Entity Framework foreign key not found during migration

Question

I'm experiencing an unexpected error when setting up a migration after adding keys and foreign keys to my data model. I'm using VS2013 Express, with .NET framework 4.5.

When creating a data model for Entity Framework, because the relationship keys between classes aren't what is expected by convention, I'm using data annotations as outlined in the MS Data Developer Center. Here's the class code:

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace BacklogTracker.Models
{
    public class WorkOrder
    {
        [Key]
        public string woNum { get; set; }
        public string woClosingStatus { get; set; }
        [ForeignKey("ID")]
        public virtual ICollection<Note> woNotes { get; set; }
        [ForeignKey("machSN")]
        public virtual Machine woMachine { get; set; }
        [ForeignKey("ID")]
        public virtual ICollection<Segment> woSegments { get; set; }
    }

    public class Machine
    {
        [Key]
        public string machSN { get; set; }
        public string machLocation { get; set; }
        public string machModel { get; set; }
    }
    public class Segment
    {
        [Key]
        public int ID { get; set; }
        public uint segNum { get; set; }
        public string segRepair { get; set; }
        [ForeignKey("ID")]
        public virtual ICollection<Note> segNotes { get; set; }
    }
    public class Note
    {
        [Key]
        public int ID { get; set; }
        public DateTime notetimestamp { get; set; }
        public string notestring { get; set; }
    }

}

However, when I try to perform a migration after updating the model by performing enable-migrations in the package manager console, I get the following error:

The ForeignKeyAttribute on property 'woMachine' on type 'BacklogTracker.Models.WorkOrder' is not valid. The foreign key name 'machSN' was not found on the dependent type 'BacklogTracker.Models.WorkOrder'. The Name value should be a comma separated list of foreign key property names.

Why is my foreign key name 'machSN' not being found?

Answer 1

I think you have some errors in your model. Default Code First convention for ForeignKey relationship expected to have declared a foreign key property in the dependend end (WorkOrder) that match with primary key property of the principal end (Machine). It is not necessary that they have the same name, check this link. So, declare a property named machSN in your WorkOrder class:

public class WorkOrder
{
    [Key]
    public string woNum { get; set; }
    public string woClosingStatus { get; set; }

    public virtual ICollection<Note> woNotes { get; set; }

    public string machSN { get; set; }
    [ForeignKey("machSN")]
    public virtual Machine woMachine { get; set; }

    public virtual ICollection<Segment> woSegments { get; set; }
}

You can find other errors in the woNotes and woSegments navigation properties. In this side of a one-to-many relationship you don't declare a FK, is in the other side, in Note and Segment classes, for example:

public class Note
{
    [Key]
    public int ID { get; set; }
    public DateTime notetimestamp { get; set; }
    public string notestring { get; set; }

    [ForeignKey("Order)]
    public string woNum { get; set; }
    public virtual WorkOrder Order{get;set;}
}

Delete also in the Segment class the ForeignKey attribute over segNotes navigation property for the same reasons explained before.

public class Segment
{
    [Key]
    public int ID { get; set; }
    public uint segNum { get; set; }
    public string segRepair { get; set; }
    public virtual ICollection<Note> segNotes { get; set; }
}