Set Session With Several Ways

First:how to read session
        1,  Session["key"].ToString()
        2, <%=Session["key"]%>

1. ASPX.CS
   It's easy as you know, here I'll foucus on "ASPX".
2. ASPX:

        Solution 1:  __doPostBack
      Here the initialize is necessary

 1<script runat="server">
 2    private void Page_Load(object sender, System.EventArgs e)
 3    {
 4        // Insure that the __doPostBack() JavaScript method is created
 5        this.ClientScript.GetPostBackEventReference(this, string.Empty);
 6
 7        if (this.IsPostBack)
 8        {
 9            string eventTarget = (this.Request["__EVENTTARGET"] == null) ? string.Empty : this.Request["__EVENTTARGET"];
10            string eventArgument = (this.Request["__EVENTARGUMENT"] == null) ? string.Empty : this.Request["__EVENTARGUMENT"];
11
12            if (eventTarget == "SetSessionPostBack")
13                this.Session["SessionValue"] = eventArgument;
14        }
15        else
16        {
17            this.Session["SessionValue"] = "Original value";
18        }
19        //show session value
20        this.Response.Write("SessionValue: " + this.Session["SessionValue"].ToString() + "<br>");
21    }
22</script>

 
        And here is the script call __dopostback

    <script type="text/javascript">
2        function setSessionValue(newValue) {
3            __doPostBack('SetSessionPostBack', newValue);
4        }
5    </script>

        Here to use function

    <form id="form1" runat="server">
2    <input id="Button1" type="button" value="button" onclick="setSessionValue('hello');" />
3    </form>

        Solution 2:  AjaxCall
      [tbd]