Essentially I have a Root class to serialize/deserialize JSON data that looks like this:
public class Root
{
[JsonIgnore]
public string JoystickName { get; set; }
public Root(string joystickName)
{
JoystickName = joystickName;
}
[JsonProperty("g")]
public string G { get; set; }
[JsonProperty(PropertyName = JoystickName)] // This line produces error
public DxsJoyConfig Joystick { get; set; }
}
*EDIT:
How do I change the property name at runtime?
I'm also running into an object reference error required at the indicated line. How can I make an instance of JoystickName within the attribute?
I have a sqlite database which has some tables and columns like the following:
int Id
text Name
text Comment
...
And my object in my project looks like this:
Public Class Entry {
public int Id { get; set; }
public String Name { get; set; }
public String Comment { get; set; }
public String Additional { get; set; }
}
This can happen, because my programm need to handle different versions of the database.
EF Core now trys to access the Additional field of the database but returns an error that it cannot find the field. (Expected behaviour)
Now my question is, if there is a way to ignore this error and return a default value for the property?
I could bypass the error by making the properties nullable. But i don't want to check each property with .HasValue() before accessing it. Because the real database has 50+ columns in the table.
https://www.entityframeworktutorial.net/code-first/notmapped-dataannotations-attribute-in-code-first.aspx
Put NotMapped as an attribute on the Additional field:
using System.ComponentModel.DataAnnotations.Schema;
Public Class Entry {
public int Id { get; set; }
public String Name { get; set; }
public String Comment { get; set; }
[NotMapped]
public String Additional { get; set; }
}
This tells EF that the field is not a column in the database.
I would advise you to split your domain object from that persisted dto object. That way you can have different dtos with different mappings. Now you can instantiate your domain object with your dto and decide inside your domain object what values are the correct default values.
public class Entry
{
public int Id { get; set; }
public string Name { get; set; }
public string Comment { get; set; }
public string Additional { get; set; }
}
public class EntryDtoV1
{
public int Id { get; set; }
public string Name { get; set; }
public string Comment { get; set; }
}
public class EntryDtoV2
{
public int Id { get; set; }
public string Name { get; set; }
public string Comment { get; set; }
public string Additional { get; set; }
}
Now you only need to create some kind of factory that creates the correct repository depending on what database version you query.
For my example, I have two classes
public class Location
{
public int Id { get; set; }
public string Name { get; set; }
public string Address1 { get; set; }
public string Address2 { get; set; }
public string Address3 { get; set; }
public string Town { get; set; }
public string County { get; set; }
public string CountryCode { get; set; }
}
public class Customer : Location
{
public string BankAccountNumber { get; set; }
public string BankSortCode { get; set; }
}
In my query, I am returning all the locations and customers.
http://localhost:80/odata/Location?select=Id,Name,Town
However if I try to select anything in the customer (edit: So I want all locations, but bank account numbers if the location is also a customer), I get an error.
http://localhost:80/odata/Location?select=Id,Name,Town,BankAccountNumber
"The query specified in the URI is not valid. Could not find a property named 'BankAccountNumber' on type 'MyNamespace.Location'."
Is there any way to select the field in inheriting types, without selecting all? Thanks.
According to OData.org, there are 2 options to query a derived type:
~/Location!Customer/
~/Location/OfType('Customer')
So your query should look like this:
http://localhost:80/odata/Location!Customer?select=Id,Name,Town,BankAccountNumber
or
http://localhost:80/odata/Location/OfType('Customer')?select=Id,Name,Town,BankAccountNumber
/EDIT:
QianLi pointed out, that the above blog entry refers to OData V2. In Odata4 inherited types are accessed in the following syntax:
http://host/service/BaseType/Model.SubType
Reference: http://docs.oasis-open.org/odata/odata/v4.0/os/part2-url-conventions/odata-v4.0-os-part2-url-conventions.html#_Toc372793786
You should add not only the Type name but also the namespace of the type.
For example:
http://services.odata.org/TripPinWebApiService/People('russellwhyte')/Trips(1001)/PlanItems/ODataSamples.WebApiService.Models.Flight?$select=StartsAt
The type Flight inherits from the type PlanItem. And ODataSamples.WebApiService.Models is the namespace.
More detailed information of derived type, you can refer to http://www.odata.org/getting-started/advanced-tutorial/ with some live example if you find the spec too long to read...
I'm using the official MongoDB C# Driver to communicate with my MongoDB Servers.
This is my complete entity scheme:
public class Person
{
public ObjectId _id { get; set; }
public String FirstName { get; set; }
public String LastName { get; set; }
public DateTime DateOfBirth { get; set; }
public List<Address> Addresses { get; set; }
}
public class Address
{
public String Street { get; set; }
public String City { get; set; }
}
Now, in several cases i just want to get the following return:
public class Person_LocationOview
{
public String LastName { get; set; }
public List<Address_CityOnly> Addresses { get; set; }
}
public class Address_CityOnly
{
public String City { get; set; }
}
The default behavior to load all fields and do the mapping by myself
MongoCursor<Person>
is senseless, because I just want to load the specific fields.
With the help of reflection I generate the fields to load and send:
var fields = new { "LastName", "Addresses.City" };
MongoCollection< BsonDocument >.FindAllAs< Person_LocationOview >( )
.SetFields( fields ).ToList( );
I thought the serializer of MongoDB would be intelligent; but the call returns following error:
System.IO.FileFormatException: Required element 'City' for property 'City' of class Models.Address_CityOnly is missing
Any ideas to this requirement?
I've updated the complete MongoDB infrastructure. Now the code works with all viewModels such as Person_LocationOview. With the full scheme classes, the code still crashes and I do not know why.
Now, all my view classes are implementing an own interface (IPartialEntityView).
In my reflection method to get the field names I'll check this inheritance and only then I will load "Addresses.FieldName(s)". If the property type is no default .NET type or does not inherit IPartialEntityView I will use the complete field "Adresses".
That works great.
Thanks for all.
I am getting an a Circular Reference Serialization Error although, to my knowledge I do not have any circular references. I am retrieving a set of Orders from the database and sending them to the client as JSON. All the code is shown below.
This is the error:
Error
A circular reference was detected
while serializing an object of type
'System.Data.Entity.DynamicProxies.Order_83CECF2AA4DE38232F9077D4B26941AB96BC61230419EA8AC42C9100E6072812'.
Description: An unhandled exception
occurred during the execution of the
current web request. Please review the
stack trace for more information about
the error and where it originated in
the code.
Exception Details:
System.InvalidOperationException: A
circular reference was detected while
serializing an object of type
'System.Data.Entity.DynamicProxies.Order_83CECF2AA4DE38232F9077D4B26941AB96BC61230419EA8AC42C9100E6072812'.
Source Error:
An unhandled exception was generated
during the execution of the current
web request. Information regarding the
origin and location of the exception
can be identified using the exception
stack trace below.
My classes are as follows:
Order
public class Order
{
[Key]
public int OrderId { get; set; }
public int PatientId { get; set; }
public virtual Patient Patient { get; set; }
public int CertificationPeriodId { get; set; }
public virtual CertificationPeriod CertificationPeriod { get; set; }
public int AgencyId { get; set; }
public virtual Agency Agency { get; set; }
public int PrimaryDiagnosisId { get; set; }
public virtual Diagnosis PrimaryDiagnosis { get; set; }
public int ApprovalStatusId { get; set; }
public virtual OrderApprovalStatus ApprovalStatus { get; set; }
public int ApproverId { get; set; }
public virtual User Approver { get; set; }
public int SubmitterId { get; set; }
public virtual User Submitter { get; set; }
public DateTime ApprovalDate { get; set; }
public DateTime SubmittedDate { get; set; }
public Boolean IsDeprecated { get; set; }
}
Patient
public class Patient
{
[Key]
public int PatientId { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string MiddleInitial { get; set; }
public bool IsMale;
public DateTime DateOfBirth { get; set; }
public int PatientAddressId { get; set; }
public Address PatientAddress { get; set; }
public bool IsDeprecated { get; set; }
}
Certification Period
public class CertificationPeriod
{
[Key]
public int CertificationPeriodId { get; set; }
public DateTime startDate { get; set; }
public DateTime endDate { get; set; }
public bool isDeprecated { get; set; }
}
Agency
public class Agency
{
[Key]
public int AgencyId { get; set; }
public string Name { get; set; }
public int PatientAddressId { get; set; }
public virtual Address Address { get; set; }
}
Diagnosis
public class Diagnosis
{
[Key]
public int DiagnosisId { get; set; }
public string Icd9Code { get; set; }
public string Description { get; set; }
public DateTime DateOfDiagnosis { get; set; }
public string Onset { get; set; }
public string Details { get; set; }
}
OrderApprovalStatus
public class OrderApprovalStatus
{
[Key]
public int OrderApprovalStatusId { get; set; }
public string Status { get; set; }
}
User
public class User
{
[Key]
public int UserId { get; set; }
public string Login { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string NPI { get; set; }
public string Email { get; set; }
}
NOTE: ADDRESS CLASS IS NEW ADDITION DURING EDIT
Address
public class Address
{
[Key]
public int AddressId { get; set; }
public string StreetAddress { get; set; }
public string City { get; set; }
public string State { get; set; }
public string Zip { get; set; }
public string Phone { get; set; }
public string Title { get; set; }
public string Label { get; set; }
}
The code that executes the serialization is here:
Excerpt from OrderController
public ActionResult GetAll()
{
return Json(ppEFContext.Orders, JsonRequestBehavior.AllowGet);
}
Thanks
You could try to remove the virtual keyword from all navigation properties to disable lazy loading and proxy creation and then use eager loading instead to load the required object graph explicitely:
public ActionResult GetAll()
{
return Json(ppEFContext.Orders
.Include(o => o.Patient)
.Include(o => o.Patient.PatientAddress)
.Include(o => o.CertificationPeriod)
.Include(o => o.Agency)
.Include(o => o.Agency.Address)
.Include(o => o.PrimaryDiagnosis)
.Include(o => o.ApprovalStatus)
.Include(o => o.Approver)
.Include(o => o.Submitter),
JsonRequestBehavior.AllowGet);
}
Referring to your previous post it looks like your application isn't relying on lazy loading anyway because you introduced there the virtual properties to load the object graph lazily, possibly causing now the serialization trouble.
Edit
It's not necessary to remove the virtual keyword from the navigation properties (which would make lazy loading completely impossible for the model). It's enough to disable proxy creation (which disables lazy loading as well) for the specific circumstances where proxies are disturbing, like serialization:
ppEFContext.Configuration.ProxyCreationEnabled = false;
This disables proxy creation only for the specific context instance ppEFContext.
(I've just seen, #WillC already mentioned it here. Upvote for this edit please to his answer.)
When you know that you need to serialize from a particular context, you can disable proxy creation for that particular query like below. This has worked for me and is better than revising my model classes.
using (var context = new MeContext())
{
context.Configuration.ProxyCreationEnabled = false;
return context.cars.Where(w => w.Brand == "Ferrari")
}
This approach takes away the proxy object type for this particular instance of the context so the returned objects are the actual class and therefore serialization is not a problem.
ie:
{Models.car}
instead of
{System.Data.Entity.DynamicProxies.car_231710A36F27E54BC6CE99BB50E0FE3B6BD4462ECA19695CD1BABB79605296EB}
The problem is that your are actually serializing an entity framework generated proxy object. Unfortunatly this has some issues when used with the JSON serializer. You might consider to map your entities to special simple POCO classes for the sake of JSON compatibility.
There is an attribute to add to Entity Framework objects
[ScriptIgnore]
This makes the code not perform Circular references.
I think they have fixed this in the latest version.
Check out the help docs under the section "Serializing and Deserializing JSON -> Serialization and Preserving Object References".
Set this setting when initializing the JSON.Net Serializer:
PreserveReferencesHandling = PreserveReferencesHandling.Objects;
So an example would be this:
var serializerSettings = new JsonSerializerSettings { PreserveReferencesHandling = PreserveReferencesHandling.Objects };
string json = JsonConvert.SerializeObject(people, Formatting.Indented, serializerSettings);
I verified that this works with my code first solution, and a circular reference in the navigation properties. If you look at the resulting JSON it should have "$id" and "$ref" properties everywhere.
An alternative solution would be to use anonymous types as the result of a LINQ query.
In my project, I am using lazy loading extensively, and disabling it was not the right thing to do.
An alternative solution, if only some values from objects are necessary, is build an anonymous class and return it, like the example below:
public JsonResult AjaxFindByName(string term)
{
var customers = context.Customers
.Where(c => c.Name.ToUpper().Contains(term.ToUpper())).Take(10)
.AsEnumerable()
.Select(c => new {
value = c.Name,
SSN = String.Format(#"{0:000\-00\-0000}", c.SSN),
CustomerID = c.CustomerID });
return Json(customers, JsonRequestBehavior.AllowGet);
}
The circular reference happens because you use eager loading on the object.
You have a couple of methods:
Turn off eager loading when your loading your Query (linq or lambda)
DbContext.Configuration.ProxyCreationEnabled = false;
Remove the virtual keyword from the Domainmodel
Detach the objects (= no eager loading functionality & no proxy)
Repository.Detach(entityObject)
DbContext.Entry(entityObject).EntityState = EntityState.Detached
Clone the properties
You could use something like AutoMapper to clone the object, don't use the ICloneable interface, because it also clones the ProxyProperties in the object, so that won't work.
In case you are building an API, try using a separte project with a different configuration (that doesn't return proxies)
PS. Proxies is the object that's created by EF when you load it from the Entity Framework. In short: It means that it holds the original values and updated values so they can be updated later. It handles other things to ;-)
For those using the proxy EF/Linq2SQL classes my solution was to simply remove the parent reference on my child entities.
So in my model, I selected the relationship and changed the Parent reference to be Internal rather than Public.
May not be an ideal solution for all, but worked for me.
You can remove the virtual keyword:
public virtual Patient Patient { get; set; } -> public Patient Patient { get; set; }
Keep in mind that when you remove the virtual keyword, lazy loading will be turned off.
I was able to solve this problem by using the method described here:
http://mytechworld.officeacuity.com/index.php/2010/02/serializing-entity-framework-objects-into-json-using-asp-net-mvc/