Dynamically populating a DropDownList, AutoPostback and JavaScript error

[user1980]

hello,

i am trying to create a request form using asp.net where when a user selects a checkbox, a dropdown should appear dynamically. I have seen few java-scripts in web, but I was wondering if I can achieve this without java-script.

I tried to make the control invisible(<asp: DropDownList ID="DropDownLis t1" runat="server" AppendDataBound Items="True" Visible="False">) and in the onselectedindex changed event, tried to make the invisible property to true. But it did not help me.
Also, I was trying to use postback for the page when a checkbox is selected(asp:Ch eckBoxList ID="chckbx" runat="server" AutoPostBack="t rue" onselectedindex changed="chckbx _SelectedIndexC hanged") and it throws me an error in IE saying the object does not support this property.


Can somebody please help me with this. Thanks in advance.

[user1980]

function window_open()
      {
       window.open("Codes.aspx","","menubar=no,status=no,scrollbars=yes,resizable=yes,toolbar=no,top=180,left=250,width=750,height=600");
      }

the ap.net control that calls it,

<asp:Button runat="server" ID="btnlookup" Text="Code" OnClientClick="window_open()" CausesValidation="false" Width="90px" />

[Frinavale]

I don't see anything wrong with this JavaScript.
I'm going to ask that a JavaScript expert take a look at this.

Does this problem prevent your code from being executed?
If so, could you remove it while we are fixing your current problem with dynamically populating the DropDownList?

-Frinny

[Dormilich]

I'm going to ask that a JavaScript expert take a look at this.

I can’t find anything wrong, works as expected when inserted in plain text HTML.

[user1980]

my page executes normally. but I just wanted to get rid of the error and also wanted to postback the page when I check the checkbox.

[Frinavale]

Well enable autopostback for the checkbox.
Put a break point on the method that handles the event and run the application.
Do you hit the break point?

-Frinny

[user1980]

ah..it does not hit the breakpoint. and the script error is displayed only when I try to check the checkbox, not when the page loads.

[Frinavale]

Okay, it sounds like the JavaScript that preforms the AutoPostback is not working.

I don't know why this would be the case. The only thing that I can think of is that your JavaScript is somehow invalid (maybe you didn't close the <script> tag?) But your JavaScript looks fine.

Try removing your JavaScript from the page.
Do you get the same error?

What web browser are you using? What version is it?

Are you using Ajax?
If so are you using any Ajax enabled controls?
These may be causing a problem...


-Frinny

[user1980]

Hi Frinny

Thank you for your quick responses.

I did try to remove the javascript from the page. it still gives me the error. I am currently using IE7 and I do not have any ajax controls.
I did try to create a new checkbox list and even that gives me the same error.

I created a new page and could figure out the how to create a dropdown when a checkbox is selected. It works fine. But my original page still has the error for the autopostback.

Your help is greatly appreciated.
Thank you...

[Frinavale]

It's too bad that you were having such a hard time with your original page.
At least the error isn't happening on your new aspx page.

So, in the method that handles the AutoPostback for the CheckBoxList (list??) you need to create list items for your DropDownList based on what was checked/selected.

(I'm not sure what language you're using.)

There are two ways to do this. You can create generate ListItem objects and add them to your DropDownList's "Items" property. Or you can bind your DropDownList to a data source.

-Frinny

[user1980]

yeah. I did use the items property to make my dropdowns work and it works fine, but still could not figure out what is wrong with original page.

Anyway thanks a lot for your help and support.