An example from NH Spatial --
I have a type...
public class Breadcrumb
{
public virtual int Id { get; set; }
public virtual IGeometry Position { get; set; }
public virtual string Description { get; set; }
}
...and in my code I do the following...
IGeometry center;
// code here to set the center to a useful point
var breadcrumbsWithinDistance = session.Query<Breadcrumb>().Where(x =>
x.Position.Distance(center) < 500);
Now, how would the LINQ engine know the mapping of *center*? Since it isn't
a property of a mapped class there's nothing already specified here for what
user type to use.
I propose that line could be replaced as...
var breadcrumbsWithinDistance = session.Query<Breadcrumb>().Where(x =>
x.Position.Distance(center.AsUserType(new
NHibernate.Type.CustomType(typeof(NHibernate.Spatial.Type.MsSql2008GeographyType),
null)
)) < 500);
(or whatever other user type is appropriate for that database engine)
What do you think?
On Mon, Aug 16, 2010 at 5:16 PM, Fabio Maulo <[email protected]> wrote:
>
> El 16/08/2010, a las 12:14, David Pfeffer <[email protected]> escribió:
>
> I would attempt to write a fix, but this isn't just a bug. There's a design
> issue to be resolved here as to how to go about implementing this.
>
>
> I'm not so sure about " a design issue"...
>
>
> One idea I have is to create an extension method, WithUserType(this object
> obj, IType type) that will be used to inform the LINQ provider as to the
> type (UserType, etc.).
>
>
> Try to write an example where the Type can't be inferred.
> Thanks.
>
>
> If this sounds like a good idea, would anyone be able to provide a few
> pointers as to where to look to hook this in? I will take a look and see if
> I can patch.
>
> Thanks.
>
> On Mon, Aug 16, 2010 at 10:53 AM, Fabio Maulo < <[email protected]>
> [email protected]> wrote:
>
>> Known issue
>> <http://216.121.112.228/browse/NH/component/10120>
>> http://216.121.112.228/browse/NH/component/10120
>>
>>
>> On Fri, Aug 13, 2010 at 2:54 PM, David Pfeffer < <[email protected]>
>> [email protected]> wrote:
>>
>>> Hello all,
>>>
>>> So I'm having a bit of difficulty trying to build a LINQ to NH Spatial
>>> provider. Specifically, I have not found a way to specify the user type for
>>> IGeometry types. So, even though I have the backend LINQ parser code plugged
>>> in, queries fail due to "No persister for: GeoAPI.Geometries.IGeometry."
>>>
>>> In Criteria and HQL specifying the user type is easy. How do I specify
>>> the user type for a LINQ query so that my backend code is invoked?
>>>
>>> Thanks!
>>>
>>
>>
>>
>> --
>> Fabio Maulo
>>
>>
>
