I am making an application using MVC 3.0 Razor and Code First Entity Framework.
I am wondering how to define primary key and Foreign Key Relation in the Model.
I know how to define Primary Key.using Key attribute.
for example, I define [Key] attribute in the Model Table Class for Primary Key.
But, really don't know how to define Foreign Key for column in class.
Please Help..................
You can just make a List<ChildType> property in the parent class and a ParentType property in the parent class.
EF will generate the key automatically.
Related
We had developed in the past some sites, from company presentation sites to eshops, in classic asp. All of these was developed in multilingual environment (el, en) most of them. From database view we had choose the following schema. For example, for products table we have two related tables one with no lingual depended fields and one for lingual depended fields with one to many relation.
CREATE TABLE ref_language (
Code Char(2)NOT NULL,
Name Varchar(20) NOT NULL,
PRIMARY KEY (Code)
);
CREATE TABLE app_product (
Id Int IDENTITY NOT NULL,
PRIMARY KEY (Id)
);
CREATE TABLE app_product_translation (
ProductId Int NOT NULL,
LanguageCode Char(2) NOT NULL,
Description Text NOT NULL,
FOREIGN KEY (ProductId) REFERENCES app_product(Id),
FOREIGN KEY (LanguageCode) REFERENCES ref_language(Code)
);
To recreate the product model we use stored procedures to join the two tables for the requested language.
Now we want to move into dot.net mvc model. And we are wondering if there is a better approach, most suitable in mvc model.
It depends on your requirements, but you can just create a class to load and cache the captions in memory, loading them using EF. Either use a static class or preferably the ASP.NET cache.
If you are doing dynamic stuff on the client side then expose the strings through a MVC of WebAPI controller if necessary.
To make this easier I would decouple your translations from products in the schema. Make your translations universal.
Just have a single table called app_translation with Id, LanguageCode and Translation field. Then reference the Id on any table that needs a translated caption.
To enforce referential integrity, you can also have a app_translation_identifier table with a single column and a unique constraint. Then FK from the app_translation.Id to app_tranlsation_identifier.Id. And also have a unique key on app_translation for the Id and LanguageCode.
I am trying to map a legacy domain class to my grails class, but when table is generated, the field associated with legacy class is Tinyblob, and not a BigInt linked with ID, and foreing key stuff.
class NewClass implements Serializable {
GrailsEntityA grailsEntityA
GrailsEntityB grailsEntityB
LegacyEntity legacyEntity
}
The table has foreing keys for GrailsEntityA and GrailsEntityA but not for LegacyEntity, the type is tinyblob, without relationship with the LegacyEntity table.
Is it possible do this? How?
I'm trying to configure an MVC 4 application using EF 5 against the System.Web.Providers Membership DB. The ADO.NET Entity Data Model appears correct. The classes generated by the EF 5.x code generator look ok, but do not have a [Key] attribute. When I try to create a User Controller, I get the following error:
Microsoft Visual Studio
Unable to retrieve metadata for 'Citrius.Admin.User'. One or more validation errors were detected during model generation:
\tSystem.Data.Entity.Edm.EdmEntityType: : EntityType 'Membership' has no key defined. Define the key for this EntityType.
\tSystem.Data.Entity.Edm.EdmEntityType: : EntityType 'Profile' has no key defined. Define the key for this EntityType.
\tSystem.Data.Entity.Edm.EdmEntitySet: EntityType: EntitySet 'Memberships' is based on type 'Membership' that has no keys defined.
\tSystem.Data.Entity.Edm.EdmEntitySet: EntityType: EntitySet 'Profiles' is based on type 'Profile' that has no keys defined.
I thought I saw a walkthrough of this, using these versions, but cannot find it. I've tried to find a solution but all the examples are of previous versions.
Am I too far out on the bleeding edge?? Any help would be appreciated...
Why dont you assign the Key manually?
Go into each one and add [Key] above the field that should be the Key.
That should get rid of these errors.
I have a Member class:
public class Member
{
// key
public Guid UserId { get; set; }
// some other fields
}
Also I have a aspnet_Users table with has UserId primary column.
We can:
1). Add additional property MembershipUser to the Member object and get it's value by calling Membership.GetUser(this.UserId) method.
Also I've add
context.Database.ExecuteSqlCommand("ALTER TABLE [dbo].[Members] WITH CHECK ADD CONSTRAINT [FK_Members_aspnet_Users] FOREIGN KEY([UserId]) REFERENCES [dbo].[aspnet_Users] ([UserId])");
to the DataContext.Seed() method to ensure that Member can not be added without aspnet_Users account.
2). Use fluent API in OnModelCreating. If this a good case how to map them correctly?
What's the best choice? Any thoughts?
No matter how I tried to avoid it, I've found the best approach is to implement my own MembershipProvider and have it use my model, rather than trying to shoehorn my model into the built-in membership provider.
If you are going down the other route you have to map the ASP.NET Membership tables to your domain and derive your Member class from the ASP_User class (or vice versa if you want to ensure that all Users you create are Members). In the end, I've discovered that although it seems like more effort up front, implementing MembershipProvider is the easier approach.
You don't. Don't add foreign key constraints against the aspnet_* tables. It's a recipe for trouble. Membership is plug-in type system, and you have to treat it as a black box.
Simply lookup the data in your tables with the MembershipUser.ProviderUserKey as it's value. Something like this:
from m in Member where UserID == (Guid)Membership.GetUser().ProviderUserKey select t;
Motivation : My EF4.1 DbContext is saving Entities in the wrong order
Reason : Lack of navigation properties on my models
How I want to fix it :
I want to set up foreign key relationships in my DbContext. The catch is that my entity objects have no navigation properties (I'm using it to populate a web service and then firing DTO objects over to my application).
The classes below would be an example. In MinorClass, I want to configure my context so that it knows MajorClassID is a foreign key. The articles I've been finding on the internet on how to explicitly define Foreign Keys involve using navigational properties, which my objects dont have.
Is there a way to map this relationship?
public class MinorClass
{
public Guid ID {get;set:}
public Guid MajorClassID {get;set;} // foreign key
public string Name {get;set;}
}
public class MajorClass
{
public Guid ID {get;set;}
public string Name {get;set;}
}
Navigation property is primary construct whereas foreign key is helper (imho wrong helper). EF recognizes ordering of DB commands by relationships which are defined by navigation properties. You cannot define relation just by foreign key. You need navigation property on at least one side of the relation.