Migration in different assembly than target assembly not supported

[viksabnis]

Steps to reproduce

Create Web project that injects and initializes the DbContext and a Models project with the DbContext and migrations

The issue

Your target project '#Target Project#' doesn't match your migrations assembly '#Migrations Assembly#'. Either change your target project or change your migrations assembly.
Change your migrations assembly by using DbContextOptionsBuilder. E.g. options.UseSqlServer(connection, b => b.MigrationsAssembly("#Target Project#")). By default, the migrations assembly is the assembly containing the DbContext.
Change your target project to the migrations project by using the Package Manager Console's Default project drop-down list, or by executing "dotnet ef" from the directory containing the migrations project.

Exception message:
Stack trace:
Your target project '<Target Project>' doesn't match your migrations assembly '<Migrations Assembly>'. Either change your target project or change your migrations assembly.
Change your migrations assembly by using DbContextOptionsBuilder. E.g. options.UseSqlServer(connection, b => b.MigrationsAssembly("<Target Project>'")). By default, the migrations assembly is the assembly containing the DbContext.
Change your target project to the migrations project by using the Package Manager Console's Default project drop-down list, or by executing "dotnet ef" from the directory containing the migrations project.

### Further technical details

EF Core version: 1.0.0 RTM
Operating system:  Windows 10

Visual Studio version: 2015 -Command line Dotnet 1.0.0

Other details about my project setup:

[rowanmiller]

@natemcmaster can you give guidance on this

[natemcmaster]

@VikSab This is a common error when working with a DbContext that is in a separate project from your web app project. Can you share more details about which projects you are using and the file structure of your code?

[viksabnis]

TestWeb.zip
I have uploaded the Test Project that i was able to reproduce the issue

[natemcmaster]

Thanks for the repro. You will see the error when invoking EF commands on the "Web" project.

The exception message you are seeing is by-design.

---

All EF commands have this check:

if (targetAssembly != migrationsAssembly) 
       throw MigrationsAssemblyMismatchError;

• targetAssembly = the target project you are operating on. On the command line, it is the project in the current working directory. In Package Manager Console, it is whatever project is selected in the drop down box on the top right of that window pane.
• migrationsAssembly = assembly containing code for migrations. This is configurable. By default, this will be the assembly containing the DbContext, in your case, Model.dll.

As the error message suggests, you have have a two options to resolve this

1 - Change target assembly.

cd ../Model
dotnet ef --startup-project ../TestWeb/ migrations add Initial

2 - Change the migrations assembly.

options.UseSqlServer(connection, b => b.MigrationsAssembly("Web"))

If you are still getting this error message even after changing either your migration assembly or your target assembly, please feel free to re-open the issue.

[viksabnis]

Looks good i was placing the --startup-project on the database command and not the ef command..

the help file doesnt seem to have this option

dotnet ef --help
Project Model (.NETCoreApp,Version=v1.0) was previously compiled. Skipping compilation.
Project TestWeb (.NETCoreApp,Version=v1.0) was previously compiled. Skipping compilation.
Entity Framework .NET Core CLI Commands 1.0.0-preview2-21431
Usage: dotnet ef [options] [command]
Options:
-h|--help Show help information
-v|--verbose Enable verbose output
--version Show version information
--assembly The assembly file to load.
--startup-assembly The assembly file containing the startup class.
--data-dir

The folder used as the data directory (defaults to current working directory).
--project-dir The folder used as the project directory (defaults to current working directory).
--content-root-path The folder used as the content root path for the application (defaults to application base directory).
--root-namespace The root namespace of the target project (defaults to the project assembly name).
Commands:
database Commands to manage your database
dbcontext Commands to manage your DbContext types
migrations Commands to manage your migrations
Use "dotnet ef [command] --help" for more information about a command.

[natemcmaster]

@VikSab it's there, but the help output doesn't show it. I'm working to fix this in #5188.

See https://docs.efproject.net/en/latest/miscellaneous/cli/dotnet.html for the "true" set of available parameters.

[viksabnis]

Should have said - that it works.. -

i was trying to apply it - but on the database or update command - didnt try it on the ef command.

The help file update would have made the fix easier to self managed thanks

[Defee]

@natemcmaster could you advise on following:

1. My Server model (DB) is separated on various contexts about 5-7 on separated dll's (packages).
2. The server models will be stored in nuget. So the contexts and configurations of EF API will be stored there too.
3. I want to run the migrations on my web project that references the packages.
4. The contexts could target one DB or multiples from various projects.

Earlier those issues can be resolved by storing particular dll and running migrate.exe on them. so the defined migrations in these dlls ran.

How could i use dotnet ef on the particular package to do the migrations defined in the particular package?

[natemcmaster]

@Defee please open a new issue for your question.

[jusefb]

Please Ignore my previous comment I was putting the --startup-project in the wrong place

[charce36]

Thanks a lot, works for me.
dotnet ef --startup-project ../XXXX.API migrations add MigrationName -c MyContext

[mshauny]

dotnet ef --startup-project ../XXXX.API migrations add MigrationName -c MyContext
Works for me too 😄 Thanks

[himalayagarg]

cd ../Model
dotnet ef --startup-project ../TestWeb/ migrations add Initial

Below is the command for Package Manager Console (Select YourApp.Data in Target Project dropdown )

Add-Migration -StartupProject YourApp.Web -Context "YourDbContext" Initial

https://docs.microsoft.com/en-us/ef/core/miscellaneous/cli/powershell