More than one developer using the entity frame 4 .edmx file at any given time

I am using EF4. Just a quick question, is this a really good framework? We currently make use of a business and data layer as separate projects. The fact that everything is in 1 file in EF4 is this a good thing? How do you distinguish between your business and data layer?

How is it possible for more than 1 developer to work on a .edmx file? We are a couple of developers working on the project, so maybe 2 developers might need to make changes to this .edmx file. How is this possible?

Is it possible to create more properties than what was created?

How do I incorporate my custom classes to be used in EF4? Lets say I have a User class, and there is a User table, then EF4 will go and create another U开发者_运维技巧ser class for me.

Thanks Brendan

Actually, having one .edmx file isn't a very good thing. But there is no critical problems in case you have any SVN project, actually.
There is a number of approaches concerning BLL, DAL, and EF models. For example, this discussion.
Actually, the mentioned discussion answers your question in a way. The context created by user is partial, so you can have different properties implementing necessary functionality in partial implementation of the model or particular entities (for example, your User class).
The better way to incorporate User class, however, is to use the Code First feature.