Where/Select/OrderBy/etc clauses referencing DB types can't execute if helper function used

[acherrymsft]

(Terrible name, I'm sorry.)

I encountered this in production code I was switching over from Linq-to-Objects to EntityFramework. Confirmed with both 1.1.0 and 1.1.1 and both UWP and .Net.

When a Select() clause is used to capture and extend data from a DbSet, any usage after the Select clause of the Included field causes the expression compiler to throw on compilation, not execution, rending the Linq statement unusable.

Full code below, but sample version:

                var results = context.Nodes.Include(node => node.Leaf) // also fails if the .Include is excluded
                    .Select(node => Create(node)) // works if replaced with "new ClientQueryObject() { Node = node) }"
                    .Where(clientquery => clientquery.Node.Leaf != null) // Also fails with OrderBy, Select, etc. -- as long as it references clientQuery.Node.Leaf
                    .ToList();

Exception message: 
Value cannot be null.
Parameter name: querySource

Stack trace:
   at Remotion.Utilities.ArgumentUtility.CheckNotNull[T](String argumentName, T actualValue)
   at Remotion.Linq.Clauses.Expressions.QuerySourceReferenceExpression..ctor(IQuerySource querySource)
   at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.Internal.NavigationRewritingExpressionVisitor.RewriteNavigationProperties(List`1 properties, IQuerySource querySource, Expression declaringExpression, String propertyName, Type propertyType, Func`2 propertyCreator, Func`2 conditionalAccessPropertyCreator)
   at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.Internal.NavigationRewritingExpressionVisitor.<>c__DisplayClass20_0.<VisitMember>b__0(IEnumerable`1 ps, IQuerySource qs)
   at Microsoft.EntityFrameworkCore.Query.EntityQueryModelVisitor.BindPropertyExpressionCore[TResult](Expression propertyExpression, IQuerySource querySource, Func`3 propertyBinder)
   at Microsoft.EntityFrameworkCore.Query.EntityQueryModelVisitor.BindNavigationPathPropertyExpression[TResult](Expression propertyExpression, Func`3 propertyBinder)
   at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.Internal.NavigationRewritingExpressionVisitor.VisitMember(MemberExpression node)
   at System.Linq.Expressions.MemberExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.Internal.NavigationRewritingExpressionVisitor.VisitBinary(BinaryExpression node)
   at System.Linq.Expressions.BinaryExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at Remotion.Linq.Clauses.WhereClause.TransformExpressions(Func`2 transformation)
   at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.Internal.ExpressionTransformingQueryModelVisitor`1.VisitWhereClause(WhereClause whereClause, QueryModel queryModel, Int32 index)
   at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.Internal.NavigationRewritingExpressionVisitor.NavigationRewritingQueryModelVisitor.VisitWhereClause(WhereClause whereClause, QueryModel queryModel, Int32 index)
   at Remotion.Linq.Clauses.WhereClause.Accept(IQueryModelVisitor visitor, QueryModel queryModel, Int32 index)
   at Remotion.Linq.QueryModelVisitorBase.VisitBodyClauses(ObservableCollection`1 bodyClauses, QueryModel queryModel)
   at Remotion.Linq.QueryModelVisitorBase.VisitQueryModel(QueryModel queryModel)
   at Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.Internal.NavigationRewritingExpressionVisitor.Rewrite(QueryModel queryModel, QueryModel parentQueryModel)
   at Microsoft.EntityFrameworkCore.Query.EntityQueryModelVisitor.OptimizeQueryModel(QueryModel queryModel)
   at Microsoft.EntityFrameworkCore.Query.EntityQueryModelVisitor.CreateQueryExecutor[TResult](QueryModel queryModel)
   at Microsoft.EntityFrameworkCore.Storage.Database.CompileQuery[TResult](QueryModel queryModel)
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.CompileQueryCore[TResult](Expression query, INodeTypeProvider nodeTypeProvider, IDatabase database, ILogger logger, Type contextType)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.<>c__DisplayClass19_0`1.<CompileQuery>b__0()
   at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQueryCore[TFunc](Object cacheKey, Func`1 compiler)
   at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQuery[TResult](Object cacheKey, Func`1 compiler)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.CompileQuery[TResult](Expression query)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.Execute[TResult](Expression query)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryProvider.Execute[TResult](Expression expression)
   at Remotion.Linq.QueryableBase`1.GetEnumerator()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at EFTest.Program.Main(String[] args) in C:\Users\acherry\documents\visual studio 2015\Projects\EFTest\EFTest\Program.cs:line 65

Steps to reproduce

namespace EFTest
{
    public class LeafData
    {
        public int Id { get; set; }
    }

    public class NodeData
    {
        public int Id { get; set; }
        public LeafData Leaf { get; set; }
    }

    public class TestData : DbContext
    {
        public DbSet<NodeData> Nodes { get; set; }
        public TestData() : base()
        {
            
        }
        public TestData(DbContextOptions<TestData> options) : base(options)
        { }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            if (!optionsBuilder.IsConfigured)
            {
                optionsBuilder.UseSqlite("Filename=Sample.db");
            }
        }
    }

    public class ClientQueryObject
    {
        public NodeData Node { get; set; }
    }



    class Program
    {
        public static ClientQueryObject Create(NodeData node)
        {
            return new ClientQueryObject()
            {
                Node = node
            };
        }

        static void Main(string[] args)
        {
            using (var context = new TestData())
            {
                var results = context.Nodes.Include(node => node.Leaf)
                    .Select(node => Create(node))
                    .Where(clientquery => clientquery.Node.Leaf != null)
                    .ToList();
            }
        }
    }
}

Workaround: The issue with the expression compiler can be circumvented by modifying ClientQueryObject:

    public class ClientQueryObject
    {
        public NodeData Node { get; set; }
        public LeafData Leaf => Node.Leaf;
    }

and

                var results = context.Nodes.Include(node => node.Leaf)
                    .Select(node => Create(node))
                    .Where(clientquery => clientquery.Leaf != null)
                    .ToList();

Further technical details

EF Core version: 1.1.1, 1.1.0
Database Provider: SQLite
Operating system: Windows 10
IDE: VS 2015

[pmiddleton]

I just confirmed this is fixed in dev. I'm not sure which PR resolved the issue.

[maumar]

also verified from my end, closing