Hi, I got an unusual problem
My mission is to copy the User object before it been updated on the db
and see the changes (before and after).
My code goes like this:
User user = db.Users.First(p => p.ID == id); // gets the user object from the db
UpdateModel(user, collection.ToValueProvider
User user_Before_Been_Updated = db.Users.First(p => p.ID == id); //this shows the same values as user does. even though that I didnt submit the changes to the db
db.SubmitChanges(); //This should update it to the db
what should I do?
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Db is a DataContext file (Linq to SQL class).
db.Users is the Users table
User user = db.Users.First(p => p.ID == id); // gets the user from the db and put it into a User class
UpdateModel() is a MVC function which updates a specific class from a collection of names and values
http://msdn.microsoft.com/
Bigi slick,
To me it seems this problem is a very basic error you might fall in to when you have thought too long and hard about the problem. ;)
You did not instantiate in the above code a new instance of your User. What you did there is pass a reference to the exact same instance of the user. You know? The whole stack/heap thing?
You need to instantiate a brand new instance of User object and then populate the properties of this object with values of the instance you have a reference to with this piece of code: db.Users.First(p => p.ID == id).
I hope that helps.
Hi labelsoft,
Actually, I tried to do it, I dont know why I didnt mention it before.
This is what I did:
User user = db.Users.First(p => p.ID == id);
User newOne = new User();
newOne = db.Users.First(p => p.ID == id);
UpdateModel(user, collection.ToValueProvider
//still newOne and user have the same values
I really dont understand why it happens
I need somehow to clone the user object before I call UpdateModel
Yeah, because you still didn't do what I said. :)
I don't know which properties your user has so I guess something like an ID and a Name? Rewrite the code like this:
User user = db.Users.First(p => p.ID == id);
User newOne = new User();
newOne.ID = user.ID;
newOne.Name = user.Name;
UpdateModel(user, collection.ToValueProvider
Or (gotta love initalizers) we can nowadays write it like this:
User user = db.Users.First(p => p.ID == id);
User newOne = new User() {.ID = user.ID, .Name = user.Name};
UpdateModel(user, collection.ToValueProvider
If any of my syntax is wrong it's because I am a VB guy by the way.
Well your cloning idea wasn't that far fetched actually.
You can implement the interface IClonable in your user object and then implement the Clone method en then put in the exact same code we discussed earlier. So:
Dim u as new User {.ID = Me.Id, .Name = Me.Name}
You can check out the details here I suppose:
http://msdn.microsoft.com/
That is the most dynamic "easy" solution that I can come up with out of the top of my head.
Hope that helps.
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by: sedgwickPosted on 2009-11-04 at 01:34:26ID: 25737657
what's the implementation of db.Users?
is it property which get users table from DB?
what's the implementation of UpdateModel()?