how to get a client id from ajax tab container - asp.net

Question

i didn't get id from ajax tabcontainer
HERE code id need to get a id from tab_container how to do !!!!!!!
<script type="text/javascript">
function my()
{
var con = document.getElementById("TabContainer1").value;
alert(con);
}
</script>
<asp:TabContainer ID="TabContainer1" runat="server" ActiveTabIndex="0" Height="100%" Width="50%">
<asp:TabPanel ID="tabpnl1" runat="server" HeaderText="Role Master">
<ContentTemplate>
<asp:TextBox ID="TextBox1" runat="server" ></asp:TextBox>
<asp:Button ID="btn" runat="server" OnClientClick="my()" />
</ContentTemplate>
</asp:TabPanel>
its shows undefined

Answer 1

to get TabContainer1 in javascript you need to change logic of your javascript function
instead of
function my()
{
var con = document.getElementById("TabContainer1").value;
alert(con);
}
try using
function my()
{
var con = document.getElementById("<%= TabContainer1.ClientID %>");
alert(con);
}
As runtime while loading element in dom its ID will be changed. So instead of using static id as "TabContainer1" you can get ClientID which will be rendered at DOM.
Also value will not be work I guess as its container so its better to use .innerHTML instead of .value.
or alternative you can change your html tag
<asp:TabContainer ID="TabContainer1" runat="server" ActiveTabIndex="0" Height="100%" Width="50%" ClientIDMode="Static">
I have added ClientIDMode="Static" so it will use "TabContainer1" in DOM as static id will be generated. In this case, you do not need to change your javascript code.
Hope this help