I'm using code first migrations. Is there a way to display pending model changes in package manager console before I scaffold a new migration?
The accepted answer tells how to get the SQL for a already scaffolded model change before applying to the database.
The original question regarded model changes pre-scaffolding (i.e. changes in the model since the last "add-migration" before running the next "add-migration" ...)
To that answer i will just say: scaffold anyway, that gives you your preview. By that i mean, run "add-migration preview" or something similar, it will create the scaffolded migration with the model changes that you are interested in. Then just delete if from your solution ...
The point here is that there is no need to "preview" when actually "doing" can be quickly undone. Some might think deleting a scaffolded migration version from the migrations section of the solution would break something, but no it is very well supported.
You can even test scaffold, then create the sql script as Colin suggest in his answer, to get the full SQL. Still nothing has been done at this point, so delete the migration version if you'd like.
There is no way that I know of to view pending changes in the model before scaffolding the migration, but I can't think of a reason not to scaffold the migration using Add-Migration so that the pending changes can be viewed in the migration file. There is no need to apply those changes to the database and the scaffolded migration can always be deleted.
Once the migration is scaffolded, if you use Update-Database -Script entity framework generates a SQL script rather than executing the changes directly.
You can get help on the EntityFramework in the package manager using get-help EntityFramework
And you can get help on the Update-Database command using the following:
get-help Update-Database
get-help Update-Database -detailed
get-help Update-Database -full
Related
We have a EF project with multiple migrations being applied almost weekly to our database. I have to remove and add a new migration because I made a typo in a property of a model and I need it to be re-created.
I followed the usual steps:
dotnet update database MOST_RECENT_CORRECT_MIGRATION -c CONTEXT_NAME
dotnet ef migrations remove
The last command should revert model snapshot changes and delete the migrations cs and designer.cs files, but instead it only reverts the model snapshot and it doesn't deletes the previous migration. Until a few migrations back it worked perfectly and I was able to follow this workflow and recreate migrations that needed naming changes and more from the PRs. I can delete the migration manually and try to come up with a working new migration but I don't want to break things in the background and I want to do things properly.
When I run it with verbose I get (among the usual enormous amount of messages) the following message that looks not good:
[...]
A manual migration deletion was detected.
[...]
Does this have anything to do with the problems I'm having? Should I just delete all the changes and recreate a new migration from, say, the last moment it worked fine?
I'm using .NET Core 3.1 and SQL Server.
I can also move on a create a new migration that drops the wrongly typed column and replaces it with the new, correct one.
In my ASP.NET Entity Framework 6 project I added a new Model and Controller.
I have automatic migration enabled but allowed data loss disabled.
When I ran the application after these changes the new table was actually created into the db, but the application told me:
Automatic migration was not applied because it would result in data loss
Without any other detail. As read in other questions I tried to issue:
Database-Update -Script
to get the "differences" but nothing happened, just the same error message.
I really don't want to force the update unless I'm sure what it's going to do.
What should I do in order to retrieve the content of the current migration?
I tried to look into the dbo.__MigrationHistory table but the Model field contains binary data.
UPDATE
I was able to decode the Model field using this method, but the edmx file contains just the whole diagram of the db, not the actual commands the the migration would issue.
Furthermore, even if add the -Verbose flag as suggested by the tool itself:
PM> Update-Database -Verbose
Using StartUp project 'MyProject'.
Using NuGet project 'MyProject'.
Specify the '-Verbose' flag to view the SQL statements being applied to the target database.
It does not show the SQL statements...
The message is displayed because you probably made some change to your model that results in a DROP command (e.g. removing property).
To see the script for that specific migration, i.e. the update between the latest migration and the one before it, you can use the following command:
Update-Database -Script -SourceMigration: <migrationBeforeTheLastOne> -TargetMigration: <lastMigration>
as stated in ChW's answer.
I have two solutions, the base solution with no migrations(which is in production, so I can not wipe the data) and now I have branched of this to set up migrations and make some model changes.
First I need to set up migrations on the branched solution (second solution) so that I can apply the model changes so I:
Turn on migrations which auto creates an InitialMigration
Enable-Migrations -ContextTypeName Context
Make a blank migration based on the suggestion from https://www.apress.com/gp/blog/all-blog-posts/secular-trends-for-the-cloud/12097630
Add-Migration InitialBlank -IgnoreChanges
Update Database * update-database*
Make my model changes
Add a migration containing my model changes * Add-Migration add_entity*
Run Update-Database
So I delete the database created as I need to run the first solution to create the initial db setup (to mimic live).
When I run the first solution it creates an entry in MigrationsHistory table named InitialCreate (201807061432030_InitialCreate), which has been auto created. I then run update-database on the second solution which applies my model changes fine although their are discrepancies in the InitialCreate MigrationId.
Migration entries in my second solution (in order they were created and the order they are in the solution):
- 201807061257015_InitialCreate
- 201807061315294_InitialBlank
- 201807061323086_add_entity
Migration entries in the migration history table after running the first then second solution:
1 | 201807061315294_InitialBlank
2 | 201807061323086_add_entity
3 | 201807061432030_InitialCreate
The second solution runs fine but when I try to add any data I get System.InvalidOperationException: 'The model backing the 'Context' context has changed since the database was created. Consider using Code First Migrations to update the database.
I have tried to create another migration on the second project to make sure their are no model changes that have not been migrated (their shouldn't be) but I get an error.
Unable to generate an explicit migration because the following explicit migrations are pending: [201807061257015_InitialCreate]. Apply the pending explicit migrations before attempting to generate a new explicit migration.
My questions:
How do I resolve the MigrationId mismatch? As the first solution did not have migrations turned on and when I do turn them on (in the second solution) it creates a new id.
Could the exception System.InvalidOperationException: 'The model backing the 'Context' be thrown by the MigrationId mismatch or could anyone point me at why this could be happening? I have had a look into this error but the solution's I found don't seem to work:
Deleting the migrations history table is no good as I can not do this in production because of customer data.
The other solution I found of adding Database.SetInitializer(null); to global.asax seems to make no difference.
Why does the order of my migrations look different once they have been applied in the migration history table?
Thanks in advance!
I am not sure if this will work but I think I may need to manually delete the first InitialCreate and edit the db entries to reflect the correct InitialCreate. Based of this SO question I just found https://stackoverflow.com/a/13108243/3172635.
I will have to try this Monday though.
Edit: I first tried deleting the InitialMigration entry in the _MigrationHistory table but this does not work as it tries to apply the InitialMigrations again but cant as the tables are already created. So what I did was update the MigrationId for the InitialMigration entry to reflect what it was in the new project.
The sql I used:
SET MigrationId='201807061257015_InitialCreate' WHERE MigrationId = '201807061432030_InitialCreate'
I am working on a entity framework project generating the Entity classes using the New-> ADO.NET Entity Data Model -> Code First From Database. I then select nearly 100 tables to generate (not all tables are suitable to go in the model).
Problem is I am regularly updating the schema, and the only way to refresh the model seems to be to delete and start again, which is fine except I have to re-select the nearly 100 tables again.
Is there any easy way of scripting this generation process?
You should look into using Entity Framework Migrations and start doing your schema changes from the code itself
Set the CompanyName.ProjectName.Infrastructure.EfRepository (the project which has your DbContext) as start up project of the solution
Open the Package manager console
Choose CompanyName.ProjectName.Infrastructure.EfRepository as default project
Run the following commands:
Enable-Migrations -ConnectionStringName "EfDataRepository"
Add-Migration Initial -ConnectionStringName "EfDataRepository"
Update-Database -ConnectionStringName "EfDataRepository" -Script -SourceMigration:0
Then delete the auto-generated Migrations folder within the EF project!
Where EfDataRepository is the connection string name.
I am working on an ASP.NET MVC project with Entity Framework with code first from database. I get the models for each table in the database. I made some changes in the models, enabled migrations and when I initial the migration I get an error:
There is already an object named 'TableName' in the database."
I tried with update-database -force but didn't help. The initial migration creates the tables that already exist!
How to make the initial migration apply the changes on the models and not create the tables from beginning?
And what is the best practice to sync changes between database and models in this case?
try to Run the
Add-Migration InitialCreate –IgnoreChanges
command in Package Manager Console. This creates an empty migration with the current model as a snapshot. and then Run the
Update-Database
command in Package Manager Console. This will apply the InitialCreate migration to the database. Since the actual migration doesn’t contain any changes, it will simply add a row to the __MigrationsHistory table indicating that this migration has already been applied.
see this
then change your models and add migration.
another approach is to simply comment all the code on up and down methods
Best and working For me idea is to comment all the code in UP and Down functions of Initial migration file and then fire
dotnet ef database update this should work fine,make sure you update migration before commenting out initial migration
If none of those answers work for you, you may check if in your code you use the method
context.Database.EnsureCreated()
Be aware that that method doesn't apply any migrations
(source) (you can check this making a sql query to the database and like "select * from __EfMigrationHistory" and be sure that there are no migrations on that database.
EF provide a really good method to help this that is
context.Database.Migrate()
that no only it will ensure that you have a database, but also use migrations and migrate yout db to the last version.
Hope it helps
This error appears when you deleted previous migrations and your new migration try to create new table that already exist. Recover previous migration and everything will be ok.
Amr Alaa solution works, but the database didn't migrate to the latest model.
Here's how it worked (using automatic migration) :
Delete Migrations folder
Execute enable-migrations
Set this two properties to true in the newly created Configuration.cs
public Configuration()
{
AutomaticMigrationsEnabled = true;
AutomaticMigrationDataLossAllowed = true;
}
Execute Update-Database -Force
Your database will be updated to latest scheme and ready.
hope this helps.