Added test to reproduce #38.

Tests/Linq/Linq/IssueTests.cs

@@ -0,0 +1,33 @@
+using System;
+using System.Diagnostics;
+using System.Linq;
+
+using NUnit.Framework;
+
+using Tests.Model;
+
+namespace Tests.Linq
+{
+	[TestFixture]
+	public class IssueTests : TestBase
+	{
+		[Test, DataContextSource(false)]
+		public void Issue38Test(string context)
+		{
+			using (var db = GetDataContext(context))
+			{
+				AreEqual(
+					from a in Child
+					select new { Count = a.GrandChildren.Count() },
+					from a in db.Child
+					select new { Count = a.GrandChildren1.Count() });
+
+				var sql = ((TestDataConnection)db).LastQuery;
+
+				Assert.That(sql, Is.Not.Contains("INNER JOIN"));
+
+				Debug.WriteLine(sql);
+			}
+		}
+	}
+}

Tests/Linq/Tests.csproj

@@ -220,6 +220,7 @@
     <Compile Include="DDL\CreateTableTest.cs" />
     <Compile Include="Linq\AsyncTest.cs" />
     <Compile Include="Linq\ColumnAliasTest.cs" />
+    <Compile Include="Linq\IssueTests.cs" />
     <Compile Include="Linq\LoadWithTest.cs" />
     <Compile Include="Linq\EnumMapping.cs" />
     <Compile Include="Linq\ExplicitInterfaceTest.cs" />

Tests/Model/ParentChild.cs

@@ -76,6 +76,9 @@ public class Child
 		[Association(ThisKey = "ParentID, ChildID", OtherKey = "ParentID, ChildID")]
 		public List<GrandChild> GrandChildren;
 
+		[Association(ThisKey = "ParentID, ChildID", OtherKey = "ParentID, ChildID", CanBeNull = false)]
+		public List<GrandChild> GrandChildren1;
+
 		public override bool Equals(object obj)
 		{
 			return Equals(obj as Child);