How to check if either none or all textboxes in an ASP.NET page have text entered?
<p>I am creating an invoice application and in the section where the user can enter line items, some of the fields will include: Quantity, Price, Extended Price, Description, etc.</p>

<p>If the user enters something into any of the fields, the corresponding fields are required, but if no data is entered into any field, then nothing is required in the corresponding fields.  What is an efficient and clean way of doing this without doing a bunch of if statements?</p>

<p>I guess this is like doing validation if only one textbox has text.</p>
