Entity Framework - LinQ projection problem

I want to create an Entity Object from a LinQ statement, but I don't want to load all its columns.

My ORDERS object has a lot of columns, but I just want to retrieve the REFERENCE and OPERATION columns so the SQL statement and result will be smaller.

This LinQ statement works properly and loads all my object attributes:

var orders = (from order in context.ORDERS
             select order);

However the following statement fails to load only two properties of my object

 var orders = (from order in context.ORDERS
               select new ORDERS
               {
                    REFERENCE = order.REFERENCE,
                    OPERATION = order.OPERATION
               });

The error thrown is:

The entity or complex type 'ModelContextName.ORDERS' cannot be constructed in a LINQ to Entities query.

What is the problem? Isn't it possible to partially load an object this way?

Thank you in advance for your answers.

---

ANSWER

Ok I should thank you both Yakimych and Dean because I use both of your answers, and now I have:

var orders = (from order in context.ORDERS
              select new
              {
                  REFERENCE = order.REFERENCE,
                  OPERATION = order.OPERATION, 
          开发者_JS百科    })
              .AsEnumerable()
              .Select(o =>
                        (ORDERS)new ORDERS
                        {
                            REFERENCE = o.REFERENCE,
                            OPERATION = o.OPERATION
                        }
        ).ToList().AsQueryable();

And I get exactly what I want, the SQL Statement is not perfect but it returns only the 2 columns I need (and another column which contains for every row "1" but I don't know why for the moment) – I also tried to construct sub objects with this method and it works well.

---

No, you can't project onto a mapped object. You can use an anonymous type instead:

var orders = (from order in context.ORDERS
              select new
              {
                  REFERENCE = order.REFERENCE,
                  OPERATION = order.OPERATION
              });

---

The problem with the above solution is that from the moment you call AsEnumerable(), the query will get executed on the database. In most of the cases, it will be fine. But if you work with some large database, fetching the whole table(or view) is probably not what you want. So, if we remove the AsEnumerable, we are back to square 1 with the following error:

The entity or complex type 'ModelContextName.ORDERS' cannot be constructed in a LINQ to Entities query.

I have been struggling with this problem for a whole day and here is what I found. I created an empty class inheriting from my entity class and performed the projection using this class.

public sealed class ProjectedORDERS : ORDERS {}

The projected query (using covariance feature):

IQueryable<ORDERS> orders = (from order in context.ORDERS
              select new ProjectedORDERS
              {
                  REFERENCE = order.REFERENCE,
                  OPERATION = order.OPERATION, 
              });

Voilà! You now have a projected query that will map to an entity and that will get executed only when you want to.

---

I think the issue is creating new entities within the query itself, so how about trying this:

context.ORDERS.ToList().Select(o => new ORDERS
{
    REFERENCE = o.REFERENCE,
    OPERATION = o.OPERATION
});