CODEWITHSUNDEEP
asp.net-mvclinq-to-sql
griegs
griegs

Reputation: 22760

Update Data using Linq2Sql

I have this in my mvc ActionResult

    [HttpPost]
    public ActionResult _ChangeDetails( [Bind(Prefix="ContactDetails")] userDetail UserDetail )
    {
        MemberChangeDetailsFormViewModel fvm = new MemberChangeDetailsFormViewModel();

        if (ModelState.IsValid)
        {
            //save
            UserDetailRepository repository = new UserDetailRepository();
            repository.Save(UserDetail);
            return RedirectToAction("Index", "Member");
        }

        fvm.ContactDetails = UserDetail;

        return View(fvm);
    }

Then in my repository I have;

if (userDetail.id != Guid.Empty)
{
    userDetail orig = dc.userDetails.Where(x => x.id == userDetail.id).Single();
    dc.userDetails.Attach(userDetail, orig);
    dc.Refresh(System.Data.Linq.RefreshMode.KeepCurrentValues, userDetail);
    dc.SubmitChanges();
}

However the "attach" is generating an error; Cannot add an entity with a key that is already in use.

I understand that it's caused because L2S already has the object attached. I have tried doing this with and without the orig object but get the same message.

What would be the best practice to update the data in the table from the model?

Upvotes: 2

Views: 499

Answers (1)

Oren Trutner
Oren Trutner

Reputation: 24208

Linq-to-SQL can't deal with two objects with the same key in the same data context. Some options:

Option 1: Use two different data contexts:

public void Update(UserDetail modifiedUser)
{
    using (UserDetailDataContext dc1 = new UserDetailDataContext())
    using (UserDetailDataContext dc2 = new UserDetailDataContext())
    {
        UserDetail originalUser = dc1.UserDetails.Single(u => u.id == modifiedUser.id);
        dc2.UserDetails.Attach(modifiedUser, originalUser);
        dc2.SubmitChanges();
    }
}

Option 2: Don't pull the original object; annotate the new object as an update:

public void Update(UserDetail modifiedUser)
{
    using (UserDetailDataContext dc = new UserDetailDataContext())
    {
        dc.UserDetails.Attach(modifiedUser);
        dc.Refresh(RefreshMode.KeepCurrentValues, modifiedUser);
        dc.SubmitChanges();
    }
}

There's more discussion in this question, and Rick Strahl has a blog entry that covers a versioning-based strategy, if you're willing to modify the table schema to add a timestamp.

Upvotes: 3

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