First do the necessary at server then save the control Panel in the session at Page MainPage.aspx
protected void btn_Click(object sender, EventArgs e)
{
Session["Ctrl"] = pnlContainer;//Panel ID
Response.Redirect("print.aspx");
}
Create a new page with the print.aspx, Html Code as follows:
Add Content PlaceHolder to html with name ph
"<asp:PlaceHolder ID="ph" runat="server" />