I want Update database by code first migration .for example I have 3 entity in contex and 1 table in database and there is a problem when I run program and get this error:There is already table.
Migration Configuration
internal sealed class Configuration : DbMigrationsConfiguration<ApplicationDbContext>
{
public Configuration()
{
AutomaticMigrationsEnabled = false;
// AutomaticMigrationDataLossAllowed = false;
}
protected override void Seed(ApplicationDbContext context)
{
// This method will be called after migrating to the latest version.
}
}
IdentityModel
public ApplicationDbContext() : base("DefaultConnection" )
{
Database.SetInitializer<ApplicationDbContext>(new MigrateDatabaseToLatestVersion<ApplicationDbContext, Migrations.Configuration>());
}
any help ?
Have you tried to use the Add-Migration "migration_name" before calling update database? Or maybe try to use Update-Database -Force.
Otherwise, I have found some steps that maybe could be useful:
Remove the existing Migrations folder in your project, and DROP the table __MigrationHistory from the existing database.
Run the enable-migrations command from the Package Manager Console.
Run the add-migration command to create an initial migration.
Remove all of the code in Up() method for the initial migration.
Run the update-database command to apply the initial migration to your database. This doesn't make any changes to existing objects (because the Up() method contains no code), but it marks the existing database as having been migrated to the initial state.
Make changes to your code-first model.
Run the add-migration command to create a new migration. The code in the Up() method of the new migration will contain only the changes to your object model.
Run the update-database command to apply the changes to your database.
That's a common problem with migrations. When you add a new migration it compares the current code model to the prior code model stored in the prior migration. If this is the first migration it will thus generate code for everything, so sometimes the code will try to add objects that already exist.
To get past this, you can comment out the code in the Up() method of the migration for the items that already exist and then apply the migration (update-database). Now it will correctly generate just the changes moving forward.
To prevent this, you should always generate an initial snapshot of your database without generating any changes:
add-migration MyStartingPoint -IgnoreChanges // ignorechanges flag tells EF to just take snapshot with no code in Up()
Here is a document on how migrations operate "under the hood".
I am adding Code First migrations to an existing Entity Framework 6 domain with existing databases. I need the following behaviour:
If the database exists, insert the InitialCreate migration but do not perform the contents of the migration Up().
If the database does not exist, create it and run the contents of Up() and Down() to create an empty but correct-schema database.
I need (1) for when I release through the Continuous Delivery deployment. I need (2) for when a developer is cleaning down their machine and starting fresh. I do not want to use automatic migrations.
I appreciate that a Migration has no concept of the Database Context, it's only responsible for generating a series of SQL instructions.
Are these my only options?
1. Move contents of Up and Down out of InitialCreate and into Configuration.Seed
The InitialCreate migration runs Up() but no changes are made. In Seed() we have access to DbContext, so we can work out if the tables exist and create them if needed.
I think this might break when there are lots of migrations to run as Seed() is called after the migrations. On an empty database, the creation of the tables would be happening after updates to those schemas.
2. Perform the Up() method as a SQL Script
Migrations allows the developer to put inline SQL into Up() and Down(). Move the creation of the database into inline SQL and add a IF NOT EXISTS at the top.
I don't like this because you lose the use of the model that is supplied with the InitialCreate. If the model is updated, the fixed SQL string won't.
3. Empty out the Up() and Down() methods, do a release, put the creation code back in, do another release
When the InitialCreate migration is run first time, it won't have anything in it. The entry will go into the migrations database without running anything.
Once that first release has been performed, I can then put the creation code back in so that when future developers run it without a database, it will create properly.
Note: This one is my current favourite as it uses Entity Framework as designed and I can personally control adding the code back in after a release.
Is there a better way?
Edit
I am unable to build the database from empty, this might be something to do with the Context model creation. It uses a bespoke pluggable method:
public MyObjectContext()
{
((IObjectContextAdapter) this).ObjectContext.ContextOptions.LazyLoadingEnabled = true;
((IObjectContextAdapter)this).ObjectContext.CommandTimeout = 180;
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
System.Type configType = typeof(AnswerMap); //any of your configuration classes here
var typesToRegister = Assembly.GetAssembly(configType).GetTypes()
.Where(type => !String.IsNullOrEmpty(type.Namespace))
.Where(type => type.BaseType != null && type.BaseType.IsGenericType && type.BaseType.GetGenericTypeDefinition() == typeof(EntityTypeConfiguration<>));
foreach (var type in typesToRegister)
{
dynamic configurationInstance = Activator.CreateInstance(type);
modelBuilder.Configurations.Add(configurationInstance);
}
base.OnModelCreating(modelBuilder);
}
All the map objects are in the same DLL, the domain entities used for the database tables are in a separate DLL.
This is what we do:
1) Create an initial migration that is a snapshot of the current database. Use -IgnoreChanges to keep any code out of the Up(). You don't need the Up() code because EF will compare the prior model (blank) to the one stored in the migration and realize you need to add all the existing objects at the time of the snapshot.
add-migration Initial -IgnoreChanges
2) Add new migrations as you develop. In a team environment you could run into the issues outlined here: https://msdn.microsoft.com/en-US/data/dn481501
3) You can generate an idempotent script that will rebuild an entire system from scratch and apply any (or all) migrations.
Update-Database -Script -SourceMigration $InitialDatabase
https://msdn.microsoft.com/en-us/data/jj591621.aspx?f=255&MSPPError=-2147217396#idempotent
I know there are many topics about this error message but none of them is similar my problem. I am using Entity Framework 6. I have changed my entity and I have to run add-migration and then update-database. but when I run add-migration the newly created class public partial class Test: DbMigration contains two empty Up and Down methods. so when I run update-database it does not make any changes on the database. and I am get this error always.
I am getting this error when I run update-database. I think the problem occur becasue UP and Down methods are empty and no changes are made into the database when I run update-database.
in Application_Start() Method in Global.asax.cs file write as first line this
Database.SetInitializer<YourDBContext>(null);
For those that want to know what was the problem.
When you create a MVC 5 project with Idenity, it adds ApplicationDbContext class to connect to the database. I had created another DBContext for my entities. When I changed my entities and run add-migration it affected only chnages that was made for those ootb entities which belong to ApplicationDbContext not my DBContext. and When I run update-database it does not update my entities. I added all my entities to ApplicationDbContext and run add-migration then update-database and it solved the problem.
I'm receiving the following error when running my mvc 4 app.
The model backing the 'DMSContext' context has changed since the database was created. Consider using Code First Migrations to update the database
I am running my app against an existing database and do no want to recreate the db each time the model changes.
I've found plenty of answers on google, but none have worked.
Specifically, I've tried adding the following to my global.asax:
Database.SetInitializer<DMSContext>(null);
and
Database.SetInitializer<DMSContext<Contact>>(null);
in the above, DMSContext is the DbContext. Contact is the Model where the change causing the error originates.
I've also tried adding the following to my context class:
public DMSContext() : base()
{
Configuration.AutoDetectChangesEnabled = false;
}
Most of the direction I've followed is from this page, but no luck.
The model backing the <Database> context has changed since the database was created
If you are working with Entity Framework Code First, its recommended that you enable migrations in your application. To do so, see this link.
Now every time you change something in your code (Mostly Entities), just build and then run Update-Database -Force in your Package Manager Console.
Let me know if you have any more questions.
Although you don't use migrations try to create one, do not run it, but you'll be able to see the differences with the database.
Check the name of the class, which inherits the DbContext. It's name have to be the same as the name of the connectionString in Web.config
<connectionStrings>
<add name="TheSameNameAsYourDbContextClass" providerName="" connectionString="" />
</connectionStrings>
I'm trying to use EF 4.3 migrations with multiple code-first DbContexts. My application is separated into several plugins, which possibly have their own DbContext regarding their domain. The application should use one single sql-database.
When I try to auto migrate the contexts in an empty database, this is only successful for the first context. Every other context needs the AutomaticMigrationDataLossAllowed-Property set to true but then tries to drop the tables of the previous one.
So my question is:
How can I tell the migration-configuration just to look after the tables defined in their corresponding context and leave all others alone?
What is the right workflow to deal with multiple DbContexts with auto-migration in a single database?
Thank you!
Here is what you can do. very simple.
You can create Configration Class for each of your context.
e.g
internal sealed class Configuration1 : DbMigrationsConfiguration<Context1>{
public Configuration1 (){
AutomaticMigrationsEnabled = false;
MigrationsNamespace = "YourProject.Models.ContextNamespace1";
}
}
internal sealed class Configuration2 : DbMigrationsConfiguration<Context2>{
public Configuration2 (){
AutomaticMigrationsEnabled = false;
MigrationsNamespace = "YourProject.Models.ContextNamespace2";
}
}
Now you add migration. You dont need to enable migration since you already did with the 2 classed above.
Add-Migration -configuration Configuration1 Context1Init
This will create migration script for context1. your can repeat this again for other Contexts.
Add-Migration -configuration Configuration2 Context2Init
To Update your database
Update-Database -configuration Configuration1
Update-Database -configuration Configuration2
This can be done in any order. Except you need to make sure each configration is called in sequence.
Code First Migrations assumes that there is only one migrations configuration per database (and one context per configuration).
I can think of two possible solutions:
Create an aggregate context that includes all the entities of each context and reference this "super" context from your migrations configuration class. This way all the tables will be created in the user's database, but data will only be in the ones that they've installed plugins for.
Use separate databases for each context. If you have shared entities between the contexts, add a custom migration and replace the CreateTable(...) call with a Sql("CREATE VIEW ...") call to get the data from the entity's "originating" database.
I would try #1 since it keeps everything in a single database. You could create a seperate project in your solution to contain your migrations and this "super" context. Just add the project, reference all of your plugins' projects, create a context that includes all of the entities, then call Enable-Migrations on this new project. Things should work as expected after that.
I have a working site with multiple contexts using migrations. However, you do need to use a separate database per context, and it's all driven off of a *Configuration class in the Migrations namespace of your project, so for example CompanyDbContext points to Company.sdf using CompanyConfiguration. update-database -configurationtypename CompanyConfiguration. Another LogDbContext points to Log.sdf using LogConfiguration, etc.
Given this works, have you tried creating 2 contexts pointing at the same database and telling the modelbuilder to ignore the other context's list of tables?
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Ignore<OtherContextsClass>();
// more of these
}
Since the migrations work with the ModelBuilder, this might do the job.
The crappy alternative is to avoid using Automatic Migrations, generate a migration each time and then manually sift through and remove unwanted statements, then run them, although there's nothing stopping you from creating a simple tool that looks at the Contexts and generated statements and does the migration fixups for you.
Ok, I have been struggling with this for a day now, and here is solution for those seeking the answer...
I am assuming that most people reading this post are here because they have a large DbContext class with a lot of DbSet<> properties and it takes a long time to load. You probably thought to yourself, gee, that makes sense, I should split up the context, since I won't be using all of the dbsets at once, and I will only load a "Partial" context based on the situation where I need it. So you split them up, only to find out that Code First migrations don't support your way of revolutionary thinking.
So your first step must have been splitting up the contexts, then you added the MigrationConfiguration class for each of the new contexts, you added the connection strings named exactly the same as your new Context classes.
Then you tried running the newly split up contexts one by one, by doing Add-Migration Context1 then doing Update-Database -Verbose...
Everything seemed to work fine, but then you notice that every subsequent Migration deleted all tables from the Previous migration, and only left the tables in from the very last migration.
This is because, the current Migrations model expects Single DbContext per Database, and it has to be a mirror match.
What I also tried, and someone suggested here doing that, is create a single SuperContext, which has All the Db sets in it. Create a single Migration Configuration class and run that in. Leave your partial Context classes in place, and try to Instantiate and use them. The EF complains that the Backing model has changed. Again, this is because the EF compares your partial dbcontext to the All-Sets context signature that was left over from your Super Context migration.
This is a major flaw in my opinion.
In my case, I decided that PERFORMANCE is more important than migrations. So, what I ended up doing, is after I ran in the Super context and had all the tables in place, I went into the database and Manually deleted _MigrationHistory table.
Now, I can instantiate and use my Partial Contexts without EF complaining about it. It doesn't find the MigrationHistory table and just moves on, allowing me to have a "Partial" view of the database.
The trade off of course is that any changes to the model will have to be manually propagated to the database, so be careful.
It worked for me though.
As mentioned above by Brice, the most practical solution is to have 1 super DbContext per application/database.
Having to use only 1 DbContext for an entire application seems to be a crucial technical and methodological disadvantage, cause it affects Modularity among other things. Also, if you are using WCF Data Services, you can only use 1 DataService per application since a DataService can map to only 1 DbContext. So this alters the architecture considerably.
On the plus side, a minor advantage is that all database-related migration code is centralized.
I just came across this problem and realised the reason I had split them into different contexts was purely to have grouping of related models in manageable chunks and not for any other technical reason. Instead I have declared my context as a partial class and now different code files with different models in them can add DbSets to the DbContext.
This way the automigration magic still works.
I've got it working with manual migrations, but you can't downgrade as it can't discrimitate between configurations in the __MigrationHistory table. If I try and downgrade then it treats the migrations from the other configurations as automatic and since I don't allow data loss it fails. We will only ever be using it to upgrade though so it works for our purposes.
It does seem like quite a bit ommision though, I'm sure it wouldn't be hard to support it provided there was no overlap between DbContexts.
Surely the solution should be a modification by the EntityFramework team to change the API to support the direct modification of the _MigrationHistory table to a table name of your choice like _MigrationHistory_Context1 such that it can handle the modification of independent DbContext entities. That way they're all treated separately, and its up to the developer to ensure that the names of entities don't collide.
Seems like there are a lot of people who share my opinion that a duplicate DbContext with references to the superset of entities is a bogus non-enterprise friendly way to go about things. Duplicate DbContexts fail miserably for modular (Prism or similar) based solutions.
I want people to know that the answer with this below is what worked for me but with one caveat: don't use the MigrationsNamespace line.
internal sealed class Configuration1 : DbMigrationsConfiguration<Context1>{
public Configuration1 (){
AutomaticMigrationsEnabled = false;
MigrationsNamespace = "YourProject.Models.ContextNamespace1";
}
}
internal sealed class Configuration2 : DbMigrationsConfiguration<Context2>{
public Configuration2 (){
AutomaticMigrationsEnabled = false;
MigrationsNamespace = "YourProject.Models.ContextNamespace2";
}
}
However, I already had the 2 databases established with their own contexts defined so I found myself getting an error saying "YourProject.Models namespace already has ContextNamespace1 defined". This was because the "MigrationsNamespace = "YourProject.Models.ContextNamespace2";" was causing the dbcontext to be defined under the YourProjects.Models namespace twice after I tried the Init (once in the migration Context1Init file and once where I had it defined before).
So, I found that what I had to do at that point was start my database and migrations from scratch (thankfully I did not have data I needed to keep) via following the directions here:
http://pawel.sawicz.eu/entity-framework-reseting-migrations/
Then I changed the code to NOT include the MigrationsNamespace line.
internal sealed class Configuration1 : DbMigrationsConfiguration<Context1>{
public Configuration1 (){
AutomaticMigrationsEnabled = false;
}
}
internal sealed class Configuration2 : DbMigrationsConfiguration<Context2>{
public Configuration2 (){
AutomaticMigrationsEnabled = false;
}
}
Then I ran the Add-Migration -configuration Configuration1 Context1Init command again and the Update-Database -configuration Configuration1 line again (for my 2nd context too), and finally, everything seems to be working great now.