>>Or just

dtOrder = biz.Find((orderNo == String.Empty) ?  (int?) null :  Convert.ToInt32(orderNo), this.dtgStartDate.Value, this.dtgEndDate.Value);

>
>I'm just not a fan of the syntax. I've tried but I just can't read it. I'd usually use TryParse but since she needed a null when it was empty there wasn't much advantage.

I posted a TryParse() version for Naomi that will do that. I've no problem with the syntax. I guess it's one of those 'the more you use it the easier it is to parse' things....
Best,
Viv