DropdownList autoposback after client confirmation - asp.net

Question

I have a dropdownlist with the autopostback set to true. I want the
user to confirm if they really want to change the value,
which on post back fires a server side event (selectedindexchanged).
I have tried adding an onchange attribute "return confirm('Please click OK to change. Otherwise click CANCEL?';") but it will not postback regardless of the confirm
result and the value in the list does not revert back if cancel
selected.
When I remove the onchange attribute from the DropdownList tag, the page does postback. It does not when the onchange attribute is added. Do I still need to wire the event handler (I'm on C# .Net 2.0 ).
Any leads will be helpful.
Thanks!

Answer 1

Have you tried to set the onChange event to a javascript function and then inside the function display the javascript alert and utilize the __doPostback function if it passes?
i.e.
drpControl.Attributes("onChange") = "DisplayConfirmation();"
function DisplayConfirmation() {
if (confirm('Are you sure you want to do this?')) {
__doPostback('drpControl','');
}
}

Answer 2

You can utilize the the CustomValidator control to "validate" dropdown by calling a javascript function in which you do the confirm():
<asp:DropDownList ID="TestDropDown" runat="server" AutoPostBack="true" CausesValidation="true"
ValidationGroup="Group1"
OnSelectedIndexChanged="TestDropDown_SelectedIndexChanged">
<asp:ListItem Value="1" Text="One" />
<asp:ListItem Value="2" Text="Two" />
</asp:DropDownList>
<script type="text/javascript">
function ConfirmDropDownValueChange(source, arguments) {
arguments.IsValid = confirm("Are you sure?");
}
</script>
<asp:CustomValidator ID="ConfirmDropDownValidator" runat="server"
ClientValidationFunction="ConfirmDropDownValueChange" Display="Dynamic" ValidationGroup="Group1" />

Answer 3

The following works when the DropDownList is triggering partial postbacks:
// caching selected value at the time the control is clicked
MyDropDownList.Attributes.Add(
"onclick",
"this.currentvalue = this.value;");
// if the user chooses not to continue then restoring cached value and aborting by returning false
MyDropDownList.Attributes.Add(
"onchange",
"if (!confirm('Do you want to continue?')) {this.value = this.currentvalue; return false};");

Answer 4

Currently, you're always returning the result of the confirm(), so even if it returns true, you'll still stop execution of the event before the postback can fire. Your onchange should return false; only when the confirm() does, too, like this:
if (!confirm('Please click OK to change. Otherwise click CANCEL?')) return false;

Answer 5

Overriding the onchange attribute will not work if you have have AutoPostBack set to true because ASP.NET will always append the following to the end of your onchange script:
;setTimeout('__doPostBack(\'YourDropDown\',\'\')', 0)
If you set AutoPostBack to false, then overriding onchange with a "confirm and __doPostBack" type script (see above, err.. below) will work but you may have to manually create the __doPostBack function.

Answer 6

if (!confirm('Please click OK to change. Otherwise click CANCEL?')) return false;
Always returns so dropdownlist's OnSelectedIndexChanged event fires whether user clicks OK or CANCEL.

Answer 7

Make sure your event is wired:
dropDown.SelectedIndexChanged += new EventHandler(dropDown_SelectedIndexChanged);
You can also apply a client-side attribute to return the confirmation. Set the index accordingly if cancelled.
dropDown.Attributes.Add("onchange", "javascript: return confirm('confirmation msg')");

Answer 8

<asp:DropDownList runat="server" ID="ddlShailendra" AutoPostBack="True" OnSelectedIndexChanged="ddlShailendra_SelectedIndexChanged" onchange="javascript: { if(confirm('Click ok to prevent post back, Cancel to make a postback'))return true;} " >
<asp:ListItem Text="tes" Value="1" ></asp:ListItem>
<asp:ListItem Text="test" Value="-1"></asp:ListItem>
</asp:DropDownList>
Write the function inline and dont have a "return" for the condition in which you want a post back. This works and is as per the standards.