This is what I do:

1. New project
2. Drop IB_SessionProps, IB_Connection, IB_Query and IB_Datasource on the
form
3. Set connection properties to be able to log on
4. Set RequestLive to true in the IB_Query and set IB_Connection to
IB_Connection1
5. Set Dataset in the IB_Datasource to IB_Query
6. Create an OnFormCreate with the line IB_Query1.Open;
7. Drop a grid on the form and connect it to the datasource.

8. Let the IDE create an OnError event handler for the IB_SessionProps
component and edit it like this:

procedure TForm4.IB_SessionProps1Error(Sender: TObject;
const ERRCODE: Integer; ErrorMessage, ErrorCodes: TStringList;
const SQLCODE: Integer; SQLMessage, SQL: TStringList;
var RaiseException: Boolean);
begin

if ERRCODE = isc_foreign_key then begin
if Sender is TIB_Statement then begin
if TIB_Statement(Sender).StatementType = stDelete then
Application.MessageBox('The ... is in use by ... and can not be
deleted.', '')
else
Application.MessageBox('There is no such ... in the .... Select an
existing one.', '');
end
else Application.MessageBox('Key vioaltion not from statement', '');

RaiseException := false;
raise EAbort.Create('');
end;

end;

9. Start the app and navigate to a record that cannot be deleted since it is
referenced by a foreign key that resides in another table and has delete
rule NO ACTION. The press the DEL-key.

The only thing my little app says is ''Key vioaltion not from statement'.

I expect to see the message 'The ... is in use by ... and can not be
deleted.'

This is the call stack if I set a breakpoint before the raise (had to copy
it by hand, so misspelling might be there. $Dnnnn means a hex value):

TForm4.IB_SessionProps1Error(???,???,$Dnnnn,$Dnnnn,-530,$Dnnnn,$Dnnnn,True)
TIB_SessionBase.DoHandleError(???,???,$Dnnnn, $Dnnnn, -530,$Dnnnn, $Dnnnn,
True)
TIB_Session.DoHandleError(???, 335544466,$Dnnnn,$Dnnnn, -530,$Dnnnn, $Dnnnn,
???)
TIB_SessionBase.HandleException($D83248)
TIB_Statement.API_Execute
TIB_UpdateSQL.SQL_Delete
TIB_Dataset.SQL_DeleteRow
TIB_BDataset.SQL_DeleteRow
TIB_Dataset.SysDeleteCursorRow
TIB_BDataset.SysDeleteCursorRow
TIB_Dataset.SysPostDeleteRow
TIB_Dataset.CheckOperation($Dnnnn,nil)
TIB_Dataset.SysExecPost(???)
TIB_BDataset.SysExecPost(???)
TIB_Dataset.SysPost(???, False)
TIB_BDataset.SysPost(???,???)
TIB_Dataset.Post
TIB_Dataset.SysDelete
TIB_Dataset.Delete
TIB_CustomGrid.KeyDown(0, [])

Should not the $D83248 (4th row in stack, at that point I can
inspect/evaluate and get the statementtype) be propagated to my function so
that I can get a more meaningful response?

Thanks for your help,

/Dany

BTW: I've tried a TIB_Session component instead to no further avail.