Referencing values in html form or java script in code behind

Question

Referencing values in html form or java script in code behind

developer155 (Programmer)

(OP)

10 Jun 05 17:17

I have aspx page with HTML form that calls JavaScript procedure OnSubmit (the java script gathers all the values in the form and puts them into a cookie). I need the values in that HTML form (preferable from javascript procedure) in the code behind to process them (call store procedure with them).
So my question is is it possible to pass the values to code behind from java script function after form has been submitted? Or do I have to change the form to server side controls and get the values that way in my code behind?

thanks

sirjon (Instructor) · Answer 1 · 2005-06-10 20:15:38

Hi,

Well that's what .net forms are for - to post back to the server.
If you need to process the values on the server, then no need to gather the data with javascript.
Make sure your form has a 'runat=server' tag and then use asp.net textboxes etc.

asp.net makes this really easy.

hth
j

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RTomes (Programmer) · Answer 2 · 2005-06-11 01:42:56

CODE

<head>
function gather(){
var del=String.fromCharCode(160)
var a='hola'
var b='hello'

var ret=a+del+b
document.forms[0].myjavascriptvars.value=ret
}
</head>
<form onsubmit="gather();return true" runat=server>
<input type=hidden name=myjavascriptvars>

CODE

sub page_load()
dim arr() as string=request.form("myjavascriptvars").ToString.Split(chr(160))
end sub

vbkris (Programmer) · Answer 3 · 2005-06-11 07:40:27

or:
<head>
function gather(){
var del=String.fromCharCode(160)
var a='hola'
var b='hello'

var ret=a+del+b
document.forms[0].myjavascriptvars.value=ret
}
</head>
<form onsubmit="gather();return true" runat=server>
<input type=hidden name=myjavascriptvars id=myjavascriptvars runat="Server">

code behind file:
Private WithEvents myjavascriptvars as HtmlInputHidden
sub page_load()
response.write(myjavascriptvars.value)
end sub

Known is handfull, Unknown is worldfull

RTomes (Programmer) · Answer 4 · 2005-06-11 11:02:35

Vbkris, that will work if it is used in a simple webform.
It is very common (an good practice) to put your work in Web User Controls.

When you do, the client side ID is not going to be myjavascriptvars because the ID and Name will change.

This is what is looks like on the client:
<input name="Control1:myjavascriptvars" id="Control1_myjavascriptvars" type="hidden" />

vbkris (Programmer) · Answer 5 · 2005-06-13 05:17:33

well from that angle you are correct...

Known is handfull, Unknown is worldfull

developer155 (Programmer) · Answer 6 · 2005-06-13 10:00:08

Thanks for all your responces: One question about
sub page_load()
dim arr() as string=request.form("myjavascriptvars").ToString.Split(chr(160))
end sub

why is the code in page_load function? when is page_load called? after the user submits the form?

ca8msm (Programmer) · Answer 7 · 2005-06-13 10:05:38

The page load event fires when the page is loaded (funnily enough!).

If you click a button to cause a postback, you will see if you step through each event that the page load event fires before the button click event (so you could place it in either event depending on what you need to do with the data).

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developer155 (Programmer) · Answer 8 · 2005-06-13 10:30:34

so what method do you think is better for gathering values from a form and passing them to code behind:

with java script and hidden fields OR

converting form and controls to server side and capturing using input directly from code behind OR

gathering the values with java script and creating a cookie and reading the cookie in the code behind (Request.Cookies..) which is the current implementation

thanks

vbkris (Programmer) · Answer 9 · 2005-06-13 10:45:42

that would actually depend on the situtation. i have never used the third method...

Known is handfull, Unknown is worldfull

ca8msm (Programmer) · Answer 10 · 2005-06-13 10:46:23

Well I can think of disadvantages for all of those methods:

Quote:

with java script and hidden fields

What happens if javascript is disabled on the client?

Quote:

converting form and controls to server side and capturing using input directly from code behind

RTomes pointed out the drawback if they are implemented within a User Control

Quote:

gathering the values with java script and creating a cookie and reading the cookie in the code behind

What if the client won't accept cookies?

There are always going to be certain hurdles when dealing with client & server side values but in this case I would have said the method described by RTomes was probably best suited to this situation. You will have to make your own mind up though as it really depends on the implementation of the page and the users that will be using the site.

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RTomes (Programmer) · Answer 11 · 2005-06-13 16:59:42

Someone that turns off JavaScript will cause major problems in almost all the websites out there. The user that does this is going to get frustrated in the first week and turn JavaScript back on.
Turning of cookies is much more common and does not effect the functionality nearly as much as turning of all JavaScript (menus, button mouse overs, ..., the list goes on and on with JavaScript)

ca8msm (Programmer) · Answer 12 · 2005-06-14 04:32:53

Quote:

Someone that turns off JavaScript will cause major problems in almost all the websites out there. The user that does this is going to get frustrated in the first week and turn JavaScript back on.

It's not always the case that the user turns javascript off - we have clients that use hand held devices and these only have text based browsers which don't support javascript so we have cases where we have to cater for these users.

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RTomes (Programmer) · Answer 13 · 2005-06-14 09:25:03

I have had simular concerns. After considering it I realized if JavaScript is turned off then the
function __doPostBack(eventTarget, eventArgument) {
will not work and that disables half of the .net controls.

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Referencing values in html form or java script in code behind