c# - Button click to add string to List<string> -

i have button when clicked take text of what's inside text box , add list of strings. then, have button when clicked output count of list text box. keep on getting count of zero, no matter try. can me i'm doing wrong?

c#

using system; using system.collections.generic; using system.linq; using system.web; using system.web.ui; using system.web.ui.webcontrols;  public partial class _default : system.web.ui.page {     list<string> itemlist = new list<string>();     protected void page_load(object sender, eventargs e)     {      }     protected void button1_click(object sender, eventargs e)     {         itemlist.add(txtitem.text);         txtitem.text = "";     }     protected void button2_click(object sender, eventargs e)     {         txtitemlistcount.text = itemlist.count.tostring();      } } 

markup

<%@ page title="home page" language="c#" masterpagefile="~/site.master" autoeventwireup="true"     codefile="default.aspx.cs" inherits="_default" %>  <asp:content id="headercontent" runat="server" contentplaceholderid="headcontent"> </asp:content> <asp:content id="bodycontent" runat="server" contentplaceholderid="maincontent">       <asp:textbox id="txtitem" runat="server"></asp:textbox>     <asp:button id="button1" runat="server" onclick="button1_click" text="button" />     <br />     <br />     <asp:textbox textmode="multiline" id="txtitemlistcount" runat="server"></asp:textbox>     <br />     <br />     <asp:button id="button2" runat="server" text="button 2"          onclick="button2_click" />   </asp:content> 

change

list<string> itemlist = new list<string>(); 

to

string itemlistkey = "itemlistkey"; list<string> itemlist {     {      if ( session[itemlistkey] == null )         session[itemlistkey] = new list<string>();      return (list<string>)session[itemlistkey];   } }