Application - store state applicable to all users
Cache - store state for every user, expiration can be set, can set dependencies regarding expiration
Database-driven Session - store session objects using SQL server Control State - provides state for control
Cookie - store state directly in file system of client, client can reject cookies
Hidden Field - store state directly in page markup
querystring - store state in URL
View State - encode state within page's markup InProc - session state is in-process with ASP.NET worker process, default
Off - no session is made available
StateServer - session state is stored on an out of process server
SQLServer - session state is stored on an out of process SQL server provides best performance
requires server affinity
state will be lost if app or server restarts

    <sessionState
        mode="InProc"
        cookieless="false"
        timeout="20" />

uses Windows service named ASPState
start service using command prompt

    C:\Windows\Microsoft.NET\Framework\v4.0.30319\net start aspnet_state

setting session object to use StateServer option with defaults

    <sessionState
        mode="StateServer"
        stateConnectionString="tcpip=127.0.0.1:42424"
        sqlConnectionString="data source=127.0.0.1;user=sa;password="
        cookieless="false"
        timeout="20" />

same as StateServer mode except use SQL server
run install script

    C:\Windows\Microsoft.NET\Framework\v4.0.30319\OSQL localhost -U sa -P pwd -I InstallSqlState.sql

-U : assigned user name
-P : password

    <sessionState
        mode="SQLServer"
        stateConnectionString="tcpip=127.0.0.1:42424"
        cookieless="false"
        timeout="20" />

declare on each page how the page is to deal with Session object

   <%@ Page language="C#" EnableSessionState=&"True" CodeFile="Default.aspx.cs" Inherits="_Default" %>

EnableSessionState options output caching saves post-rendered content so that it will not have to be regenerated for subsequent requests

    <%@ OutputCache Duration="60" VeryByParam="None" %>

Duration - number of seconds a page is stored in the cache
VaryByParam - determines which versions of the page are cached caching is ASP.NET is a trade-off between CPU & memory
in last example the number of possible cache items can be determined by

    cacheItems = (number of pageIds) * (number of subPageIds) * (number of possible languages)

with 10 potential page IDs, five potential subpage IDs & 4 possible languages there can be 200 versions of the page to be cached
need to consider resource expense difference between caching and building a page can extended how outputCache directive works
need to create custom output-cache provider
derived type must override the base class' Add, Get, Remove & Set methods
configuring for custom provider in web.config or machine.config

    <caching>
        <outputCache defaultProvider="AspNetInternalProvider">
            <providers>
                <add name="myCustomProvider" 
                     type="foo.bar.CustomProvider, CustomProvider" />
            </providers>
        </outputCache>
    </caching>

cache directive

    <%@ OutputCache Duration="90" VaryByParam="pageId,subpageId" providerName="myCustomProvider" %>

cache only specific blocks of web page
achieved by caching user controls
modular design required
by default user controls are cached on a per page basis
change by using Shared attribute

    <%@ OutputCache Duration="90" VaryByParam="pageId,subpageId" Shared="true" %>

cached user control exists only for the first request
if HTML is retrieved from the OutputCache the control does not exist on the .aspx page
PartialCachingControl is created and acts as proxy

    protected void Page_Load()
    {
        if(PossiblyCachedControl != null)
        {
            // code to manipulate control
        }
    }

what was in System.Web.Caching has be refactored into System.Runtime.Caching
lets other app types use caching without the need for System.Web dll can cache SOAP responses

    [WebMethod(CacheDuration=60)]
    public string GetServerTime()
    {
        return DateTime.Now.ToLongTimeString();
    }