.NET 2.0 C# VS make dropdownlist visible/invisible via radio button control (client side)

I have a radiobuttonlist with 2 choices,  "car" or "truck".

If "car" is selected, I want 2 different dropdownlists (dd1 and dd2) to appear!

However if " truck" is selected, I want dropdownlist (dd3) to appear and dd1 and dd2 to disappear.

The opposite is true if "car" is selected, dd3 will disappear and dd1 and dd2 will appear again.

When the web page first appears,  dd1, dd2 and dd3 dropdownlists are all invisible and radiobuttonlist is not selected ?

Need something simple.

Thanks for help here.
RSSIAdminAsked:
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mrichmonCommented:
Well the above while simple, is not user freidnly as it submits the page each time the user changes a radio button, so then you have to deal with scroll isuues, etc.

Better is to have all have the Visible=true and allow javascript to select which show up on the screen.

The javascript would look like:

function updateDDLs()
{
    if(rbl[0].checked)
    {
        dd1.style= "";
        dd2.style= "";
        dd3.style= "display:none;";
     }
    else if(rbl[1].checked)
    {
        dd1.style= "display:none;";
        dd2.style= "display:none;";
        dd3.style= "";
     }
   else
    {
        dd1.style= "display:none;";
        dd2.style= "display:none;";
        dd3.style= "display:none;";
     }
}

Then the drpdowns look need to start out with style="display: none;" and need an onChange="updateDDLs();" attribute.

Then it will dynamically update without submitting/reloading the page each time the user makes a change.
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whityumCommented:
turn on autopostback for the rbl, have a function for onselectedindexchanged, and say
if(rbl.SelectedValue == "car"){
dd1.Visible = true;
dd2.Visible = true;
dd3.Visible = false;
}else{
dd1.Visible = false;
dd2.Visible = false;
dd3.Visible = true;
}
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whityumCommented:
also have visible = false in the tag on the aspx page.
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whityumCommented:
he will have to get the client IDs of the drop downs if he does it that way.
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RSSIAdminAuthor Commented:
mrichmon ---

Thanks so much for the input. (both look good!)  The Javascript would save round trips

Does above show all the code I will need to get this  to work. For example do I need some kind of pointer or  reference  to rb1[0] and rb2 etc.  like form.document.rb1.. etc  ?  what is style?

function updateDDLs()
{
    if(rbl[0].checked)
    {
        dd1.style= "";
        dd2.style= "";
        dd3.style= "display:none;";
     }


Help, Tom
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whityumCommented:
.Net assigns an ID you can access via the ClientID property, e.g. rbl.ClientID.ToString()

you would have to build the javascript string dynamically, like
string s = "if(document.form[0]." + rbl.ClientID.ToString() + ".checked == true){";
s += "{";
s += "document.form[0]." + dd1.ClientID.ToString() + ".style = 'display: inline';"
....

and register the script to the page




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mrichmonCommented:
Yes.

It would be

document.getElementById("rbl")[0].checked
for the radio button.

Basically you use document.getElementById("ID of control")

This works for the ID you assign from the asp page as long as it is not repeated in a repeater.
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RSSIAdminAuthor Commented:

Thanks so much for the answer to my questions.

Tom
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