How to validate a B2B idea - I will not promote

I have an idea for a B2B SaaS kind of a product. I think it will be possible to build an mvp for it fairly quickly, but I've seen on this sub before that it is better to validate the idea before starting development on it. But I am confused as to how I can validate my idea. I can think of putting up a landing page and a form to collect interest, but this doesn't seem quite right for b2b. How else can I do this and if companies do show interest, how can I ensure that they will purchase the product once we have it ready? Thanks in advance!