Databases - Delphi

Delphi - KA Dao

Installing and using KA Dao, a freeware component that provides access to MS Access without using the BDE.

The available help is pretty good, but it is not integrated into the Delphi help. Just open KADAO.HLP. Basic instructions are described via

Contents / Tips and tricks /
     How to make an simple application using KADao as a Table component?

Installation | License Issue | cgi Issue

Installation

KA Dao is available from www.delphi.pari.bg, www.delphiwarrior.freeservers.com, and www.torry.net - just download and un-zip the package. In general, the installation instructions (Readme.txt) are pretty good (and pretty simple)

Open KADao.dpk in Delphi and click install.

There are a few things that must be done different depending on the Delphi version. (For instance, Delphi 6 uses a different *.dpk file than Delphi 3-5).

On my systems, installing KADao.dpk compiles the source files, creates *.dcu files in the same directory as KADao.dpk, and places the components on the KA Dao tab of the Component Palette. This allows me to design a form and use the components to display data. However, when I compile the application ...

[Fatal Error] Project2.dpr(6): File not found: 'KDaoTable.dcu'

This is fixed by adding the directory to

Tools / Environment Options... / Library / Library path

License Issue

On some systems, there is a "license issue"

On Windows 98 SE and XP Pro - no problems
On Windows 98 and 2000 Pro, I received the following error
... EOleSysError ... 'Class is not licensed for use.' Process stopped.

Apparently this is just an annoyance, the program will run anyway (tested under Windows 2000 Pro). If you just double click the *.exe (instead of running the application from the Delphi IDE), then the license error is not shown.

This error can be turned off by adding EOleSysError (just select Add... and paste the string) to

Tools / Debugger Options... / Language Exceptions

Basically, KADao checks for one of 2 valid MS Access database drivers. If the first option is not found, then it checks the second. On the failing system, there are 2 registry entries

HKEY_CLASSES_ROOT\DAO.DBEngine.35
HKEY_CLASSES_ROOT\DAO.DBEngine.36

The first one does not have a valid license, but the second one does. The systems that don't have problems have only one registry entry.

cgi Issue

When I use KA Dao in an application, the database (*.mdb file) can be located anywhere. But when I use the components in a cgi file, the database MUST be on the same computer as the *.exe file.

This code

  UserDataModule := TUserDataModule.create(self);
  Global_String  := UserDataModule.KADaoDatabase1.Database;

indicates that the default value of Database

G:\NIST\Main Database\Jet databases\General.mdb

was replaced with

c:\inetpub\wwwroot\rlc\General.mdb

This occurs because KDaoDataBase.pas checks the existence of the file via FileExists (in Sysutils) which eventually calls the Windows SDK function FindFirstFile ... apparently it gives an incorrect response when IIS has control. (Perhaps it is part of the "sandbox" ... but it is probably a design problem.)

Testing indicates that FileExists in a cgi file works for any file on the local machine, but not for files on another machine (it does not matter if they are mapped via a drive letter or accessed directly). It also does not work with a USB drive on the same machine (tested with Windows 2000 and Windows XP).

Author: Robert Clemenzi - clemenzi@cpcug.org

Delphi - KA Dao

Installation

License Issue

cgi Issue

URL: http:// cpcug.org / user / clemenzi / technical / Databases / Delphi / KADao.html