JavaScript function:
function setValidations() {
var ddlst = document.getElementById(“<%=ddlPiggyback.ClientID%>”);
var Text = ddlst.options[ddlst.selectedIndex].text;
if (Text == ’0′) {
ValidatorEnable(document.getElementById(“<%=rfvPiggybackComments.ClientID%>”), false);
}
else {
ValidatorEnable(document.getElementById(“<%=rfvPiggybackComments.ClientID%>”), true);
}
}
In drop down (aspx side)
<asp:DropDownList ID=”ddlPiggyback” runat=”server” onchange=”setValidations();”>
<asp:ListItem>0</asp:ListItem>
<asp:ListItem>1</asp:ListItem>
<asp:ListItem>2</asp:ListItem>
</asp:DropDownList>