>>I know of no explicit tool
>>
>>but

>>USE your_frx
>>
>>replace CLASS with ctargett FOR CLASS=='OldCLASS' and BASECLASS='TEXTBOX' 
>>use
>>compile classlib your_frx
>>

>>is fast enough
>
>You could do that, but you cant see the context and if you make a mistake you don't have an easy way to compare with the previous state what could be wrong and then you must start again from scratch using a copy, so this is one of the benefits of doing this replace in plain text with any editor, it is safer and you can visually see what are you changing in the correct context as PRG-like code, easy enough to understand for any programmer.

That is a matter of taste, need and skill.

I don't need to see things happen on a replace.
If you mistakenly change your text represenation and create the vcx/scx, you need to start from backup as well.

I can read a vcx, so it's much more easy to do that on vcx base. On a vcx I can do a replace / update that will specificly change records where on a text based search and replace the context might be much harder to check.
At least I think a conditional replace is more easy to express in a replace / update then in a search. Like to give me the search command for:
change class of textbox, but only if textbox is class xyz and the class containing it is a container
I can do that with a single SQL UPDATE, but how I should see the class of an object that is several hundred lines below DEFINE CLASS on an text editor is a complete riddle to me.

I have done this over and over, recursing through directory tree on that. Last time was introducing of git as my frame needs to move in the directory tree.

@Denis
I have a tool (builder) where I can select multiple objects in a container to change classes. It's a copy from UT downloads I guess. Or was a builder it shipped with VFP and I have altered it to my needs?. Long ago that. But that is not that reliable and can crash a form, so I'm reluctant to hand it to somebody else.