dynamic drop downs

igotyourdotnet · Dec 6, 2006

i have 2 drop downs that have months in them such as
1/1/2005 and 1/31/2005

I need to my starting month drop down to be a month behind the end of month

so something like this:
if month ending = 1/31/2006
I need start month = 12/31/2005

how can I do thi? is it possible?
its kind of a backwards thing, but the month end dropdown can be populated
from a querystring so if 1/31/2006 is passed I need to set the start month
to be 12/31/2005

Steven Cheng[MSFT] · Dec 6, 2006

Hello Mike,

From your description, you have an ASP.NET page which has two dropdownlists
and they'll display two month values and you want to make one list's
selected month 1 month behind another(start and end), correct?

As for this scenario, I think it is a typical dropdownlist synchornize
issue, I'm wondering how would like to implement the synchronizing between
the two values, use server-side code logic or client-side script?

Generally, most page will use client script to manipulate such cascading
value changes in associated dropdownlists. you can hook the
dropdownlist(<select> html element)'s client-side "onchange" event. BTW,
are the months items in each list fixed? For example, both of the list only
contains 12 months(items)? If so, you can even use selectedIndex value to
determine how to adjust each list's selected value.

Please feel free to let me know your detailed scenario and requirement.

Sincerely,

Steven Cheng

Microsoft MSDN Online Support Lead

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Guest · Dec 6, 2006

If you are doing it server-side you can determine the startDate doing
something like this:

'This is where you would convert your querystring to a datetime object
Dim endDate As DateTime = System.Convert.ToDateTime("1/31/2006")

'startDate will be the last day of the month previous to the endDate
Dim startDate As DateTime =
endDate.AddDays(-endDate.DaysInMonth(endDate.Year, endDate.Month))

You could then select the listbox item that matches the date.

Like Steven said, most people do this on the client-side so that you don't
have to do a post-back to figure out what to select in the dropdown. If you
know JavaScript its not that hard to do.

Guest · Dec 7, 2006

Mike,

So, did you want to do this client side or server side? Do you still need
help with this?

Steven Cheng[MSFT] · Dec 8, 2006

Hi Mike,

Here is a simple example page which use pure client-side script to
synchornize the two dropdownlist(<select>), both of them contain 24 months:

===================================
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Untitled Page</title>
<script type="text/javascript">
function sync_lists(source)
{
var lst1 = document.getElementById("lstStart");
var lst2 = document.getElementById("lstEnd");

if(lst1.selectedIndex == lst1.options.length-1)
{
lst1.selectedIndex = lst2.selectedIndex - 1;
}
else if(lst2.selectedIndex == 0)
{
lst2.selectedIndex = lst1.selectedIndex + 1;
}
else
{

if(source == 0)
{
lst2.selectedIndex = lst1.selectedIndex + 1;
}
else
{
lst1.selectedIndex = lst2.selectedIndex - 1;
}
}
}

</script>
</head>
<body>
<form id="form1" runat="server">
<div>
<select id="lstStart" name="lstStart" onchange="sync_lists(0);" >
<option selected="selected" >06-01</option>
<option>06-02</option>
<option>06-03</option>
<option>06-04</option>
<option>06-05</option>
<option>06-06</option>
<option>06-07</option>
<option>06-08</option>
<option>06-09</option>
<option>06-10</option>
<option>06-11</option>
<option>06-12</option>
<option>07-01</option>
<option>07-02</option>
<option>07-03</option>
<option>07-04</option>
<option>07-05</option>
<option>07-06</option>
<option>07-07</option>
<option>07-08</option>
<option>07-09</option>
<option>07-10</option>
<option>07-11</option>
<option>07-12</option>
</select>

<select id="lstEnd" name="lstEnd" onchange="sync_lists(1);">
<option >06-01</option>
<option selected="selected">06-02</option>
<option>06-03</option>
<option>06-04</option>
<option>06-05</option>
<option>06-06</option>
<option>06-07</option>
<option>06-08</option>
<option>06-09</option>
<option>06-10</option>
<option>06-11</option>
<option>06-12</option>
<option>07-01</option>
<option>07-02</option>
<option>07-03</option>
<option>07-04</option>
<option>07-05</option>
<option>07-06</option>
<option>07-07</option>
<option>07-08</option>
<option>07-09</option>
<option>07-10</option>
<option>07-11</option>
<option>07-12</option>
</select>
</div>
</form>
</body>
</html>
======================================

Hope this helps some.

Sincerely,

Steven Cheng

Microsoft MSDN Online Support Lead

This posting is provided "AS IS" with no warranties, and confers no rights.

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dynamic drop downs

igotyourdotnet

Steven Cheng[MSFT]

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Steven Cheng[MSFT]

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