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    <p>EDMX + POCO class generator results in EFv4 code, not EFv4.1 code but you don't have to bother with these details. EFv4.1 offers just different API which does exactly the same (and it is only wrapper around EFv4 API).</p> <p>Depending on the way how you use datasets you can reach some very hard problems. Datasets are representation of the change set pattern. They know what changes were done to data and they are able to store just these changes. EF entities know this only if they are attached to the context which loaded them from the database. Once you work with detached entities you must make a big effort to tell EF what has changed - <a href="https://stackoverflow.com/questions/3635071/update-relationships-when-saving-changes-of-ef4-poco-objects/3635326#3635326">especially when modifying relations</a> (detached entities are common scenario in web applications and web services). For those purposes EF offers another template called <a href="https://stackoverflow.com/questions/5091974/what-is-the-purpose-of-self-tracking-entities/5092097#5092097">Self-tracking entities</a> but they have <a href="https://stackoverflow.com/questions/3814706/self-tracking-entities-vs-poco-entities/3815968#3815968">another problems</a> and limitations (for example missing lazy loading, you cannot apply changes when entity with the same key is attached to the context, etc.). </p> <p>EF also doesn't support several features used in datasets - for example <a href="http://www.ladislavmrnka.com/2011/03/unique-key-constraints-in-entity-framework/" rel="nofollow noreferrer">unique keys</a> and <a href="https://stackoverflow.com/questions/4407348/batching-db-commands-in-entity-framework-4-0">batch updates</a>. It's fun that newer MS APIs usually solve some pains of previous APIs but in the same time provide much less features then previous APIs which introduces new pains.</p> <p>Another problem can be with performance - EF is slower then direct data access with datasets and have higher memory consumption (and yes there are some memory leaks reported). </p> <p>You can forget about using EF for accessing tables which you don't know at design time. EF doesn't allow any dynamic behavior. Table names and the type of database server are fixed in mapping. Another problems can be with the way how you use triggers - ORM tools don't like triggers and EF has limited features when working with database computed values (possibility to fill value in the database or in the application is disjunctive).</p> <p>The way of filling POCOs from EF + Datasets sounds like this will not be possible when using only EF. EF has some allowed mapping patterns but possibilities to map several tables to single POCO class are extremely limited and constrained (if you want to have these tables editable). If you mean just loading one entity from EF and another entity from data adapter and just make reference between them you should be OK - in this scenario repository sounds like reasonable pattern because the purpose of the repository is exactly this: load or persist data. Unit of work can be also usable because you will most probably want to reuse single database connection between EF and data adapters to avoid distributed transaction during saving changes. UoW will be the place responsible for handling this connection.</p> <p>EF mapping is related to database design - you can introduce some object oriented modifications but still EF is closely dependent on the database. If you want to use some advanced domain model you will probably need separate domain classes filled from EF and datasets. Again it will be responsibility of repository to hide these details. </p>
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    1. POStrategies for replacing legacy data layer with Entity framework and POCO classes
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    1. COThank you! Great answer:) I was thinking of writing my own mapping classes to translate the EF + dataset entities to my domain model entities and vice versa. Should this mapping be done in the repository classes so the methods return domain model entities or should that be done in the classes that uses the repository classes?
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    2. COI think this is all responsibility of repositories.
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    3. COI'm struggling a bit with my repository implementation. I have declared a class Document as my aggregated root (in my domain model) and I have a DocumentRepository<Document> which inherits from a generic Repository<t> with the standard methods such as Get, GetAll, Insert, Delete, Save. Inside the DocumentRepository class I use EF and EF has generated persistant ignorant POCO entities for me that I plan to use inside the repository (overkill?). How would you implement say DocumentRepository.GetAll(Spesification object)? GetAll () must return a list of Document (domain object). Thanks!
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