Update with LINQ help needed

[Nilla]

hi, I'm trying to write the simplest db application using C#, ASP and
LINQtosQL but cannot get the Update function to work. I have used the
codemodel from a sample called IntroToLinq.

My Insert and Get functions work, but the Update does nothing. No
errors are thrown and no changes are made.
Here's my code
In the DBHelper class:
public static void Update<T>(T obj, Action<Tupdate) where T : class
{
using (var db = GetDatabaseData ())
{
db.GetTable<T>( ).Attach(obj);
update(obj);
db.SubmitChange s();
}
}

public static void UpdateMyclass(M yclass iss)
{
Update<Myclass> (iss, delegate(Myclas s i)
{
i.ID = iss.ID;
i.Description = iss.Description ;
i.Status = iss.Status;
});
}
In my codebehind for the page where I want to save:

Myclass theObj = MyDB.GetObjById (TextBox1.Text) ;
theObj.Descript ion = TextBox2.Text;
theObj .ID = TextBox1.Text;

try
{
MyDB.UpdateMycl ass (theObj);
............etc .

What is missing in this code? Is there another easy (working..) way
to save this object in the DB using Linq?
THANKS!

[Marc Gravell]

It looks like you are updating object from itself? So there won't be any
changes detected...

* You get/create "theObj" with some values
* You pass "theObj" to UpdateMyclass as "iss"
* UpdateMyclass creates a delegate, capturing "iss", that when given an
instance "i", updates "i" from "iss"
* UpdateMyclass calls Update<MyClassp assing "iss" as "obj", and the
delegate
* Update<Tgets a context, and attaches "obj"; it then invokes the
delegate and commits

Unwrap that, and the values got copied from the orignal instance to the
same instance...

What did you want to do?

Marc

[Marc Gravell]

By the way, you can "Attach(obj , true)", which will mark it as dirty. It
won't know *what* is dirty, though - so all values will get updated
(normally only changed values are UPDATEd).

Marc

[Nilla]

Thank you Marc!

The textbox TextBox2.Text contains a new description for the object,
thats where the difference from original object is.
I tried to use Attach(obj,true ) but I got some errors then. (I will
try to recreated it to see what the problem was.)

[Nilla]

Ok, I got you now. Thanks for the help, it works fine.

[Marc Gravell]

I'm glad it is sorted ;-p

Marc