Question

With a plain connection to SQL Server, you can specify what columns to return in a simple SELECT statement.

With EF:

Dim who = context.Doctors.Find(3) ' Primary key is an integer

The above returns all data that entity has… BUT… I would only like to do what you can with SQL and get only what I need.

Doing this:

 Dim who= (From d In contect.Doctors
                     Where d.Regeneration = 3
                     Select New Doctor With {.Actor = d.Actor}).Single

Gives me this error:

The entity or complex type XXXXX cannot be constructed in a LINQ to Entities query.

So… How do I return only selected data from only one entity?

Answer 1

The best way to do this is by setting the wanted properties in ViewModel “or DTO if you’re dealing with upper levels”
Then as your example the ViewModel will be:

public class DoctorViewModel{
public string Actor {get;set;}
// You can add as many properties as you want
}

then the query will be:

var who = (From d In contect.Doctors
                     Where d.Regeneration = 3
                     Select New DoctorViewModel {Actor = d.Actor}).Single();

Sorry i wrote the code with C# but i think the idea is clear 🙂