No context type was found in the assembly

问题:

I'm using .NET 4.0, MVC3, and EF5 with code first.

My solution is split up into three projects, with the dependencies as indicated:

Project.Web -> Project.BLL -> Project.DAL

The Project.DAL layer contains my entity framework data context class and all my entities, but my startup project is Project.Web, so it contains my Web.config, connection strings, and the actual SQL compact database.

I'm trying to enable migrations so I can add a new table to my EF model without wiping the existing data. However, when I run "Enable-Migrations", I get

No context type was found in the assembly 'Project.Web'.

If I set the startup project as Project.DAL, the error changes to

Could not load assembly 'Project.Web'. (If you are using Code First Migrations inside Visual Studio this can happen if the startUp project for your solution does not reference the project that contains your migrations. You can either change the startUp project for your solution or use the -StartUpProjectName parameter.)

Does anyone know why this error is being caused or what I can do to fix it?

回答1:

I eventually found the answer in this question. Basically, in the Package Manager Console there's a "Default project" dropdown. You need to set this to the project that contains your EF context.

回答2:

I found similar post: Enable Migrations with Context in Separate Assembly?

Example:

enable-migrations -ContextProjectName MyProject.DBContexts -contexttypename MyProject.DBContexts.MyContextName -Verbose

回答3:

For whom who made this mistake like I did:

Your context class must inherits from DbContext, just like that:

public class DirectorRequestContext : DbContext
{
    public DbSet<DirectorRequest> DirectorRequests { get; set; }
}

回答4:

Also happens if for some reason your class with the connection isn't in the project. So right click and 'add to project' sorts that out.