Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.



Published on


  • Be the first to comment

  • Be the first to like this


  1. 1. Microsoft ASP.NET: An Overview of Caching Holly Mazerolle Developer Support Engineer Microsoft Developer Support Microsoft Corporation
  2. 2. Overview <ul><li>Introduction to ASP.NET caching </li></ul><ul><li>Output caching </li></ul><ul><li>Fragment caching </li></ul><ul><li>Data caching </li></ul>
  3. 3. Introduction to Caching in ASP.NET <ul><li>Caching is the most critical factor in creating scalable, high performance Web applications </li></ul><ul><li>Caching locations </li></ul><ul><ul><li>Web server, proxy server, and client browsers </li></ul></ul><ul><li>Types of caching </li></ul><ul><ul><li>Output caching </li></ul></ul><ul><ul><li>Fragment caching </li></ul></ul><ul><ul><li>Data caching </li></ul></ul>
  4. 4. Output Caching <ul><li>What is output caching? </li></ul><ul><li>@ OutputCache directive and the cache object </li></ul><ul><li>Output caching attributes: </li></ul><ul><ul><li>Duration </li></ul></ul><ul><ul><li>Location </li></ul></ul><ul><ul><li>VaryByParam </li></ul></ul><ul><ul><li>VaryByHeader </li></ul></ul><ul><ul><li>VaryByCustom </li></ul></ul>
  5. 5. What Is Output Caching? <ul><li>Pages that use the output cache are executed one time, and the page results are cached </li></ul><ul><li>The pre-executed page is then served to later requests </li></ul><ul><li>Performance and scalability both benefit </li></ul><ul><ul><li>Server response times reduced </li></ul></ul><ul><ul><li>CPU load reduced </li></ul></ul><ul><li>Appropriate caching of pages affects site performance dramatically </li></ul>
  6. 6. @ OutputCache Directive and the Cache Object <ul><li>@ OutputCache declaratively controls caching behavior </li></ul><ul><ul><li>For .aspx, .asmx, or .ascx </li></ul></ul><ul><li>The cache object programmatically controls caching behavior </li></ul><%@ OutputCache Duration=&quot;600“ Location=&quot;Any“ VaryByParm=“none” %> Is equivalent to: [C#] Response.Cache.SetExpires(DateTime.Now.AddSeconds(600)); Response.Cache.SetCacheability(HttpCacheability.Public);
  7. 7. OutputCache Members: Duration and Location <ul><li>Duration sets the time to cache the output </li></ul><ul><ul><li>In seconds </li></ul></ul><ul><ul><li>Required </li></ul></ul><ul><li>Location sets the location to cache the output </li></ul><ul><ul><li>Server : The output is held in memory on the Web server and is used to satisfy requests </li></ul></ul><ul><ul><li>Downstream : A header is added to the response to indicate to proxy servers to cache the page </li></ul></ul><ul><ul><li>Client : A header is added to the response indicating to browsers to cache the page </li></ul></ul><ul><ul><li>Any : Output cache can be located on any of these locations </li></ul></ul><ul><ul><li>None : No output caching is turned on for the item </li></ul></ul><%@ OutputCache Duration=&quot;600&quot; Location=&quot;Any“ VaryByParam=“none” %>
  8. 8. OutputCache Members: VaryByParam and VaryByHeader <ul><li>VaryByParam </li></ul><ul><ul><li>The cache stores multiple copies of a page based on specific Querystring or Form parameters and any combinations thereof </li></ul></ul><ul><li>VaryByHeader </li></ul><ul><ul><li>The cache stores multiple copies of a page based on HTTP headers </li></ul></ul><%@ OutputCache Duration=&quot;10“ VaryByParam=&quot;location;count&quot; %> <%@ OutputCache Duration=&quot;60“ VaryByHeader=&quot;Accept-Language&quot; %>
  9. 9. OutputCache Members: VaryByCustom <ul><li>VaryByCustom </li></ul><ul><ul><li>If the value is “Browser,” cache varies by browser type and major version </li></ul></ul><ul><ul><li>If the value is a custom string, you must override HttpApplication.GetVaryByCustomString in the Global.asax and implement your own caching logic </li></ul></ul>
  10. 10. Fragment Caching <ul><li>What is fragment caching? </li></ul><ul><li>VaryByControl </li></ul><ul><li>Nested cached user controls </li></ul><ul><li>Cached controls are not programmable </li></ul>
  11. 11. What Is Fragment Caching? <ul><li>Just as you can vary the versions of a page that are output cached, you can output cache regions of a page </li></ul><ul><li>Regions are defined based on user controls </li></ul><ul><li>User controls contain their own @OutputCache directive </li></ul><ul><li>Fragment caching supports </li></ul><ul><ul><li>VaryByParam </li></ul></ul><ul><ul><li>VaryByControl </li></ul></ul><ul><li>Location not supported because fragments must reside on server to be assembled </li></ul>
  12. 12. Fragment Caching a User Control <ul><li>[*.ascx] </li></ul><ul><li><%@ Language=&quot;C#&quot; %> </li></ul><ul><li><%@ OutputCache Duration=&quot;10“ VaryByControl=&quot;State;Country&quot; </li></ul><ul><li>VaryByParam=&quot;*&quot;%> </li></ul><ul><li><script runat=server> </li></ul><ul><li>public String State { </li></ul><ul><li>get { return state.Value; } </li></ul><ul><li>set { state.Value = State; } } </li></ul><ul><li>public String Country { </li></ul><ul><li>get { return country.Value; } </li></ul><ul><li>set { country.Value = Country; } } </li></ul><ul><li></script> </li></ul>
  13. 13. VaryByControl <ul><li>VaryByControl </li></ul><ul><ul><li>The sixth attribute supported by OutputCache </li></ul></ul><ul><ul><li>Only supported in user control caching </li></ul></ul><ul><ul><li>Caching is based on user control properties </li></ul></ul><%@ OutputCache Duration=&quot;10“ VaryByControl=&quot;State;Country“ VaryByParam=&quot;*&quot;%>
  14. 14. Nested Cached User Controls <ul><li>User controls can be nested </li></ul><ul><li>Cached user controls can also be nested </li></ul><ul><li>Since multiple versions of a user control are cached, this creates a hierarchy of cached output </li></ul><ul><li>This caching tree </li></ul><ul><ul><li>Is very efficient and powerful </li></ul></ul><ul><ul><li>Requires almost nothing from a developer </li></ul></ul><ul><li>Varying by many properties could create a large tree, and therefore, a large memory footprint </li></ul>
  15. 15. Cached Controls Are Not Programmable <ul><li>Do not try to programmatically access a user control that is in the cache </li></ul><ul><li>Cached controls are not added to the control tree </li></ul><ul><li>Trying to access a cached control will throw an exception </li></ul>
  16. 16. Data Caching <ul><li>What is data caching? </li></ul><ul><li>Working with the cache object </li></ul><ul><li>Cache dependencies </li></ul><ul><li>Scavenging memory </li></ul><ul><li>Using callbacks with caching </li></ul>
  17. 17. What Is Data Caching? <ul><li>The data cache holds application data such as strings, datasets, and other objects </li></ul><ul><li>Adding items to the data cache is easy </li></ul><ul><li>Although similar to the familiar application variables model, it is much more powerful </li></ul>Cache (“counter”) = mycount.text Application(“counter”) = mycount.text
  18. 18. Working with the Cache Object <ul><li>Cache object features </li></ul><ul><ul><li>Dependencies allow logic to invalidate cached items </li></ul></ul><ul><ul><li>Scavenging (automatic expiration) </li></ul></ul><ul><ul><li>Callbacks when an item is removed from cache </li></ul></ul><ul><li>To use dependencies or callbacks, use Cache.Insert or Cache.Add </li></ul><ul><li>Code using cached items must be able to both create or insert, and retrieve cached items </li></ul>Public Function GetProductData() As DataSet If (IsNothing(Cache(&quot;ProductData&quot;)) Then Cache(&quot;ProductData&quot;) = LoadDataSet()   Return Cache(&quot;ProductData&quot;) End Function
  19. 19. Cache Dependencies <ul><li>File-based dependencies </li></ul><ul><ul><li>Cached item invalidated when files change </li></ul></ul><ul><li>Key-based dependencies </li></ul><ul><ul><li>Cached item invalided when another cached item changes </li></ul></ul><ul><li>Time-based dependencies </li></ul><ul><ul><li>Absolute time-based invalidations </li></ul></ul><ul><ul><li>Sliding time-based invalidations </li></ul></ul>
  20. 20. Scavenging Memory <ul><li>Automatic system that initiates when memory becomes scarce </li></ul><ul><li>Tag cached items with relative importance </li></ul><ul><ul><li>CacheItemPriority </li></ul></ul><ul><ul><li>CacheItemPriorityDecay </li></ul></ul><ul><li>Items must be added to cache using .Add or .Insert to make use of these enumerations </li></ul>
  21. 21. Using Callbacks with Caching <ul><li>Create Callbacks with this delegate: </li></ul><ul><li>CacheItemRemovedCallback </li></ul><ul><li>Callbacks are used to receive notification when an item is evicted from the cache </li></ul><ul><ul><li>Cleanup </li></ul></ul><ul><ul><li>Update </li></ul></ul><ul><ul><li>Recreate </li></ul></ul><ul><ul><li>Logging </li></ul></ul><ul><li>Items must be added to caching using .Add or .Insert to use callback functionality </li></ul>
  22. 22. Review <ul><li>Code that uses items from the data cache must be able to create the object, load the cache, or retrieve the object before using it. </li></ul><ul><li>Caching can hide problems. Test without caching. </li></ul><ul><li>Use tracing, performance counters, and stress software to identify caching wins. </li></ul>
  23. 23. Additional Information about Caching <ul><li>INFO: ASP.NET Caching Overview </li></ul><ul><li>HOW TO: Control Page Output Caching in ASP.NET by Using Visual Basic .NET </li></ul><ul><li>HOW TO: Perform Fragment Caching in ASP.NET by Using Visual Basic .NET </li></ul>
  24. 24. <ul><li>Thank you for joining today’s Microsoft Support </li></ul><ul><li>WebCast. </li></ul><ul><li>For information about all upcoming Support WebCasts, </li></ul><ul><li>and access to the archived content (streaming media </li></ul><ul><li>files, PowerPoint ® slides, and transcripts), please visit: </li></ul><ul><li>http:// / </li></ul><ul><li>Your feedback is sincerely appreciated. Please send any </li></ul><ul><li>comments or suggestions about the Support </li></ul><ul><li>WebCasts to [email_address] . </li></ul>