Hi
If our requirement is make visible the textbox field while “other” selection on dropdown then we can achieve using so many ways .
For example using Javascript,Jquery,or autopostback event on dropdown. But javscript or jquery is the best method to do this task. It will avoid the post back on server so performance of page will be faster.
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="JavaScriptTest.aspx.cs" Inherits="JavaScriptTest" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title><script type="text/javascript">
function Unvisible()
{
document.getElementById("TextBox1").style.visibility="hidden";
}function FilterStatus()
{
var drpFilterType = document.getElementById("drpFilterType");
var selectedFilterType = drpFilterType
.options[drpFilterType.selectedIndex].value;if (selectedFilterType == "Other")
{document.getElementById("TextBox1").style.visibility="visible";
}
else
{
document.getElementById("TextBox1").style.visibility="hidden";
}}
</script></head>
<body onload = "javascript:Unvisible();">
<form id="form1" runat="server">
<div>
<asp:dropdownlist id="drpFilterType" runat="server"
onchange="return FilterStatus()" >
<asp:ListItem Value="MonthFilter">Month</asp:ListItem>
<asp:ListItem Value="YearFilter">Year</asp:ListItem>
<asp:ListItem Value="Other">Other</asp:ListItem>
</asp:dropdownlist><br />
<br />
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
</div>
</form>
</body>
</html>
Chandradev's Blog 
instead of writing following line or code and calling on load event, why you not call FilterStatus function on dropdown load event
function Unvisible()
{
document.getElementById(“TextBox1″).style.visibility=”hidden”;
}
Hi
Thanks for your comment. Here on page load i m making textboxt visible false and while select “other” in dropdown i m calling “FilterStatus()” on onchange event.
we can also call “filterStatus()” function on page load or onchange event.It will give same op.
I try ur answer buti can’t get it
Hi
It was working code. Could you tell me what error are you getting ? There might be syntax error while doing copy paste of code.
It gives error:
Microsoft JScript runtime error: Object expected
Hi @raheel
Plz Keep the break point in your javascript and confirm that the selected value is coming or not. This error generally come in this senario
hi
when using master pages we don’t have body tag .then where we need to call onload method