I ran the EF 5.x DbContext Fluent Generator to generate my code first files and mappings. What I would like is to have all the generated classes include a base interface IEntity. I am also thinking about an abstract base class EntityBase with with properties for Id and rowVersion. I am sure a lot of people have done this but i cant seem to find it in my searches
So for example all my entities would look like this
partial class Person : EntityBase, IEntity
thanks
I am far from an expert, so treat this with caution.
You have the right idea, just create a partial class and put the inheritance/interface references in that one.
You don't modify the generated classes at all, that's the beauty of partial classes.
Related
I was using EF 4.x database-first approach. I have the edmx file and it generated the C# class that derived from EntityObject. I have an ASP.NET MVC 4 application that uses the generated class as model. The client validation that validates the required fields worked fine.
Now I moved to EF 5 and used the DbContext generator, it generates the POCO C# class. I found that the required field validation no longer works in EF 5.
I think the problem is that in EF 4.x EntityObject generator, the generated class has [EdmScalarPropertyAttribute(EntityKeyProperty=false, IsNullable=false)] attribute. However in the EF 5.x POCO class, no data annotation attributes are generated. So the required field information is lost.
So my questions are:
Why does the EF 5.x DbContext generator not generate
[Required] annotations from the edmx file?
Where is the right place to
put these data annotations? Should I modify the .tt file to generate
the [Required] attribute? Or manually write a [MetadataType] partial
class and define data annotation attributes in a separate
class?
1) I don't know why. I just know that Db-first approach doesn't add any data annotations to properties.
2) Indeed creating a separate partial class! Here is an example. Because EF will overwrite and regenerate all POCO classes every time you update your model, any changes (also data annotations) to those classes will be lost...
Perhaps you can find this link useful.
EF Validation
Simply add Metadata class with the required validation:
[MetadataType(typeof(UserMetadata))
public partial class User
{
...
}
public class UserMetadata
{
[UserValidate("State")]
public string State;
// etc.
}
hope this can help
I'm new to Entity Framework and the database first approach. Can anyone please help me?
Here is the case:
I have a clean, ordinary domain class (Person) with only properties. This class is defined in a VS-project that will only contain domain classes, without any reference to Entity Framework or other things that belong in a data access layer.
I also have a database table (tblPerson). I have created an EDMX for it and used DbContext Generator to create POCO-classes for it.
It is important to keep entity framework references separate from the project with the domain class, and I want to use a repository pattern combined with dependency injection.
The question is:
How do I "map" the Entity Framework POCO-class to my existing domain class? They have the same properties. I have read something about proxies, buddy classes and more, but didn't find any good examples.
Please help.
Lets say that the domain model class looks like this (just an example):
public class Person
{
public int Id { get; set; }
public string Name { get; set; }
}
and the database table has the same colums:
Id (int, not null, primary key)
Name (nvarchar(50), not null)
Update:
Ok, I found a solution. I did what Ladislav Mrnka suggested and derived from ObjectContext. Here is a page that describes how it's done: Entity Framework 4.0 – Part4: How to use your own POCO’s
If you want to map your "domain objects" to the EF generated POCO classes, then you can use a mapper such as AutoMapper https://github.com/AutoMapper/AutoMapper/wiki
Ok, I found a solution. I did what Ladislav Mrnka suggested and derived from ObjectContext.
Here is a page that describes how it's done: Entity Framework 4.0 – Part4: How to use your own POCO’s
Does it makes sense to introduce an abstract IdableEntity base class, that has a public Guid Id { get; set;} property, and then derive all my entities from it, so I don't have to add key field to each one of them? Will I face any pitfalls if I do in theory?
I used to never do this since my DbContext model was rather simple and consisted of a few classes. Now I am designing a large entity number model that may benefit from it.
Speaking from experience of this exact thing - yes it makes sense. Note that this EF base class doesn't have to be the heirarchical root though - it could inherit from a base class that implements things like INotifyPropertyChanged, IChangeTracking, etc. So your inheritance chain would look like this:
BaseDataClass <- BaseEFDataObject <- [actual EF entities]
Starting from an EF 4 entity diagram and using T4 templates one can create POCO classes that can be used inside the Domain Model. The generated code looks like this:
public partial class Product
{
public virtual int Id
{
get;
set;
}
public virtual string Name
{
get;
set;
}
//and so on
}
Is there any elegant approach to add my own code for implementing the properties? for example, the Name setter I would like to be implemented by lowering all the characters. I would like that my code resist to repeated regeneration of the POCO classes from the EF diagram.
This requirement is somewhat similar to adding validation code to the POCO classes. This issue is already solved by creating a separate validation class and linking it to the POCO through the MetadataType attribute. That separate validation class is not overwritten by repeatedly regenerating POCOs from the EF diagram.
Thanks,
Lucian
No there is no easy way to do that. You must not touch generated code because your changes will be deleted after each regeneration. You options are:
Write entities yourselves and don't use generator - you will get full control over entity code
Modify T4 template in generator to either add your direct code (this can be quite hard to generalize) or simply add call to partial methods (you must also declare these methods in generator) in getter and setter and in your partial part of entity class implement partial methods you need.
Our organization is looking to standardize on Entity Framework once v4 comes out. As a result, I am looking at what it would take to migrate our application that uses NHibernate for persistence to EF4 using POCO support. In a couple of places we use single table inheritance (also known as Table Per Hierarchy). I have been unable to get it to work using the following.
Payment (base class [should be abstract but having trouble there as well])
CreditCardPayment (concrete implementation)
ACHPayment (concrete implementation)
CheckPayment (concrete implementation)
Right now, I am mapping them with only the base class properties. All of these classes are in the same namespace. They have a discrimimator that is called PaymentTypeId in the database, so the Payment mapping has a condition of "When PaymentTypeId = 0". Each of the subclasses have the same condition with different values (i.e. CreditCardPayment = 1, etc.).
When I try to load each a list of all payments using DataContext.Payments.ToList() (DataContext inherits from ObjectContext) I am getting the following exception:
"Object mapping could not be found for Type with identity 'DataLayer.DataModel.CreditCardPayment'."
I can't figure out what this means, as the POCO CreditCardPayment class lives in the same namespace as the POCO Payment class does (in fact in the same file).
What am I missing?
This is complaining not about database mapping, but model to CLR mapping.
The EF can't for some reason find your CreditCardPayment class.
Now one possible reason is that you haven't loaded the metadata for it yet.
For example if you have this:
Assembly 1:
- Payment
Assembly 2 references Assembly 1:
- CreditCardPayment extends Payment
Then when you query the EF doesn't know where CreditCardPayment lives.
The way to get around this is with LoadAssembly i.e:
using (DataContext ctx = new DataContext())
{
ctx.MetadataWorkspace.LoadFromAssembly(typeof(CreditCardPayment).Assembly);
// now do your query.
}
You need to tell to LoadFromAssembly every assembly that isn't directly reference by your DataContext class.
Note: typeof(Payment).Assembly is directly referenced because of the IQueryable<Payment> Payments property.
Hope this helps
Alex
Microsoft.
What I didn't represent before (I didn't think it relevant, but it was). Was that CreditCardPayment inherited from an intermediary class named "CreditPayment" and ACHPayment inherited from CashPayment. CreditCardPayment and CashPayment live in the same namespace and file, but were not represented in the EF mapping. Once I added those within the mapping file, everything worked ok.
So, even thought EF does not ever map to one of those types directly, it seems to need to know about them, because it changes the basetype of the CreditCardPayment classes et al. Thank you for your help on this.