Question

Using entity framwork with lazy loading – Have the following question on loading related entities when the entities
are null.

Say I have two tables employee and employeedetails. Assume in the above case not all employee entries have an entry in the employeedetails table.
If I want to look up a list of Employees

(from e in objectcontext.employees                                  
                              select new EmployeeEntity
                              {
                                  EmpID= e.EmployeeID,
                                  FirstName = e.FirstName,
                                  Address = e.employeedetails.Address
                              }).ToList();

EmployeeEntity is the data class into which we stuff the results.

The above code breaks if even one employee in the returned list
does not have a entry in table employeedetails. This is obvious since e.employeedetails will be null for those customers who do not have a details entry

What is the best way to rewrite the above query?

Would something like this be acceptable ?

(from e in objectcontext.employees                                  
                              select new EmployeeEntity
                              {
                                  EmpID= e.EmployeeID,
                                  FirstName = e.FirstName,
     Address = e.employeedetails  == null ? "" :    e.employeedetails.Address,
                              }).ToList();

I am not clear on the efficiency of this above query – Would this statment do the null check at DB level?

Should I instead do an explicit include like

objectcontext.include("employeedetails")...

And then loop through the results to check for null?

Answer 1

Yes, this statement would indeed perform a null check in the SQL query that is generated. Most likely, it will simply be a NVL or COALESCE.

That’s the way you should be doing it.