And ... it's back. OK, I think I've narrowed it down to the exact
problem. Before I broke everything down into an example I had a
helper func that did the object projection (so I wouldn't have to
repeat the "new User { ... }" code wherever I did a projection). This
is when things go boom.
static void Main()
{
var userRepo = new UserRepository(new TestDb());
var abe = userRepo.GetAll().Where(u => u.Name == "Abe").SingleOrDefault();
Console.WriteLine("{0}", abe.Id);
}
Works:
public class UserRepository
{
TestDb _db;
public UserRepository(TestDb db)
{
_db = db;
}
public IQueryable<User> GetAll()
{
return from u in _db.Users
select new User
{
Email = u.Email,
Id = u.UserID,
Name = u.Name
};
}
}
Doesn't work:
public class UserRepository
{
TestDb _db;
public UserRepository(TestDb db)
{
_db = db;
}
public IQueryable<User> GetAll()
{
return from u in _db.Users select LoadUser(u);
}
User LoadUser(Users record)
{
return new User
{
Email = record.Email,
Id = record.UserID,
Name = record.Name
};
}
}
Since I have a work-around this isn't nearly a priority as when I
thought there was no way to project types. So no worries if this
can't get attention. Apologies for all the going back and forth.
-Abe
On Thu, Jul 1, 2010 at 1:10 AM, Abe Gillespie <[email protected]> wrote:
> OK, totally weird. After not looking at it for a few days and then
> endeavoring to put a complete, compilable example together for you,
> I'm now not having the issue.
>
> Sorry for the troubles. Enjoy your vacation!
>
> -Abe
>
> On Thu, Jun 24, 2010 at 3:54 PM, Jonathan Pryor <[email protected]> wrote:
>> On Thu, 2010-06-24 at 14:53 -0400, Abe Gillespie wrote:
>>> I'll be the first to admit I'm no Linq genius (hardly), but I'm
>>> thinking the deferred execution of the whole thing ultimately has the
>>> "new" op showing up in the where clause. If I have this right it's
>>> essentially doing the following query:
>>>
>>> var me = from u in _db.Users
>>> where u.Status == "active" && new User(u).Name == "Abe"
>>> select new User(u);
>>>
>>> Don't worry, I'm using DI to send the database context into the
>>> constructor. I just threw the example together ... not even sure if
>>> it would compile.
>>
>> Trying to get something that (1) compiles, and (2) actually hits the
>> error you're encountering would be extremely helpful so that we're (1)
>> on the same page wrt where the bug lies, and (2) can sanely discuss
>> workarounds. :-)
>>
>> To the best of my knowledge, this:
>>
>> userRepo.GetAll().Where(u => u.Name == "abe")
>>
>> should NOT result in creation of anything within the .Where()
>> expression.
>>
>> For good measure, in order to better mimic what I *think* you're
>> attempting to do, I wrote this:
>>
>> class E {
>> public int ID;
>> public string Name;
>> }
>>
>> [Test]
>> public void TESTME()
>> {
>> Northwind db = CreateDB();
>> var nancy = GetEmployees (db).Where (e =>
>> e.Name == "Nancy Davolio")
>> .SingleOrDefault ();
>> Console.WriteLine (nancy.Name);
>> }
>>
>> static IQueryable<E> GetEmployees(Northwind db)
>> {
>> return from e in db.Employees
>> where e.Region == "WA"
>> select new E {
>> ID = (int) e.EmployeeID,
>> Name = e.FirstName + " " + e.LastName,
>> };
>> }
>>
>> I believe this is vaguely close to what you did, in that we're taking
>> the database types (Employee), selecting them into a user type (E), and
>> then further querying that to select a specific entry ("nancy").
>>
>> This works as is, no exceptions generated.
>>
>> I would appreciate it if you could provide a compiling, valid, FAILING
>> sample UNLESS the compiling+failing sample is close to my previous
>> sample which has an explicit 'new' within the 'where'.
>>
>> Thanks,
>>
>> - Jon
>>
>>
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>>
>
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