In LINQ to SQL, I want to avoid setting some columns if others haven't changed? Say I have

```
dim row = (From c in dataContext.Customers Where c.Id = 1234 Select c).Single()
row.Name = "Example"
' line 3
dataContext.SubmitChanges()   ' line 4

```

Great, so LINQ to SQL fetches a row, sets the name to "Example" in memory, and generates an update SQL query **only when necessary**--that is, no SQL will be generated if the customer's name was already "Example".

So suppose on line 3, I want to detect if row has changed, and if so, set row.UpdateDate = DateTime.Now. If row has not changed, I don't want to set row.UpdateDate so that no SQL is generated. Is there any good way to do this?