multi-step registration process issues in asp.net

Question

I have a multi-step registration process, backed by a single object in domain layer, which have validation rules defined on properties.

How should I validate the domain object when the domain is split across many views, and I have to save the object partially in the first view when posted?

I thought about using Sessions but that's not possible cause the process is lengthy and amount of data is high, So I don't want to use session.

I thought about saving all the data in an relational in-memory db (with the same schema as main db) and then flushing that data to main db but issues arisen cause I should route between services (requested in the views) who work with the main db and in-memory db.

I'm looking for an elegant and clean solution (more precisely a best practice).

UPDATE AND Clarification:

@Darin Thank you for your thoughtful reply, That was exactly what I've done till now. But incidentally I've got a request which have many attachments in it, I design a Step2View e.g. which user can upload documents in it asynchronously , but those attachments should be saved in a table with referential relation to another table that should have been saved before in Step1View.

Thus I should save the domain object in Step1 (partially), But I can't, cause the backed Core Domain object which is mapped partially to a Step1's ViewModel can't be saved without props that come from converted Step2ViewModel.

Answer 1

One option is to create set of identical tables that will store the data collected in each step. Then in the last step if all goes well you can create the real entity by copying the temporary data and store it.

Other is to create Value Objects for each step and store then in Cache or Session. Then if all goes well you can create your Domain object from them and save it