I tried it out with a new project I am doing. The only thing I did not like abou it, was the messing about with the designer files in the DBML, adding the override to the ID property for each entity. Changing tool generated code is for me an absolute taboo, as you can only do that if you work alone.

What I ended up doing instead was to declare a
public abstract int GetID();
in my entitybase, and then a
public override int GetID()
{
return this.ID;
}

in each partial class of my entities.

Then,

public bool IsNew {
get { return GetID() == 0; }
}

back in the entity class should do the trick without mocking about with generated code.

Also, the attach method in existing records does not make much sense, does it? Why attach here (at least check if the entity is already attached first?):

public void Save(T entity) {
if (entity.IsNew) {
_context.GetTable().InsertOnSubmit(entity);
}
else
{ _context.GetTable().Attach(entity, true);
}
_context.SubmitChanges();
}

Thanks again for the insight!

Take a look at this post: http://www.joe-stevens.com/2009/07/10/linq-to-sql-with-wcf-services/

The post example is silverlight, bit it explains why you get this issue and how you can resolve it.

Cheers
Joe

public virtual void Save(T entity)
{
if (entity.IsNew)
{
_context.GetTable().InsertOnSubmit(entity);
}
else
{
//The Exection throw here…
_context.GetTable().Attach(entity, true);
}
_context.SubmitChanges();
}

This is the Exception message:

An entity can only be attached as modified without original state if it declares a version member or does not have an update check policy.

Can some one help me with this?

Joe

Thanks for all the articles. They have really been a big help to me.

Take care

I don’t seem to have a previous comment from you, what is the problem?

Joe

The console application it just to easily recreate the model after making changes to the database.

If you don’t want to use SQLMetal you can set inheritance modifiers from the properties window for the DBML file.

Cheers

Thanks so much.