ASP.NET MVC Entity Framework - Entity Update - Overwriting Database Values with Null Values - asp.net

Question

I am currently looking for a design pattern or rather a best practice in implementing Repository<Entity>.Update() method for a ASP.NET MVC 4 application which uses Entity Framework 5 with Code First approach.
Problem:
The problem I encountered is that when an entity is queried from the database and shown on a view it may not have all the attributes populated. As a result when the repository.Update(entity) method is invoked, the entity passed to the Update() method may have un-bound properties having null values. However they may have some values in the database. As an example Customer.Misc in below code.
So the problem comes here. According to this approach all the properties which were not bound on the view are set to Null in the database after the first Update() method call.
class Customer
{
public int Id { get; set; }
public string Name { get; set; }
public string Misc { get; set; }
}
[HttpGet]
public ActionResult Update(int id)
{
Repository<Customer> repo = new Repository<Customer>();
return View(repo.GetById(id)); // View only binds Customer.Name
}
[HttpPost]
public ActionResult Update(Customer customer)
{
Repository<Customer> repo = new Repository<Customer>();
repo.Update(customer); // Customer.Misc is null
...
}
public void Update(TEntity entity)
{
var entry = DbContext.Entry<TEntity>(entity);
if (entry.State == EntityState.Detached)
{
ObjectContext.ApplyCurrentValues(EntitySetName, entity);
}
DbContext.SaveChanges();
}
Solutions I could think:
Bind all entity attributes on the view:
I think this is not feasible and at the same time it may lead to performance issues since all attributes get populated.
Implement a custom method to copy property values to avoid null values being copied.
EntityHelper.CopyNotNullValues(source, target) and ignore null values in the source entity. If we do this we might not be able to set any of the values to null if required.
Implement View Models and transform data back and forth with the Domain Model.
This is the best approach I could think of so far. All the attributes bound to the View Model will get populated always, on the Update POST, copy all View Model values to the Domain Model.
Really appreciate your thoughts on this.

Answer 1

In Entity Framework, using ChangeObjectState or ApplyCurrentValues will cause data loss. The only way to work around this issue in this case is attaching the input entity and mark the properties to be updated. See below example:
public void Update(TEntity entity, string[] updatedProperties)
{
DbContext.Entities.Attach(entity);
var entry = DbContext.Entry<TEntity>(entity);
for (int i = 0; i < updatedProperties.Length; i++)
{
entry.SetModifiedProperty(updatedProperties[i]);
}
DbContext.SaveChanges();
}
[HttpPost]
public ActionResult Update(Customer customer)
{
Repository<Customer> repo = new Repository<Customer>();
repo.Update(customer, new string[]{ "Name" }); // Only update name
...
}
It's the best solution I can think of. You wanna have least code and good performance. It's as difficult as finding an easy and well paid job.