Save/Validate Entity

I'm a novice with domain driven design and learning to apply it in my current project. I hope some of you guys have already walked the path and can help me out.

I have a question with regard to saving UI changes back to an Entity (Order).

The scenario:

a. An approver opens the Order (Aggregate root) pending approval on the Web. Makes some changes and clicks the button "Approve".

b. The UI translates the Order changes to a DTO and posts it across to a Web service for processing.开发者_JAVA百科

c. The service pulls the Order from OrderRepository via say call to orderRep.GetByID(ApplicationNumber)

Question

1. How do I post the UI changes available in the OrderDTO to Order?

2. What are the different things I need to take care while hydrating the Order? (If we have to ensure that the domain object (Order) doesn't land up in invalid state due to changes)

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Each user operation should correspond to a different command method in the application service layer. Much of the time it will correspond to exactly one call on a domain object.

You probably don't have fine-grained enough methods on your Order domain object.

Approve() should probably only be a method, not a public setter. Throw an exception within Approve() if it would place the Order object in an invalid state.