I'm using WAF ( WPF Application Framework ) in here: https://waf.codeplex.com.
And I open the BookLibrary project in it sample.
I have an model named Author and it related class.
And this is it DbContext:..
internal class BookLibraryContext : DbContext
{
public BookLibraryContext(DbConnection dbConnection)
: base(dbConnection, false)
{
Database.SetInitializer<BookLibraryContext>(null);
}
public BookLibraryContext()
: base(#"Data Source=|DataDirectory|\Resources\BookLibrary2.sdf")
{
}
public bool HasChanges
{
get
{
ChangeTracker.DetectChanges();
// It is necessary to ask the ObjectContext if changes could be detected because the
// DbContext does not provide the information when a navigation property has changed.
return ObjectContext.ObjectStateManager.GetObjectStateEntries(EntityState.Added).Any()
|| ObjectContext.ObjectStateManager.GetObjectStateEntries(EntityState.Modified).Any()
|| ObjectContext.ObjectStateManager.GetObjectStateEntries(EntityState.Deleted).Any();
}
}
private ObjectContext ObjectContext { get { return ((IObjectContextAdapter)this).ObjectContext; } }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Configurations.Add(new PersonMapping());
modelBuilder.Configurations.Add(new BookMapping());
modelBuilder.Configurations.Add(new AuthorMapping());
}
}
When i run the project. An exception occured:
{"The specified table does not exist. [ Author ]"}
How do i add new table named Author ? I know using Entity Framework migration or edit the database structor with tools.
But I see the method named HasChange(). It may do something to reflect my database. But I don't know to make it work. Please help me
You are using Database.SetInitializer<BookLibraryContext>(null); which causes Entity Framework to do no initialization when starting up, meaning your Data needs to already match your classes.
You can use the following initializers instead of null:
CreateDatabaseIfNotExists. This will create a new database if none exists. However, changing the model will not recreate the database, and the program will error.
DropCreateDatabaseIfModelChanges This will create a new database if the model changes, or leave the existing database if the model has stayed the same.
DropCreateDatabaseAlways This will create a new database every time the program is run.
MigrateDatabaseToLatestVersion This will process Entity Framework Migrations, to preserve the data in the database and add or remove tables as necessary (also called Data Motion).
Migrations are the hardest to set up, but the easiest to maintain, in the long run. However, for testing, any option would be fine.
An example of using one of the initializers would be:
Database.SetInitializer(new DropCreateDatabaseIfModelChanges<BookLibraryContext>());
Related
I am trying to use EF Core 3.0 migrations with a hybrid of an existing tables and new tables built with code first. To prevent the scaffolding of the existing tables I would like to decorate the model class with an attribute (fluently or annotations) so that the migration code generation for those tables is skipped but the model is still built into the DbContext class.
The approach I'm taking is to add the following lines to OnConfiguring
optionsBuilder.ReplaceService<IMigrationsSqlGenerator, SkipMigrator>();
And then creating a SkipMigrator with the following code
public class SkipMigrator:SqlServerMigrationsSqlGenerator
{
public SkipMigrator(
MigrationsSqlGeneratorDependencies dependencies,
IMigrationsAnnotationProvider migrationsAnnotations)
: base(dependencies, migrationsAnnotations){}
protected override void Generate(
MigrationOperation operation,
IModel model,
MigrationCommandListBuilder builder)
{
if (operation.FindAnnotation("SkipMigrations")!=null)
{
Console.WriteLine("Skipping table:");
}
else
{
base.Generate(operation,model,builder);
}
}
}
I assumed that the Generate method was what triggered the creation of the migration code file but it never gets called. Id there a different place I should be intercepting the code generation?
If there a different/simpler way to tell migrations to skip tables yet still keep them in my DbContext?
Your means of trying to create your own IMigrationsSqlGenerator was correct, and I've used that approach before to alter the SQL that is generated as part of a migration.
services.AddDbContext<MyDbContext>(opt =>
{
opt.UseSqlServer();
opt.ReplaceService<IMigrationsSqlGenerator, SkipMigrator>();
});
However, as of EF Core 5.0 it's now much easier to exclude specific tables from migrations using the ExcludeFromMigrations() method on a TableBuilder:
public class ReportingContext : DbContext
{
public DbSet<User> Users { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<User>().ToTable(nameof(Users), t => t.ExcludeFromMigrations());
}
}
More info: https://devblogs.microsoft.com/dotnet/announcing-entity-framework-core-efcore-5-0-rc1/#exclude-tables-from-migrations
If there a different/simpler way to tell migrations to skip tables yet still keep them in my DbContext?
Yes, but it requires a different approach.
Instead of using your current DbContext class for creating migrations, create a SecondDbContext class only for the very purpose of creating migrations. This new SecondDbContext class will hold the DbSets<T> that you want EF to do its migrations on.
Then simply specify the second context when calling add-migration UpdateTable -c SecondDbContext and then update-database -c SecondDbContext.
I'm using doing database first development and using Scaffold-DbContext to create my entity models project. In that project, I have a partial dbContext where I override methods like SaveChangesAsync to set certain properties like, "LastModifiedBy".
I'm looking to soft-delete records using dateDeleted/userDeleted columns. When I go to override the OnModelCreating routine, I see that it's already defined on the auto-generated partial context.
I'm trying to do something like the following:
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<SomeEntity>().HasQueryFilter(x => x.DateDeleted == null);
}
Does anyone have any suggestion as to how I can do this in a partial class way that still allows me to regenerate the original context on the fly using Scaffold-DbContext?
Also note, I'm using .NET Core 2.1.5
ANSWER FROM David Browne - Microsoft
Add a static property on the partial context
public static bool GlobalFiltersAdded { get; set; } = false;
Then add a routine to add your filters:
private void AddGlobalFilters(ModelBuilder modelBuilder){
SomeContext.GlobalFiltersAdded = true;
}
Then in your generated context add the following:
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
AddGlobalFilters(modelBuilder);
//OTHER LOGIC WILL BE HERE
}
Options:
1) Delete the generated OnModelCreating after re-scaffolding. It's already a manual process, and generates a compile error if you forget.
2) Use a DbContext inherited from the generated DbContext.
3) Use a 3rd party tool or library like: EF Core Power Tools
Following is a part of code in my DbContext that creates data and seeds data.
public class labSchedulerDbContext :DbContext
{
static abDbContext()
{
Database.SetInitializer(new abDatabaseInitializer());
}
public abDbContext() :base (nameOrConnectionString:"abDbContext")
{
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
}
}
Rest of the code is just declaring models.
In my setinitializer class with seed
public class abDatabaseInitializer : DropCreateDatabaseIfModelChanges<abDbContext>
{
.....
}
Code is working fine. Problem I have is when I created site in IIS and ran it. It runs fine but after few hours it will delete the database and initialize and seed data again. Thus we lose the data added. I tried to comment out lines where setinitilizer file is being called. Still didn't work. I refreshed apppool and site maybe it was cached files. But still no luck.
Can you please tell me how I can disable the whole initializer file once a database is created so no matter what it doesn't go and drops db and create a new one.
Cod
You can use this other initializer:
CreateDatabaseIfNotExists: This is default initializer. As the name suggests, it will create the database if none exists as per the configuration. However, if you change the model class and then run the application with this initializer, then it will throw an exception
The only thing that you have to do is to drop the database yourself before you deploy a new version with a different model. (Provided that's what you want to do).
I am using EF5 with the DefaultMembershipProvider and want to control the schema used in SQL Server for the tables created by the DefaultMembershipProvider.
EF5 says this is doable as:
modelBuidler.Entity<MyEntity>().ToTable("MyTable", "MySchema");
but as these are not "my" entities I cannot do it this way.
Questions:
1) So how do I do this in EF5?
2) Is this dealt with in EF6 when using DbModelBuilder.HasDefaultSchema?
Yes indeed I would upgrade to EF6 and then make your context look like this, e.g.:
public partial class BlogContext : DbContext
{
public BlogContext()
: base("BlogDb")
{
Database.SetInitializer<BlogContext>(null);
}
public DbSet<BlogPost> BlogPosts { get; set; }
public DbSet<Category> Categories { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Conventions.Remove<PluralizingEntitySetNameConvention>();
modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
modelBuilder.HasDefaultSchema("");
}
}
You see setting the default schema at the end to "", which also works, in my case, Oracle 12c takes the login user name as schema and everything works fine. Of course you could also load the schema name from configuration and insert it there.
Note: Automatic migrations will NOT work anymore, as this seems to confuse the system quite much. See here for a possible solution so that at least explicit migrations will work somehow: Entity Framework using IdentityDbContext with Code First Automatic Migrations table location and schema?
I created a DbContext like so :
public class myDB : DbContext
{
public DbSet<Party> Parties { get; set; }
public DbSet<Booking> Bookings { get; set; }
}
This generated my DataBase and the two tables above..Great
I then decided to add another DbSet into the mix & I got an error:
the model backing the 'Party' context has changed since the database was created
I'm aware of the fixes for this using modelbuilder.IncludeMetadataInDatabase = false; and Database.SetInitializer<ClubmansGuideDB>(null);
1) What's the correct way to add my new classes to the context and have them generated in the DataBase?
2) In my futile attempts to solve this myself I deleted the tables and tried to re-run the app with no success I then deleted the full database and re-run and it doesn't re-generate the DB. How can I start from scratch - is there some cache somewhere?
I believe you're looking for:
Database.SetInitializer<ClubmansGuideDB>(new DropCreateDatabaseIfModelChanges<ClubmansGuideDB>());
As of EF 4.1 and above.
Note that this assumes you have permission to even drop your database. I do this locally for ease of development but disable it in staging/production (I do a manual Schema Compare and push my changes).
By the way, for testing, if you need to force recreate the database, you can do:
using (var context = new ClubmansGuideDB()) {
context.Database.Initialize(force: true);
}
(using if you don't already have a reference to your DB)
You can let the Entity Framework recreate the whole database by using a Database Initializer or if you want to migrate data you can look at the Code First Migrations
The following would recreate your database when the model changes:
Database.SetInitializer<myDB>(new DropCreateDatabaseIfModelChanges<myDB>());
Try putting this in your Global.asax.cs Application_Start() method.
Database.SetInitializer<DatabaseContext>(null);
To reset the database from scratch on app run make a class like this
//Where myDB is your context
public class EntityBase: DropCreateDatabaseAlways<myDB>
{
}
Then in your Application_Start() method you can do this
Database.SetInitializer(new EntityBase());