代码优先级联删除，不使用Fluent API

Question

I have these two entities

class AUT
{
    public Guid ID { get; set; }
    public string Name { get; set; }

    public Engineer Engineer { get; set; }
}

class InstallationSetup
{
    public virtual AUT ApplicationUnderTesting { get; set; }

    public Guid ID { get; set; }
    // Loads of properties etc
}

class Engineer
{
    public Guid ID { get; set; }
    public string Name { get; set; }
}

Using code first and some data annotations these entities create a database. I'm using EF 5, When I delete an Application, it should only delete itself and any InstallationSetup that has been referenced to it. It shouldn't delete the Engineer. However when I do try and delete it, I get the error:

The DELETE statement conflicted with the REFERENCE constraint "FK_dbo.InstallationSetups_dbo.AUTs_ApplicationUnderTesting_ID". The conflict occurred in database "UXLab", table "dbo.InstallationSetups", column 'ApplicationUnderTesting_ID'. The statement has been terminated.

So, I'm guessing that because there is another table with an entry relying on the AUT to be there, by deleting the AUT you will leave InstallationSetup with null foreign key thus a broken row.

I should be able to (preferably not using Fluent API) tell entity framework that any thing that has a reference to AUT should also be deleted? This is what I want to achieve.

Answer 1

you just have to add a column that is similar as your generated Foreign key column, when entity framework generates this FK column it set cascading delete to disabled.

class AUT
{
   public Guid ID { get; set; }
   public string Name { get; set; }

  public Engineer Engineer { get; set; }
}

class InstallationSetup
{
    public virtual AUT ApplicationUnderTesting { get; set; }
    public int ApplicationUnderTestingId {get; set;}   <--- Add this.

   public Guid ID { get; set; }
// Loads of properties etc
}

class Engineer
{
 public Guid ID { get; set; }
 public string Name { get; set; }
}

If you generate your database again, you see that some things are changed. The automatically generated column AUTs_ApplicationUnderTesting_ID is no longer there and the ApplicationUnderTestingId column is now used for your foreign key relationship.

EF will enable cascading delete automatically now.