Dropdownlist Chain Visible

17 Mar 2006 1:08 PM

newsgroups.jd

I have a chain of drop down lists that populate based on the selection
from the previous drop down list. The 3rd and 4th drop down list, plus
a calendar - I would only like visible if certain choices are made in
the first and second drop down list.

I did using with similar to ....

Public Sub _OnSelectedIndexChanged1(ByVal Sender As Object, ByVal e As
EventArgs)
        If DropDownList1.SelectedValue = "Choose a Report Category"
Then
            DropDownList2.Visible = False
            DropDownList3.Visible = False
            masterCalendar.Visible = False
        Else : DropDownList2.Visible = True
        End If
    End Sub
Public Sub _OnSelectedIndexChanged2(ByVal Sender As Object, ByVal e As
EventArgs)
        If DropDownList2.SelectedValue = "Daily Reports" Then
            masterCalendar.Visible = True
        Else : masterCalendar.Visible = False
        End If
    End Sub

The questions I have is this.

1. Is this the best way to accomplish this?
2. How does changing the visibility properties affect multiple users,
using the site at the same time?

Thanks ahead of time... new to asp.net.

JD

17 Mar 2006 4:08 PM

Cerebrus

Hi JD,

I think that such UI modifications are best handled at the Client end
itself, and so you should use Client side scripting to enable / disable
or set visibility of such controls at the client browser.

I'm assuming that you've set the AutoPostBack property to True, and
with each SelectionChange, the event is raised, and the form posts back
to the server. In my opinion, there's always a performance penalty to
setting the AutoPostBack property of any control to True.

Of course, if the data in your Dropdown list is bound to a database,
then you cannot avoid posting back to the server. If it's only a
question of toggling visibility and filling some static items, then I
would suggest using Javascript (or VBScript) to do it.

To summarize, there are some validations that are best done at the
Client side, and some others that are most useful at the Server side.

Hope this helps,

Regards,

Cerebrus.

21 Mar 2006 2:28 PM

newsgroups.jd

Thanks...

You are correct I am using AutoPostBack and all the drop down lists are
populated by a database. Once this is done, I was going to create a
small front end for adding and removing items from the database ( to
edit the lists and URLs ). I had considered using static entries, but
so far between 4 dropdownlists I am up to over 100 entries.

JD

Cerebrus wrote:
Show quoteHide quote

> Hi JD,
>
> I think that such UI modifications are best handled at the Client end
> itself, and so you should use Client side scripting to enable / disable
> or set visibility of such controls at the client browser.
>
> I'm assuming that you've set the AutoPostBack property to True, and
> with each SelectionChange, the event is raised, and the form posts back
> to the server. In my opinion, there's always a performance penalty to
> setting the AutoPostBack property of any control to True.
>
> Of course, if the data in your Dropdown list is bound to a database,
> then you cannot avoid posting back to the server. If it's only a
> question of toggling visibility and filling some static items, then I
> would suggest using Javascript (or VBScript) to do it.
>
> To summarize, there are some validations that are best done at the
> Client side, and some others that are most useful at the Server side.
>
> Hope this helps,
>
> Regards,
>
> Cerebrus.