Bulk Update in Entity Framework Core

If TimeEntry has a connection toInvoice You can possibly do something like this (check the navigation properties):

var timeEntries = context.TimeEntries.Where(t => timeEntryIds.Contains(te.Id)).ToArray();

foreach(var timeEntry in timeEntries)
    invoice.TimeEntries.Add(timeEntry);

context.Invoices.Add(invoice);

//save the entire context and takes care of the ids
context.SaveChanges();