walter clark 0 Light Poster

I've been programming in C++ for 20 years and finally got the size of my mains down.
I've been programming in C++/CLI for about 20 days, and I'm back to my old buggy-boo, uncontrolled file size. In this case it is the Form1.h file. It has about 20 controls using 1,900 lines and growing.
I'm about 1/4 the way through Ivor Horton's latest but no mention yet on offloading code. I couldn't find any advice using Google and key words "Form1.h Size" and "too large".
Can anyone here, tell me where I can get advice or leave a few words on Form1.h Size?
Come to think of it. Why in the heck did MS choose Form1.h for us to put all that source code instead of Form1.cpp?

Walt