Cannot save twice in SubSonic3

Question

Hi. I want to Save my record first to get it auto-populated ID. then make changes later so I wrote as

product.Save(); .......... product.image = "/a.jpg"; product.Save();

The problem is the second save doesn't work. I tried to call its IsDirty() and it return false which means subsonic doesn't think it has changed. Actually it has. Now I have to wrote as product.Save(); .......... product = new product(o=>o.product_id == product.product_id); product.image = "/a.jpg"; product.Save();

And it is worked. I believe it is bug.