How to implement a controller for a widget with a form

[ovekaaven]

It would be nice to have documentation, or an example, for how to do the following:

Part 1 (easy enough): a widget that contains a form written in Razor. (Orchard Core's own Forms module is too inflexible.)

Part 2 (the part I can't figure out): a controller implemented in C#, that would check the submitted form data and if there's a mistake, can send the user back to the original page with the form contents still intact, so the user can correct the mistake and try again. (Not that difficult if there's no need to remember the form contents, but there is, and I have no idea how to get the form data back to the page.)

Our website has been OC-based for close to a year and I still don't know how to do it. I once tried to look at the source code of the Forms module to see how it does it, but it was a total mess and I couldn't follow it.

[MikeAlhayek]

@ovekaaven

Orchard Core's own Forms module is too inflexible.

Maybe list what you would like to accomplish here so we know the limitation.

Part 2 (the part I can't figure out)
Are you using Workflow to handle the submitting logic? If you, I recently implemented a workflow task that does what you seems to be after Http Redirect To Form Location Task. So when the validation failed, you can just redirect back to the form.