How can you see the sql that is causing an error on SubmitChanges in LINQ to SQL?

using (MyDataContext ctx = new MyDataContext())
{
    StringWriter sw = new StringWriter();
    ctx.Log = sw;

    // execute some LINQ to SQL operations...

    string sql = sw.ToString();
    // put a breakpoint here, log it to a file, etc...
}

context.GetChangedSet();