C# insertion of a record with CurrencyManager AddNew() method during the insertion of a father table record (with CurrencyManager AddNew() too)

[polocar]

Hi,
I have noticed a strange behaviour of CurrencyManager objects in C# (I
use Visual Studio 2005 Professional Edition).
Suppose that you have a SQL Server database with 2 tables called
"Cities" and "Persons", and that:
"Cities" has 2 fields called "IDCity" and "NameCity"
"Persons" has 3 fields called "IDPerson", "NamePerson " and
"IDCityAddr ess"
with "IDCity" and "IDCityAddr ess" fields relationed with the
classical father-child relation (the value for "IDCityAddr ess" is
required, you can't set it to null).
Suppose to define 2 DataTable objects called "dtCities" and
"dtPersons" (bound to the 2 tables), and 2 CurrencyManager objects
in this way:
cmCities = (CurrencyManage r)BindingContex t[dtCities];
cmPersons = (CurrencyManage r)BindingContex t[dtPersons,
"Cities_Persons "];
(where "Cities_Persons " is the relation that binds "IDCity" of
"dtCities" to "IDCityAddr ess" of "dtPersons" ).
Now, think to insert a new city with the statement:
cmCities.AddNew ();
and, before confirming the "dtCities" record insertion with the
cmCities.EndCur rentEdit() statement, insert a new person with the
statement:
cmPersons.AddNe w();
(of course in the C# form there will be some TextBox controls bound to
the various fields of the 2 current records of the tables).
Ok, now you can't confirm the "dtPersons" record insertion with
the cmPersons.EndCu rrentEdit() statement before confirming the
"dtCities" record insertion (the "IDCityAddr ess" value is
required in "dtPersons" , and that value doesn't exist yet in the
"IDCity" field of "dtCities") , so you must necessarily give
this order to the statements:
cmCities.EndCur rentEdit();
cmPersons.EndCu rrentEdit();
but when the first statement is executed, cmPersons.Posit ion is set to
-1, and the "dtPersons" new record isn't saved in
"dtPersons" .
This behaviour doesn't happen if I add a "dtPerson" record during
the modify of a "dtCities" record (cmPersons remains set to its
value and the cmPersons.EndCu rrentEdit() statement saves the new record
correctly, adding it to the table).

Can you explain me why??? Is there a way to insert a person during the
insertion of a city without being forced to introduce other additional
code?

Thank you very much