c# - Is it possible to prevent EntityFramework 4 from overwriting customized properties?

Question

I am using EF 4 Database first + POCOs. Because EF has no easy way to state that incoming DateTimes are of kind UTC, I moved the property from the auto-generated file to a partial class in another file.

    private DateTime _createdOn;
    public virtual System.DateTime CreatedOn
    {
        get { return _createdOn; }
        set
        {
            _createdOn =
                (value.Kind == DateTimeKind.Unspecified)
                    ? _createdOn = DateTime.SpecifyKind(value, DateTimeKind.Utc)
                    : value;
        }
    }

However, now every time I update the model, the automated properties get created again in the T4-generation. Of course this causes the following compilation error: "The type 'Foo' already contains a definition for 'CreatedOn'".

Is there any way to tell EF to not generate that property and to let me handle it on my own?

Update

Thanks for everyone's answers...

I created a new custom property with a different name.

    public virtual System.DateTime CreatedOnUtc
    {
        get
        {
            return (CreatedOn.Kind==DateTimeKind.Unspecified)
                ? DateTime.SpecifyKind(CreatedOn, DateTimeKind.Utc)
                : CreatedOn;
        }
        set
        {
            CreatedOn =
                (value.Kind == DateTimeKind.Unspecified)
                    ? CreatedOn = DateTime.SpecifyKind(value, DateTimeKind.Utc)
                    : value;
        }
    }

I also set all of the setters and getters of the auto-generated property to Private with the exception of those properties that I needed to use in a Linq-to-Entities query (sigh). In those cases, I set those getters to internal.

I sure wish there was a dropdown on DateTime types to specify what "Kind" of DateTime that EF should treat it as. That would have saved hours and the extra complication.

Answer 1

A different approach is to hook into the ObjectMaterialized event in the DbContext and set the kind there.

In my DbContext constructor, i do this:

    ((IObjectContextAdapter)this).ObjectContext.ObjectMaterialized += new ObjectMaterializedEventHandler(ObjectMaterialized);

and then the method looks like this:

private void ObjectMaterialized(object sender, ObjectMaterializedEventArgs e)
        {
            Person person = e.Entity as Person;
            if (person != null) // the entity retrieved was a Person
            {
                if (person.BirthDate.HasValue)
                {
                    person.BirthDate = DateTime.SpecifyKind(person.BirthDate.Value, DateTimeKind.Utc);
                }
                person.LastUpdatedDate = DateTime.SpecifyKind(person.LastUpdatedDate, DateTimeKind.Utc);
                person.EnteredDate = DateTime.SpecifyKind(person.EnteredDate, DateTimeKind.Utc);
            }
        }

The downside is that you need to make sure you set it for each property that you care about but at least it gets set at the lowest possible level.