QualityCentral

Public Report

Report From: Delphi-BCB/Midas/TClientDataSet [ Add a report in this area ]

Report #: 3660

Status: Closed

Backwards compatibility issue/feature change with midas.dll from D7.

Project: Delphi

Build #: 7.0.4.453

Version: 7.0

Submitted By: Craig Stuntz

Report Type: Minor failure / Design problem

Date Reported: 3/3/2003 7:28:21 AM

Severity: Infrequently encountered problem

Last Updated: 12/15/2006 4:03:01 AM

Platform: 95, 98, 2000, NT, XP

Internal Tracking #: 156503

Resolution: Fixed (Resolution Comments)

Resolved in Build: : 7.0.8.1

Duplicate of: None

Voting and Rating

Overall Rating: (2 Total Ratings)

4.00 out of 5

Total Votes: None

Description

Reported by Anders Melander on borland.public.delphi.database.multi-tier

In versions of midas.dll prior to v7, it was possible to cancel an update to an individual field by assigning the "unassigned" (varEmpty) value to TField.NewValue in the TDataSetProvider.BeforeUpdateRecord event handler.

With Delphi 7 this method no longer works as "unassigned" is interpreted by midas.dll as the NULL value.

Steps to Reproduce:

Open the attached application and follow the steps given there.

Workarounds

The following function can be used to cancel the update of a single TClientDataSet field and has been verified to work with midas.dll v5-7.

type
  TClientDataSetCracker = class(TClientDataSet);

procedure UndoField(Field: TField);
begin
  TClientDataSetCracker(Field.DataSet).DSBase.PutBlank(Field.DataSet.ActiveBuffer,
    0, Field.Index+1, BLANK_NOTCHANGED);
end;

The function should be considered a work around as it relies on undocumented MIDAS internals.

---------

The following function can be used to cancel the update of a single TClientDataSet field and has been verified to work with midas.dll v5-7.

type
  TClientDataSetCracker = class(TClientDataSet);

procedure UndoField(Field: TField);
begin
  TClientDataSetCracker(Field.DataSet).DSBase.PutBlank(Field.DataSet.ActiveBuffer,
    0, Field.Index+1, BLANK_NOTCHANGED);
end;

The function should be considered a work around as it relies on undocumented MIDAS internals.

Attachment

None

Comments

None

Quality Central

Developer Tools

Database Tools