VerifyRenderingInServerForm : no suitable method found to override

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ASP.NET

I am writing a code to export to excel a gridview. I am using updatepanel, so whole page doesnot loads. So, i wrote a code :

aspx.cs Code

protected void Export_click(object sender, EventArgs e)
    {
        GridView gv = (GridView)TBMMasterContentPalceHolder.FindControl("myGridView");
        Response.Clear();
        Response.AddHeader("content-disposition", "attachment;filename=Suppliers.xls");
        Response.Charset = "";
        Response.ContentType = "application/vnd.xls";
        System.IO.StringWriter stringWrite = new System.IO.StringWriter();
        System.Web.UI.HtmlTextWriter htmlWrite = new HtmlTextWriter(stringWrite);
        gv.RenderControl(htmlWrite);
        Response.Write(stringWrite.ToString());
        Response.End();

    }
    public override void VerifyRenderingInServerForm(Control control) //To prevent Export To Excel Error
    {
    }

asp Code

<asp:Button ID="btnExport" runat="server" Text="  Export  " OnClick="Export_click" />
<Triggers>
        <asp:PostBackTrigger ControlID="btnExport" />
</Triggers>

But here, i am getting the error in VerifyRenderingInServerForm(Control control) function. Error is :

no suitable method found to override

How to solve the error ?