When I use Entity Framework, I want to query out a record in a context and add it to another context with the same schema, after query out the record, I detach it from the context, but the related entities are all away, is there any way to solve it?
Thanks in advance!
This is "by design". EF can detach entities only one by one but in the same time EF doesn't support object graphs composed of attached and detached entities. Because of that when you detach entity it will break all relations to the rest of attached object graph. Detaching whole object graph is currently not supported but you can vote for this feature on Data UserVoice.
As a workaround you can turn off lazy loading on your context, use eager loading described by @CodeWarrior to load exactly data you need to pass to other context. Once you have data loaded serialize them to stream and immediately deserialize them to the new instance of the object graph. This is the way how to make deep clone of entity graph which is detached but has all relations intact (turning lazy loading off is needed otherwise serialization will load all other navigation properties as well which can result in much bigger object graph then expected). The only requirement is that your entities must be serializable by serializer of your choice (be aware of circular references which usually require some special handling or additional attributes on your entities).