any idea about asynchronous drop downlist, on selected item of drop downlist with out causing server round trip how can we populate selected item into textbox.(with out postback or callback)

Hey Use AJAX Extension controls .Which are available at http://ajax.asp.net/default.aspx?tabid=47 .Download and install and use it.DOcumentation also there you can download it use it.

coming to your problem I solved using AJAX controls as

<script runat="server">

    protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
        TextBox1.Text = DropDownList1.SelectedItem.Value;
    }
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:ScriptManager ID="ScriptManager1" runat="server">
        </asp:ScriptManager>
        <asp:UpdatePanel ID="UpdatePanel1" runat="server">
            <ContentTemplate>
                <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged"
                    Width="100px">
                    <asp:ListItem Selected="True">first_item</asp:ListItem>
                    <asp:ListItem>second_item</asp:ListItem>
                </asp:DropDownList>
                <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
            </ContentTemplate>
        </asp:UpdatePanel>

    </div>
    </form>
</body>
</html>

I think this works

aravindkishore, please use code tags when you post code. :icon_wink:

error creating update panel any idea

Did you put the Update panel under the Script Manager? And did you install the AjaxToolKitExtender.vsi?

yes i had installed AjaxToolKitExtender.vsi other than update panel i can see all controls

never mind i got javascript without postback in dropdownlist