dynamic update the data using EF4 in asp.net mvc

for example, i have a data table named [User], and mapping to User enetity with EF4:

Id, FullName, EmailAddress, Fax, Tel

in the web page, i just only want to update the "EmailAddess" and "Fax" 2 properties below:

@using (Html.BeginForm("Edit", "User"))
{
    <label>Email Address:</label>
    @Html.TextBox("EmailAddress")
    <label>Fax:</label>
    @Html.TextBox("Fax")
    <input type="submit" value="Update" />
}

and controller i did for this:

public ActionResult Edit(User user) {

var _user = GetUsers().Where(a => a.Id == user.Id).SingleOrDefault();

_user.Fax = user.Fax;
_user.EmailAddress = user.EmailAddress;

context.SaveChanges();
}

yes, i updated it and successful, but next time i also want to update "Tel", so i need to change the code like this:

_user.Fax = user.Fax;
_user.EmailAddress = user.EmailAddress;
_user.Tel = user.Tel;

if i have 100 fields, i will be crazy for doing it :(

So, how can i only update the models to d开发者_JAVA技巧atabase for related fields in web page?

thanks

---

You should definitely look into AutoMapper ( http://automapper.codeplex.com/ ).

AutoMapper.Mapper.CreateMap(typeof(User), typeof(UserViewModel));

AutoMapper.Mapper.CreateMap<User, UserViewModel>()
    .ForMember(d => d.Property1, f => f.MapFrom(s => s.Property1))
    .ForMember(d => d.Property2, f => f.MapFrom(s => s.Property2))
    .ForMember(d => d.Property3, f => f.MapFrom(s => s.Property3));

Then in your Edit you can do the following

public ActionResult Edit(User user) {
    var _user = GetUsers().Where(a => a.Id == user.Id).SingleOrDefault();

    AutoMapper.Mapper.Map(user, _user);

    context.SaveChanges();
}

Entity framework will only update the fields that have actually changed.

Pretty sure that's about all you need.