Stopping a field change being recorded as a modification to a POCO object

I am developing with silverlight, and RIA services. I have a POCO object defined on the server side like this,

public class AssessmentRoad
{
    [Key]
    public int Id { get; set; }
    [Required]
    public int RoadLength { get; set; }
    public int RoadId { get; set; }
    [Required]
    public string RoadName { get; set; }
    [Required]
    public string Suburb { get; set; }
    public bool HasModified { get; set; }
}

The field HasMod开发者_StackOverflow社区ified is calculated and used on the client side only.

RIA services when I call SaveChanges decides that the entities need saving because the HasModified field has changed.

Is there an attribute I can use to make sure this doesn't happen? Or do I need to use a partial class etc?

On second thoughts perhaps the HasModified field shouldn't be there at all, and this should be wrapped up in a ViewModel instead?

Add this property to a client-side partial class. See http://msdn.microsoft.com/en-us/library/ee707331(v=VS.91).aspx.