Checking for a null object in EF causes an additional database hit ... how come?

I am working with Entity Framework ... I have a database table for Patient which has a non-enforced foreign key relationship to the Employee table so I can associate a manager to a patient.

I created my entity in EF for the Patient, the Employee and an association between Patient and Employee, which I name to ManagerEmployee.

I also created another partial class for Patient that will allow me to easily get at the name of the employee from my business object class, also called Patient.

  public string开发者_高级运维 ManagerName
  {
       get { return this.ManagerEmployee == null ? string.Empty : this.ManagerEmployee.Name; }
  }

So I have:

• Patient Entity
• Patient Partial Class (to help with some of the data retrieval)
• Patient DTO (reads from the Patient Entity)

The problem that I am having is that if the ManagerId (in this case is a Guid) does not related to an employee, or is not set (Guid.Empty) ... even though I am eager loading, it still makes another hit on the database.

IQueryable<Data.Patient> query = ctx.ObjectContext.Patients.Include("ManagerEmployee");

So if I have a 1000 records, that have this value set, all is well, but if the value for ManagerId is NOT set on any of these records, it makes 1+1000 database hits.

Wondering if anyone else has had this problem? There may be some bigger problem with the construction of my EF entities and/or associations, so I'm open to other suggestions.

Thanks!

This is now pretty old but in case you haven't already found the solution, my suggestion is to turn off lazy loading. What is most likely happening is that when you try to access a property that is null, lazy loading is happening. See http://www.asp.net/entity-framework/tutorials/maximizing-performance-with-the-entity-framework-in-an-asp-net-web-application if you're using database first, or http://www.asp.net/entity-framework/tutorials/reading-related-data-with-the-entity-framework-in-an-asp-net-mvc-application for MVC Code First.