Does anyone knows if it is possible to just rename a database table with Code First in Entity Framework 5?
I just have simple models and a database initializer, but since my database already contains data I've commented that initializer out. So, I don't want to drop and create a whole new database.
When I add new columns to such a model I use the Package Manager Console and run update-database. to update my database. Does this also work for renaming tables? Does the update-database command automatically knows what the old name was?
I don't have a lot of experience with CF yet and learning new stuff every day. Without CF it's 'easy' to just run an alter table command and refresh the dbml file... But with CF? I don't have a clue!
use
<Table("TableName")> _
Public Class ClassName
....
Obviously the update-database command knows what the old name was... So, in case of data loss warnings, you may choose to apply the -force option.
Related
I renamed a few tables and some columns. When I run the Add-Migration command, the migration generates code that drops the old tables and columns and adds ones with the new names. This results in losing the data they contained.
Since I don't want to lose the data, I want to edit the migration, removing the drop and add commands, and replacing them with rename commands.
But after I edit a migration, how do I apply that change?
If I run the Update-Database command, that applies it to the database. But not to the snapshot that Entity Framework maintains of my schema (stored in ApplicationDbContextModelSnapshot).
I need a way to incorporate my edits into the model. How can I accomplish this?
So, this is definitely the messy part of code first.
As far as the question asked, as GuruStron suggested, the only way I found to have a valid custom migration is to edit it such that the result is the same as what the original, generated migration produced. This keeps it up to date with the database snapshot. And running Update-Database will run your custom update code.
I think my biggest problem was that I had too many changes going on at once. After struggling with this for a while, I undid some of my changes and added them back bit-by-bit. Entity Framework will rename a table or column if it can figure out that the new name refers to the same column. If it finds many changes, it can't figure this out.
In the end, I had to customize the migration a little for a couple of columns that were being dropped (customized them to be renamed instead). But I was able to get Entity Framework to rename my tables and other columns.
The key: make small changes at a time and carefully review the migration before applying them to the database. If you need to customize the migration, do it such that the end result doesn't change.
You don't.
I suppose you are developing using a code first approach, since the question has this tag on it.
If you are using code first, you must change your models and let Entity Framework change the database schema for you.
Suggested reading:
Migration in Entity Framework Core
Entity Framework Core Migrations
I am working on a project which is using Entity Framework code first for its data structure. It was created with code first, but was never migrated again and only has its initial migration data stored. Since then, the database has been modified directly through server explorer in VS2015.
There is no migration information about any changes and the database has critical information which I cannot lose.
Which brings me to my Questions.
If I create a new migration and update the database from it, will it wipe all changes which were not recorded in migrations and still leave the changes which were made as well?
The details of your question is a bit sketchy, but I will make some assumptions in order to help you along. Please correct where I am wrong.
I assume that you want to keep the data which resulted from the changes which were effected directly to the database, but you do not want to keep the changes that was effected to the database - in other words: keep the data but not the datastructures.
My advice is as follows
Always perform a full backup of your database when you are about to do something you are uncertain about.
If you can identify the tables you want to update, you can always use the SELECT INTO statement to create a quick backup of the specific tables only. These tables will not be removed when you do a EF database migration unless you explicitly script the deletion.
You can build the SELECT INTO statement into your EF migration via the Sql() method, or you can manually run the command against the database.
More information:
Click here to learn about EF code first migrations in general
Click here for a comprehensive code first migration reference
I believe following two posts will help you.
EF 4.3 Migration Walkthrough : http://blogs.msdn.com/b/adonet/archive/2012/02/09/ef-4-3-code-based-migrations-walkthrough.aspx
update:
Code First Migrations with an existing database
https://msdn.microsoft.com/en-us/data/dn579398.aspx
My application has a one context that is injected using Autofac. I also have plugins which created and maintained their own contexts on the same database. I'm bringing it all in-line now so that the plugins just use the main context.
The issue I now face is that because the tables already exist in the database, I can't update-database because it says PluginTable already exists in the database. I can't do an add-migration and then remove the Up / Down entries because the plugins aren't within the same project.
Note: I think this is only an issue because the tables already exist so I need to get the current migration entries up to date so it doesn't try and recreate the tables.
Note: I considered re-building the migration file but again, the same problem will happen because add migration doesn't work.
I don't know what code to post that will help with this but I'm just wondering if we can tell ef to ignore tables that already exist on its creation process (this sounds daft as I type it but I'm not sure what else to do).
EDIT: Perhaps the question I should be asking is how to get the add-migration to take note of the other projects so I can just do a blank add migration and get the migration file up to date
Not sure what you mean by the can't add-migration, but if you need to run a migration to establish a baseline:
Add-Migration MyBaseline –IgnoreChanges
https://msdn.microsoft.com/en-us/data/dn579398.aspx?f=255&MSPPError=-2147217396#option1
I'm using EF 6.0.0 and .Net 4.5.
I face a very confusing problem. Me and one of my colleagues are working on the domain model section of our project on two different clients. The problem is:
1- Me and my colleagues start with the absolutely identical project and we are completely synced with the source control.
2- When I change the model for example add a property then Add-Migration FromA then Update-Database it works great. The generated code file contains just one command that is to add the column.
3- Meanwhile, after the db is updated and just before I check in something to source control, my colleague adds another property and then Add-Migration FromA then Update-Database. And guess what? This generated code file has a command to drop the column I newly added!!!
I added another column using native Sql, and fortunately the column is not going to be deleted.
I deleted the __MigrationHistory table and the remove column didn't get generated.
I turned off initializer Database.SetInitializer<MyContext>(null), no success.
So, my guess is that EF Migrations compares current model with the last one stored in __MigrationHistory table not the last local snapshot stored in .resx file. Am I right? Any way to solve the problem?
I tried finding the answer to this question before posting, but couldn't.
We are using a remote database with Entity Framework and I do not know the approach it was used to create the database. What I would like to do is add a class to the project, add the class to DbSet an create the table automatically. Now, when I use update-database in nuget, i get "migrations not enabled for this database" and its true, there is no configuration file or anything that suggest the approach it was used for creation of this.
I wouldn't want to enable-migrations as I don't want to mess something up or loss data. (or should i?) The existing tables are working fine with the repository...
I created a table manually, added a class that maps the properties by name and hoped that entity framework will pick it up, but no luck.
Here it is in a nutshell: I want to add a new table in a remote database that will be picked up by Entity Framework an generate a class for me. There is also NO .edmx file that can update the model. How was this done then... (?)
I am a new to Entity Framework, so apologies it some of this does not make sense. I am happy to clarify.
Thanks,
Thank you for your responses. I managed to fix this by adding a new class into the repository, using code first approach and then I created a table manually in the database.. The Entity Framework pick it up somehow :)
I was doing this before, but the problem was that I had the DbSet name to plural and database to singular. For instance: Products was the DbSet name and Product table in database. The actual class is still singular.
Thanks again!