Jon,
You're exactly correct, your test case is closer to what I'm doing.
Here's a more complete example:
public class User
{
public User(Users dbUser)
{
Id = dbUser.UserID;
Name = dbUser.Name;
}
public int Id { get; set; }
public string Name { get; set; }
}
public interface IUserRepository
{
IQueryable<User> GetAll();
}
public class DbLinqUserRepository : IUserRepository
{
TestDb _db = new TestDb(new NpgsqlConnection("string"));
public IQueryable<User> GetAll()
{
return from u in _db.Users
where u.Status == "active"
select new User(u);
}
}
class Program
{
static void Main(string[] args)
{
IUserRepository userRepo = new DbLinqUserRepository();
// I want just me, so ...
var abe = userRepo.GetAll().Where(u => u.Name ==
"Abe").SingleOrDefault();
}
}
Who might I get in touch with that could fix this quickly? I've
debugged down into DbLinq and see exactly where it's throwing the
exception precisely where you said - SqlProvider.cs, Ln 314. But
since I'm pretty unfamiliar with the codebase it's probably worth it
more to me to pay someone rather than figure it out myself. With whom
might I get in touch that can help?
Thanks.
-Abe
On Thu, Jun 24, 2010 at 10:31 AM, Jonathan Pryor <[email protected]> wrote:
> On Wed, 2010-06-23 at 19:59 -0700, xanadont wrote:
>> Yep, here you go:
>
> Perhaps unsurprisingly, that stack trace isn't entirely helpful as it
> lacks line numbers. It does provide some help, though, in that it
> raises a question: WHY is it in SqlProvider.GetLiteral()?!
>
> SqlProvider.GetLiteral() is for getting literals, like '1', not for
> creating instances.
>
> A more complete example may be in order. For example, given your
> original sample:
>
> var mine = from i in Context.Items
> select new MyItem
> {
> Id = i.ID,
> Value = i.Value
> };
>
> Our unit tests already contain similar tests, e.g. in
> ReadTest_Operands.cs:H4_Select_MemberInit_Class() [0]
>
> [Test]
> public void H4_Select_MemberInit_Class()
> {
> Northwind db = CreateDB();
> var q = from p in db.Products
> where p.ProductID > 5
> select new ProductWrapper2 { ProductID = (int)p.ProductID,
> SupplierID = (int?)p.SupplierID };
> int count = 0;
> foreach (ProductWrapper2 p in q)
> {
> Assert.IsTrue(p.ProductID > 5, "Failed on ProductID>=20");
> count++;
> }
> Assert.IsTrue(count > 0, "Expected some products with ProductID>5,
> got none");
> }
>
> Furthermore, IL-wise every anonymous class is an actual named class
> (just with a name that you can't express in C#), so every 'select new
> {...}' expression also needs to hit the same code path...
>
> My assumption is that you're not actually calling 'new' within a select
> block, but within a 'where' block; for example, I'm able to get the same
> exception message message and stack trace with:
>
> Northwind db = CreateDB();
> var q = from p in db.Products
> where p.ProductID > new Nullable<int>(5).Value
> select new ProductWrapper3(
> (int)p.ProductID, (int?)p.SupplierID);
>
> The issue above is the 'new' within the 'where'. The workaround, of
> course, is to avoid using 'new' outside of the 'select' expression.
>
> This issue has been added to:
>
> http://code.google.com/p/dblinq2007/issues/detail?id=260
>
> As for fixing it, (1) I'm not entirely sure what this entails; (2) I'm
> going on vacation soon; and (3) I'm currently working on another
> project. Sorry. :-/
>
>> I'm not sure what you mean by "with the exception that you can't use
>> 'new' to create new Entity instances"
>
> An entity is a type that the DataContext has a type mapping for
> (specifically that DataContext.Mapping.GetMetaType(Type) returns a
> non-null value for), e.g. every type that is exposed by DataContext
> fields and properties (when using AttributeMappingSource).
>
> The reason for this is that DataContext needs to keep a reference to
> every entity type it creates for change-tracking purposes (e.g. you
> update a property value then call DataContext.SubmitChanges() to commit
> the property values), and one of the features of selecting a specific
> type is that you disable change tracking; if you could select on an
> entity type, you wouldn't actually disable change tracking (as the
> DataContext wouldn't know that in this situation you didn't want change
> tracking), which could result in hard to understand bugs.
>
> - Jon
>
> [0]
> http://dblinq2007.googlecode.com/svn/trunk/src/DbLinq/Test/Providers/ReadTest_Operands.cs
>
>
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