Is There a .RemoveAll equivalent in Entity Framework ?

Question

Hello,

It looks pretty easy, but I may have missed someting in the doc...?

 

I'm trying to delete all rows in a table, with LINQ to Entity.

How should I do that ?

 

With DLINQ, I would use the .RemoveAll statement, but with Entities, I only found .Delete, to which I should pass an object (and no query result).

 

How should I handle that ?

Answer 1

 

Sorry, no, there is no "RemoveAll" equivalent in the entity framework.  For this release, your alternatives are either to load the objects into memory and then delete them or to write regular SQL direct to the database.

 

In a future release of the entity framework, we will be introducing eSQL DML which would make it possible to create an ESQL statement that would delete all of the entities in a particular entityset or whatever in a single operation to the database.

 

- Danny

Answer 2

-> " to load objects into memory and then to delete them"

 

* Do you mean that once loaded, I should remove them one by one with DeleteObject ?

 

* What is the forecast date for the future release ?

 

If the delay for any usable version of ELINQ is too long, I will have to switch to another technology, that's why I need to have an approaching delay...(1 month, 3, month, 6 months, 1 year...?)

 

Thank you very much for answering.

Stephanie

Answer 3

Yes, to delete entities using the entity framework you have to load them into memory and then call delete on each one.

 

As far as your question about date for the future release of the entity framework goes, our first release, of course, is scheduled for April 2008.  At that time the entity framework will certainly be usable for a great many scenarios.  I will not, though, have DML in eSQL.  This is certainly a feature (along with many others) which we believe is very important, but it just won't make the first release.  It means that you can modify objects, but you just have to load them into memory and take advantage of the change tracking mechanism and then call SaveChanges to persist the modifications you have made. 

 

DML in eSQL is something we hope to release in the second version of the entity framework, and it will enable making batch operations as part of a query in the same way you can do in SQL today without actually loading the entities into memory--delete all entities which meet a certain condition, update all entities so that property x gets value y that meet some other condition, etc.  Unfortunately, it's too early to tell when that next release will be, but the entity framework should still be quite valuable in it's first release even without this feature.  Many similar frameworks do not have a query language with DML and are still quite usable.

 

What is the scenario where you need RemoveAll functionality, by the way?  One of the key design points for the entity framework from the beginning has been that it specifically enables drilling through the framework to talk directly to the store so that we can make sure that when you are building an entity framework solution you don't run into a wall where you can't achieve some functionality that isn't specifically enabled in the framework.  So for a great many scenarios I believe you could do something like RemoveAll just by adding your own method to the partial class for a strongly typed context which would encapsulate clearing all the rows from a particular underlying table or tables by writing SQL directly or something like that.

 

- Danny

Answer 4

Note that, in LINQ to SQL (DLINQ), the .RemoveAll statement takes the enumeration of entities you want to delete and iterates through each one, calling delete.  That is, the following code in LINQ to SQL:

 

Code Snippet

 

using (NorthwindDataContext context = new NorthwindDataContext())

{

    context.MyCustomers.RemoveAll(context.MyCustomers);

    context.SubmitChanges();

}

 

is simply a shortcut that executes exactly the same query and update statements as the following:

Code Snippet

 

using (NorthwindDataContext context = new NorthwindDataContext())

{

    foreach (Customer c in context.Customers)

        context.Customers.Remove(c);

    context.SubmitChanges();

}

 

Or, in Entity Framework:

Code Snippet

 

using (NorthwindEntities nwind = new NorthwindEntities())

{

    foreach (MyCustomer c in nwind.MyCustomers)

        nwind.DeleteObject(c);

    nwind.SaveChanges();

}

 

As Danny says, in the future we would like a way you could do set-based DML which would execute a searched update/delete at the database, but neither DLINQ nor the Entity Framework support that today.

HTH,

 

-Mike

Answer 5

How about this extension method to help a bit? Of course, this is not a set-based update and loads the entities into memory if they're not there already.

    public static class EntityFrameworkExtensions
    {
        public static void DeleteAll<TEntity>(
            this ObjectContext context,
            EntityCollection<TEntity> collection)
            where TEntity : class, IEntityWithRelationships
        {
            if (!collection.IsLoaded)
                collection.Load();

            while (collection.Any())
            {
                var entity = collection.First();
                context.DeleteObject(entity);
            }
        }
    }

Pete.

Answer 6

I can't imagine that someone supposedly connected with the development of Entity Framework would show such a lack of understanding of how SQL works, what it does well and how to use it effectively. Forcing the user to retrieve all the rows over the network and then individually delete them is absolutely, completely and fundamentally an inexcusable failure on the part of Entity Framework.

Steve G.

Answer 7

I have to agree with Steve G here,

It seems strange that such a simple piece of functionality is missing.

I do not mean DML, etc, etc.

Just a DeleteAll function that translates to "delete from table"

I was looking for the same thing while doing some unit tests, so I wanted to make sure the db is clear before inserting the test data.

Iterating is cumbersome and performance tanks.

You can execute plain sql but it kind of beat the purpose of an orm.

Any ways, here is a way to do it: http://stackoverflow.com/questions/915329/is-it-possible-to-run-native-sql-with-entity-framework

Answer 8

I also agree

Answer 9

I don't think that your code sniplets would work because they change the enumerated object inside the enumeration which causes an exception.

Maybe using "any" and "first" as proposed by Sumo10 is a solution...

Answer 10

Is this a planned feature?  Hopefully in EF in .net 4.5??? 

Answer 11

It is inane that this feature is still missing.  How many versions are we going to wait while stuff like "Code First" gets priority of basic ORM functions.

Answer 12

You could use this and this deletes the table in the data.
entity.ExecuteStoreCommand("delete tablename");