Code First Migrations: Alpha 2 Released
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Visit msdn.com/data/ef for the latest information on current and past releases of EF.
For Code First Migrations see https://msdn.com/data/jj591621
Six weeks back we released the first preview of Code First Migrations. This preview was called ‘Code First Migrations August 2011 CTP’. However, after some changes to how we name our releases it is best to think of that release as ‘Code First Migrations Alpha 1’. Today we are happy to announce that ‘Code First Migrations Alpha 2’ is available.
Alpha 2 is still is primarily focused on the developer experience inside of Visual Studio. We realize this isn’t the only area in which migrations is important and our team is also working on scenarios including team build, deployment and invoking migrations from outside of Visual Studio as well as from custom code.
Note: If you have received the following error when trying to use Code First Migrations Alpha 2 it is most likely due to bugs that were causing a dependency on SQL Compact and a dependency on a local SQL Express instance. We have released an updated package that resolves both these issues, please ensure you have updated the EntityFramework.Migrations package to version 0.6.2. You will need to close and re-open Visual Studio after updating the package, failure to do so will result in an error stating that “The project 'Demo' does not contain any migration contexts”. If you continue to get errors after updating to the latest package and re-starting Visual Studio then please start a thread in our Pre-Release Forum.
Add-Migration : Exception has been thrown by the target of an invocation.
At line:1 char:14
+ Add-Migration <<<< Init2
+ CategoryInfo : NotSpecified: (:) [Add-Migration], TargetInvocationException
+ FullyQualifiedErrorId : System.Reflection.TargetInvocationException,System.Data.Entity.Migrations.AddMigrationCommand
What Changed
The short answer… a lot! You gave us a lot of feedback on our first alpha and we summarized it in the 'Code First Migrations: Your Feedback' blog post. The changes are pretty widespread so we would recommend reading the Code First Migrations Alpha 2 Walkthrough to get an overview of the new functionality. Here are some of the more notable changes:
- We did a lot of work to improve the ‘no-magic’ workflow, including a code based format for expressing migrations. Our walkthrough also starts with the no-magic approach and then shows how to transition to a more-magic approach for folks who want to use it.
- A provider model is now available. Providers need to inherit from the System.Data.Entity.Migrations.Providers.DbMigrationSqlGenerator base class and are registered in a new Settings class that is added when you install the NuGet package. Alpha 2 includes a provider for SQL Server (including SQL Azure) and SQL Compact.
- We’ve taken a NuGet package name change. Alpha 1 was released as EntityFramework.SqlMigrations, but given the design changes that name makes less sense. We have now dropped the ‘Sql’ and are now just EntityFramework.Migrations.
- We’ve improved how we do type resolution to find your context etc. In the first preview there were a number of issues around how we discovered your context, especially in solutions with multiple projects. This would result in various errors when trying to run either of the migration commands. We’ve done some work to make this more robust in Alpha 2.
Feedback
We really want your feedback on this work so please download it, use it and let us know what you like and what you would like to see change. You can provide feedback by commenting on this blog post.
The key areas we really want your feedback on are:
- Shape of the API for expressing migrations. The API for migrations isn’t complete yet but Alpha 2 contains a large part of what we expect the final API to look like. We’d love your feedback on whether we are heading down the right path.
- Will you use the automatic migrations functionality? We support a purely imperative workflow where all changes are explicitly expressed in code. A lot of folks have told us that is how they want to work. We want to know if we should continue to invest in the option of having sections of the migrations process handled automatically.
Getting Started
The Code First Migrations Alpha 2 Walkthrough gives an overview of migrations and how to it for development.
Code First Migrations Alpha 2 is available via NuGet as the EntityFramework.Migrations package.
Known Issues & Limitations
We really wanted to get your feedback on these design changes so Alpha 2 hasn’t been polished and isn’t a complete set of the features we intend to ship.
Some known issues, limitations and ‘yet to be implemented’ features include:
- You must start using migrations targeting an empty database that contains no tables or targeting a database that does not yet exist. Code First Migrations assumes that it is starting against an empty database. If you target a database that already contains some/all of the tables for your model then you will get an error when migrations tries to recreate the same tables. We are currently working on a boot strapping feature that will allow you to start using migrations against an existing schema.
- VB.Net is not yet supported. Migrations can currently only be scaffolded in C#, we are adding VB.Net code generation at the moment and will release another Alpha shortly that includes VB.Net support. You can, however, use a C# project to work with migrations that reference a domain model and context that are defined in a separate VB.Net project(s).
- There is an issue with using Code First Migrations in a team environment that we are currently working through. Code First Migrations generates some additional metadata alongside each migration that captures the source and target model for the migration. The metadata is used to replicate any automatic migrations between each code-based migration. If the source model of a migration matches the target model of the previous migration then the automatic pipeline is skipped. The issue arises when two developers add migrations locally and then check-in. Because the metadata of their migrations are captured during scaffolding they don’t reflect the model changes made by the other developer, even if the second developer to check-in sync’s before committing their changes. This can cause the automatic pipeline to kick in when the migrations are run. We realize this is the key team development scenario and are working to resolve it at the moment.
- No outside-of-Visual-Studio experience. Alpha 2 only includes the Visual Studio integrated experience. We also plan to deliver a command line tool and an MSDeploy provider for Code First Migrations.
- Downgrade is currently not supported. When generating migrations you will notice that the Down method is empty, we will support down migration soon.
- Migrate to a specific version is not supported. You can currently only migrate to the latest version, we will support migrations up/down to any version soon.
Prerequisites & Incompatibilities
Migrations is dependent on EF 4.1 Update 1, this updated release of EF 4.1 will be automatically installed when you install the EntityFramework.Migrations package.
Important: If you have previously run the EF 4.1 stand alone installer you will need to upgrade or remove the installation before using migrations. This is required because the installer adds the EF 4.1 assembly to the Global Assembly Cache (GAC) causing the original RTM version to be used at runtime rather than Update 1.
This release is incompatible with “Microsoft Data Services, Entity Framework, and SQL Server Tools for Data Framework June 2011 CTP”.
Support
This is a preview of features that will be available in future releases and is designed to allow you to provide feedback on the design of these features. It is not intended or licensed for use in production. If you need assistance we have an Entity Framework Pre-Release Forum.
ADO.NET Entity Framework Team