Using Linq to Entities 3.5 to select null columns

问题

I am using Entity Framework 3.5. My model has a Mediator table and a MediatorAvailabilities table. Most Mediators do not have an entry in MediatorAvailabilities (Availability = Null) but I still need to bring back the mediator whether or not there is a related MediatorAvailabilities.

My query below is only bring back a mediator if there is a related Availability. Again how do I get mediators even if Availability = null?:

Dim mediators = (From m In entity.Mediators.Include("MediatorAvailabilities") _
Where(m.MediatorAvailabilities.Any(Function(a) a.Availability = String.Empty Or a.Availability.Contains("Weekends") = True))
                         Where (m.isActive = True) _
                        Order By m.Sequence _
                        Select New RankingCriteria() With { _
                            .FirstName = m.FirstName, _
                            .LastName = m.LastName, _
                            .CompanyName = m.CompanyName, _
                            .PhoneHome = m.PhoneHome, _
                            .PhoneWork = m.PhoneWork, _
                            .PhoneMobile = m.PhoneMobile, _
                            .Email = m.Email _
                        }).ToList()

What's the correct way to do this?

回答1:

I think you need to add a.Availability is Nothing in your Any method call like so:

Where(m.MediatorAvailabilities.Any(Function(a) a.Availability is Nothing Or a.Availability = String.Empty Or a.Availability.Contains("Weekends") = True))

来源：https://stackoverflow.com/questions/7017889/using-linq-to-entities-3-5-to-select-null-columns