Question

EF4.1-Code-First-Gurus!

I wonder if there is a more elegant way to handle the following ASP.NET MVC 3 EF 4.1 Code First scenario: Lets say we have the following POCOs:

public class Entity
{
    [Key]
    public int Id { get; set; }

    [ScaffoldColumn(false)]
    public DateTime CreatedOn { get; set; }

    [ScaffoldColumn(false)]
    public DateTime ModifiedOn { get; set; }
}

and

public class Person : Entity
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public DateTime Birthday { get; set; }
}

Lets assume we have created some standard editing views, which are not including CreatedOn/ModifiedOn fields, because, they will be set in the repository and not by the user.

In my repository I have the following Update method. The methods excepts a list of fields, which should be updated (leaving CreatedOn/ModifiedOn fields out):

    public void Update(Person person, List<string> properties)
    {
        Person tmpPerson = context.People.Single(x => x.Id == person.Id);
        context.People.Attach(tmpPerson);

        foreach (PropertyDescriptor descriptor in TypeDescriptor.GetProperties(person))
        {
            if (properties.Contains(descriptor.Name))
                descriptor.SetValue(tmpPerson, descriptor.GetValue(person));
        }

        tmpPerson.ModifiedOn = DateTime.Now;
    }

Now the controller is calling this method like this:

    [HttpPost]
    public ActionResult Edit(Person person)
    {
        if (ModelState.IsValid) {

            personRepository.Update(person, new List<string> { "FirstName", "LastName", "Birthday"});

            personRepository.Save();
            return RedirectToAction("Index");
        } else {
            return View();
        }
    }

This all works like a charm. However, I really dislike, that I have to specify the fields manually. How would you handle this requirement? Of course I could add CreatedOn/ModifiedOn fields as hidden fields to the view, but I dont want to bload the form to much (There are much more fields).

Maybe this is a similar question:
How To Update EF 4 Entity In ASP.NET MVC 3?

I highly appreciate your help!
Joris

Answer 1

Yes there is more elegant version:

public void Update(Person person, params Expression<Func<Person,object>>[] properties)
{
    context.People.Attach(person);

    DbEntityEntry<Person> entry = context.Entry(person);

    foreach (var property in properties)
    {
        entry.Property(property).IsModified = true;
    }

    person.ModifiedOn = DateTime.Now;
}

You will call the method this way:

[HttpPost]
public ActionResult Edit(Person person)
{
    if (ModelState.IsValid) 
    {

        personRepository.Update(person, p => p.FirstName, 
            p => p.LastName, p => p.Birthday);
        personRepository.Save();
        return RedirectToAction("Index");
    } 
    else 
    {
        return View(person);
    }
}