CODEWITHSUNDEEP
linqasp.net-mvc-3entity-framework-4linq-to-objectsentitycollection
PilotBob
PilotBob

Reputation: 3117

How can I use set operations to delete objects in an entitycollection that match a collection of view models?

Here is a very basic example of what I want to do. The code I have come up with seems quite verbose... ie looping through the collection, etc.

I am using a Telerik MVC grid that posts back a collection of deleted, inserted and updated ViewModels. The view models are similar but not exactly the same as the entity.

For example... I have:

Order.Lines. Lines is an entity collection (navigation property) containing OrderDetail records. In the update action of my controller using the I have a List names DeletedLines pulled from the POST data. I also have queried the database and have the Order entity including the Lines collection.

Now I basically want to tell it to delete all the OrderDetails in the Lines EntityCollection.

The way I have done it is something like:

foreach (var line in DeletedLines) {
   db.DeleteObject(Order.Lines.Where(l => l.Key == line.Key).SingleOrDefault())
}

I was hoping there was a way that I could use .Interset() to get a collection of entities to delete and pass that to DeleteObject.. however, DeleteObject seems to only accept a single entity rather than a collection.

Perhaps the above is good enough.. but it seemed like there should be an easier method.

Thanks, BOb

Upvotes: 1

Views: 109

Answers (2)

danludwig
danludwig

Reputation: 47375

Are the items in DeletedLines attached to the context? If so, what about this?

foreach (var line in DeletedLines) db.DeleteObject(line);

Response to comment #1

Ok, I see now. You can make your code a bit shorter, but not much:

foreach (var line in DeletedLines) {
   db.DeleteObject(Order.Lines.SingleOrDefault(l => l.Key == line.Key))
}

I'm not sure if DeleteObject will throw an exception when you pass it null. If it does, you may be even better off using Single, as long as you're sure the item is in there:

foreach (var line in DeletedLines) {
   db.DeleteObject(Order.Lines.Single(l => l.Key == line.Key))
}

Upvotes: 2

James Manning
James Manning

Reputation: 13589

If you don't want to re-query the database and either already have the mapping table PK values (or can include them in the client call), you could use one of Alex James's tips for deleting without first retrieving:

http://blogs.msdn.com/b/alexj/archive/2009/03/27/tip-9-deleting-an-object-without-retrieving-it.aspx

Upvotes: 0

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