How keep original value for some field when execute Edit on MVC?

Option 1:

You could use a readonly attribute:

Something like:

@Html.EditorFor(model => model.DriverID, new { htmlAttributes = new { 
        @Value = @Html.Action("getNextDriverID"), @readonly = "readonly"} })

Don't worry about the @Value part as this allows me to call an action method to auto generate a value.

In context, yours would look like:

@Html.EditorFor(model => model.UserId, new { htmlAttributes = new {@readonly = "readonly"} })

Please Note

This answer refers to using razor view engine.

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Option 2:

Another option would be to use a different viewModel altogether:

public class edit User{

    public int userId {get; set;}
    public string Name {get; set;}
    public bool Sex {get; set;}
}

And then 'fill' your data using this in your `Edit ActionResult.

from there, you could then set the values in your [HttpPost] Action method using (linq or otherwise), before then saving to your database.

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Option 3: Using ViewBags

since you are only looking to edit 2 parts of your model, you might just want to use the ViewBag:

Controller:

ViewBag.Item1 = xyz;
ViewBag.Item2 = xyz;

View:

@Html.TextBox("Item1")
@Html.TextBox("Item2")

Then in your post method, you could add these as string parameters:

public ActionResult Edit(string Item1, string Item2)
{
 ...

You could and actually should make a specific viewmodel for your edit page. Like:

public class UserViewModel
{
    public string Name {get; set;}
    public bool Sex {get; set;}
}

Then instead of returning the complete user to and from the view, use the UserViewModel.

public ActionResult EditAdmin(int userId)
{ 
        User user = persons.Users.Find(userId);
        return View(new UserViewModel 
            { 
                Id = user.Id,
                Name = user.Name, 
                Sex = user.Sex 
            });
}

[HttpPost]
public ActionResult EditAdmin(UserViewModel user)
{ 
        var dbUser = persons.Users.Find(user.Id);
        dbUser.Name = user.Name;
        dbUser.Sex = user.Sex;

        persons.Entry(dbUser).State = EntityState.Modified;
        persons.SaveChanges();
}

Fetch the existing version from the database, and then change just the 'modifiable' fields:

public ActionResult EditAdmin(User user)
{ 
    var currentPerson = db.Persons.FirstOrDefault(p => p.id = user.id);
    if (currentPerson == null)
        return HttpNotFound();

    currentPerson.Name = user.Name;
    currentPerson.Sex = user.Sex;
    // Id and Password are not updated.

    db.SaveChanges();
}

• You might also want to do some optimistic concurrency checking as well, to ensure that the version being updated, is in fact current. Ideally, if you have a timestamp, use this, otherwise, you are faced with comparing all fields.

Edit
See also @Kris' comment and Ric's point about creating tailored view models and hence NOT polluting your views with ORM / data tier entities. I also still contend you need to carry a timestamp or hash through the ViewModel to prevent the last one wins overwriting problem.