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LINQ-NHibernate - select only a few fields (including assembly) for a complex object

I use Fluent NHibernate in one of my projects (and an ASP.NET MVC application), and LINQ to query data (using LINQ to NHibernate libraries).

Object names are given to protect the innocent.

Let's say I have the following classes Foo, Bar, Baz and their corresponding tables in a database (MySQL).

Foo has many-to-many relationships with both bars (the FooBar table) and the Baz (the FooBaz table) defined in the Fluent mappings. Thus, the class interface is defined as follows:

public class Foo {
    public virtual int id { get; set; }
    public virtual string name { get; set; }
    public virtual string email { get; set; }
    public virtual IList<Bar> bars { get; set; }
    public virtual IList<Baz> bazes { get; set; }
}

This is a pretty standard class. We see that the Foo object will have a list of bars and bases.

The problem occurs when you try to execute a LINQ query.

, ( where ):

var foos = from foo in session.Linq<Foo>()
           where email.equals("foo@bar.com")
           select foo;

IList<Foo> listFoos = foos.ToList();

Foos, (id, name, email, bars, bazes). log4net , NHibernate .

, . , , .

, :

var foos = from foo in session.Linq<Foo>()
           where email.equals("foo@bar.com")
           select new Foo() 
           {
               id = foo.id,
               name = foo.name,
               email = foo.email,
               bars = foo.bars
           };

IList<Foo> listFoos = foos.ToList();

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System.IndexOutOfRangeException: L'index se trouve en dehors des limites du tableau. (read: "Index is out of bounds for the array.")

[IndexOutOfRangeException: L'index se trouve en dehors des limites du tableau.]
   NHibernate.Transform.TypeSafeConstructorMemberInitResultTransformer.InvokeMemberInitExpression(MemberInitExpression expression, Object[] args, Int32& argumentCount) +404
   NHibernate.Transform.TypeSafeConstructorMemberInitResultTransformer.TransformTuple(Object[] tuple, String[] aliases) +150

[QueryException: could not instantiate: Foo]
   NHibernate.Transform.TypeSafeConstructorMemberInitResultTransformer.TransformTuple(Object[] tuple, String[] aliases) +265
   NHibernate.Loader.Criteria.CriteriaLoader.GetResultColumnOrRow(Object[] row, IResultTransformer resultTransformer, IDataReader rs, ISessionImplementor session) +171
   NHibernate.Loader.Loader.GetRowFromResultSet(IDataReader resultSet, ISessionImplementor session, QueryParameters queryParameters, LockMode[] lockModeArray, EntityKey optionalObjectKey, IList hydratedObjects, EntityKey[] keys, Boolean returnProxies) +330
   NHibernate.Loader.Loader.DoQuery(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies) +704
   NHibernate.Loader.Loader.DoQueryAndInitializeNonLazyCollections(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies) +70
   NHibernate.Loader.Loader.DoList(ISessionImplementor session, QueryParameters queryParameters) +111
   NHibernate.Loader.Loader.ListIgnoreQueryCache(ISessionImplementor session, QueryParameters queryParameters) +18
   NHibernate.Loader.Loader.List(ISessionImplementor session, QueryParameters queryParameters, ISet`1 querySpaces, IType[] resultTypes) +79
   NHibernate.Impl.SessionImpl.List(CriteriaImpl criteria, IList results) +407
   NHibernate.Impl.CriteriaImpl.List(IList results) +41
   NHibernate.Impl.CriteriaImpl.List() +35
   NHibernate.Linq.<GetEnumerator>d__0.MoveNext() +71
   System.Collections.Generic.List`1..ctor(IEnumerable`1 collection) +7665172
   System.Linq.Enumerable.ToList(IEnumerable`1 source) +61
   FooRepository.List(Int32 count) in C:\...\FooRepository.cs:38
   FooController.List() in C:\...\FooController.cs:30
   lambda_method(ExecutionScope , ControllerBase , Object[] ) +39
   System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters) +17
   System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) +178
   System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +24
   System.Web.Mvc.<>c__DisplayClassa.<InvokeActionMethodWithFilters>b__7() +52
   System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation) +254
   System.Web.Mvc.<>c__DisplayClassc.<InvokeActionMethodWithFilters>b__9() +19
   System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodWithFilters(ControllerContext controllerContext, IList`1 filters, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +192
   System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +399
   System.Web.Mvc.Controller.ExecuteCore() +126
   System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) +27
   System.Web.Mvc.ControllerBase.System.Web.Mvc.IController.Execute(RequestContext requestContext) +7
   System.Web.Mvc.MvcHandler.ProcessRequest(HttpContextBase httpContext) +151
   System.Web.Mvc.MvcHandler.ProcessRequest(HttpContext httpContext) +57
   System.Web.Mvc.MvcHandler.System.Web.IHttpHandler.ProcessRequest(HttpContext httpContext) +7
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +181
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +75
+5
4

...

-, NHibernate , "" , .

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, IList, ( , Eager). .

        using( var session = sessionFactory.OpenSession() )
        {
            session.BeginTransaction();

            var foos =
                session.CreateCriteria(typeof(Foo))
                       .List<Foo>();

            var miniFoos = 
               foos.Select(f => new { f.email, f.bars })
                   .Where(f => f.email.Equals("foo@bar.com)
                   .ToList();

            session.Close();
         }
+6

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+2

,

   ... 
   Select(a => new Forum {
   Id = a.Id, 
   Name = a.Name, 
   CategoryName = a.Categories.Select(b => b.Name).First() 
   })

CategoryName - Entity Forum DB

Entity .

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+1

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the problem is that the property names and column names do not match, and when using the nhibernate / linq projection, nhibernate does not check the column name and property name. therefore, if you yourself define them in the properties of the result (I think this is a called result set) in the criteria, before executing the query, it should work.

It is quite simple, try

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