How often do you split the description of one class into several files using partial?

Question

C++ / C#

Why is this approach bad? So far I see only positives.
Also sometimes I break ui functions into separate files - is this normal? Or how and where (in which class) to register ui functions (click on a button, drag & drop on a window, etc.)

Answer 1

In my projects, partial is present only for the form description classes in WinForms.
And clearly it is no longer needed. Classes are needed for some specific functionality, and if there is so much code in one class that it is more convenient to split it into files, then obviously such a class can be divided into smaller classes.

Answer 2

Never broke in my life. Never! Maybe because I've never coded in C#? :-)