I generated Entity Model from my database in my MVC5 App.
When I try to add [DispalyName] to some properties it works fine, but after some time app refreshes this class by itself and removes all my custom code
public partial class Patient
{
public Patient()
{
this.PatientDetails = new HashSet<PatientDetail>();
}
public int PatientID { get; set; }
[DisplayName("Last Name")]
public string LastName { get; set; }
public string FirstName { get; set; }
public virtual ICollection<PatientDetail> PatientDetails { get; set; }
}
Why MVC does it and how to disable that?
I believe since you're using Database first, the entities will get completely re-created every time you refresh, thus you lose your custom attributes.
Also, to go off of Joe's comment, you should make a view model and put your [Display] attributes there and not directly on the entity.
Related
I've hit a snag while building a .net mvc site. I have 2 related objects and am struggling with properly linking them. Specifically:
public class Address
{
public int AddressId { get; set; }
public string Street { get; set; }
public string City { get; set; }
public string State { get; set; }
public string PostCode { get; set; }
[ForeignKey("AddressCategory")] // <-- EF adds field to below object's table
public int AddressCategoryId { get; set; }
public virtual AddressCategory AddressCategory { get; set; }
}
public class AddressCategory
{
public int AddressCategoryId { get; set; }
public string Description { get; set; }
}
Adding the [ForeignKey] data annotation to the Address object results in EF adding an Address_AddressId column to the AddressCategory table, which I don't want (or need) to happen.
I've tried to omit the ForeignKey attribute, but then I run into other errors because .net can't link the tables (e.g. Unknown column 'Extent1.AddressId' in 'field list'). Additionally, I wouldn't be able to use:
var addresses = db.Addresses.Include(l => l.AddressCategory);
Is there any way to link the 2 tables without EF adding an additional column to the AddressCategory table?
Thank you to #cloudikka for responding. After much trial-and-error I seem to have gotten it to work simply by omitting any ForeignKey reference from either object. I let EF rebuild the database and perform all scaffolding (CRUD forms) and they have been created perfectly.
My take-away is that foreign key attributes should be used for parent-child relationships, but not for look-up tables. I clearly have much to learn about asp.net mvc!
I am trying to figure out a way to develop a database model using Entity Framework that does not do updates or deletes. The business requirements want the complete history of all changes that are made to each record in the system, for analysis reasons. So instead I want to always modify by inserting a new record to the database.
Is there a clean way to get Entity Framework to do that? Or am I going to be jumping through a lot hoops to get this sort of behavior. The basic model is pretty simple, some stuff, like constructors, removed since they don't add much to the discussion:
public class Container
{
public Guid Id { get; private set; }
public ICollection<Container> RelatedContainers { get; private set; }
public ICollection<Item> Items { get; private set; }
}
public class Item
{
public Guid Id { get; private set; }
public string Name { get; private set; }
public string Value { get; private set; }
}
Basically you need to override SaveChanges() method in DbContext. In your method get all the objects that have the EntityState Deleted or Modified and set the status UnChanged.
public class YourDbContext:DbContext{
public override int SaveChanges(){
foreach ( var ent in this.ChangeTracker
.Entries()
.Where(p =>p.State == System.Data.EntityState.Deleted
p.State == System.Data.EntityState.Modified))
{
ent.State =System.Data.EntityState.Unchanged;
}
}
}
I'm learning EF Code First and am having trouble when updating existing records. I've boiled it down to this simple example:
This works:
using(var db = new DataContext()){
var p = db.People.Find(1);
p.Name="New Name";
Console.WriteLine(p.Gender.Name); //<--Unnecessary property access
db.SaveChanges(); //Success
}
...but this fails (when the WriteLine is removed):
using(var db = new DataContext()){
var p = db.People.Find(1);
p.Name="New Name";
db.SaveChanges(); //DbValidationError "Gender field is required."
}
Why do I have to access/load the Gender propery if I'm not using it and the data is already correctly stored in the database? I just want to change the Name on an existing record. In this example, Gender is a one-to-many association stored as Gender_Id in the People table. The classes are defined like this:
public class Person
{
[Key]
public int PersonId { get; set; }
[Required, MaxLength(50)]
public string Name { get; set; }
[Required, Column("Gender")]
virtual public GenderCode Gender { get; set; }
}
public class GenderCode
{
[Key]
public int Id { get; set; }
[Required, MaxLength(10)]
public string Name { get; set; }
}
public class DataContext:DbContext
{
public DbSet<Person> People { get; set; }
public DbSet<GenderCode> GenderCodes { get; set; }
}
Of course, the fully defined classes are to have many more fields. I'd rather not have to access every dependant property every time I want to modify an unrelated value.
Is there a way to load an object, change a field, and save it without loading all related objects first?
Yes, this is necessary because of some horrible design mistakes in EF.
Check out my similar question, EF: Validation failing on update when using lazy-loaded, required properties
One trick is declaring FK properties along with the OO relations:
[ForeignKey("GenderId"), Column("Gender")]
virtual public GenderCode Gender { get; set; }
[Required]
public int GenderId { get; set; }
It is because you are using data annotations and Required attribute has also meaning for validation. Once you set navigation property as Required by data annotation it must be filled / loaded when you are going to persist entity to the database.
I'm using MVC3 VS2010 with EF4.1, I have created my DB using SQL Server and I import it to the MVC3 Web Application.
I have a challenge here, when I come to Update Model from Database I do lost all my models files modifications, for example if I'm using attributes in some models for validation or so all that is overwritten with the new model properties.
Is there anyway to Update Model from Database without losing models' information?
OR
where should I define validation on my models instead of using the models' files directly?
Update: As this is still relatively popular, I have created a blog post on this.
http://jnye.co/Posts/19/adding-validation-to-models-created-by-entity-framework-database-first-c
If you want to validate your models, and not use viewModels, use partial classes to define validation attributes. For example:
Say you have a model like
public class User {
public string Name { get; set; }
}
If you wanted to put a string length validator on it you would need to create a partial class and utilise the MetadataTypeAttribute (this lives in System.ComponentModel.DataAnnotations)
The following classes should be defined in their own separate file, NOT put in the same file as your auto generated models.
[MetadataTypeAttribute(typeof(UserMetadata))]
public partial class User {
}
You then define your validation in the UserMetadata class as follows
public class UserMetadata{
[StringLength(50)]
public string Name {get; set;}
}
EDIT
I just found this article which explains the solution in a little more detail
http://themonitoringguy.com/tips-tricks/validating-microsoft-entity-framework-objects-c-mvc/
No, the files will be regenerated every time.
All the classes are defined as partial so you can easily add DataAnnotations using the MetadataTypeAttribute.
Let's say you have a User class defined as follow:
public partial class User {
public string Name {get;set;}
}
Create a IUser interface
public interface IUser {
[Required]
[DisplayName("User name")]
string Name {get;set;}
}
And then extend the User class to specify that IUser will be used as metadata.
[MetadataType(typeof(IUser))]
public partial class User {} //Empty class body
The first rule of any designer is: It it generates any code you can't modify it because it will be completely deleted next time you update anything in the designer.
All generated classes are partial so you can create your own partial part and put your custom logic there. You obviously can't add attributes to properties defined in auto generated part. In case of data annotations it is possible either through buddy classes or by custom T4 template which will contain your own logic to decide which data annotation should be added during code generation. Both scenarios are mostly considered as a bad practice because you should have separate view model per view with validation needed exactly for that view.
Check the namespace of the MainClass is same as Partial, and have the same Attributes. That is my solution.
example:
Metadata: Create this everywhere u want
public class FormMetadata
{
public int Id { get; set; }
public string Description { get; set; }
public Nullable<bool> IsEnable { get; set; }
public Nullable<System.DateTime> CreationDate { get; set; }
public int CompanieId { get; set; }
public string RegularExpression { get; set; }
public virtual ICollection<Field> Fields { get; set; }
[JsonIgnore]
public virtual Company Company { get; set; }
}
MainClass
namespace Transactions.Model
{
public partial class Form
{
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
public Form()
{
this.Fields = new HashSet<Field>();
}
public int Id { get; set; }
public string Description { get; set; }
public Nullable<bool> IsEnable { get; set; }
public Nullable<System.DateTime> CreationDate { get; set; }
public int CompanieId { get; set; }
public string RegularExpression { get; set; }
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
public virtual ICollection<Field> Fields { get; set; }
public virtual Company Company { get; set; }
}
}
Partial To Use the MetadataType
namespace Transactions.Model
{
[MetadataTypeAttribute(typeof(FormMetadata))]
public partial class Form
{
}
}
If you have problems to Create a Class Partial in the same NameSpace? Don't worry:
Create a Folder
Create the Class Partial in this folder
Change Namespace at the same of MainClass
I am using the Entity Framework code first for data access and I have a Company class which has a collection of Employees. The Employee class also has a Company property.
I would like to be able to serialize a Company and include the list of employees in the serialization.
Here is Company:
public class Company
{
public long Id { get; set; }
public string Name { get; set; }
public DateTime? Established { get; set; }
public virtual IList<Employee> Employees { get; set; }
public DateTime? DateCreated { get; set; }
public DateTime? DateUpdated { get; set; }
}
Here is Employee
public class Employee
{
public long Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public int Age { get; set; }
public virtual Company Company { get; set; }
public DateTime? DateCreated { get; set; }
public DateTime? DateUpdated { get; set; }
}
I get a serialization Exception "Self referencing loop detected for type" when I try to serialize a Company object.
Thanks.
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.
Updated Answer
You can either:
reconfigure json.net to ignore
selfreference loops
use the [JsonIgnore] Attribute
use a custom converter that remove
the navigation in the child
or you can use Data Transfer Objects
In case this helps anyone, I thought I'd document how we resolved this same error for our purposes when using Entity Framework 4.3.1 and JSON.Net 4.5.3.
We are using the Database First DbContext approach. For our needs, we could resolve it using the [JsonIgnore] attribute. The trick is just that since changes to the automatically generated entity classes are overwritten when you refresh from the database, with Database First you can add the attributes using the "metadata buddy class" approach given in this StackOverflow post.
Below is a code excerpt. We had a "Query" object (class Query) that had relationships to "Company" and "User" objects. In a new class file, we declare the partial class with a [MetadataType] attribute, and then in the QueryMetadata class we specified, we annotate the members we want to ignore— namely the public virtual members that EF4.x adds to express the relationships (a.k.a. navigation properties).
The Query entity also has foreign key fields (named FK_User and FK_Company in our case). These fields do not need the [JsonIgnore] attribute— they can be serialized with their foreign key values.
[MetadataType(typeof(QueryMetadata))]
public partial class Query
{
}
public class QueryMetadata
{
[JsonIgnore]
public virtual Company company { get; set; }
[JsonIgnore]
public virtual User user { get; set; }
}
However, if we actually had to also serialize the related Company or User objects, we'd hit a brick wall! The approach suggested by John Bubriski here wouldn't work for us since we want to rely on Entity Framework change tracking.
If you are getting this error using WebApi you can put the following in WebApiConfig.cs so json.net ignores circular refs
config.Formatters.JsonFormatter.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;
Microsoft : Loop Reference handling in Web API
If you're using WebAPI EntityFrameworkCore 2.0 this solution doesn't work, you need to set it on Startup.cs->ConfigureServices:
.AddJsonOptions(options => {
var settings = options.SerializerSettings;
settings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
});