SqlBool where = (SOMEFIELD == some_value);
if(!(~some_ctrl).IsNull){
  where = where && OTHERFIELD = ~some_ctrl;
}
if(!(~find).IsNull){
  String s = ~find;
  s << '%';
  where = where && Like(THIRDFIELD, s);
}
sql * Select(SqlAll())
  .From(SOMETABLE)
  .Where(where);