>Is it OK or not really a good code
>
>

>string strOrderNo = this.txtOrderNo.Text;
>                        int? OrderNo;
>                        if (strOrderNo.Equals(String.Empty))
>                            OrderNo = null;
>                        else
>                            OrderNo = Convert.ToInt32(strOrderNo);
>
>                        _dtOrder = biz.Find(OrderNo, this.dtgStartDate.Value, this.dtgEndDate.Value);

>

That should be fine. I'd probably do something like this, but it's mostly a style preference:

int? orderNo = null;
if (!string.IsNullOrEmpty(strOrderNo))
   orderNo = Convert.ToInt32(strOrderNo);

dtOrder = biz.Find(orderNo, this.dtgStartDate.Value, this.dtgEndDate.Value);