I am currently working on validating a dropdown list on the client side based on its selected index/value. My goal is to create a function that triggers an alert when the selected index is 0, or alternatively execute the SelectedIndexChandged method in the code behind.
The following code snippet has been developed for this purpose:
function validateDropDown() {
var indexService = document.getElementById('<%= ddlService.ClientID>').selectedIndex;
var indexTower = document.getElementById('<%= ddlManager.ClientID>').selectedIndex;
if (indexTower == 0) {
document.getElementById('<%= ddlService.ClientID%>').disabled = true;
document.getElementById('<%= ddlDate.ClientID%>').disabled = true;
alert("Please select a Tower");
return false;
}
else{
document.getElementById('<%= ddlService.ClientID%>').disabled = false;
document.getElementById('<%= ddlDate.ClientID%>').disabled = false;
_doPostBack('<%= ddlManager.ClientID%>');
}
}
However, I am encountering an error at runtime with the following line of code:
_doPostBack('<%= ddlManager.ClientID%>');
The specific error message being displayed is:
Javascript Runtime error : Object required.
It's worth noting that my application includes a master page and the dropdown list in question resides within the content page.
If anyone could provide assistance with resolving this issue, it would be greatly appreciated. Thank you in advance!