NHibernate sample

I really like your idea of converting GraphQL to IQueryable and have been trying to do a sample using NHibernate.

Do you know any reason why this wouldn’t work with NHibernate.

I get following exception in Executor.cs. I am on .Net 4.5 using NHibernate 4

NHibernate.Exceptions.GenericADOException was unhandled HResult=-2146232832 Message=Could not execute query[SQL: SQL not available] Source=NHibernate SqlString=SQL not available StackTrace: at NHibernate.Impl.SessionImpl.List(IQueryExpression queryExpression, QueryParameters queryParameters, IList results) at NHibernate.Impl.AbstractSessionImpl.List(IQueryExpression queryExpression, QueryParameters parameters) at NHibernate.Impl.AbstractQueryImpl2.List() at NHibernate.Linq.DefaultQueryProvider.ExecuteQuery(NhLinqExpression nhLinqExpression, IQuery query, NhLinqExpression nhQuery) at NHibernate.Linq.DefaultQueryProvider.Execute(Expression expression) at NHibernate.Linq.DefaultQueryProvider.Execute[TResult](Expression expression) at Remotion.Linq.QueryableBase1.GetEnumerator() at System.Collections.Generic.List1..ctor(IEnumerable1 collection) at System.Linq.Enumerable.ToList[TSource](IEnumerable1 source) at GraphQL.Net.Executor1.Execute(TContext context, GraphQLField field, ExecSelection1 query) in C:\scratch\graphql-net\GraphQL.Net\Executor.cs:line 56 at GraphQL.Net.Executor1.Execute(GraphQLSchema1 schema, GraphQLField field, ExecSelection1 query) in C:\scratch\graphql-net\GraphQL.Net\Executor.cs:line 17 at GraphQL.Net.GraphQL1.ExecuteQuery(String queryStr) in C:\scratch\graphql-net\GraphQL.Net\GraphQL.cs:line 44 at QueryApi.Program.Program.Main(String[] args) in C:\scratch\QueryApi\QueryApi\Program\Program.cs:line 21 at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args) at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args) at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() at System.Threading.ThreadHelper.ThreadStart_Context(Object state) at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ThreadHelper.ThreadStart() **InnerException: HResult=-2146233075 Message=Operation could destabilize the runtime. Source=Anonymously Hosted DynamicMethods Assembly StackTrace: at lambda_method(Closure , Object[] ) at NHibernate.Linq.ResultTransformer.TransformTuple(Object[] tuple, String[] aliases) at NHibernate.Hql.HolderInstantiator.Instantiate(Object[] row) at NHibernate.Loader.Hql.QueryLoader.GetResultList(IList results, IResultTransformer resultTransformer) at NHibernate.Loader.Loader.ListIgnoreQueryCache(ISessionImplementor session, QueryParameters queryParameters) at NHibernate.Loader.Loader.List(ISessionImplementor session, QueryParameters queryParameters, ISet1 querySpaces, IType[] resultTypes) at NHibernate.Loader.Hql.QueryLoader.List(ISessionImplementor session, QueryParameters queryParameters) at NHibernate.Hql.Ast.ANTLR.QueryTranslatorImpl.List(ISessionImplementor session, QueryParameters queryParameters) at NHibernate.Engine.Query.HQLQueryPlan.PerformList(QueryParameters queryParameters, ISessionImplementor session, IList results) at NHibernate.Impl.SessionImpl.List(IQueryExpression queryExpression, QueryParameters queryParameters, IList results) InnerException:`**

[chkimes]

Looks like it all boils down to this issue:

https://nhibernate.jira.com/browse/NH-3665

NHibernate has apparently ignored it for the past two years (I don’t know how, that seems like a very common way to write a query), so I don’t expect them to fix it anytime soon. From my investigations, I actually think it is a problem with Remotion, the library that converts LINQ into a more manageable AST.

I have figured out a workaround, though. Calling .Take(1).ToList().FirstOrDefault() instead of just .FirstOrDefault() will bypass this problem for NHibernate. I’ll do some more testing on it and if it fixes the issue I’ll incorporate it by sniffing the queryable provider for NHibernate and applying the workaround.

[efarr]

@gursharan001, Did you ever create your sample app working against NHibernate? Is it available somewhere? Thanks!