WCF RIA Services SP1，实体框架4，仅更新已更改的列

// change state of entity as Unmodified/Unchanged...
original.EntityState = Unchanged;

// this is copy form database...
// Use different context
MyOrderContext context = new MyOrderContext();
Order dbOriginal = context.Orders.First( x=>x.OrderID == original.OrderID);

foreach(PropertyInfo p in copy.GetTypes().GetProperties()){
   Object originalValue = p.GetValue(dbOriginal);
   Object newValue = p.GetValue(original);
   if(originalValue!=null && newValue!=null 
       && originalValue.Equals(newValue)){
       continue;
   }
   // resetting this will 
   // make entity\'s only current
   // property as changed
   p.SetValue(original,originalValue);
   p.SetValue(original,newValue);
}