Your so-called "TextBoxes" will actually be either an
HTML element or a
You should learn to look at the HTML that ASP.NET produces, so that you can work with the HTML and *NOT* with ASP.NET's private (and somewhat distorted) view of your page. If you didn't know, this is trivial to do: Just click on the browser's VIEW menu and then on the SOURCE (or PAGE SOURCE, depending on which browser) menu item. Voila. You will be looking at the HTML as the browser sees it.
Note that HTML form elements, including <input> and <textarea> *NEVER* have null values. They can't. Their values are *ALWAYS* strings. And they *can* have a blank string ("") but they can't be NULL.
NOW... My question to you: Why don't you use ASP.NET code to change the style of the <div>s to display: none;
SURELY you KNOW the value you are going to assign to a TextBox contained in a <div> before you actually have to produce the <div> via ASP.NET code?
... any other content for the div ...
<asp:TextBox cssClass="magic" id="whatever" runat="server" value="some value" />
... still more other content for the div ...
If all your text boxes have that same cssClass (name of your choice), then it's easy.
*** BUT IGNORE ALL THIS! GO READ YOUR FIRST THREAD THAT THIS IS A DUPLICATE OF! ***