Should I use upsert iaction method or edit and create separately?

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C#7.1

I'm new and learning how to build an MVC application and while implementing CRUD operations and I'm wondering if the logic from Edit and Create should be placed inside one single method as some tutorials seem to suggest.

Is this a good practice, and why?

Does this respect SOLID principles?

Thank you so much in advance <3

What I have tried:

I used both Edit and Create separately, as well as Upsert and I'm looking for more insight on both ways of doing the same thing.