HtmlSelect and RequiredFieldValidator

[BK]

I'm having a really strange problem with and HtmlSelect server control
(listbox) and a RequiredFieldValidator that I am trying to use to make sure
that someone has items in the listbox.

The way that the HtmlSelect is populated is via a combination of client-side
javascript and another aspx page (launched by the javascript).

Anyway, everything seems to work just fine in terms of populating the
HtmlSelect. However, when I postback the form, the RequiredFieldValidator
always thinks that there is nothing in the HtmlSelect and fails validation
(I am only using server-side validation, by the way). I have the
ControlToValidate and all those things hooked up properly. Is there some
trick to setting the RequiredFieldValidator for an HtmlSelect control? Some
property that I am not setting?? I suspect that there is some small setting
that I am missing, but I have spent way too much time on this to keep
struggling.

Any help is appreciated,
Thanks

 

[Karl Seguin]

I wouldn't expect server-side validation to work on client-side added items.

Take a look at: http://openmymind.net/FAQ.aspx?documentId=1

but the quick answer is that when you add items in javascript, they aren't
added to the viewstate which means they won't be recreated on
postback...explains why your htmlselect is empty...

Karl

 

[Patrick Olurotimi Ige]

As Karl explained don't expect HtmlSelect to validate

 

[BK]

OK, this sort of makes sense to me. But, all the documentation that I have
read says that the RequiredFieldValidator works with an HtmlSelect server
control. I guess what you are saying is that the items need to be added
server-side for this to work?

Also, if this is the case, then is there a way to add them to the viewstate
in the described scenario or will I have to do some kind of convoluted
CustomValidation where I check the Request collection? Based upon the FAQ
below, I am assuming that converting to web controls wouldn't solve the
problem either - this seems to be a client vs server side issue with regard
to how the validation works.

Brian

 

[BK]

Well, it doesn't sound like it has anything to do with HtmlSelect, per se,
validating. It seems like it has to do with the values not being in
Viewstate. If that is the case, then validation would not work with ANY
items that are added to a form via client-side code.

 

[Karl Seguin]

You are pretty much right about everything. Though I would expect the
client-side validation to still work (not necessarily ideal since it only
works in IE...)

-items need to be added server-side
-going to dropdownlist (server control) wouldn't change anything
-you'll need to write your own validator and use request.form

Cheers,
Karl

--
MY ASP.Net tutorials
http://www.openmymind.net/ - New and Improved (yes, the popup is
annoying)
http://www.openmymind.net/faq.aspx - unofficial newsgroup FAQ (more to
come!)

 

[Brock Allen]

OK, this sort of makes sense to me. But, all the documentation that I

have read says that the RequiredFieldValidator works with an
HtmlSelect server control. I guess what you are saying is that the
items need to be added server-side for this to work?

Yes, you're correct. If you look at the javascript emitted when you do have
server side validation controls you'll see there's an array that's initalized
at the bottom somewhere with the IDs of all the client side validation elements.
This is what the client side framework drives off of.

 

[BK]

I'm still having trouble with this, here is what I have done (I'm not using
client-side validation, by the way - customer requirement):

1) As I mentioned before, everything works fine client-side in terms of
items being added to the HtmlSelect control. I get a nice list of items in
my form, as expected. In addition, I have a hidden input field that holds a
string representation of the values, so that I can persist between
postbacks. For the sake of argument, lets call my HtmlSelect (which is
runat=server) "lstValues" and my hidden input (which is also runat=server)
"hdnValues".

2) Now, from what I understand, I should be able to truly populate the
HtmlSelect control (as .NET sees it) on the server-side, so that when
validation rolls around in the page event cycle, it will see that items have
been added. This is where confusion sets in.

3) It seems that Page_Init is too early to set any values because
"hdnValues" is always an empty string. So, that doesn't work.

4) I have tried adding IPostbackDataHandler to my page and implementing
LoadPostbackData, but this doesn't seem to work. The values are set, but the
validation still fails.

5) I have tried adding multiple other events that supposedly occur before
validation and populating lstValues there, but all to no avail. Validation
still fails.

6) I have googled and read everything that I can find, but nothing seem to
work.

This cannot be this difficult. I feel like I have all that I need on the
client-side, I just need to know what to do and where to do it in the
code-behind in order to catch the page event before validation and populate
lstValues with the items that I have. Also, from what I understand (and I
have observed the problem, so I know its true) CustomValidators don't work
with HtmlSelect - the event doesn't fire, so that is not an option either.

Any help is appreciated, I have been working on this all day....

TIA
BK

 

[BK]

Thanks. I'm still having problems with this - I posted the details in a
previous message. Everything on the client side of the house works fine. I
just cannot seem to figure out what to do on the server side to convince
..NET that there is something in the HtmlSelect. I have tried MANY different
ways and all of them fail validation.

 

[Karl Seguin]

The information will be available in the Page_Load event. It's loaded in
the LoadPostbackData event of the individual contorl - not the pages.

Why not just write your own validation event....By the time you get to a
bottom's click event, the data is there, write a function "IsCustomValide()"
which checks to see if hdnValues has a value?

Karl

--
MY ASP.Net tutorials
http://www.openmymind.net/ - New and Improved (yes, the popup is
annoying)
http://www.openmymind.net/faq.aspx - unofficial newsgroup FAQ (more to
come!)

 

[BK]

There is a requirement to use the validation controls (if possible, I
guess). And, there is a common page structure that does the standard
Page.Validate and Page.IsValid. So, it would be preferrable to have these
evaluate properly. Is there not a page event that I can override, load the
HtmlSelect with the values in the hdnValues field and expect the validators
to work?

If I am understanding you correctly, you are suggesting that I simply write
a function to see if something is there. If my purpose were simply to know
if something had been entered that would be a fine solution, but what I am
really trying to do is understand how I fit this within the context of using
the server-side validation controls (requiredfieldvalidator), since that is
the architecture that has been laid out.

If the server-side validation is driving off of viewstate, isn't there a
page event somewhere during the postback that I can modify the viewstate so
that the requiredfieldvalidator sees that the HtmlSelect is no longer
empty???