I'm building an Asp.net MVC5 + EF6 solution with 3 projects.
I have enabled automatic migration in my project.
The below diagram shows my project structure.
I have a main project and two sub projects.
I have a BaseContext in a main project.
Sub project has their own context classes which derives from
BaseContext.
All above contexts are connecting to one database.
Models:
A Model in Project2
public class Product
{
[Key]
public int ProductId {get;set;}
...
}
A Model in Project3
public class Order
{
[Key]
public int OrderId {get;set;}
[ForeignKey("Product")]
public int ProductId {get;set}
public virtual Product Product;
...
}
An property from Project3 entity (Order.ProductId) references a property from Project2 entity (Product.ProductId) as a foreign key reference.
When I run update-databasecommand in project 1 & 2 everything is going well.
But when run update-database command in project 3 It gives an error:
There is already an object named 'Product' in the database.
Right now I'm using update-database -script command to generate script and manually altering the script. But when project grows, it becomes a difficult task to alter sql scripts each and every time.
I ignored the Product entity by adding modelBuilder.Ignore<Product>() inorder to skip table creation for Productentity, in Project3, but it's ignores the entire relationship.
How can I solve this issue?
You can't do this. One context == one database. When you run a migration against a database for a particular context, it will be based on that context, and will remove any non-applicable tables or try to drop and recreate the database.
You should move all your entities into a class library, along with a single instance of a context that includes them all. Then, you can migrate against the class library and simply reference in your other projects.
Alternatively, you can sort of do what you want by going with an existing database approach. Essentially, you turn off migrations entirely on your base context, and then each sub context can then only include the entities that belong to it. However, you're going to be completely responsible for managing the database, yourself, at that point.
public class BaseContext : DbContext
{
public BaseContext()
: base("ConnectionString")
{
Database.SetInitializer<BaseContext>(null);
}
}
Related
On a project I am working on I am having some troubles trying to add properties to an entity from an external NuGet package.
The external team originally used the EntityFramework to create their database, and awhile back my team used it initially in order to create ours, now having two separate databases but initial creation used the common NuGet package.
On the external team's side, they haven't changed the table at at all, but on our side we've added new columns and properties to our database and now we need it within our DBContext. How do I map these new fields to an Entity so that I can access and set the properties. I hoped it was protected but since it is public I can't just overwrite the DbSet<Profile> Profile call.
External Package:
DataContext (Class that extends DBContext and has a public DbSet<Profile> Profile {get;set;})
Profile (Entity that is mapped to the "Profile" table in the database)
Since I can't modify the Profile class, how do I go about adding new columns that are there in the table?
My initial approach was to create:
DataContextExt (class that extends DataContext and added public DbSet<ProfileExt> ProfileExt {get;set;}
ProfileExt (Entity that extends Profile and has the additional fields that aren't part of the original
This seems to get me the furthest, but since ProfileExt extends Profile, I get an error when using it due to the "Discriminator" column since they are both the same entity technically.
I then tried to remove Profile by overriding the OnModelCreating() and map my ProfileExt to Profile but that failed as well, it didn't seem to change the model builder at all.
public class DataContextExt : DataContext
{
public DbSet<ProfileExt> ProfileExt { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Ignore<Profile>();
modelBuilder.Entity<ProfileExt>().ToTable("Profile");
Database.SetInitializer<ApplicationDbContext>(null);
}
}
Does anyone have any suggestions on what I should try next going forward?
EDIT:
Currently the project is design to access the information VIA a Stored Procedure and then I mapped that to my ProfileExt, but when it comes to saving it is designed to use
Entity = await DB.Set<TModel>().FindAsync(Key.Compile()(Model)).ConfigureAwait(false);
Model is instance of ProfileExt when it reaches this point
If I try to pass a ProfileExt through(without its own DbSet) as Profile it fails saying ProfileExt is not in the context, and if I do register it (with its own DbSet) it throws the Discriminator error since once is an instance of another.
From the sounds of things you are using a library and initial schema provided by some third party. You don't share code modifications with that team but you've gone and changed part of their schema in your copy of this Profile table.
Why not keep the two DbContexts completely separate rather than trying to inherit to override?
One option would be not to add columns to a table/entity that you do not have ownership of to extend. Move your custom columns to something like a MasterProfile table which shares a ProfileId as it's PK. From there you can declare a MasterProfile entity with a one-to-one relationship with Profile.
public class MasterProfile
{
[Key]
public int ProfileId { get; set; }
// add custom columns here...
public virtual Profile Profile { get; set; }
}
then configure relationship:
modelBuilder.Entity<MasterProfile>()
.HasRquired(x => x.Profile)
.WithOptional();
This way you can read your custom object in your DbContext along with Profile without a breaking change to the schema.
Another option you could explore is to define your own Profile entity definition for your DbContext while reusing the other entity declarations from the 3rd party.
For example: Given a 3rd party library which defines the following classes:
3rdParty.User
3rdParty.Profile
3rdParty.TableA
3rdParty.TableB
3rdParty.TableC
and they are accessed by a 3rdParty.DataContext
I can define a MyApp.DataContext that does not need to extend 3rdParty.DataContext. That DbContext can reference a Profiles collection that is declared as:
MyApp.Profile
which contains the full set properties from our Profile table. Provided you don't have to worry about references to 3rdParty.Profile you don't need to create custom entities for every table, you can reference 3rdParty.TableA etc. in your MyApp.DataContext.
I.e.
public class DataContext : DbContext
{
public DbSet<Profile> Profiles { get; set; }
public DbSet<3rdParty.TableA> TableAs { get; set; }
public DbSet<3rdParty.TableB> TableBs { get; set; }
public DbSet<3rdParty.TableC> TableCs { get; set; }
}
The catch would be that this will only work if the class you define is not referenced by many other entities. Every 3rdParty entity definition we include in our DbContext can no longer reference a 3rdParty.Profile since our DbContext cannot have two entities mapped to the same table.
For instance, if Profile references a User, that isn't a problem since MyApp.Profile can reference 3rdParty.User, however if 3rdParty.User has a reference back like:
public virtual ICollection<Profiles> { get; set; }
which will be pointing back to the Profile in the 3rdParty assembly, this is a deal breaker. We will need to recreate a MyApp.User as well. This could cascade if something like User needs to be re-declared and that class is referenced by the majority of other entities. (I.e. public virtual User CreatedBy { get; set; })
It may be an option worth exploring.
I have created a DbContext, similar to the one below
public class ProductsDB : DbContext
{
public virtual DbSet<Product> Products { get; set; }
//..other stuff..
}
Here's Product;
[Table("product")]
public class Product
{
[Column("Product_ID")]
public int ID { get; set; }
//other fields...
}
This all works fine until I create a class that inherits from "Product";
[Table("CentralProducts")]
public class CentralProduct : Product
{
//fields...
}
When I run integration tests I get an error that states that dbo.CentralProducts doesn't exist. It doesn't, and for the database that ProductsDB is connecting to I don't want it to.
I have tried the various inheritance options but they either require the addition of a table to my database, or the addition of a discriminator column to the Product table.
I had hoped that since my context doesn't consume CentralProducts it would not require it to exist. I was using table-per-type inheritance so there shouldn't be any need for something consuming dbo.Product to be able to access dbo.CentralProduct. Is there a way to configure EF6 to allow for this?
The reason I am trying to do this is that I have two databases, each with a common set of tables. I would like to create two DbContexts, one for each database, each containing the core entities but also including a few differences. In this particular case, the second DbContext has a Product table that includes an additional field, hence my attempt at inheritance to solve the problem.
I have some issues with Entity framework 6.2. I change ef version and now I have a lot bug..
EF version: 6.2
Visual studio version: 15.5.2
.Net version: 4.7.1
OS: Windows 10 Pro 1709
1.NotMapped why not working any more with inheritance? My example class:
public class BaseClass {
public string MappedProp {get;set;}
public virtual string NotBeMappedProp {get;set;}
}
public class Test : BaseClass {
public string MappedProp {get;set;}
[NotMapped]
public override string NotBeMappedProp {get;set;}
}
add-migration not found entity framework on project. But I installed it already. Besides, I deleted all packages folder. However still continue same exception.
I open clean project but suprise... I have a new proplem. My foreign keys thrown an exception.
Unable to determine the principal end of an association between the
types x1 and x2. The principal end of this association must be
explicitly configured using either the relationship fluent API or data
annotations.
My code part looking like that:
public class Student{
.....
public string Name {get;set;}
public long? LocationId {get;set;}
[ForeingKey("LocationId")]
public Location Address {get;set;}
......
}
public class Location{
public long Id {get;set;}
........
}
It is working with previous version.
I have no migration, I updated my database, check table but entity framework still said, there is an migration.
the model backing the context has changed since the database was
created
Try add abstract modifier to BaseClass definition. NotMapped attribute should be at the lowest level. If you need to map overridden property you should map it with Column attribute directly in inherited class.
Try run command Install-Package EntityFramework -Version 6.2.0 -Project {{EFProjectName}} to reinstall package and reference it correctly.
You better want to specify ForeignKey attribute in Address class and its StudentId property(or whatever you call it). It is one-to-zero-or-one relationship.
Information about migrations are stored in the database table __MigrationHistory along with compiled db model to speed things up(checking everytime if code suits database is time consuming) and that is the reason you get that error. You have different compiled model in your code and different stored in the migration history. You can create empty migration running command Add-Migration -Name ManualDbUpdate -IgnoreChanges to overcomes this, but you must be sure code model and database model are equal. If not you are going to get exceptions.
I've been banging my head all day long. I'm new to MVC 5 (MVC and ASP.NET in general) and I can't figure out how do I add an extra table to my current Database (created using CodeFirst approach), and read its content.
Heck, I don't know how to read the other columns I have in the AspNetUsers Table from Identity.
Would someone kindly tell me how this is done? Thanks a million
Edit:
Ok. So I have been tirelessly looking for a solution, and I've come across 35% of it.
I've stumbled upon a book called "Getting Started with Entity Framework 6 Code First using MVC 5 with Tom Dykstra"
Now I know that for creating a table you just create a class under the Model folders, and use a DbSet<> command where you had applied the DbContext call.
Now, what's the problem here? I started from a blank template, since that is the suggestion from "Pro ASP.NET MVC 5" from Adamn Freeman, and I don't want Google, Facebook Authentication.
I have been able to populate the defacto AspNetUsers table with custom fields, and insert Data into it.
What I want to with it, is to create a relational table with a foreign key which should reside in the defacto AspNetUsers table, and I don't how to do it.
Create the entity class (new table). You must specify an attribute as the primary key that should be named (CLASSNAME)ID Ex:
public class Product
{
public int ProductID { get; set; }
public string PropriedadeTeste { get; set; }
}
Map this entity in your implementation of DbContext. This means that Products table will contain Product objects:
public class EFDbContext : DbContext
{
public EFDbContext() : base("DatabaseName") { }
public DbSet<Product> Products { get; set; }
}
Enable migrations in your project (in the Package Manager Console)
Enable-Migrations -ProjectName SportStore.Domain -ContextTypeName ENTER_NAMESPACE_HERE.EFDbContext
Generate the migration - in this example, it will be generated a file named something like 201409172255007_Product.cs, in the Migrations folder:
Add-Migration -ProjectName PROJECT_NAME Product
Update the database:
Update-Database -ProjectName PROJECT_NAME -TargetMigration Product
I need a view-model in my ASP.NET MVC 5 project, but when I added one to the models folder, a new entity was added to the database and I was forced to add a migration and update my database. I do not want this to happen, as it is a view-model I am adding and not a model I need to persist back to the database. I want to scaffold some of the controller and views so I have added a primary key to the class. I did not add the newly created view-model to my DbContext class.
ViewModel:
public class RolesViewModel
{
public int RolesViewModelId { get; set; }
public string Role { get; set; }
}
Is there a way to create a view-model that doesn't automatically get added to the DbContext class, and therefore cause the data model to change?
Many thanks,
Jason.
Whether you call it a view model, an entity, etc. it's just semantics. Everything is just a class, and the context it's used in determines what you refer to it as. In the case of entities, that's adding a reference either explicitly or implicitly in your DbContext, and that's the only way you'll end up with something added to your database. I emphasized the "or implicitly* part because if any class that is referenced in the your DbContext, or any class connected to any class referenced there, also references your "view model", it will end up in your database. Entity Framework will automatically follow your class hierarchies and create tables for all relationships, even if you do not reference a particular class in those hierarchies directly in your DbContext.
In your case Scaffolding will add the following code below in your appContext Class
public DbSet<RolesViewModel> RolesViewModel { get; set; }
You can still use scaffolding if you wish, however remember to remove that entry and no table will be created by code first. It will keep your database clean.