The debugger shows me that in the following code
_taxRate =
PersistentObjectSpace.FindObject<TaxRate>(CriteriaOperator.Parse("[TaxCodeId] = ?", TaxCodeId));
var _product2 =
PersistentObjectSpace.FindObject<Product>(CriteriaOperator.Parse("[ItemId] = ?", ItemId));
_taxRate is a poco but _product2 is a proxy
The objects are
[Table("TaxCode")]
[DefaultProperty("TaxCode")]
[ImageName("BO_List")]
public class TaxRate : BasicBo
{
[Key] public short TaxCodeId { get; set; }
[Required]
[RuleRequiredField(DefaultContexts.Save)]
[StringLength(20, ErrorMessage = "The field cannot exceed 20 characters. ")]
public string TaxCode { get; set; }
[Required]
[RuleRequiredField(DefaultContexts.Save)]
public decimal Percentage { get; set; }
public override string ToString()
{
return TaxCode;
}
}
and
[Table("MyExtItem")]
[DefaultProperty("ProductCode")]
[NavigationItem("Config")]
public class Product : BasicBo
{
[Key]
public int ItemId { get; set; }
public string ItemName { get; set; }
[Column("Item Number")] public string ProductCode { get; set; }
[MaxLength(10)] public string UnitName { get; set; }
public int? ProductImageId { get; set; }
[ForeignKey("ProductImageId")] public virtual ProductImage ProductImage { get; set; }
[ForeignKey("ItemId")] public virtual ExtMaterialProperty ExtMaterial { get; set; }
}
This is expected behaviour when EF is configured to support lazy loading.
TaxRate holds no references to other entities so EF can return a concrete instance.
Product contains two references to other entities, ProductImage and ExtMaterial.
If I run the code:
var product = context.Products.Single(x => x.ItemId == itemId);
to get a product, EF uses a proxy in order to be prepared for when I try to access something like ProductImage.
var imageName = product.ProductImage.Name;
You can disable the proxies using Configuration.ProxyCreationEnabled on the DbContext. (EF6) This does mean that any references will need to be eager loaded or explicitly loaded, as Lazy Loading will not function without the proxies.
I am using Entity Framework 6 with MVC and Web API and I have been toying with whether to use Data Transfer Objects (DTO's) for the JSON api side of things..
I came across AutoMapper and having written some DTO's manually thought (still think) this should be a good way to manage the DTO's.
So, New to it, installed via Nuget, I tried my first mapping. The mblUser class derived from IdentityUser as the source, and I want a simple APIUser to go down the wire..heres the classes:
public class mblUser : IdentityUser
{
public async Task<ClaimsIdentity> GenerateUserIdentityAsync(UserManager<mblUser> manager, string authenticationType = DefaultAuthenticationTypes.ApplicationCookie)
{
//authentication type added to provide for Bearer type of authentication. Still defaults to cookie though so as not to impact the code
// Note the authenticationType must match the one defined in CookieAuthenticationOptions.AuthenticationType
var userIdentity = await manager.CreateIdentityAsync(this, authenticationType );
// Add custom user claims here
return userIdentity;
}
[Display(Name = "Date of Birth IDVIEW")]
[DataType(DataType.DateTime)]
[DisplayFormat(DataFormatString = "{0:d}",
NullDisplayText = "Please Enter Your Date of Birth",
ApplyFormatInEditMode = true)]
public DateTime? DateOfBirth { get; set; }
public string Title { get; set; }
public string FirstName { get; set; }
public string MiddleName { get; set; }
public string LastName {get; set;}
public string DisplayName { get; set; }
public virtual Leader Leader { get; set;}
public virtual Guardian Guardian { get; set; }
public virtual Participant Participant { get; set; }
[NotMapped]
[Display(Name ="Full Name")]
public string FullName
{
get
{
return FirstName + (MiddleName !=null ? " " + MiddleName : "") + (LastName != null ? " " + LastName :"");
}
}
[NotMapped]
[Display(Name ="Details Complete")]
public bool DetailsComplete
{
get
{
if (string.IsNullOrEmpty(FullName.Trim()) || string.IsNullOrEmpty(Email) )
{
// set true if we have something of a name and an email address..
return false;
}
else
{
return true;
}
}
}
}
.. and heres the APIUser:
public class APIUser
{
private string Id { get; set; }
private string Email { get; set; }
private string UserName { get; set; }
private string Title { get; set; }
private string FirstName { get; set; }
private string MiddleName { get; set; }
private string LastName { get; set; }
private string DisplayName { get; set; }
private string PhoneNumber { get; set; }
}
... and heres the mapping code:
// GET: api/userSettings/5
[ResponseType(typeof(APIUser))]
public async Task<IHttpActionResult> GetmblUser(string username)
{
mblUser User = await UserManager.FindByNameAsync(username);
if (User == null)
{
return NotFound();
}
Mapper.CreateMap<mblUser, APIUser>();
APIUser dto = Mapper.Map<APIUser>(User); <-- here all User members are valid and populated.
return Ok(dto); <--at a breakpoint here.. all dto members are null.
}
I figure I must be doing some kind of Newbie error or something but cant figure out what? I did wonder if it is because the mblUser is derived from IdentityUser but the documentation is far from clear on that issue.
Out of interest, I did spot another issue that seems related here and I do indeed have AutoMapper.Net4 in my references as well as AutoMapper, but I have also seen that it is required elsewhere, so am a bit stuck ..
Any help would be appreciated.
You need to make your properties public before they can be mapped.
public class APIUser
{
public string Id { get; set; }
public string Email { get; set; }
public string UserName { get; set; }
public string Title { get; set; }
public string FirstName { get; set; }
public string MiddleName { get; set; }
public string LastName { get; set; }
public string DisplayName { get; set; }
public string PhoneNumber { get; set; }
}
I'm writing a Web API project in C# that uses Entity Framework to pull data from a DB, serialize it and send it to a client.
My project has 2 classes, Post and Comment (foreign key from Post).
These are my classes.
Post class:
public partial class Post
{
public Post()
{
this.Attachment = new HashSet<Attachment>();
this.Comment = new HashSet<Comment>();
}
public int PostId { get; set; }
public string Title { get; set; }
public string Content { get; set; }
public System.DateTime Created { get; set; }
public Nullable<System.DateTime> Modified { get; set; }
public virtual ICollection<Attachment> Attachment { get; set; }
public virtual ICollection<Comment> Comment { get; set; }
}
Comment class:
public partial class Comment
{
public int CommentId { get; set; }
public string Content { get; set; }
public System.DateTime Posted { get; set; }
public bool Approved { get; set; }
public int AnswersTo { get; set; }
public int PostId { get; set; }
public virtual Post Post { get; set; }
}
My problem is that when I try to get via Web API a Post, it spits me the following error:
Object graph for type 'APIServer.Models.Comment' contains cycles and cannot be serialized if reference tracking is disabled.
And when I try to get a Comment via Web API, the error is as follows:
Object graph for type 'System.Collections.Generic.HashSet`1[[APIServer.Models.Comment, APIServer, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]' contains cycles and cannot be serialized if reference tracking is disabled.
If I annotate the Comment class with
[DataContract(IsReference = true)]
the errors disappear, but the serialization only returns the ID of the comment and ignores the other fields.
Any suggestions on how to solve this?
Thanks in advance,
Léster
Here are 2 solutions
Solution #1:
I had this same problem and so I decorated my class with DataContract and the members with DataMember like you mention. HOWEVER, I don't like editing auto-generated code directly because I have to redo it every time I regenerate the file. In order to get around this, I used the MetadataType attribute. In your case, it would look like this...
First, you will keep the auto generated entity as is:
public partial class Comment
{
public int CommentId { get; set; }
public string Content { get; set; }
public System.DateTime Posted { get; set; }
public bool Approved { get; set; }
public int AnswersTo { get; set; }
public int PostId { get; set; }
public virtual Post Post { get; set; }
}
Next, in another file, you will create another partial class and decorate it like this:
[MetadataType(typeof(Metadata))]
[DataContract(IsReference = true)]
public partial class Comment
{
private class Metadata
{
[DataMember]
public int CommentId { get; set; }
[DataMember]
public string Content { get; set; }
[DataMember]
public System.DateTime Posted { get; set; }
[DataMember]
public bool Approved { get; set; }
[DataMember]
public int AnswersTo { get; set; }
[DataMember]
public int PostId { get; set; }
[DataMember]
public virtual Post Post { get; set; } // you can remove "virtual" if you wish
}
}
MetadataType will essentially add the attributes from the Metadata buddy class to the ones with the same name in Comment (not directly, but for our purposes, it's close enough... that's a topic for a different post). Of course, if your Comment entity changes, you'll need to update this accordingly.
Solution #2:
Having to edit your second file every time you make a change is only a slight improvement from directly editing auto-generated files. Fortunately, there is another approach that is much easier to maintain. Details can be found here but as a summary, all you need to do is decorate your OperationContract that is consuming Comment with an additional attribute, ReferencePreservingDataContractFormat. Note that there is a slight error in the code provided on that page that would cause infinite recursion. As noted in this post, the fix is quite simple: instead of recursing at all, just create a new DataContractSerializer
The advantage to this approach is that no matter how much you change Comment, you still don't need update anything.
As an example for your code, let's say you are using Comment as follows:
[OperationContract]
Comment FindComment(string criteria);
All you need to do is add
[OperationContract]
[ReferencePreservingDataContractFormat]
Comment FindComment(string criteria);
And then somewhere else you need to define ReferencePreservingDataContractFormat which will look like this:
//From http://blogs.msdn.com/b/sowmy/archive/2006/03/26/561188.aspx and https://stackoverflow.com/questions/4266008/endless-loop-in-a-code-sample-on-serialization
public class ReferencePreservingDataContractFormatAttribute : Attribute, IOperationBehavior
{
public void AddBindingParameters(OperationDescription description, BindingParameterCollection parameters)
{
}
public void ApplyClientBehavior(OperationDescription description, System.ServiceModel.Dispatcher.ClientOperation proxy)
{
IOperationBehavior innerBehavior = new ReferencePreservingDataContractSerializerOperationBehavior(description);
innerBehavior.ApplyClientBehavior(description, proxy);
}
public void ApplyDispatchBehavior(OperationDescription description, System.ServiceModel.Dispatcher.DispatchOperation dispatch)
{
IOperationBehavior innerBehavior = new ReferencePreservingDataContractSerializerOperationBehavior(description);
innerBehavior.ApplyDispatchBehavior(description, dispatch);
}
public void Validate(OperationDescription description)
{
}
}
class ReferencePreservingDataContractSerializerOperationBehavior : DataContractSerializerOperationBehavior
{
public ReferencePreservingDataContractSerializerOperationBehavior(OperationDescription operationDescription) : base(operationDescription) { }
public override XmlObjectSerializer CreateSerializer(Type type, string name, string ns, IList<Type> knownTypes)
{
return new DataContractSerializer(type, name, ns, knownTypes,
0x7FFF, //maxItemsInObjectGraph
false, //ignoreExtensionDataObject
true, //preserveObjectReferences
null //dataContractSurrogate
);
}
public override XmlObjectSerializer CreateSerializer(Type type, XmlDictionaryString name, XmlDictionaryString ns, IList<Type> knownTypes)
{
return new DataContractSerializer(type, name, ns, knownTypes,
0x7FFF, //maxItemsInObjectGraph
false, //ignoreExtensionDataObject
true, //preserveObjectReferences
null //dataContractSurrogate
);
}
}
And that's it!
Either method will work just fine--pick the one that works for you.
You can disable Lazy Loading on your Comment class by removing virtual from the Post property definition...
public partial class Comment
{
public int CommentId { get; set; }
public string Content { get; set; }
public System.DateTime Posted { get; set; }
public bool Approved { get; set; }
public int AnswersTo { get; set; }
public int PostId { get; set; }
public Post Post { get; set; }
}
This should sort out the circular reference exception.
Been stuck on this for a while so i thought i would ask. I am sure there is something simple i am missing here. Trying to learn Asp.net mvc 4 on my own by building a simple app.
Here is the model:
public class Category
{
public int Id { get; set; }
[Required]
[StringLength(32)]
public string Name { get; set; }
//public virtual ICollection<Note> Notes { get; set; }
private ICollection<Note> notes;
public ICollection<Note> Notes
{
get
{
return this.notes ?? (this.notes = new List<Note>());
}
}
}
public class Note
{
public int Id { get; set; }
[Required]
public string Content { get; set; }
[Required]
[StringLength(128)]
public string Topic { get; set; }
public int CategoryId { get; set; }
public virtual Category Category { get; set; }
public virtual IEnumerable<Comment> Comments { get; set; }
public virtual ICollection<Tag> Tags {get; set;}
public Note()
{
Tags = new HashSet<Tag>();
}
}
public class Tag
{
public int Id { get; set; }
public string Name { get; set; }
public virtual ICollection<Note> Notes { get; set; }
public Tag()
{
Notes = new HashSet<Note>();
}
}
I call this method in a repository from the controller:
public IQueryable<Note> GetAll()
{
var query = _db.Notes.Include(x => x.Category).Include(y => y.Tags);
return query;
}
On the home controller i am trying to return a list of all the notes and wanted to include the category name that it belongs to as well as the tags that go with the note. At first the did not show up so i read some tutorials about eager loading and figured out how to get them to show.
However, my method is not that efficient. The mini-profiler is barking at me for duplicate queries because the navigation properties for category and tags are sending queries for the notes again. IS there any way to just return the properties i need for the category and tag objects?
I have tried several methods with no luck. I was hoping i could do something like this:
var query = _db.Notes.Include(x => x.Category.Name).Include(y => y.Tags.Name);
But i get an error: Cannot convert lambda expression to type 'string' because it is not a delegate type
I have seen that error before that was caused by some missing using statements so i already double checked that.
Any suggestions? Thanks for the help
//here is my data models:
public class People
{
public int PeopleID { get; set; }
[Required]
public string Name { get; set; }
}
[Table("User")]
public class User : People
{
[Required]
public string LoginName { get; set; }
[Required]
public string PassWord { get; set; }
}
//and i stored an item into the People table
context.People.Add(new People { Name = "Jack" });
context.SaveChanges();
//and now "Jack" is promoted as an user of this system
//how can I update his data and let him has is LoginName and Password?
This is a common design mistake.
Objects can't change their type; you shouldn't be using inheritance in this case.
Instead, the User can have a reference to a Person (another hint: your entity names should be singular, regardless of what you name the table)
First of all you need to declare discriminator column. For example PeopleType which couln't discriminate users from all peolple by specific value.
So in your scenatio you will need to create Jack as User but you could assecc it as item of people
[Table("People")]
public class People
{
public int PeopleID { get; set; }
[Required]
public string Name { get; set; }
public int Type { get; set; }
}
public class User : People
{
[Required]
public string LoginName { get; set; }
[Required]
public string PassWord { get; set; }
}
Overide it in DbContext
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<People>().Map<User>(m => { m.Requires("PoepleType").HasValue(1 /* any value you like */); })
}