--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/UnitTests/Linq/ConcatUnionTest.cs	Thu Mar 27 21:46:09 2014 +0400
@@ -0,0 +1,633 @@
+using System;
+using System.Linq;
+
+using BLToolkit.Data.DataProvider;
+using BLToolkit.Data.Linq;
+using BLToolkit.DataAccess;
+
+using NUnit.Framework;
+
+namespace Data.Linq
+{
+	using Model;
+
+	[TestFixture]
+	public class ConcatUnionTest : TestBase
+	{
+		[Test]
+		public void Concat1()
+		{
+			var expected =
+				(from p in Parent where p.ParentID == 1 select p).Concat(
+				(from p in Parent where p.ParentID == 2 select p));
+
+			ForEachProvider(db => AreEqual(expected, 
+				(from p in db.Parent where p.ParentID == 1 select p).Concat(
+				(from p in db.Parent where p.ParentID == 2 select p))));
+		}
+
+		[Test]
+		public void Concat11()
+		{
+			ForEachProvider(db => AreEqual(
+				(from ch in    Child where ch.ParentID == 1 select ch.Parent).Concat(
+				(from ch in    Child where ch.ParentID == 2 select ch.Parent)),
+				(from ch in db.Child where ch.ParentID == 1 select ch.Parent).Concat(
+				(from ch in db.Child where ch.ParentID == 2 select ch.Parent))));
+		}
+
+		[Test]
+		public void Concat12()
+		{
+			ForEachProvider(db => AreEqual(
+				(from p  in    Parent where p.ParentID  == 1 select p).Concat(
+				(from ch in    Child  where ch.ParentID == 2 select ch.Parent)),
+				(from p  in db.Parent where p.ParentID  == 1 select p).Concat(
+				(from ch in db.Child  where ch.ParentID == 2 select ch.Parent))));
+		}
+
+		[Test]
+		public void Concat2()
+		{
+			var expected =
+				(from p in Parent where p.ParentID == 1 select p).Concat(
+				(from p in Parent where p.ParentID == 2 select p)).Concat(
+				(from p in Parent where p.ParentID == 4 select p));
+
+			ForEachProvider(db => AreEqual(expected, 
+				(from p in db.Parent where p.ParentID == 1 select p).Concat(
+				(from p in db.Parent where p.ParentID == 2 select p)).Concat(
+				(from p in db.Parent where p.ParentID == 4 select p))));
+		}
+
+		[Test]
+		public void Concat3()
+		{
+			var expected =
+				(from p in Parent where p.ParentID == 1 select p).Concat(
+				(from p in Parent where p.ParentID == 2 select p).Concat(
+				(from p in Parent where p.ParentID == 4 select p)));
+
+			ForEachProvider(db => AreEqual(expected, 
+				(from p in db.Parent where p.ParentID == 1 select p).Concat(
+				(from p in db.Parent where p.ParentID == 2 select p).Concat(
+				(from p in db.Parent where p.ParentID == 4 select p)))));
+		}
+
+		[Test]
+		public void Concat4()
+		{
+			var expected =
+				(from c in Child where c.ParentID == 1 select c).Concat(
+				(from c in Child where c.ParentID == 3 select new Child { ParentID = c.ParentID, ChildID = c.ChildID + 1000 }).
+				Where(c => c.ChildID != 1032));
+
+			ForEachProvider(db => AreEqual(expected, 
+				(from c in db.Child where c.ParentID == 1 select c).Concat(
+				(from c in db.Child where c.ParentID == 3 select new Child { ParentID = c.ParentID, ChildID = c.ChildID + 1000 })).
+				Where(c => c.ChildID != 1032)));
+		}
+
+		[Test]
+		public void Concat401()
+		{
+			var expected =
+				(from c in Child where c.ParentID == 1 select c).Concat(
+				(from c in Child where c.ParentID == 3 select new Child { ChildID = c.ChildID + 1000, ParentID = c.ParentID }).
+				Where(c => c.ChildID != 1032));
+
+			ForEachProvider(db => AreEqual(expected, 
+				(from c in db.Child where c.ParentID == 1 select c).Concat(
+				(from c in db.Child where c.ParentID == 3 select new Child { ChildID = c.ChildID + 1000, ParentID = c.ParentID })).
+				Where(c => c.ChildID != 1032)));
+		}
+
+		[Test]
+		public void Concat5()
+		{
+			ForEachProvider(
+				new[] { ProviderName.DB2, ProviderName.Informix },
+				db => AreEqual(
+					(from c in Child where c.ParentID == 1 select c).Concat(
+					(from c in Child where c.ParentID == 3 select new Child { ChildID = c.ChildID + 1000 }).
+					Where(c => c.ChildID != 1032)), 
+					(from c in db.Child where c.ParentID == 1 select c).Concat(
+					(from c in db.Child where c.ParentID == 3 select new Child { ChildID = c.ChildID + 1000 })).
+					Where(c => c.ChildID != 1032)));
+		}
+
+		[Test]
+		public void Concat501()
+		{
+			ForEachProvider(new[] { ProviderName.DB2, ProviderName.Informix },
+				db => AreEqual(
+					(from c in    Child where c.ParentID == 1 select new Child { ParentID = c.ParentID }).Concat(
+					(from c in    Child where c.ParentID == 3 select new Child { ChildID  = c.ChildID + 1000 }).
+					Where(c => c.ParentID == 1)),
+					(from c in db.Child where c.ParentID == 1 select new Child { ParentID = c.ParentID }).Concat(
+					(from c in db.Child where c.ParentID == 3 select new Child { ChildID  = c.ChildID + 1000 })).
+					Where(c => c.ParentID == 1)));
+		}
+
+		[Test]
+		public void Concat502()
+		{
+			ForEachProvider(new[] { ProviderName.DB2, ProviderName.Informix },
+				db => AreEqual(
+					(from c in    Child where c.ParentID == 1 select c.Parent).Concat(
+					(from c in    Child where c.ParentID == 3 select c.Parent).
+					Where(p => p.Value1.Value != 2)),
+					(from c in db.Child where c.ParentID == 1 select c.Parent).Concat(
+					(from c in db.Child where c.ParentID == 3 select c.Parent)).
+					Where(p => p.Value1.Value != 2)));
+		}
+
+		[Test]
+		public void Concat6()
+		{
+			ForEachProvider(new[] { ProviderName.SqlCe },
+				db => AreEqual(
+					   Child.Where(c => c.GrandChildren.Count == 2).Concat(   Child.Where(c => c.GrandChildren.Count() == 3)),
+					db.Child.Where(c => c.GrandChildren.Count == 2).Concat(db.Child.Where(c => c.GrandChildren.Count() == 3))));
+		}
+
+		[Test]
+		public void Concat7([IncludeDataContexts("Northwind")] string context)
+		{
+			using (var db = new NorthwindDB())
+				AreEqual(
+					   Customer.Where(c => c.Orders.Count <= 1).Concat(   Customer.Where(c => c.Orders.Count > 1)),
+					db.Customer.Where(c => c.Orders.Count <= 1).Concat(db.Customer.Where(c => c.Orders.Count > 1)));
+		}
+
+		[Test]
+		public void Concat81()
+		{
+			ForEachProvider(
+				db => AreEqual(
+					   Parent.Select(c => new { ID1 = c.ParentID, ID2 = c.ParentID, }).Concat(
+					   Child. Select(c => new { ID1 = c.ParentID, ID2 = c.ChildID,  })),
+					db.Parent.Select(c => new { ID1 = c.ParentID, ID2 = c.ParentID, }).Concat(
+					db.Child. Select(c => new { ID1 = c.ParentID, ID2 = c.ChildID,  }))));
+		}
+
+		[Test]
+		public void Concat82()
+		{
+			ForEachProvider(
+				db => AreEqual(
+					   Child. Select(c => new { ID1 = c.ParentID, ID2 = c.ChildID,  }).Concat(
+					   Parent.Select(c => new { ID1 = c.ParentID, ID2 = c.ParentID, })),
+					db.Child. Select(c => new { ID1 = c.ParentID, ID2 = c.ChildID,  }).Concat(
+					db.Parent.Select(c => new { ID1 = c.ParentID, ID2 = c.ParentID, }))));
+		}
+
+		[Test]
+		public void Concat83()
+		{
+			ForEachProvider(
+				db => AreEqual(
+					   Parent.Select(c => new { ID1 = c.ParentID, ID2 = c.ParentID, ID3 = c.Value1 ?? 0,  }).Concat(
+					   Child. Select(c => new { ID1 = c.ParentID, ID2 = c.ChildID,  ID3 = c.ParentID + 1, })),
+					db.Parent.Select(c => new { ID1 = c.ParentID, ID2 = c.ParentID, ID3 = c.Value1 ?? 0,  }).Concat(
+					db.Child. Select(c => new { ID1 = c.ParentID, ID2 = c.ChildID,  ID3 = c.ParentID + 1, }))));
+		}
+
+		[Test]
+		public void Concat84()
+		{
+			ForEachProvider(
+				db => AreEqual(
+					   Child. Select(c => new { ID1 = c.ParentID, ID2 = c.ChildID,  ID3 = c.ParentID + 1, }).Concat(
+					   Parent.Select(c => new { ID1 = c.ParentID, ID2 = c.ParentID, ID3 = c.Value1 ?? 0,  })),
+					db.Child. Select(c => new { ID1 = c.ParentID, ID2 = c.ChildID,  ID3 = c.ParentID + 1, }).Concat(
+					db.Parent.Select(c => new { ID1 = c.ParentID, ID2 = c.ParentID, ID3 = c.Value1 ?? 0,  }))));
+		}
+
+		[Test]
+		public void Concat85()
+		{
+			ForEachProvider(
+				db => AreEqual(
+					   Parent.Select(c => new { ID1 = c.ParentID, ID2 = c.Value1 ?? 0,  ID3 = c.ParentID, }).Concat(
+					   Child. Select(c => new { ID1 = c.ParentID, ID2 = c.ParentID + 1, ID3 = c.ChildID,  })),
+					db.Parent.Select(c => new { ID1 = c.ParentID, ID2 = c.Value1 ?? 0,  ID3 = c.ParentID, }).Concat(
+					db.Child. Select(c => new { ID1 = c.ParentID, ID2 = c.ParentID + 1, ID3 = c.ChildID,  }))));
+		}
+
+		[Test]
+		public void Concat851()
+		{
+			ForEachProvider(
+				db => AreEqual(
+					   Parent.Select(c => new { ID1 = c.ParentID, ID2 = c.ParentID,     ID3 = c.ParentID, }).Concat(
+					   Child. Select(c => new { ID1 = c.ParentID, ID2 = c.ParentID + 1, ID3 = c.ChildID,  })),
+					db.Parent.Select(c => new { ID1 = c.ParentID, ID2 = c.ParentID,     ID3 = c.ParentID, }).Concat(
+					db.Child. Select(c => new { ID1 = c.ParentID, ID2 = c.ParentID + 1, ID3 = c.ChildID,  }))));
+		}
+
+		[Test]
+		public void Concat86()
+		{
+			ForEachProvider(
+				db => AreEqual(
+					   Child. Select(c => new { ID1 = c.ParentID, ID2 = c.ParentID + 1, ID3 = c.ChildID,  }).Concat(
+					   Parent.Select(c => new { ID1 = c.ParentID, ID2 = c.Value1 ?? 0,  ID3 = c.ParentID, })),
+					db.Child. Select(c => new { ID1 = c.ParentID, ID2 = c.ParentID + 1, ID3 = c.ChildID,  }).Concat(
+					db.Parent.Select(c => new { ID1 = c.ParentID, ID2 = c.Value1 ?? 0,  ID3 = c.ParentID, }))));
+		}
+
+		[Test]
+		public void Concat87()
+		{
+			ForEachProvider(
+				new[] { ProviderName.Informix },
+				db => AreEqual(
+					   Child. Select(c => new Parent { ParentID = c.ParentID }).Concat(
+					   Parent.Select(c => new Parent { Value1   = c.Value1   })),
+					db.Child. Select(c => new Parent { ParentID = c.ParentID }).Concat(
+					db.Parent.Select(c => new Parent { Value1   = c.Value1   }))));
+		}
+
+		[Test]
+		public void Concat871()
+		{
+			ForEachProvider(
+				new[] { ProviderName.Informix },
+				db => AreEqual(
+					   Parent.Select(c => new Parent { Value1   = c.Value1   }).Concat(
+					   Child. Select(c => new Parent { ParentID = c.ParentID })),
+					db.Parent.Select(c => new Parent { Value1   = c.Value1   }).Concat(
+					db.Child. Select(c => new Parent { ParentID = c.ParentID }))));
+		}
+
+		[Test]
+		public void Concat88()
+		{
+			ForEachProvider(
+				db => AreEqual(
+					   Child. Select(c => new Parent { Value1   = c.ChildID,  ParentID = c.ParentID }).Concat(
+					   Parent.Select(c => new Parent { ParentID = c.ParentID, Value1   = c.Value1   })),
+					db.Child. Select(c => new Parent { Value1   = c.ChildID,  ParentID = c.ParentID }).Concat(
+					db.Parent.Select(c => new Parent { ParentID = c.ParentID, Value1   = c.Value1   }))));
+		}
+
+		[Test]
+		public void Concat89()
+		{
+			ForEachProvider(
+				new[] { ProviderName.Informix },
+				db => AreEqual(
+					   Child. Select(c => new Parent { Value1   = c.ParentID, ParentID = c.ParentID }).Concat(
+					   Parent.Select(c => new Parent { ParentID = c.ParentID                        })),
+					db.Child. Select(c => new Parent { Value1   = c.ParentID, ParentID = c.ParentID }).Concat(
+					db.Parent.Select(c => new Parent { ParentID = c.ParentID                        }))));
+		}
+
+		[Test]
+		public void Union1()
+		{
+			ForEachProvider(db => AreEqual(
+				(from g  in    GrandChild join ch in    Child  on g.ChildID   equals ch.ChildID select ch).Union(
+				(from ch in    Child      join p  in    Parent on ch.ParentID equals p.ParentID select ch)),
+				(from g  in db.GrandChild join ch in db.Child  on g.ChildID   equals ch.ChildID select ch).Union(
+				(from ch in db.Child      join p  in db.Parent on ch.ParentID equals p.ParentID select ch))));
+		}
+
+		[Test]
+		public void Union2()
+		{
+			ForEachProvider(db => AreEqual(
+				from r  in
+					(from g  in GrandChild join ch in Child  on g.ChildID   equals ch.ChildID select ch.ChildID).Union(
+					(from ch in Child      join p  in Parent on ch.ParentID equals p.ParentID select ch.ChildID))
+				join child in Child on r equals child.ChildID
+				select child,
+				from r in
+					(from g  in db.GrandChild join ch in db.Child  on g.ChildID   equals ch.ChildID select ch.ChildID).Union(
+					(from ch in db.Child      join p  in db.Parent on ch.ParentID equals p.ParentID select ch.ChildID))
+				join child in db.Child on r equals child.ChildID
+				select child));
+		}
+
+		[Test]
+		public void Union3()
+		{
+			ForEachProvider(db => AreEqual(
+				(from p  in    Parent select new { id = p.ParentID,  val = true }).Union(
+				(from ch in    Child  select new { id = ch.ParentID, val = false })),
+				(from p  in db.Parent select new { id = p.ParentID,  val = true }).Union(
+				(from ch in db.Child  select new { id = ch.ParentID, val = false }))));
+		}
+
+		[Test]
+		public void Union4()
+		{
+			ForEachProvider(db => AreEqual(
+				(from p  in    Parent select new { id = p.ParentID,  val = true }).Union(
+				(from ch in    Child  select new { id = ch.ParentID, val = false }))
+				.Select(p => new { p.id, p.val }),
+				(from p  in db.Parent select new { id = p.ParentID,  val = true }).Union(
+				(from ch in db.Child  select new { id = ch.ParentID, val = false }))
+				.Select(p => new { p.id, p.val })));
+		}
+
+		[Test]
+		public void Union41()
+		{
+			ForEachProvider(db => AreEqual(
+				(from p  in    Parent select new { id = p.ParentID,  val = true }).Union(
+				(from ch in    Child  select new { id = ch.ParentID, val = false }))
+				.Select(p => p),
+				(from p  in db.Parent select new { id = p.ParentID,  val = true }).Union(
+				(from ch in db.Child  select new { id = ch.ParentID, val = false }))
+				.Select(p => p)));
+		}
+
+		[Test]
+		public void Union42()
+		{
+			ForEachProvider(db => AreEqual(
+				(from p  in    Parent select new { id = p. ParentID, val = true  }).Union(
+				(from ch in    Child  select new { id = ch.ParentID, val = false }))
+				.Select(p => p.val),
+				(from p  in db.Parent select new { id = p. ParentID, val = true  }).Union(
+				(from ch in db.Child  select new { id = ch.ParentID, val = false }))
+				.Select(p => p.val)));
+		}
+
+		[Test]
+		public void Union421()
+		{
+			ForEachProvider(db => AreEqual(
+				(from p  in    Parent select new { id = p. ParentID, val = true  }).Union(
+				(from p  in    Parent select new { id = p. ParentID, val = false }).Union(
+				(from ch in    Child  select new { id = ch.ParentID, val = false })))
+				.Select(p => p.val),
+				(from p  in db.Parent select new { id = p. ParentID, val = true  }).Union(
+				(from p  in db.Parent select new { id = p. ParentID, val = false }).Union(
+				(from ch in db.Child  select new { id = ch.ParentID, val = false })))
+				.Select(p => p.val)));
+		}
+
+		[Test]
+		public void Union5()
+		{
+			ForEachProvider(
+				new[] { ProviderName.Informix },
+				db => AreEqual(
+					(from p1 in    Parent select p1).Union(
+					(from p2 in    Parent select new Parent { ParentID = p2.ParentID }))
+					.Select(p => new Parent { ParentID = p.ParentID, Value1 = p.Value1 }),
+					(from p1 in db.Parent select p1).Union(
+					(from p2 in db.Parent select new Parent { ParentID = p2.ParentID }))
+					.Select(p => new Parent { ParentID = p.ParentID, Value1 = p.Value1 })));
+		}
+
+		[Test]
+		public void Union51()
+		{
+			ForEachProvider(
+				new[] { ProviderName.Informix },
+				db => AreEqual(
+					(from p1  in   Parent select p1).Union(
+					(from p2 in    Parent select new Parent { ParentID = p2.ParentID })),
+					(from p1 in db.Parent select p1).Union(
+					(from p2 in db.Parent select new Parent { ParentID = p2.ParentID }))));
+		}
+
+		[Test]
+		public void Union52()
+		{
+			ForEachProvider(
+				new[] { ProviderName.Access, ProviderName.Informix },
+				db => AreEqual(
+					(from p1 in    Parent select new Parent { ParentID = p1.ParentID }).Union(
+					(from p2 in    Parent select p2)),
+					(from p1 in db.Parent select new Parent { ParentID = p1.ParentID }).Union(
+					(from p2 in db.Parent select p2))));
+		}
+
+		[Test]
+		public void Union521()
+		{
+			ForEachProvider(
+				new[] { ProviderName.Access, ProviderName.Informix },
+				db => AreEqual(
+					(from p1 in    Parent select new Parent { ParentID = p1.ParentID }).Union(
+					(from p2 in    Parent select p2))
+					.Select(p => p.Value1),
+					(from p1 in db.Parent select new Parent { ParentID = p1.ParentID }).Union(
+					(from p2 in db.Parent select p2))
+					.Select(p => p.Value1)));
+		}
+
+		[Test]
+		public void Union522()
+		{
+			ForEachProvider(
+				new[] { ProviderName.Access, ProviderName.Informix },
+				db => AreEqual(
+					(from p1 in    Parent select new Parent { Value1 = p1.Value1 }).Union(
+					(from p2 in    Parent select p2)),
+					(from p1 in db.Parent select new Parent { Value1 = p1.Value1 }).Union(
+					(from p2 in db.Parent select p2))));
+		}
+
+		[Test]
+		public void Union523()
+		{
+			ForEachProvider(
+				new[] { ProviderName.Access, ProviderName.Informix },
+				db => AreEqual(
+					(from p1 in    Parent select new Parent { ParentID = p1.ParentID }).Union(
+					(from p2 in    Parent select p2)),
+					(from p1 in db.Parent select new Parent { ParentID = p1.ParentID }).Union(
+					(from p2 in db.Parent select p2))));
+		}
+
+		[Test]
+		public void Union53()
+		{
+			ForEachProvider(
+				new[] { ProviderName.Access, ProviderName.Informix },
+				db => AreEqual(
+					(from p1 in    Parent select new Parent { ParentID = p1.ParentID }).Union(
+					(from p2 in    Parent select new Parent { Value1   = p2.Value1   })),
+					(from p1 in db.Parent select new Parent { ParentID = p1.ParentID }).Union(
+					(from p2 in db.Parent select new Parent { Value1   = p2.Value1   }))));
+		}
+
+		//[Test]
+		public void Union54()
+		{
+			ForEachProvider(
+				//new[] { ProviderName.Access, ProviderName.Informix },
+				db => AreEqual(
+					(from p1 in    Parent select new { ParentID = p1.ParentID,    p = p1,           ch = (Child)null }).Union(
+					(from p2 in    Parent select new { ParentID = p2.Value1 ?? 0, p = (Parent)null, ch = p2.Children.First() })),
+					(from p1 in db.Parent select new { ParentID = p1.ParentID,    p = p1,           ch = (Child)null }).Union(
+					(from p2 in db.Parent select new { ParentID = p2.Value1 ?? 0, p = (Parent)null, ch = p2.Children.First() }))));
+		}
+
+		//[Test]
+		public void Union541()
+		{
+			ForEachProvider(
+				//new[] { ProviderName.Access, ProviderName.Informix },
+				db => AreEqual(
+					(from p1 in    Parent select new { ParentID = p1.ParentID,    p = p1,           ch = (Child)null }).Union(
+					(from p2 in    Parent select new { ParentID = p2.Value1 ?? 0, p = (Parent)null, ch = p2.Children.First() }))
+					.Select(p => new { p.ParentID, p.p, p.ch }),
+					(from p1 in db.Parent select new { ParentID = p1.ParentID,    p = p1,           ch = (Child)null }).Union(
+					(from p2 in db.Parent select new { ParentID = p2.Value1 ?? 0, p = (Parent)null, ch = p2.Children.First() }))
+					.Select(p => new { p.ParentID, p.p, p.ch })));
+		}
+
+		[TableName("Parent")]
+		public abstract class AbstractParent
+		{
+			public abstract int  ParentID { get; set; }
+			public abstract int? Value1   { get; set; }
+		}
+
+		[Test]
+		public void UnionAbstract1([DataContexts] string context)
+		{
+			using (var db = GetDataContext(context))
+			{
+				var list = db.GetTable<AbstractParent>().Union(db.GetTable<AbstractParent>()).ToList();
+				Assert.AreEqual(Parent.Count(), list.Count);
+			}
+		}
+
+		[Test]
+		public void ObjectUnion1([DataContexts] string context)
+		{
+			using (var db = GetDataContext(context))
+				AreEqual(
+					(from p1 in    Parent where p1.ParentID >  3 select p1).Union(
+					(from p2 in    Parent where p2.ParentID <= 3 select p2)),
+					(from p1 in db.Parent where p1.ParentID >  3 select p1).Union(
+					(from p2 in db.Parent where p2.ParentID <= 3 select p2)));
+		}
+
+		//////[Test]
+		public void ObjectUnion2([DataContexts] string context)
+		{
+			using (var db = GetDataContext(context))
+				AreEqual(
+					(from p1 in    Parent where p1.ParentID >  3 select p1).Union(
+					(from p2 in    Parent where p2.ParentID <= 3 select (Parent)null)),
+					(from p1 in db.Parent where p1.ParentID >  3 select p1).Union(
+					(from p2 in db.Parent where p2.ParentID <= 3 select (Parent)null)));
+		}
+
+		[Test]
+		public void ObjectUnion3([DataContexts] string context)
+		{
+			using (var db = GetDataContext(context))
+				AreEqual(
+					(from p1 in    Parent where p1.ParentID >  3 select new { p = p1 }).Union(
+					(from p2 in    Parent where p2.ParentID <= 3 select new { p = p2 })),
+					(from p1 in db.Parent where p1.ParentID >  3 select new { p = p1 }).Union(
+					(from p2 in db.Parent where p2.ParentID <= 3 select new { p = p2 })));
+		}
+
+		//////[Test]
+		public void ObjectUnion4([DataContexts] string context)
+		{
+			using (var db = GetDataContext(context))
+				AreEqual(
+					(from p1 in    Parent where p1.ParentID >  3 select new { p = new { p = p1, p1.ParentID } }).Union(
+					(from p2 in    Parent where p2.ParentID <= 3 select new { p = new { p = p2, p2.ParentID } })),
+					(from p1 in db.Parent where p1.ParentID >  3 select new { p = new { p = p1, p1.ParentID } }).Union(
+					(from p2 in db.Parent where p2.ParentID <= 3 select new { p = new { p = p2, p2.ParentID } })));
+		}
+
+		//////[Test]
+		public void ObjectUnion5([DataContexts] string context)
+		{
+			using (var db = GetDataContext(context))
+				AreEqual(
+					(from p1 in    Parent where p1.ParentID >  3 select new { p = new { p = p1, ParentID = p1.ParentID + 1 } }).Union(
+					(from p2 in    Parent where p2.ParentID <= 3 select new { p = new { p = p2, ParentID = p2.ParentID + 1 } })),
+					(from p1 in db.Parent where p1.ParentID >  3 select new { p = new { p = p1, ParentID = p1.ParentID + 1 } }).Union(
+					(from p2 in db.Parent where p2.ParentID <= 3 select new { p = new { p = p2, ParentID = p2.ParentID + 1 } })));
+		}
+
+		[Test]
+		public void ObjectUnion()
+		{
+			using (var db = new NorthwindDB())
+			{
+				var q1 =
+					from p in db.Product
+					join c in db.Category on p.CategoryID equals c.CategoryID into g
+					from c in g.DefaultIfEmpty()
+					select new
+					{
+						p,
+						c.CategoryName,
+						p.ProductName
+					};
+
+				var q2 =
+					from p in db.Product
+					join c in db.Category on p.CategoryID equals c.CategoryID into g
+					from c in g.DefaultIfEmpty()
+					select new
+					{
+						p,
+						c.CategoryName,
+						p.ProductName
+					};
+
+				var q = q1.Union(q2).Take(5);
+
+				foreach (var item in q)
+				{
+					Console.WriteLine(item);
+				}
+			}
+		}
+
+		public class TestEntity1 { public int Id; public string Field1; }
+		public class TestEntity2 { public int Id; public string Field1; }
+
+		[Test]
+		public void Concat90()
+		{
+			using(var context = new TestDbManager())
+			{
+				var join1 =
+					from t1 in context.GetTable<TestEntity1>()
+					join t2 in context.GetTable<TestEntity2>()
+						on t1.Id equals t2.Id
+					into tmp
+					from t2 in tmp.DefaultIfEmpty()
+					select new { t1, t2 };
+
+				var join1Sql = join1.ToString();
+				Assert.IsNotNull(join1Sql);
+
+				var join2 =
+					from t2 in context.GetTable<TestEntity2>()
+					join t1 in context.GetTable<TestEntity1>()
+						on t2.Id equals t1.Id
+					into tmp
+					from t1 in tmp.DefaultIfEmpty()
+					where t1 == null
+					select new { t1, t2 };
+
+				var join2Sql = join2.ToString();
+				Assert.IsNotNull(join2Sql);
+
+				var fullJoin = join1.Concat(join2);
+
+				var fullJoinSql = fullJoin.ToString(); // BLToolkit.Data.Linq.LinqException : Types in Concat are constructed incompatibly.
+				Assert.IsNotNull(fullJoinSql);
+			}
+		}
+	}
+}