How to implement a many-to-many relationship using Linq to Sql ? Part II : add/remove support

re: How to implement a many-to-many relationship using Linq to Sql ? Part II : add/remove support

Carl — Wed, 05 Nov 2008 21:40:26 GMT

I get a System.InvalidOperationException when I try to remove a newly added product:

Cannot remove an entity that has not been attached.

On line 22 of Nortwind.custom.cs.

Can this easily be fixed?

re: How to implement a many-to-many relationship using Linq to Sql ? Part II : add/remove support

MadSpartan — Wed, 24 Sep 2008 12:40:37 GMT

Thanks a lot for the code... It really solved my hands...

One question though (just out of curiousity)... I was testing it and when creating the add delegate intead of writing:

(ods, p) => ods.Add( new Order_Detail {

OrderID = this.OrderID, Product = p,

Quantity=1 }, ....

I wrote:

(ods, p) => ods.Add( new Order_Detail {

Order = this, Product = p,

Quantity=1 }, ....

which seems a lot more OO to me (and nevertheless makes equal sense since actually setting the Order sets the OrderID too). This makes the .NET runtime throw an ArgumentOutOfRange exception when adding the new Order_Details which almost drove me nuts before spotting the difference...

Anyway, does anybody know why is this happening? And why it is not happenning with the Product property?

re: How to implement a many-to-many relationship using Linq to Sql ? Part II : add/remove support

Chris — Tue, 17 Jun 2008 08:50:55 GMT

Hi,

This works great. How would I use it in a dynamic data appliaction?

Dave Ebbo linked to this as a solution, but I am unsure how that would work.

http://blogs.msdn.com/davidebb/archive/2007/12/12/dynamic-data-screencast-is-now-available.aspx

Thanks

Chris

Mitsu's blog : How to implement a many-to-many relationship using Linq to Sql ? Part II : add/remove support

Weddings — Thu, 05 Jun 2008 12:50:40 GMT

In my previous post ( http://blogs.msdn.com/mitsu/archive/2007/06/21/how-to-implement-a-many-to-many-relationship-using-linq-to-sql.aspx ), I had proposed a simple solution for implementing many-to-many relationships using Linq to Sql. Actually, this

Mitsu's blog : How to implement a many-to-many relationship using Linq to Sql ? Part II : add/remove support

Dating — Mon, 26 May 2008 22:47:12 GMT

re: How to implement a many-to-many relationship using Linq to Sql ? Part II : add/remove support

Ecard guy — Tue, 20 May 2008 01:23:01 GMT

Thank you for providing all of this helpful information.

It would be very helpful to understand what's different about Linq to Entities that allows it to support many2many whilst Linq to SQL does not.

How to implement a many-to-many relationship using Linq to Sql ? (转)

江南白衣 — Sun, 11 May 2008 19:14:05 GMT

In this article, I will show one possible solution to implement many-to-many relationship using Linq to Sql.

re: How to implement a many-to-many relationship using Linq to Sql ? Part II : add/remove support

Mitsu Furuta — Fri, 09 May 2008 02:11:53 GMT

Hi Nelis,

I don't see what you mean. Please could you detail more ?

This solution is only a client side syntax simplification to allow direct access between to entities of a many to many relationship. (just in memory solution).

It does not change the way data are physically loaded. If in your case you choose to use linq to sql deferred loading, it's your choice.

If you prefer preloading details entities, you can use DataContext load options.

re: How to implement a many-to-many relationship using Linq to Sql ? Part II : add/remove support

Nelis — Thu, 08 May 2008 15:01:33 GMT

How come, nobody complains about detail objects being fetched on a one-by-one basis? Lots of database roundtrips...

Am I missing something?

Implement a many-to-many relationship in LINQ to SQL

Hot Topics — Sat, 26 Apr 2008 21:06:12 GMT

Mitsu Furata explores many-to-many relationships in LINQ to SQL in these two posts: How to implement