EF Core Migration Error "Could not drop constraint" which was removed in previous migration

Question

Using Entity Framework Core Code-First development:

In the last migration I ran, I switched a relationship from (simplified)

public class SiteUser
{
    public int Id {get; set;}

    public int EmployeeId { get; set; }

    [InverseProperty("SiteUser")]
    public virtual Employee Employee { get; set; }
}

public class Employee
{
    public int Id {get; set;}

    [InverseProperty("Employee")]
    public virtual SiteUser SiteUser { get; set; }
}

(which implies that SiteUser is a subset of Employee, opposite from the intended behavior) to

public class SiteUser
{
    public int Id { get; set; }
}

public class Employee
{
    public int Id {get; set;}

    public int SiteUserId { get; set; }

    [ForeignKey("SiteUserId")]
    [InverseProperty("Employee")]
    public virtual SiteUser SiteUser { get; set; }
}

This of course gave me a migration that, among other things, dropped a foreign key constraint:

protected override void Up(MigrationBuilder migrationBuilder)
{
    migrationBuilder.DropForeignKey(
        name: "FK_SiteUser_Employee_EmployeeId",
        table: "SiteUser");
    //etc
}

I ran that migration and updated the database from it, and it worked fine. Tables and foreign key constraints were correctly updated to the new model. However, I'm trying to do a new migration now, and when I try to run Update-Database, I get

System.Data.SqlClient.SqlException (0x80131904): 'FK_SiteUser_Employee_EmployeeId' is not a constraint.
Could not drop constraint. See previous errors.

My reaction is, well, duh EF, you dropped that constraint in the last migration; why are you trying to drop it again?

The new migration C# file doesn't have anything in it about dropping that constraint, so why is it trying? And how can I tell EF to stop crashing on this DROP CONSTRAINT line?

Answer 1

It looks like you may be hitting issue #7535. This will be fixed in version 2.0.0.