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.
Is the essence of Project, the creation of which is necessary to check whether there is already an entity with the same name. When editing needs such as checking, but keep in mind that the old and the new name of the entity can be matched.
You also need to display an error message. For this I use interface IValidatableObject, but do not know how to tell the Validate method the object is currently being edited or created
DbContext.ValidateEntity takes the IDictionary<Object, Object> items as the second parameter. You can pass any data there and the data you pass will be passed to IValidatableObject.Validate in the ValidationContext.Items
Assuming you refer to check EF cant do for you.
This is actually difficult to check. You are checking an entity after it has been added to the context. It should not check itself and needs to consider other items in context that are not yet saved. As well as the DB. There are several 3 combinations plus an self recognition. Record a an entity record in LOCAL when ID is blank/new ie multiple new inserts needs careful coding. (Consider using temp IDs)
the not yet saved entries should be in context
Context.Set<TPoco>().Local
and get data from DB and keep in a temp list. BUT dont put in context.
Or use a SECOND context.
var matchingSet = Context.Set<TPoco>().AsNoTracking() // not into context...
.Where(t=>t.field == somevalue).ToList();
So what about logical and actual duplicates on the DB. Logical duplicates are duplicates on a field with no unique index that from a business perspective should be unique.
If you want to check those...
You need to read the DB.... BUT if these records are currently being changed, you CAN NOT just put them into the Context. You would overwrite them.
But what if the values the logical key values have changed?
Something caused a logical dup on a record on the DB may no longer be a dup once saved or vice verse. Is that still a dup or not ?
So you need to decide how you match LOCAL versus loaded records.
Ie check LOCAL and matching DB records and decidr what to do if a record is in both, only local or only db.
LOCAL ONLY and DB Only is easy.
But in both... That is your business process decision.
Problem is solved using method ModelState.AddModelError (string, string) in actions Edit and Create.
[HttpPost]
[HandleError(View="AjaxError")]
public ActionResult Edit(ProjectsViewData data)
{
if (ModelState.IsValid)
{
if (!ContainsProject(data.CurrentObject.Name))
{
db.Projects.Attach(data.CurrentObject);
db.ObjectStateManager.ChangeObjectState(data.CurrentObject, EntityState.Modified);
db.SaveChanges();
return Projects(data);
}
else
{
int projectId = (from p in db.Projects
where p.Name == data.CurrentObject.Name
select p.ProjectID).FirstOrDefault();
if (projectId == data.CurrentObject.ProjectID)
{
db.Projects.Attach(data.CurrentObject);
db.ObjectStateManager.ChangeObjectState(data.CurrentObject, EntityState.Modified);
db.SaveChanges();
return Projects(data);
}
else
{
ModelState.AddModelError("Name", Localizer.ProjectAlreadyExists);
}
}
}
data.ObjectToEdit = data.CurrentObject;
return Projects(data);
}
[HttpPost]
[HandleError(View = "AjaxError")]
public ActionResult Create(ProjectsViewData data)
{
if (ModelState.IsValid)
{
if (!ContainsProject(data.CurrentObject.Name))
{
db.Projects.AddObject(data.CurrentObject);
db.SaveChanges();
return Projects(data);
}
else
{
ModelState.AddModelError("Name", Localizer.ProjectAlreadyExists);
}
}
data.ObjectToAdd = data.CurrentObject;
return Projects(data);
}
Helper method:
private bool ContainsProject(string projectName)
{
if (projectName != null)
{
projectName = Regex.Replace(projectName.Trim(), "\\s+", " ");
List<string> projects = new List<string>();
var projectNames = (from p in db.Projects
select p.Name.Trim()).ToList();
foreach (string p in projectNames)
{
projects.Add(Regex.Replace(p, "\\s+", " "));
}
if (projects.Contains(projectName))
{
return true;
}
else
{
return false;
}
}
else
{
return false;
}
}
Im learning MVC 4. I have created a database first project using EF5. In my edit view I want to add a product number to a customer. When I hit save I get the message below. I think it is because product number is null in the product table, hence it cannot update. Can I get around this? I have added my edit control
public ActionResult Edit(int id = 0)
{
UserProfile userprofile = db.UserProfiles.Find(id);
if (userprofile == null)
{
return HttpNotFound();
}
//ViewBag.userId = new SelectList(db.Devices, "DeviceID", "DeviceIMEI", userprofile.UserId);THIS CREATES A NEW ENTRY IN USERPROFILE TABLE
ViewBag.Device_DeviceID = new SelectList(db.Devices, "DeviceID", "DeviceIMEI", userprofile.Device);
ViewBag.ShippingDetails_ShippingDetailsID = new SelectList(db.ShippingDetails, "ShippingDetailsID", "Address1", userprofile.ShippingDetails_ShippingDetailsID);
return View(userprofile);
}
//
// POST: /User/Edit/5
[HttpPost]
public ActionResult Edit(UserProfile userprofile)
{
if (ModelState.IsValid)
{
db.Entry(userprofile).State = EntityState.Modified;
db.SaveChanges();
return RedirectToAction("Index");
}
//ViewBag.userId = new SelectList(db.Devices, "DeviceID", "DeviceIMEI", userprofile.UserId);
ViewBag.Device_DeviceID = new SelectList(db.Devices, "DeviceID", "DeviceIMEI", userprofile.Device);
ViewBag.ShippingDetails_ShippingDetailsID = new SelectList(db.ShippingDetails, "ShippingDetailsID", "Address1", userprofile.ShippingDetails_ShippingDetailsID);
return View(userprofile);
}
"Store update, insert, or delete statement affected an unexpected number of rows (0). Entities may have been modified or deleted since entities were loaded. Refresh ObjectStateManager entries"
It looks like you dont pass Id of UserProfile from
view to controller.
You should add
#Html.HiddenFor(model => model.Id)
to your form in view
You're posting a view model, which is disconnected from your entity framework, and trying to tell the EF that it has changed -- which it doesn't know about. Try something like this instead,
var obj = yourContext.UserProfiles.Single(q=>q.Id==userProfile.Id);
obj = userprofile; // ... Map userprofile to the tracked object, obj
yourContext.SaveChanges();
Try this:
if (ModelState.IsValid)
{
db.UserProfiles.Attach(userProfile);
db.SaveChanges();
return RedirectToAction("Index");
}
I have this in my mvc ActionResult
[HttpPost]
public ActionResult _ChangeDetails( [Bind(Prefix="ContactDetails")] userDetail UserDetail )
{
MemberChangeDetailsFormViewModel fvm = new MemberChangeDetailsFormViewModel();
if (ModelState.IsValid)
{
//save
UserDetailRepository repository = new UserDetailRepository();
repository.Save(UserDetail);
return RedirectToAction("Index", "Member");
}
fvm.ContactDetails = UserDetail;
return View(fvm);
}
Then in my repository I have;
if (userDetail.id != Guid.Empty)
{
userDetail orig = dc.userDetails.Where(x => x.id == userDetail.id).Single();
dc.userDetails.Attach(userDetail, orig);
dc.Refresh(System.Data.Linq.RefreshMode.KeepCurrentValues, userDetail);
dc.SubmitChanges();
}
However the "attach" is generating an error; Cannot add an entity with a key that is already in use.
I understand that it's caused because L2S already has the object attached. I have tried doing this with and without the orig object but get the same message.
What would be the best practice to update the data in the table from the model?
Linq-to-SQL can't deal with two objects with the same key in the same data context. Some options:
Option 1: Use two different data contexts:
public void Update(UserDetail modifiedUser)
{
using (UserDetailDataContext dc1 = new UserDetailDataContext())
using (UserDetailDataContext dc2 = new UserDetailDataContext())
{
UserDetail originalUser = dc1.UserDetails.Single(u => u.id == modifiedUser.id);
dc2.UserDetails.Attach(modifiedUser, originalUser);
dc2.SubmitChanges();
}
}
Option 2: Don't pull the original object; annotate the new object as an update:
public void Update(UserDetail modifiedUser)
{
using (UserDetailDataContext dc = new UserDetailDataContext())
{
dc.UserDetails.Attach(modifiedUser);
dc.Refresh(RefreshMode.KeepCurrentValues, modifiedUser);
dc.SubmitChanges();
}
}
There's more discussion in this question, and Rick Strahl has a blog entry that covers a versioning-based strategy, if you're willing to modify the table schema to add a timestamp.
I'm using the latest Asp.Net MVC version.
For some reason, when my POST (Action Create) in my controller gets hit.
I can't seem to be able to add it to the entityset.
What i have is,
1) My EntityModel (*.edmx file)
2) Controller which references the entity:
private db.DataContainer _db = new db.DataContainer();
3) My method (i'm using Guid as pk):
[HttpPost]
public ActionResult Create(Client client)
{
try
{
client.Id = Guid.NewGuid();
/* method 2
Client cl = new Client();
cl.Id = Guid.NewGuid();
cl.email = client.email;
cl.Adres = client.Adres;
cl.companyName = client.companyName;
cl.fax = client.fax;
cl.phone = client.phone;
*/
// client.Id = Guid.NewGuid();
_db.ClientSet.AddObject(client);
_db.SaveChanges();
return RedirectToAction("Index");
}
catch (Exception ex)
{
var ex_message = ex.Message;
var ex_data = ex.Data;
var ex_ix = ex.InnerException;
return View();
}
}
4) Following is my InnerException:
[System.Data.SqlClient.SqlException] = {"Cannot insert the value NULL into column 'Id', table 'lst.dbo.ClientSet'; column does not allow nulls. INSERT fails.\r\nThe statement has been terminated."}
Both doesn't seem to work :(
GUIDs are not supported as primary keys in the Entity Framework. You will need to modify your save method to generate a new GUID for your added objects http://msdn.microsoft.com/en-us/library/dd283139.aspx
It seems that changing my "saveCommand" has given my a temporarily solution:
I chaned:
_db.SaveChanges()
To
_db.SaveChanges(System.Data.Objects.SaveOptions.None);