Sorry Alexey, but in the fixed version there are some new errors with Entity.Remove().

Exception:

  
Referential integrity violation on attempt to remove 'Model.TestA', Key='TestA, (2305)'.
Association: TestB-TestA-TestA (AssociationInfo)
Referencing Entity Key: TestB, (2308)
Referenced Entity Key: TestA, (2305)

Example:

  
// Create data  
Xtensive.Orm.Key KeyA2, KeyB1, KeyB2;
using( var session = domain.OpenSession( new SessionConfiguration( SessionOptions.ServerProfile ) ) )
{
  using( var transaction = session.OpenTransaction() )
  {
    var TestA1 = new TestA( session ) { Text = "A1" };
    KeyA2 = new TestA( session ) { Text = "A2" }.Key;
    KeyB1 = new TestB( session ) { Text = "B1", TestA = TestA1 }.Key;
    KeyB2 = new TestB( session ) { Text = "B2", TestA = TestA1 }.Key;
    transaction.Complete();
  }
}

// Exception
using( var session = domain.OpenSession( new SessionConfiguration( SessionOptions.ClientProfile ) ) )
{
  var TestA2 = session.Query.Single<TestA>( KeyA2 );
  var TestB1 = session.Query.Single<TestB>( KeyB1 );
  var TestB2 = session.Query.Single<TestB>( KeyB2 );
  TestB2.Remove();
  var TestA1 = TestB1.TestA;
  TestB1.TestA = TestA2;
  // Exception!
  TestA1.Remove();
}

KeyNotFoundException:

  
Entity with Key = 'TestB, (-2)' does not exist.

Example:

  
using( var session = domain.OpenSession( new SessionConfiguration( SessionOptions.ClientProfile ) ) )
{
  var TestA = new TestA( session ) { Text = "A" };
  var TestB = new TestB( session ) { Text = "B", TestA = TestA };
  TestB.Remove();
  // Exception!
  using( session.Activate() )
    session.SaveChanges();
}

Exception with EntitySet:

  
SQL error occured.
SQL error details 'Type: ReferentialConstraintViolation;'
Query 'INSERT INTO [TestA-TestBs-TestB] ([TestA], [TestB]) VALUES (@p0_0, @p0_1); [p0_0='2177';p0_1='-1']'
Original message 'A foreign key value cannot be inserted because a corresponding primary key value does not exist. [ Foreign key constraint name = FK_TestA-TestBs-TestB_Slave_TestB ]'

Example:

  
EntitySet-Field within the Entity TestA:

[Field, Association( OnOwnerRemove = OnRemoveAction.Cascade, OnTargetRemove = OnRemoveAction.Clear )]
public EntitySet<testb> TestBs { get; private set; }

using( var session = domain.OpenSession( new SessionConfiguration( SessionOptions.ClientProfile ) ) )
{
  var TestB = new TestB( session ) { Text = "B" };
  var TestA = new TestA( session ) { Text = "A", TestBs = { TestB } };
  TestB.Remove();
  // Exception!
  using( session.Activate() )
    session.SaveChanges();
}