Delete child objects in Entity Framework

Question

I'm using EF and when I do this:

            foreach (var reg in detail.Regs)
            {
                this.db.Regs.DeleteObject(reg);
            }

I get this:

Collection was modified; enumeration operation may not execute.

What I'm I doing wrong here???

Answer 1

The reason for that is because as you delete the objects from the context, EF is actively update the Regs navigation property count which means the detail.Regs collection is being changed during the foreach loop which always cause the exception you are getting.

You can create a new collection object and keep deleting from it like this:

foreach (var reg in detail.Regs.ToList())
{
    this.db.Regs.DeleteObject(reg);
}

Or even you can make it cleaner by using LINQ ForEach method:

detail.Regs.ToList().ForEach(r => db.Regs.DeleteObject(r));