1 reply to this topic

[tarnschaf]

Hi,

I was able to reproduce this in a simple VCL forms app.

The "TextAfter" setting of a NxVirtualColumn does not work in a NextDbGrid. It works fine, however, in a NextGrid. TextBefore works as well.

I tried to find the problem in the code, but I couldn't. It looks like the field FTextAfter is set properly, but when the Text is concated, "TextAfter" returns an empty string.

Thanks for any help..

Michael

[tarnschaf]

EDIT: It looked like a Delphi bug, but I found out that it is a bug of the DB Grid component.
EDIT 2: Finally I found the real problem.

The main problem seems to be inside the class TNxDbColumns. The function GetItem is overwritten to always return a TNxDBCustomColumn. Although I understand that this saves a lot of code, it is dangerous as at least one column type (the virtual column) does not have TNxDBCustomColumns as a base class.

Many times there is a (run-time) check if the column is in fact a DB column before accessing specific properties. But at some points the check is missing or too late -> this leads to unexpected program behaviour.

If I may recommend you one thing: Don't overwrite the GetItem / Item[] methods. This way type problems will show up at compile time. And, by the way, this also solved the problem with "TextAfter". I assume it will fix some access violation errors I got when including a virtual column in a DB grid as well.

If you are interested in my changes, drop me a note and I will send the file to you - however, I think the fix is straightforward.