how to configure cascade delete with EF Fluent API - entity-framework

Question

I have the following classes and EF convention created the tables fine - all good. Now I want to configure cascade delete on the ToDoList (so that when I delete a ToDoList, all the ToDoItems and UserToDoLists also gets deleted automatically). Must I re-specify what EF convention is able to detect in order to set WillCascadeOnDelete? How do I specify this relationship in fluent API?
public class ToDoList
{
public int Id { get; set; }
public string Description { get; set; }
public virtual ICollection<ToDoItem> ToDoItems { get; set; }
public virtual ICollection<UserToDoList> UserToDoLists { get; set; }
}
public class ApplicationUser : IdentityUser
{
public ApplicationUser()
: base()
{
}
public virtual ICollection<UserToDoList> UserToDoLists { get; set; }
}
// a todolist can have many users and a user can have many todolist
// junction table will have addition fields
public class UserToDoList
{
public string UserId { get; set; }
public virtual ApplicationUser User { get; set; }
public virtual int ToDoListId { get; set; }
public virtual ToDoList ToDoList { get; set; }
// additional fields
public bool IsOwner { get; set; }
public int Ordinal { get; set; }
public bool AllowEdit { get; set; }
}
public class UserToDoListConfig : EntityTypeConfiguration<UserToDoList>
{
public UserToDoListConfig()
{
HasKey(ut => new { ut.UserId, ut.ToDoListId });
}
}
public class ToDoListConfig : EntityTypeConfiguration<ToDoList>
{
public ToDoListConfig()
{
Property(t => t.Description).IsRequired().HasMaxLength(50);
HasMany(t =>t.UserToDoLists).??
}
}

Answer 1

That's a simple one-to-many relationship from ToDoList to your junction table UserToDoList, so you just have to set up the mapping like this
HasMany(m => m.UserToDoLists)
.WithRequired(m => m.ToDoList)
.HasForeignKey(m => m.ToDoListId);
and EF will handle your cascading deletes automatically, because ToDoList is required on the junction table side.