do I need to configure my mockAreasRepository for the outcome of calling SaveChangesAsync()?
Yes because it is async you need to mock the return of a completed task to allow the method
await _areaRepository.SaveChangesAsync()
to be able to continue.
You also need to update the test to be async as well by returning a Task and await the method under test.
[Fact]
public async Task ReturnAreaForCreateArea() { //<-- note test is now async as well
//Arrange
var _mockAreaRepository = new Mock<IAreaRepository>();
_mockAreaRepository
.Setup(x => x.AddArea(testArea));
_mockAreaRepository
.Setup(x => x.SaveChangesAsync())
.ReturnsAsync(true); //<-- returns completed Task<bool> when invoked
var _mockMapper = new Mock<IMapper>();
_mockMapper
.Setup(_ => _.Map<Area>(It.IsAny<AreaForCreationDto>()))
.Returns(testArea);
_mockMapper
.Setup(_ => _.Map<AreaDto>(It.IsAny<Area>()))
.Returns(testAreaDto);
var _mockLogger = new Mock<ILogger<AreasController>>();
var _sut = new AreasController(_mockAreaRepository.Object, _mockLogger.Object, _mockMapper.Object);
// Act
var result = await _sut.CreateArea(testAreaForCreationDto);//<-- await
// Assert
Assert.NotNull(result);
var objectResult = Assert.IsType<CreatedAtRouteResult>(result);
var model = Assert.IsAssignableFrom<AreaDto>(objectResult.Value);
var areaDescription = model.Description;
Assert.Equal("Test Area For Creation", areaDescription);
}
Below is the setup that I am trying to test.
The controller:
public ActionResult UpsertStudent(StudentModel studentModel)
{
try
{
if (!CheckStudentUpdateForEdit(studentModel))
{
return Json(new { result = STUDENT_EXISTS });
}
// remaining code removed for brevity
}
private bool CheckStudentUpdateForEdit(StudentModel studentModel)
{
var returnVal = true;
var existingStudent = _updateStudentManager.GetStudentInfo(studentModel.Id);
if (existingStudent.StudentType == "Day Scholar")
{
returnVal = true;
}
else
{
returnVal = false;
}
return returnVal;
}
The Test method:
public void AllowStudentUpdates_Success()
{
var studentModel = new StudentModel()
{
StudentName = "Joe",
Id = "123",
StudentType = "Day Scholar"
};
var studentToAdd = new Student()
{
Id = "123",
Name = "Joe",
StartDate = DateTime.UtcNow.ToShortDateString(),
StudentType = "Day Scholar",
EndDate = "08/10/2016"
};
_studentRulesHelper.Setup(x => x.GetStudentRule(studentModel, true)).Returns(studentToAdd);
_productRulesHelper.Setup(x => x.ReturnStudentRule(studentModel, true)).Returns(studentToAdd);
var res = _controller.UpsertStudent(studentModel) as JsonResult;
if (res != null) Assert.AreEqual("{ result = True }", res.Data.ToString());
}
When it hits the UpsertDoc call, it goes to the actual call in the controller and tries to execute CheckStudentUpdateForEdit() the GetStudentInfo() tries to get an object from the db and returns a null object as there is no student with the id that's passed from the test method.
The test then fails with Null Reference exception.
Now the system under test is not supposed to hit the db. I don't know why this is doing the other way!
Anyone else writing this test will also try to pass a dummy object which is bound to fail at GetStudentInfo() the way the test is setup now.
What do I do to make this work?
I am not sure if I have understood you problem correctly, but looking at the code snippets provided, the test will go and hit the database, because the mock object and its expectation is not defined.
I would have implemented the solution like this -
I am making some assumptions that your _updateStudentManager object is for the class that is doing the DB interaction for Student. I'll call it say StudentRepository. And to allow you to mock the behavior I would make it Interface driven.
So typically my setup would look like this -
//Interface
public interface IStudentrepository
{
StudentModel GetStudentInfo(int studentId);
}
//Class implementing IStudentrepository
public class StudentRepository : IStudentrepository
{
public StudentModel GetStudentInfo(int studentId)
{
//Implementation goes here
}
}
Now in my controller, I would have an instance of IStudentrepository, which can be injected via constructor.
public class StudentController
{
private readonly IStudentrepository updateStudentManager;
public StudentController(IStudentrepository updateStudentManager)
{
this.updateStudentManager = updateStudentManager;
}
}
//Rest of the code for controller....
Now while writing my Test, I will create a mock object of IStudentrepository, define the expectation for the mock object, and inject it when creating the controller object. Something like this.
[TestMethod]
public void TestMethod1()
{
//--Arrange--
//Define a mock object for student repository
var mock = new Mock<IStudentrepository>();
//Define the expectations of the mock object
mock.Setup(s => s.GetStudentInfo(It.IsAny<int>()))
.Returns(new StudentModel {/*return the required object */ });
//Instantiate controller and inject the mock object
StudentController _controller = new StudentController(mock.Object);
//--Act--
var res = _controller.UpsertStudent(studentModel) as JsonResult;
//--Assert--
if (res != null) Assert.AreEqual("{ result = True }", res.Data.ToString());
}
Now when your test method calls the GetStudentInfo method, instead of hitting the db, it will return the value as set in mock object.
This is just a high level implementation, and of course you can modify it as per your design. Hope it helps
I am testing the OData Action using ODataActionsSample, which is downloaded from http://aspnet.codeplex.com/sourcecontrol/latest#Samples/WebApi/OData/v4/ODataActionsSample/ODataActionsSample/, as a server and calling the "CheckOut" action which is,
[HttpPost]
public IHttpActionResult CheckOut(int key)
{
var movie = _db.Movies.FirstOrDefault(m => m.ID == key);
if (movie == null)
{
return BadRequest(ModelState);
}
if (!TryCheckoutMovie(movie))
{
return BadRequest("The movie is already checked out.");
}
return Ok(movie);
}
The action returns the movie with updated "DueDate" proprety in the sample program which is calling the action from javascript as below:
// Invoke "checkout" or "return" action. Both actions take no parameter data.
function invokeAction(url) {
ajaxRequest("post", url)
.done(function (updated) {
updateMovie(updated);
})
.fail(function (jqXHR, textStatus, errorThrown) {
//parent.errorMessage(errorThrown);
parent.errorMessage(url);
});
}
self.update(data);
// Update the model with new data from the server.
function updateMovie(data) {
var dueDate = data.DueDate ? new Date(data.DueDate) : null;
self.dueDate(dueDate);
if (data["#ODataActionsSample.Models.CheckOut"]) {
self.checkoutUrl(data["#ODataActionsSample.Models.CheckOut"].target);
}
else {
self.checkoutUrl(null);
}
if (data["#ODataActionsSample.Models.Return"]) {
self.returnMovieUrl(data["#ODataActionsSample.Models.Return"].target);
}
else {
self.returnMovieUrl(null);
}
}
However, the call from OData Client returns the movie without the DueDate updated. The client code is as below:
string serviceUri = "http://localhost:44221/OData/";
var container = new Container(new Uri(serviceUri));
var movieQuery = from movie in container.Movies select movie;
DataServiceCollection<ODataActionsClient.Movie> trackedMovies = new DataServiceCollection<ODataActionsClient.Movie>(movieQuery, TrackingMode.AutoChangeTracking, "Movies",null,null);
var myMovie = trackedMovies[0];
try
{
var checkouttedMovie = myMovie.CheckOut().GetValue();
}
catch (Exception ex)
{
Console.WriteLine(ex.InnerException.ToString());
}
What is wrong with my code in the client side ?
The default value for merge option is AppendOnly : No current values are modified.
OverwriteChanges : All current values are overwritten with current store values, regardless of whether they have been changed.
PreserveChanges: Current values that have been changed are not modified, but any unchanged values are updated with the current store values. No changes are lost in this merge.
So you have to decide which option you want to achieve, in this case I think OverwriteChanges is good enough.
FYI : https://msdn.microsoft.com/en-us/library/system.data.objects.mergeoption(v=vs.110).aspx
I'm working with ASP.Net MVC4, I customize my login, this is ok, I would like save this object USER and I can access from differents controllers and differents Areas. I was trying to defined this object as "static" but I can't acces to values of object:
if (Servicio.ValidarUsuario())
{
string Mensaje = "";
Models.AdmUsuario oAdmUsuario = new Models.AdmUsuario();
oAdmUsuario.Au_codusuario = login.UserName;
Servicio.RetornaEntidad<Models.AdmUsuario>(ref Mensaje, "admsis.adm_usuario", oAdmUsuario.getPk(), oAdmUsuario);
***Models.AdmUsuario.UserWeb = oAdmUsuario;***
FormsAuthentication.SetAuthCookie(login.UserName, false);
Session["Modulo"] = null;
Session["Menu"] = null;
return RedirectToAction("index", "raMainReclamo", new { area = "Reclamos" });
}
In the model I define:
public static AdmUsuario UserWeb;
But I can't access to value.
Do you have any idea, how I can to access the values of an object from different controllers in different areas?
You need a way to store the object between requests. You could put the object in Session Memory and pull it back out.
{
// Other Code
Session["AdmUsuario"] = oAdmUsuario;
return RedirectToAction("index", "raMainReclamo", new { area = "Reclamos" });
}
Controller in Reclamos Area
public class raMainReclamoController : Controller
{
public ActionResult Index() {
var oAdmUsuario = Session["AdmUsuario"] as Models.AdmUsuario;
// Other Code
}
}
However, the a more standard approach would be to persist the object to a database and then pull it back out. You could read up on using Entity Framework to access a sql database. I like to use RavenDB for storage as it makes saving objects really easy.
** UPDATE IN RESPONSE TO COMMENTS **
This is just psuedo code as I don't know what you are using to connect to postgres.
{
// Other Code
oAdmUsuario = postgresContext.Store(oAdmUsuario);
postgresContext.SaveChanges();
return RedirectToAction("index", "raMainReclamo", new { area = "Reclamos", id = oAdmnUsuario.Id });
}
Controller in Reclamos Area
public class raMainReclamoController : Controller
{
public ActionResult Index(int id) {
var oAdmUsuario = postgresContext.GetById<Models.AdmUsuario>(id);
// Other Code
}