Database errors in Quantum Grid demos in Delphi XE Professional

Question

Whenever I open one of the Quantum Grid demos in Delphi XE Pro (on Windows 7 32-bit), the following error is displayed for every table (I think) in the project:

error message http://www.tranglos.com/img/qgerror.png

The message is:

Network initialization failed.
File or directory does not exist.
File: C:\PDOXUSRS.NET
Permission denied.
Directory: C:\.

I understand permission issues writing to c:\, but the result is that while I can build and run the demo projects, no data is displayed, which makes the demos rather useless. And what kind of database writes its configuration to c:\ directory in the 21st century anyway? :) (Yes, I know very little about Paradox databases, but I won't ever be using one either. I just want to learn how to use the grid.)

Using BDE Administrator I've tried changing the Paradox "NET DIR" value to a folder with write permissions on the C drive. Result: now the database tables cannot find their data:

Path not found.
File: C:..\..\Data\GENRES.DB.

...and the unhelpfully truncated path gives no indication where the files are expected to be.

Is there a way to work around the problem so that the demos can load their sample data correctly?

Answer 1

Using BDE Admin to change the location for PDOXUSRS.NET helped, but it wasn't sufficient. DevExpress did the right thing in specifying a relative folder for the data location, and the relative folder seems perfectly allright, but for some reason the DB can't find it.

Solution: under the \Demos\ folder find all the *.dfm files that contain the string

..\..\Data

and replace that string with the absolute path to the demos folder. That done, all the demos open correctly.

Answer 2

Did you install the BDE correctly? It should use the DBDEMOS files. Do you see such an alias in the BDE administration utility? Can you open that database in one of the Delphi demos?

The BDE is not a XXI century database, it was developed twenty years ago and never upgraded lately. It's an obsolete tecnology, but because it comes still with every release of Delphi with a known database it is still often used in demos because nothing new has to be installed.

Anyway that file is not its configuration file. It's a sharing lock file to allow more than one user to use the database concurrently. Because it is a file based database without a central server, it has to use such kind of shared files. Usually its position is changed to a network share, but it defaults to C:\ for historical reasons.

Anyway it's not only the BDE still attempting to write in the prong directories. I still see a full bunch of applications attempting to write to C:\ (especially logs) or other read-only positions.

Answer 3

I know this message from our own applications. It has to do with security measures introduced with Windows Vista. The operating system trying to protect critical files denies access to them. There is a method how to bypass this mechanism without compromising security. Try to run your application in compatibility mode. When application is running in compatibility mode, read / write operations from / to system folders are redirected to "safe" directories located in C:\Users[Current User]\AppData\Local\VirtualStore. More info on http://www.windowsecurity.com/articles/Protecting-System-Files-UAC-Virtualization-Part1.html.