Disable control without postback

  • Thread starter Thread starter Geoff
  • Start date Start date
G

Geoff

Is there any way to change the enabled property of a dropdownlist without a
postback, depending on the selection in another dropdownlist?

Select Case ddlReport.SelectedValue

Case "Profit"

ddlFormat.Enabled = True

Case "Trial Balance"

ddlFormat.Enabled = False

End Select
 
Geoff,
Is there any way to change the enabled property of a dropdownlist without
a
postback, depending on the selection in another dropdownlist?
Click to expand...

No

Cor
 
Cor Ligthert said:
No
Click to expand...

I assume that it's possible to disable another control using
JScript/VBScript without a postback, but that's slightly off-topic here.
 
Geoff,
It sounds like you are talking ASP.NET.

As Herfried suggests. If you want to do it server side, then you need to do
a postback. If you don't want a postback, then you will have to do it client
side with JavaScript or VBScript.

For help with client side JavaScript & VBScript you may want to ask this
"down the hall" in one of the microsoft.public.dotnet.framework.aspnet
newsgroups.

Hope this helps
Jay
 
Geoff,

Although you have two answers from VBNet ASPNET experts who denies my answer
to you, my answer stays No.

This can be the information created in a webform page at client side, which
contains all information of the data in the serverside controls (from which
the dropdownlist is one) on your page.

<input type="hidden" name="__VIEWSTATE"
value="dDw5MzcwNzM4OTU7Oz6sJm5Bgc+8ub9mK/REAxFYaxmlmQ==" />

I knew lot of JavaScript, however I do not know how to change this in a way
that I could assure that the information stays consistent.

Cor
 
Cor,
Although you have two answers from VBNet ASPNET experts who denies my
answer to you, my answer stays No.
Click to expand...
That comment doesn't even warrant a response!

however I do not know how to change this in a way that I could assure that
the information stays consistent.
Click to expand...

You can turn off the ViewState for selected controls or all controls using
the Control.EnableViewState which DropDownList inherits.

The Page directive also has EnableViewState attribute.

Hope this helps
Jay
 
Addendum:
I assume that it's possible to disable another control using
JScript/VBScript without a postback, but that's slightly off-topic here.
Click to expand...

\\\
....
<html...>
...
<head>
...
<script type="text/javascript"><![CDATA[
function disableDropdown() {
document.forms[0].elements[0].disabled = true;
}
]]></script>
</head>
<body>
<h1>Dropdown list sample</h1>
<form>
<p>
<select size="1">
<option>Item1</option>
<option>Item 2</option>
</select>
</p>
</form>
<p><a href="javascript:disableDropdown();">Disable dropdown list</a></p>
</body>
</html>
///
 
Jay,
You can turn off the ViewState for selected controls or all controls using
the Control.EnableViewState which DropDownList inherits.
Click to expand...

You are right, and have with that given the direct answer for this question.

By setting the ViewState to False it should be pretty easy for everybody who
knows a little bit of JavaScript,

So my answer becomes Yes.

:-)

Cor
 
Geoff,

I was thinking a lot more in your question than there probably is, when it
is as simple as you ask is can be this a piece of JavaScript, however with
that is in my opinion still the data in the box with a postback sent back to
the server side ass well as the the selectedindex. When you want to affect
that you should do more using that viewstate enabled is false.

You can put a HTML button on your form to test it

<script language=javascript>
<!--

function Button1_onclick() {
if (document.all("DropDownList1").disabled == false) {
document.all("DropDownList1").disabled = true}
else
{
document.all("Dropdownlist1").disabled = false}
}

//-->
</script>

When you want to integrate it in VBNet you can use

Dim scriptString As String = "The script including javatags"
Page.RegisterStartupScript("Button1_OnClick", scriptString)


Cor
 
You can turn off the ViewState for selected controls or all controls using
the Control.EnableViewState which DropDownList inherits.

The Page directive also has EnableViewState attribute.
Click to expand...

But the user should beware that events will go wonky if you do either
of these. If you really want a dropDownList that reacts reasonably to
client-side disabling then one's best bet is to derive a class from
DropDownList and do the work yourself. You could probably achieve this
with a few very minor overrides, but I haven't looked at it in detail.

Of course, this is all probably way beyond what the original poster was
asking. On the other hand, all this is likely to bite him pretty soon.
 
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