It is weird since I use the simple membership initialization my EF model cannot create a new table. My code was able to create the new table needed if there is a transaction required for the model.
This is my model :
public class EmployeeDBContext : DbContext
{
public EmployeeDBContext()
: base("DefaultConnection")
{
Database.SetInitializer<EmployeeDBContext>(new CreateDatabaseIfNotExists<EmployeeDBContext>());
}
public DbSet<EA_Employee> Employees { get; set; }
public DbSet<EA_EmployeePerformance> EmployeePerformances { get; set; }
public DbSet<EA_EmployeeRank> EmployeeRanks { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();
modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
}
}
[Table("EA_EmployeePerformance")]
public class EA_EmployeePerformance
{
[Key]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
[Display(Name = "Employee Performance Id")]
public int EmployeePerformanceId { get; set; }
[Index("Performance", IsUnique = true)]
[MaxLength(20)]
[Required]
public string Performance { get; set; }
public EA_EmployeePerformance()
{
Performance = "";
}
}
Whenever I SaveChanges(), the DB throws me
"Invalid object name dbo.EmployeePerformance".
I check the database and the database only contains tables required from simple membership.
How can I auto create the tables when a transaction is occurred for that model?
--------- EDITED ---------
Now I know what is my problem. The problem is because I use multiple dbContext in one database. It is gonna be tricky to do the migration because migration only works on one dbContext isn't it?
So in my case the problem is because the original AccountDBContext from the simple membership is taking over my database, that is why my other dbContext such as the EmployeeDBContext cannot create the new table (please correct me if i'm wrong).
Is there a way for me to keep the multiple dbContexts in a single database?
First you have to change your Db Initializer to DropCreateDatabaseIfModelChanges otherwise, you will still have the old database and you will never get the model changes without deleting the database manually.
database. It is gonna be tricky to do the migration because migration only works on one dbContext isn't it?
For migration I recommend you to create one DbContext for migration that called for Example MigrationDbContext which contains the the all DbSets and the POCO objects, also when the POCO objects belong to other assembly then just reference them.
Try using Migrations, this will help you manage your changes in your code and update the database scheme accordingly.
Here is a guide for how to use it Migrations.
Related
I have a Table "IncomingChecks" in my database. I've created it using EF Code first. Now, I've added a view to my database based on this table named "ViewIncomingChecks" using Sql Server Management Studio and I want to use its data in my app using Entity Framework.
I copied the model class and changed its name and added it to the context:
public class ViewIncomingCheck
{
[Key]
public int Id { get; set; }
//...
}
public class CheckDataContext : DbContext
{
public virtual DbSet<ViewIncomingCheck> ViewIncomingChecks { get; set; }
//...
}
now when I run the app, it throws an exception saying the DB Context has been changed and needs a migration. I even tried to add a migration (which seems to be the wrong option) and when I add the migration, it says that the object ViewIncomingChecks is already in the database.
How can I use this view in my code?
Edit
My current solution is to have another context just for the views. This way it doesn't conflict with the EF Migrations. Is this the best option or is there a better way to deal with it.
According to what I have done in my project:
First add public virtual DbSet<ViewIncomingCheck> ViewIncomingChecks
{ get; set; } to your DbConext
Now create a migration something called ViewDbSetAdded
Remove all the code from the both Up and Down method and it will look like as follows:
Migration Code:
public partial class ViewDbSetAdded : DbMigration
{
public override void Up()
{
}
public override void Down()
{
}
}
Now run update-database command and it will run an empty migration.
I've got an existing DB and new WPF project.
1) I scaffolded db context with Scaffold-DbContext and recieved DbContext.cs and a file for each entity that represents a DB tables. That's OK.
Here is example of one of them:
public partial class SomeEntity
{
public long SomeEntityID { get; set; }
public int SomeInt { get; set; }
}
2) I've manually updated this entity (no changes in DbContext.cs) :
public partial class SomeEntity
{
public long SomeEntityID { get; set; }
public int SomeInt { get; set; }
public string SomeString { get; set; }
}
3) I've used Add-Migration command. Now I've got a migration file that describes required changes and DbContextSnapshot.cs. Snapshot includes changes I've just made with SomeEntity. Database is not updated.
4) I've used Update-Database command. Database updated to match last migration. But my DbContext.cs doesn't know anything about changes in DB. It is still the same old good DbContext that I had after scaffolding DB.
Is this OK? Should I now change DbContext manually to match changes that I've made to my entities and applied them to DB? Is there a way to update DbContext.cs from DB after changes without 'rescaffolding'? (Because, for example, all comments and attributes in entity files will be lost, because they will be replaced with new ones if I use Scaffold-DbContext again)
You will have to run scaffolding again, but keep in mind that the generated classes are partial, so you can put your changes in another file
I've previously used NHibernate and Fluent Migrator in projects to create a database (if it didn't already exist) and update the schema through migration scripts. I'm looking over Entity Framework (6) to do a comparison and I'm having trouble replicating that functionality.
In my App.config, I've set up my connection string and db providers. I then went ahead and created a data model that I would like to be represented as a table in the database.
namespace DataModels
{
public class StoreClient
{
public int Id;
public string DisplayName;
public StoreClient()
{
}
}
}
I then went ahead and created a database context.
namespace DataModels
{
public class StoreContext : DbContext
{
public DbSet<StoreClient> StoreClients { get; set; }
}
}
On service start I created an instance of StoreContext and tried to add and call db.SaveChanges();, but this is failing because there is no schema that matches my StoreClient.
My question is simple. How do I configure my StoreContext (or EF in general) to automatically create my database schema, and how do I set it up to migrate when I make changes to that schema?
This seems simple, but my searching around hasn't gotten me anything that looks remotely familiar coming from the NHibernate world.
If you want your db to be created automatically try to put some code in your Application_Start() method.
for example:
Database.SetInitializer(new MigrateDatabaseToLatestVersion<StoreContext, Configuration>());
StoreContext context = new StoreContext();
context.Database.Initialize(true);
Where Configuration class is created upon automatic migrations are enables in the console. Check out this msdn demo.
Also i am not shure that your code firs model will work that way. If not try changing your fields with properties.
namespace DataModels
{
public class StoreClient
{
public int Id { get; set; }
public string DisplayName { get; set; }
public StoreClient()
{
}
}
}
This goes for both Entity Framework 4 (4.3.1) and 5.
I have a User class (to go with my Entity Framework MembershipProvider). I've removed some of the properties to simplify. The actual User is from the MVCBootstrap project, so it's not part of the same assembly as the other classes.
public class User {
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public Guid Id { get; set; }
[Required]
[StringLength(256)]
public String Username { get; set; }
}
And then I have this class:
public class NewsItem {
public Int32 Id { get; set; }
[Required]
[StringLength(100)]
public String Headline { get; set; }
[Required]
public virtual User Author { get; set; }
[Required]
public virtual User LastEditor { get; set; }
}
Then I create the database context (The DbSet for the user is in the MembershipDbContext):
public class MyContext : MVCBootstrap.EntityFramework.MembershipDbContext {
public MyContext(String connectString) : base(connectString) { }
public DbSet<NewsItem> NewsItems { get; set; }
}
Running this code will give me this exception when the database is being created:
Introducing FOREIGN KEY constraint 'FK_dbo.WebShop_dbo.User_LastEditor_Id' on table 'WebShop' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.
Could not create constraint. See previous errors.
So I change the database context:
public class MyContext : MVCBootstrap.EntityFramework.MembershipDbContext {
public MyContext(String connectString) : base(connectString) { }
public DbSet<NewsItem> NewsItems { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder) {
base.OnModelCreating(modelBuilder);
modelBuilder.Configurations.Add(new NewsItemConfiguration());
}
}
And this configuration:
public class NewsItemConfiguration : EntityTypeConfiguration<NewsItem> {
public NewsItemConfiguration() {
HasRequired(n => n.Author).WithOptional();
HasRequired(n => n.LastEditor).WithOptional();
}
}
Or is this wrong?
Anyway, when I run the code, the database get's created, and the database seems okay (looking at foreign key constraints etc.).
But, then I get the 10 latest NewsItems from the context, and start loading them into view models, part of this is accessing the Author property on the NewsItem. The controller doing this takes forever to load, and fails after a long, long time. When running in debug mode, I get an exception in this piece of code: this.AuthorId = newsItem.Author.Id;, then exception I get is this:
A relationship multiplicity constraint violation occurred: An EntityReference can have no more than one related object, but the query returned more than one related object. This is a non-recoverable error.
It's probably something simple and stupid I'm doing wrong, I'm sure I've get similar code running on several sites, so .. what is causing this? Are my models wrong, is it the database context, or?
This part
Introducing FOREIGN KEY constraint 'FK_dbo.WebShop_dbo.User_LastEditor_Id' on table 'WebShop' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints. Could not create constraint. See previous errors.
is actually a SQL Server issue (and an issue of many other RDBMS's). It is a complex issue resolving multiple cascade paths, and SQL Server decides just to punt and not try. See
Foreign key constraint may cause cycles or multiple cascade paths?
You were trying to configure your model to delete the child Author and LastEditor objects when the NewsItem is deleted. SQL Server won't do that.
Come to think of it... is that what you want? It seems you would want to disassociate the Author and LastEditor from the NewsItem, not delete them from the database.
Your object model requires a 1:1 relationship between NewsItem and Author, and between NewsItem and LastEditor. I'm not sure what this refers to in the code
this.AuthorId = newsItem.Author.Id;
but it seems to me, you should be making the assignment the other way around, e.g.
newsItem.Author = myAuthorInstance;
or if you include foreign key properties in your model and if you have previously saved your author instance and have an Id:
newsItem.AuthorId = myAuthorInstance.Id;
If you share the generated DB schema (relevant parts) that would make it easier to diagnose the issue.
User can be an author of several news items. Also, user can be editor of several news items.
Hence, relationship have to be "one-to-many":
public class NewsItemConfiguration : EntityTypeConfiguration<NewsItem> {
public NewsItemConfiguration() {
HasRequired(n => n.Author).WithMany();
HasRequired(n => n.LastEditor).WithMany();
}
}
Error:
Unhandled Exception: System.Data.SqlClient.SqlException: The operation failed because an index or statistics with name 'IX_ID' already exists on table 'PrivateMakeUpLessons'.
Model (Simplified, building in a separate test project for debugging):
public abstract class Lesson
{
public Guid ID { get; set; }
public string Room { get; set; }
public TimeSpan Time { get; set; }
public int Duration { get; set; }
}
public abstract class RecurringLesson : Lesson
{
public int DayOfWeek { get; set; }
public DateTime StartDate { get; set; }
public DateTime EndDate { get; set; }
public string Frequency { get; set; }
}
public class PrivateLesson : RecurringLesson
{
public string Student { get; set; }
public string Teacher { get; set; }
public virtual ICollection<Cancellation> Cancellations { get; set; }
}
public class Cancellation
{
public Guid ID { get; set; }
public DateTime Date { get; set; }
public virtual PrivateLesson Lesson { get; set; }
public virtual MakeUpLesson MakeUpLesson { get; set; }
}
public class MakeUpLesson : Lesson
{
public DateTime Date { get; set; }
public string Teacher { get; set; }
public virtual Cancellation Cancellation { get; set; }
}
Configuration:
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Lesson>().ToTable("Lessons");
modelBuilder.Entity<RecurringLesson>().ToTable("RecurringLessons");
modelBuilder.Entity<PrivateLesson>().ToTable("PrivateLessons");
modelBuilder.Entity<MakeUpLesson>().ToTable("PrivateMakeUpLessons");
modelBuilder.Entity<Cancellation>()
.HasOptional(x => x.MakeUpLesson)
.WithRequired(x => x.Cancellation);
base.OnModelCreating(modelBuilder);
}
Notes:
This worked fine in EF 4.2. Is there something wrong with my model? The actual model is much more complicated which is why I have all the classes abstracted out. Also, I am working against an existing database so I need to use Table-Per-Type inheritance.
If I change the relationship of Cancellation to PrivateMakeUpLesson from 1 to 0..1 to 0..1 to 0..1 it works. This is undesirable because you can't have a PrivateMakeUpLesson without a Cancellation.
Also, if I make PrivateMakeUpLesson NOT inherit from Lesson then it also works, but it IS a lesson and needs to remain so for existing business logic.
I'd appreciate any guidance. Thank you!
Edit:
Starting a bounty. I can't find any documentation on what changed between EF 4.2 and EF 4.3 with regard to the index generation for code first. It's clear that EF 4.3 is creating more indexes and that the naming scheme has changed but I want to know if there's a bug in EF or if there is something fundamentally wrong with my model or fluent API configuration.
As of EF 4.3, indexes are added for freign key columns during database creation. There is a bug that can cause an index to be created more than once. This will be fixed in a future EF release.
Until then, you can work around the issue by creating your database using Migrations instead of database initializers (or the Database.Create() method).
After generating the initial migration, you will need to delete the redundant call to Index().
CreateTable(
"dbo.PrivateMakeUpLessons",
c => new
{
ID = c.Guid(nullable: false),
...
})
.PrimaryKey(t => t.ID)
.ForeignKey("dbo.Lessons", t => t.ID)
.ForeignKey("dbo.Cancellations", t => t.ID)
.Index(t => t.ID)
.Index(t => t.ID); // <-- Remove this
To continue creating your database at run-time, you can use the MigrateDatabaseToLatestVersion initializer.
In my opinion this is clearly a bug.
The problem starts with the observation that EF creates an index IX_ID at all. If you strip down the model to the following...
public abstract class Lesson
{
public Guid ID { get; set; }
}
public class RecurringLesson : Lesson
{
}
public class MyContext : DbContext
{
public DbSet<Lesson> Lessons { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<RecurringLesson>().ToTable("RecurringLessons");
}
}
... and let EF create the database schema you get two tables Lessons and RecurringLessons as expected for a TPT inheritance mapping. But I am wondering why it creates two indices for the table RecurringLessons:
Index PK_RecurringLessons (clustered, unique) with Index column ID
Index IX_ID (not clustered, not unique) with Index column ID again
I don't know if there is any benefit for the database to have a second index on the same column. But for my understanding it doesn't make sense 1) to create an index on the same column that is already covered in the PK clustered index, and 2) to create a not unique index on a column which is the primary key and therefore necessarily unique.
Moreover due to the one-to-one relationship EF tries to create an index on the table of the dependent of this association which is PrivateMakeUpLessons. (It's the dependent (and not the principal) because Cancellation is required in entity MakeUpLesson.)
ID is the foreign key in this association (and primary key at the same time because one-to-one relationships are always shared primary key associations in Entity Framework). EF apparently always creates a index on the foreign key of a relationship. But for one-to-many relationships this is not a problem because the FK column is different from the PK column. Not so for one-to-one relatonships: The FK and PK are the same (that is ID), hence EF tries to create an index IX_ID for this one-to-one relationship which already exists due to the TPT inheritance mapping (which leads to a one-to-one relationship as well from database perspective).
The same consideration as above applies here: The table PrivateMakeUpLessons has a clustered PK index on column ID. Why is a second index IX_ID on the same column required at all?
In addition EF doesn't seem to check that it already wants to create an Index with name IX_ID for the TPT inheritance, leading finally to the exception in the database when the DDL is sent to create the database schema.
EF 4.2 (and before) didn't create any indices (except PK indices) at all, this was introduced in EF 4.3, especially indices for FK columns.
I didn't find a workaround. In the worst case you have to create the database schema manually and avoid that EF tries to create it (= disable database initialization). In the best case there is a way to disable automatic FK index creation, but I don't know if it's possible.
You can submit a bug report here: http://connect.microsoft.com/VisualStudio
Or maybe someone from EF development team will see your question here and provide a solution.
I got a very similar error to this one in my code a while back. Try putting the cancellation list inside the Lesson class. That's what solved my problem.
Below I describe 2 scenarios what is probably going wrong. Please read in depth by clicking the links I provided to know more about my explanation.
First
Lesson and RecurringLesson are abstract classes (so you want to have it as the base classes).
You are creating a table of the Lesson and the RecurringLesson entities which will result in a Table per hierarchy structure.
brief description
Creating a class of the base table will result in one big table which contains the columns of all inherited tables. So all properties of PrivateLesson, MakeUpLesson and all others inherited entities will be stored in the Lessons table. EF will add also a Discriminator column. The value of this column defaults to the persistent class name (like "PrivateLesson" or "MakeUpLesson") only the column matching to that particular entity (matching the Discriminator value) will be used in that particular row.
BUT
You are also mapping the inherited classes like PrivateLesson and MakeUpLesson. This will force EF to use the Table per Type structure which results in one table per class. This can cause conflicts you are facing right now.
Second
Your example shows you have an one-to-one relationship (Cancellation -> MakeUpLesson) and a one-to-many relationship (Cancellation -> PrivateLesson) because PrivateLesson and MakeUpLessonare both (indirect) inherited from Lesson in combination with the first described scenario can cause problems because it will result in 2 foreign key relationships in the database per entity. (one using Table per hierarchy structure and one using the Table per Type structure).
Also this post can help you defining a correct one-to-one definition.
Please verify by performing the following steps:
I assume you have your own test environment so you can create new test databases
1.
Delete the relationships to the Cancellation by commenting out all properties to this class:
public class PrivateLesson : RecurringLesson
{
public string Student { get; set; }
public string Teacher { get; set; }
//public virtual ICollection<Cancellation> Cancellations { get; set; }
}
public class Cancellation
{
public Guid ID { get; set; }
public DateTime Date { get; set; }
//public virtual PrivateLesson Lesson { get; set; }
//public virtual MakeUpLesson MakeUpLesson { get; set; }
}
public class MakeUpLesson : Lesson
{
public DateTime Date { get; set; }
public string Teacher { get; set; }
//public virtual Cancellation Cancellation { get; set; }
}
And remove the configuration to it:
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Lesson>().ToTable("Lessons");
modelBuilder.Entity<RecurringLesson>().ToTable("RecurringLessons");
modelBuilder.Entity<PrivateLesson>().ToTable("PrivateLessons");
modelBuilder.Entity<MakeUpLesson>().ToTable("PrivateMakeUpLessons");
//modelBuilder.Entity<Cancellation>()
// .HasOptional(x => x.MakeUpLesson)
// .WithRequired(x => x.Cancellation);
base.OnModelCreating(modelBuilder);
}
2.
Create a new empty database
3.
Let EF generate the table structure for you in this empty database.
4.
Verify the first scenario. If that's true this need to be fixed first by using the Table per hierarchy structure OR the Table per Type structure. Probably you want to use the Table per hierarchy structure because (if I understand your question well) there is already an production environment.
When my project was updated from EF 6.0.2 to EF 6.1.1, I had such a problem, then back to 6.0.2, after the return of an older version, the error disappeared