ASP.NET Detect if Javascript disabled field

Question

I am hoping there is an answer for this...

Setup: Pretty complex ASP.NET Application doing a bunch of user interaction, some of which requires that Javascript disables some fields when others are clicked (had to do it in Javascript, b/c the postback issues in ASP.NET made it impossible, so had to it client side).

That code is all well where Javascript does the classic document.getElementById(currObj).disabled = true;

The problem: When I am ready to submit the page, how can I make ASP.NET (C#) notice if a field (Textbox or Radio box) has been disabled client side, so it does NOT submit that field in the form? Is this even possible?

Much thanks in advance!

Answer 1

Any disabled fields don't submit but normal and even hidden ones do. This is how disabled fields work.

<input type="text" name="Test_1" value="off" disabled="disabled" />
<input type="text" name="Test_2" value="on" />
<input type="hidden" name="Hidden_1" value="hide_off" disabled="disabled" />
<input type="hidden" name="Hidden_2" value="hide" />

In the example only Test_2 and Hidden_2 will submit because the others are disabled.

You can see it at work in this jsfiddle: http://jsfiddle.net/bJ7Rq

Answer 2

The only way ASP.NET knows that a control has been disabled is if it was disabled from .NET and the Enabled = false property has been written to ViewState. When you disable a field on the client-side, this isn't the case, so ASP.NET will retain the default Enabled value.

As previous commenters have mentioned, the value of a disabled field will be completely excluded from the POST body sent to the server on postback. In the case of a basic TextBox on a page, that would mean the Text property would revert to String.Empty . To differentiate between an empty string in an enabled field and an actual disabled field, I think you'd need to look directly at the Request.Form object to see if the key exists. For example, if I had a TextBox named myTextBox on a blank page, Request.Form["myTextBox"] would be null for a disabled field. For an enabled field, it'd be whatever string value the field contained, including String.Empty if it were blank. Of course, if the control is in a naming container (eg, a ContentPlaceholder or something) that messes with the name property on the actual field in HTML, you'd need to use the full HTML name .

So for example:

bool fieldIsEnabled = Request.Form["myTextBox"] == null;

It's not elegant, but it should get the job done (excluding checkboxes, which would also be null if the box wasn't checked).