Test case

src/NHibernate.Test/NHSpecificTest/GH3306NullableEntityCorrelatedSubquery/Fixture.cs

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+using System.Linq;
+using NUnit.Framework;
+
+namespace NHibernate.Test.NHSpecificTest.GH3306NullableEntityCorrelatedSubquery
+{
+	[TestFixture]
+	public class Fixture : BugTestCase
+	{
+		private const string NAME_JOE = "Joe";
+		private const string NAME_ALLEN = "Allen";
+
+		protected override void OnSetUp()
+		{
+			using (var session = OpenSession())
+			using (var tx = session.BeginTransaction())
+			{
+				var joe = new Customer { Name = NAME_JOE };
+				session.Save(joe);
+
+				var allen = new Customer { Name = NAME_ALLEN };
+				session.Save(allen);
+
+				var joeInvoice0 = new Invoice { Customer = joe, Number = 0 };
+				session.Save(joeInvoice0);
+
+				var allenInvoice1 = new Invoice { Customer = allen, Number = 1 };
+				session.Save(allenInvoice1);
+
+				tx.Commit();
+			}
+		}
+
+		protected override void OnTearDown()
+		{
+			using (var session = OpenSession())
+			using (var tx = session.BeginTransaction())
+			{
+				session.Delete("from Invoice");
+				session.Delete("from Customer");
+				tx.Commit();
+			}
+		}
+
+		[Test]
+		public void NullableEntityInCorrelatedSubquery()
+		{
+			using (var s = OpenSession())
+			{
+				var customers = s.Query<Customer>().Where(c => c.Name == NAME_JOE);
+				var results = s.Query<Invoice>()
+					.Where(i => customers.Any(c => c.Invoices.Any(ci => ci.Customer == i.Customer))).ToList();
+
+				Assert.That(results.Count, Is.EqualTo(1));
+			}
+		}
+	}
+}

src/NHibernate.Test/NHSpecificTest/GH3306NullableEntityCorrelatedSubquery/Mappings.hbm.xml

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+<?xml version="1.0" encoding="utf-8" ?>
+<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
+									 assembly="NHibernate.Test"
+									 namespace="NHibernate.Test.NHSpecificTest.GH3306NullableEntityCorrelatedSubquery">
+
+  <class name="Customer" >
+    <id name="ID" type="Int32">
+      <generator class="native" />
+    </id>
+    <property name="Name" type="String" />
+
+    <set name="Invoices" inverse="true" >
+      <key column="CustomerID"/>
+      <one-to-many class="Invoice"/>
+    </set>
+  </class>
+
+  <class name="Invoice">
+    <id name="ID" type="Int32">
+      <generator class="native" />
+    </id>
+
+    <property name="Number" type="Int32" column="`Number`" />
+    <many-to-one name="Customer" not-found="ignore" column="CustomerID" class="Customer" />
+  </class>
+
+</hibernate-mapping>

src/NHibernate.Test/NHSpecificTest/GH3306NullableEntityCorrelatedSubquery/Model.cs

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+using System.Collections.Generic;
+
+namespace NHibernate.Test.NHSpecificTest.GH3306NullableEntityCorrelatedSubquery
+{
+	public class Customer
+	{
+		public virtual int ID { get; protected set; }
+		public virtual ISet<Invoice> Invoices { get; set; }
+		public virtual string Name { get; set; }
+	}
+
+	public class Invoice
+	{
+		public virtual int ID { get; protected set; }
+		public virtual Customer Customer { get; set; }
+		public virtual int Number { get; set; }
+	}
+}