Attach

Attaches a record to the context. This is optimistic behavior: the Entity Framework expects the record to exist and only looks at other records that make use of this attached record. Any modification made to the attached record is not passed to the database.

Source: link

State = EntityState.Modified

Indicates to the Entity Framework that the object (therefore, the record) has been modified and should be persisted in the database by invoking the SaveChanges method.

A priori, records loaded by selection are not marked to be persisted. The programmer should do this manually. This is to prevent SaveChanges from making any improper changes to the database in entities that should not be modified.

CurrentValues.SetValues

Changes the values directly and marks the entry of the object as modified. A call to SaveChanges will update the updated values by SetValues .

See more about CurrentValues here .

See more about SetValues and other methods and properties of CurrentValues here .

Another answer to this question is almost completely based on another question I found in SOen .

The author of the question was exploring some ways to update a record and among them he listed a few:

Method 1 - Load the original record, change each property and then save.

var original = db.Users.Find(updatedUser.UserId);

if (original != null)
{
    original.BusinessEntityId = updatedUser.BusinessEntityId;
    original.Email = updatedUser.Email;
    original.EmployeeId = updatedUser.EmployeeId;
    original.Forename = updatedUser.Forename;
    original.Surname = updatedUser.Surname;
    original.Telephone = updatedUser.Telephone;
    original.Title = updatedUser.Title;
    original.Fax = updatedUser.Fax;
    original.ASPNetUserId = updatedUser.ASPNetUserId;

    db.SaveChanges();
}

Vangatens are able to use a ViewModel , so you can have a class without all the properties of the domain class and then facilitate View's projection. With this, you need to set the properties that you are going to save, so you do not need to have all fields of the domain class in the view and you can save the change of only the fields you have changed.

Disadvantages are in:
Have two requests to the database. One to retrieve the original record (the record that is in the database with the current data) and the request to persist the data in the database ( db.SaveChanges() ).

Method 2 - load the original record and make use of db.Entry(T)CurrentValues.SetValues(); .

var original = db.Users.Find(updatedUser.UserId);

if (original != null)
{
    db.Entry(original).CurrentValues.SetValues(updatedUser);
    db.SaveChanges();
}

Here, the advantages are to set the modified properties with only two command lines. Home Only the changed properties will be sent to the database.

Disadvantages because your view needs to have all properties (here, **updateUser** is not a viewModel, but a class of its own) Two requests are also made to the database. One to get the original record and one to save the record.