Zeeshan Hirani - All Comments

re: Comparing Anonymous Types

Curt — Thu, 04 Sep 2008 01:24:09 GMT

Not a bad explanation. Made things clearer to me for sure.

re: DataContext.GetChangeSet to find what objects have changed

Steve S — Fri, 29 Aug 2008 22:15:20 GMT

Hi z,

Many thanks for that. It is just what I wanted, except I am working in VB.NET (using VWD Express 2008).

Could you point me to the correct (VB.NET) syntax for your penultimate line of code?

changenext = ....

I am not sufficiently familiar with Reflection (yet).

Also in your code, you have created a new NorthWindDataContext.

How can I hookup these traces to the datacontext that is being defined and used declaratively (with a formview )in the .aspx markup?

Thanks,

Steve

re: Single Table Inheritance in Entity Framework

Spencer — Wed, 27 Aug 2008 22:15:55 GMT

Very helpful and works great as far as it goes, but when I try to create an association between a descendant and another class, it fails. I have two fields in my table, entity_type and entity_id. The entity_id is a key to the other table. So, extending your example, if there were a class for Office and a class for Cubicle, then an Office has an association to the SalariedEmployee and the Cubicle has an association to the HourlyEmployee. I can't seem to get these to map and am stuck. I get an error about Multiplicity is not valid... It makes sense, since it is not allowing me to map the entity_id field--it keeps mapping the id for each table, which is wrong.

re: Avoiding Roundtrip with Load in Entity Framework

Mike.Borozdin — Sun, 24 Aug 2008 09:30:57 GMT

Great as usual!

re: Single Table Inheritance in Entity Framework

Mike.Borozdin — Sun, 24 Aug 2008 09:25:10 GMT

Excellent post! Keep it up!

re: Many To Many Mappings in Entity Framework

quachnguyen — Sat, 23 Aug 2008 06:14:21 GMT

Thank for you replying.

But I got run-time error with message

The data source for GridView with id 'grdView' did not have any properties or attributes from which to generate columns. Ensure that your data source has content.

I also create column with databound filed.

Please show me how to fix problem,

Thanks

re: Single Table Inheritance in Entity Framework

Dan — Fri, 22 Aug 2008 22:06:03 GMT

Best walk-though of this I've seen. I wouldn't have been able to determine that I needed to delete the discriminator column from the base type without this post. Thanks!

re: Many To Many Mappings in Entity Framework

zhirani — Fri, 22 Aug 2008 18:15:58 GMT

Welcome to the hard facts of entity framework.

Try this

NorthwindEntities entity = new NorthwindEntities();

var product = entity.Products.First(p => p.ProductID == 1);

product.Order_Details.Load();//must be done.

var order = product.Order_Details.Select(o => o.Orders);

lblCount.Text = order.Count().ToString();

grdView.DataSource = order;

grdView.DataBind();

re: Many To Many Mappings in Entity Framework

quachnguyen — Fri, 22 Aug 2008 14:08:02 GMT

NorthwindEntities entity = new NorthwindEntities();

var product = entity.Products.First(p => p.ProductID == 1);

var order = product.Order_Details.Select(o => o.Orders);

lblCount.Text = order.Count().ToString();

grdView.DataSource = order;

grdView.DataBind();

Could you please correct me? It's returned 0 row. But When I execute with management tool, It return 38 records.

Thanks,

QuachNguyen

re: Different Implementation of Cast in Linq To SQL And Entity Framework

RichardD — Thu, 21 Aug 2008 22:32:55 GMT

The EF implementation seems right to me - it matches the behaviour of the Cast method with Linq to Objects.

If you only want to return the items which can successfully be cast to a type, use the OfType method instead. Hopefully, the SQL and EF versions should be able to convert that to a database query which only returns the required records.