Question

This seems like the most common relationship but for some reason I cannot get code-first EF working. When I run the code below I get the following error:

*{“Introducing FOREIGN KEY constraint ‘Recording_RecordingLocation’ on table ‘Recordings’ may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.\r\nCould not create constraint. See previous errors.”}*

I have researched SO and other places but have not been able to figure this out. I must be having a minor stroke so if this is duplicative I apologize. I don’t think it is because all other reference questions I found were for many-to-many relationships… many-to-one.

My scenario is quite simple…

I have an entity (Recording) that has two required properties RecordingLocation and EditingLocation which are both of the same type WorkLocation. Each Recording has exactly one RecordingLocation and one EditingLocation (not many-to-many). I also have the requisite navigation properties.

Each WorkLocation is stand-alone and is not intrinsically linked to the Recording — it’s just a physical place where some work on that Recording took place. So when I delete a recording I do not want to delete the associated WorkLocations.

public class Recording
{
    [Key]
    public virtual int Id { get; set; }

    //... other properties not shown here

    public virtual int RecordingLocationId { get; set; }
    public virtual WorkLocation RecordingLocation { get; set; }

    public virtual int EditingLocationId { get; set; }
    public virtual WorkLocation EditingLocation { get; set; }
{


public class WorkLocation
{
    [Key]
    public virtual int Id { get; set; }
    public virtual WorkLocationType Type { get; set; }
    public virtual string Description { get; set; }
    public virtual LogicalStatus Status { get; set; }
}

// I'll use this on the front-end to filter a selection list
// but don't necessarily assume a Work Location is bound to only items of this type
public enum WorkLocationType
{
    RecordingLocation,
    EditingLocation,
    MasteringLocation
}

What am I missing to get this working?

Answer 1

Your navigation properties RecordingLocation and EditingLocation are required because the corresponding foreign key properties are not nullable. By convention EF assumes that cascading delete is active for a required one-to-many relationship which causes a problem if you have more than one such relationship refering to the same table – hence the exception.

You must disable cascading delete (also your business logic seems to require it) which is only possible in Fluent API:

public class MyContext : DbContext
{
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Recording>()
            .HasRequired(r => r.RecordingLocation)
            .WithMany()
            .HasForeignKey(f => f.RecordingLocationId)
            .WillCascadeOnDelete(false);

        modelBuilder.Entity<Recording>()
            .HasRequired(r => r.EditingLocation)
            .WithMany()
            .HasForeignKey(f => f.EditingLocationId)
            .WillCascadeOnDelete(false);
    }
}