Model binding issue in LINQ to SQL

Question

I am just now starting to work with LINQ, and am pretty familiar with MVC. I have a strongly typed view that is updating a record. I have successfully done a creation:

This works fine, and creates a record in the database:

public ActionResult Create(TABLEMODEL tableModel)
{
    DBDataContext db = new DBDataContext();
    if (ModelState.IsValid)
    {
        db.TABLEMODEL.InsertOnSubmit(tableModel);
        db.SubmitChanges();
    }
}

But when trying to update:

public ActionResult Manage(TABLEMODEL tableModel)
{
    DBDataContext db = new DBDataContext();
    if (ModelState.IsValid)
    {
        db.SubmitChanges();
    }
}

This fails, in the sense that it does not update the record in the database. No actual error/exception occurs, and I can step through it just fine.

I am sure I am missing something, but cannot find what. I appreciate any help on this matter.

UPDATE
I did notice that if I get a record using the DataContext:

DBDataContext db = new DBDataContext();
var m = db.TABLEMODELs.Single(m => m.ID == 1);
m.Name = "UpdatedName";
db.SubmitChanges();

This does update, so I assume I am somehow not binding from my model to the LINQ context.

My Solution
I found that you need to retrieve the object and then update that with the form. Simple enough.

[HttpPost]
public ActionResult Manage(int ID, FormCollection form)
{
    DBSDataContext db = new DBSDataContext();
    var t= db.TABLEMODELs.Single(b => b.ID == ID);
    UpdateModel(t);
    if (ModelState.IsValid)
    {
        db.SubmitChanges();
    }
    return View(t);
}

Answer 1

You should re-query the original tableModel, map the updated row and then update.

Perhaps something like this (example only, not knowing anything about your schema):

var originalTableModel = db.GetById( tableModel.Id);
originalTableModel.FirstName = tableModel.FirstName;
db.SubmitChanges();