my objects dissaper after postback

here i am giving needed code
i cant reach objects after button clicked
 
 
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2 <%@ Page Language="C#" AutoEventWireup="true" CodeFile="SelectWhichPokemon.aspx.cs" Inherits="SelectWhichPokemon" %>
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4 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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6 <html xmlns="http://www.w3.org/1999/xhtml">
7 <head id="Head1" runat="server">
8 <title&g ...