public static class ContextObject_Helper
    {
        public static int UpdateEntity<T>(this ObjectContext objectContext, T entity, string entitySetName) where T: EntityObject
        {
            // Attach specify entity
            objectContext.AttachTo(entitySetName, entity);// Get object state by specify entity.
            System.Data.Objects.ObjectStateEntry state = objectContext.ObjectStateManager.GetObjectStateEntry(entity);// Get all members from entity.
            MemberInfo[] members = entity.GetType().GetMembers();// Get all properties except EntityKey.
            IEnumerable<MemberInfo> properties = members.Where(m => m.MemberType == MemberTypes.Property && m.Name != "EntityKey");foreach (MemberInfo mInfo in properties)
            {
                //Find property that used System.Runtime.Serialization.DataMemberAttribute.
                object[] attrs = mInfo.GetCustomAttributes(typeof(System.Runtime.Serialization.DataMemberAttribute), true);if (attrs.Length > 0)
                {
                    object[] emdAttrs = mInfo.GetCustomAttributes(typeof(System.Data.Objects.DataClasses.EdmScalarPropertyAttribute), true);
                    if (emdAttrs.Length > 0)
                    {
                        var edm = emdAttrs[0] as System.Data.Objects.DataClasses.EdmScalarPropertyAttribute;
                        if (!edm.EntityKeyProperty)
                            state.SetModifiedProperty(mInfo.Name);
                    }
                }
            }return 0;
        }
    }

PubsEntities pubsEnt = new PubsEntities();
Author auth = new Author()
{
    au_id = "427-17-2319",
    au_lname = "Dull",
    au_fname = "Ann",
    phone = "415 836-7128",
    address = "3410 Blonde St.",
    city = "Palo Alto",
    state = "CA",
    zip = "99999",
    contract = true
};
pubsEnt.UpdateEntity(auth, pubsEnt.Authors.EntitySet.Name);
pubsEnt.SaveChanges();