Re: Patch for QueryTranslator Invalid Cast to object array

The problem is with your IResultTransformer class.
You need to create a new object[] { my, domain, entities}, instead of new
MyEntity[] { my, domain, entities}

On Wed, Jun 11, 2008 at 11:51 AM, Stefan Simroth <[email protected]> wrote:

> Hello NHibernate developers,
>
> there seems to be an issue with a hard cast in the QueryTranslator class,
> line 1452 (trunk) - resp. line 1288 (1.2.1) ...
>
> The hard cast in method GetResultList to an object[] fails in the case of
> my company's product, when using an IResultTransformer.
>
> I chose to use an IResultTransformer implementation for Criteria's and
> Query's to be able to set a required property. It seems an appropriate way
> to me and my tests (and the running app) ensure that it works.
>
> However, I had to patch the QueryTranslator at the locations mentioned
> above, because it threw an invalid cast exception (stacktrace below) -
> because the IList of my objects could not be casted to an object[].
> Debugging it, showed me that the "results" list contained my domain objects,
> but it could not be casted to an object[]. It was a collection of my domain
> types and my domain types are no object[]. Now, some time passed by since
> then, and our product works fine with the patch, so unfortunately I forgot
> the exact reason, but I'd guess, I used the generic Query signature and so
> the results list was a generic list that cannot be casted to object[]. But
> also ArrayList or Hashtable cannot be casted to object[]...
>
> A little experiment, gave me the compiler error:
>
> Cannot convert type
> 'System.Collections.Generic.List<ConsoleApplication1.Project>' to 'object[]'
>
> class Program
> {
>        static void Main(string[] args)
>        {
>                List<Project> projects = new List<Project>();
>                object[] objs = (object[]) projects;
>        }
>
>        class Project { }
> }
>
> => same thing doesn't work with ArrayList or Hashtable ...
>
>
> ----
> The code snippet from QueryTranslator in question:
>
>
>        for (int i = 0; i < results.Count; i++)
>        {
>                object[] row = (object[]) results[i];
>                results[i] = holderInstantiator.Instantiate(row);
>        }
>
> ----
> Patch - with a "safe" cast:
>
>        object[] row = results[i] as object[];
>        if (row != null)
>        {
>                results[i] = holderInstantiator.Instantiate(row);
>        }
>
>
>
> The included patch is for the NHibernate 2.0 trunk.
> The same problem exists in earlier versions, namely 1.2.
>
> I might be totally missing the root of the problem, but please excuse this,
> as I am not familiar with the NHibernate internals, but tried to apply a
> patch at the right place to enable the very useful feature of the
> IResultTransformer to our case - and maybe to others in future.
>
>
> Here is the stacktrace:  (version 1.2.1)
>
>   at NHibernate.Hql.Classic.QueryTranslator.GetResultList(IList results,
> IResultTransformer resultTransformer) in
> d:\dev\yap\nhibernate\trunk\src\NHibernate\Hql\Classic\QueryTranslator.cs:line
> 1291
>   at NHibernate.Loader.Loader.ListIgnoreQueryCache(ISessionImplementor
> session, QueryParameters queryParameters) in
> d:\dev\yap\nhibernate\trunk\src\NHibernate\Loader\Loader.cs:line 1744
>   at NHibernate.Loader.Loader.List(ISessionImplementor session,
> QueryParameters queryParameters, ISet querySpaces, IType[] resultTypes) in
> d:\dev\yap\nhibernate\trunk\src\NHibernate\Loader\Loader.cs:line 1738
>   at NHibernate.Hql.Classic.QueryTranslator.List(ISessionImplementor
> session, QueryParameters queryParameters) in
> d:\dev\yap\nhibernate\trunk\src\NHibernate\Hql\Classic\QueryTranslator.cs:line
> 1124
>   at NHibernate.Impl.SessionImpl.Find(String query, QueryParameters
> parameters, IList results) in
> d:\dev\yap\nhibernate\trunk\src\NHibernate\Impl\SessionImpl.cs:line 1763
>
>
>
> Hope to could have helped a bit ...
> Nevertheless, big thanx for such a great software!
>
> ... best regards,
>
> Stefan
>
>
> --
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>>>
> Index: QueryTranslator.cs
> ===================================================================
> --- QueryTranslator.cs  (revision 3539)
> +++ QueryTranslator.cs  (working copy)
> @@ -1449,8 +1449,11 @@
>                        {
>                                for (int i = 0; i < results.Count; i++)
>                                {
> -                                       object[] row = (object[])
> results[i];
> -                                       results[i] =
> holderInstantiator.Instantiate(row);
> +                                       object[] row = results[i] as
> object[];
> +                                       if (row != null)
> +                                       {
> +                                               results[i] =
> holderInstantiator.Instantiate(row);
> +                                       }
>                                }
>
>                                if (holderConstructor == null &&
> resultTransformer != null)
>
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