how to load associated entities at server side for MS Entity frame work?

Question

Suppose I have a couple of table:

person(personid, name, email)
employee(personid,cardno, departmentID)   //personid,departmentID is foreign key
department(departmentID, departmentName)
employeePhone(personID, phoneID)   //this is relationship table
phone(phoneID, phonenumer)

When EntityFramework generate entity class for employee, this class have members like:

public partial class employee{
  int _personid;
  string _cardno;
  string _departmentName;
  person _person;
  department _department;  
  //......
}

by default, when this class is loaded, only data available for employee table column, not data for associated entities data loaded. If I use Linq to get the data at client side, Include should be used for linq query.

My question is: I want to the associated entities data loaded at server side when the employee is instantiated at server side. So when I get the entity at client side, all data available already so that I can easy to bind it to UI.

How to implement this request?

Answer 1

What you are hoping for is Lazy loading of the dependent Entities. There is an article located at the link below that talks about this and at the bottom of the article it also give you an explanation of how to perform a lazy load should you still feel the need.

See "Configuring Lazy Loading in Entity Framework" in this article: Entity Framework and Lazy Loading

Answer 2

Don't bind entity types to your UI. This couples the UI to the entity layer. Loading will be the least of your problems. With a coupled UI, you violate the single responsibility principle, require blacklists/whitelists to be maintained to have any form of security, break types which can't deal with circular references, you have poor performance because you load all fields from all related types, etc., etc., etc.

Instead, create a dedicated view model and project onto it:

var pm = (from e in Context.Employees
          where e.Id == id
          select new EmployeePresentation
          {
              EmployeeNumber = e.Number,
              Name = e.Person.Name,
              // etc.
          }.First();

Because this is LINQ to Entities, the fields you reference in Person, etc., are automatically loaded, without requiring eager loading, lazy loading, or explicit Load(). But only those fields, not the entirety of Person, as with every other method.

Update, per comments Using presentation models is also important for updates. It is not the case that I want a user to be able to update every field that they can see. Different presentation models for the same entity might have different validation/scaffolding rules since they're used at different points in data flow within the app. Also, the user should implicitly update fields they cannot see (e.g., timestamp).

Generically, my updates look like this (ASP.MVC Web app):

public ActionResult Update(EmployeePresentation model)
{
    if (!ModelState.IsValid)
    {
        // User violated validation rule on presentation model.
        return View(model);
    }
    Repository.Update(model.Id, delegate(Employee employee) 
    {
        model.UpdateEmployee(employee);
    });
    return RedirectToAction("Index");
}

Note that there is no possibility of the user ever updating something they're not allowed to, in a typechecked, type-safe way, and that the model binding, the presentation model and the repository can all be extended for custom behavior.