Post Back not working in aspx page

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C#

ASP.NET

Hi All,

I'm new in .Net. I've a faced a problem. I'm using an aspx page that is inherited from master page in Visual Studio 2010. I've found that PostBack is not working for LinkButton click event & DropDownList indexChanged. Though normal Button & ImageButton is working fine. Please help me how DropDownList & LinkButton will work...

Here is my full code.

<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder_Body" runat="server">
<asp:DropDownList ID="ddlPageSelector" runat="server" AutoPostBack="True" OnSelectedIndexChanged="ddlPageSelector_SelectedIndexChanged">
                                                    </asp:DropDownList>
</asp:Content>

protected void ddlPageSelector_SelectedIndexChanged(object sender, EventArgs e)
        {
            Response.Write(ddlPageSelector.SelectedValue);
        }

But same code is working in VisualStudio 2008.
Please help me out ...