Understanding State Management in ASP.NET: Key Concepts and Examples

1. State Management Not like the State of Virginia

2. What is State in ASP.NET? • Services (like web services) are Stateless. • This means if you make a second request to a server, it will not remember what your last request was. • ASP.NET adds the concept of State to web pages • This allows you to have objects persist across page requests

3. Why Use State? • Almost every page online uses state • It’s hard to find a meaningful static web page • State allows pages to dynamically respond to different users and events • Example Uses: • Enforcing page authentication • Remembering your shopping cart • Personalized search results

4. State Objects • Simply put: a collection of objects • Collection<string, object> • Ex: Session[“UserId”] = 4; • Objects: • Session • ViewState • Application • Cache • Cookies

5. Session • Lifetime: • From the first request til timeout/cleared session • It is possible for session to last longer than the server host if stored using SQL Session Storage • Scope: • Only to the owner of the session • Persists across pages. Inaccessible from other sessions • Usage: • Accessing data shared across pages (ex. Login info)

6. ViewState • Lifetime: • The life of the page • Rendered to the page • Scope: • Just that request. Does not persist across pages or across sessions • Rebuilt for the following requests • Usage: • Control selection data (form data, checkbox selections, drop down list selections, etc.)

7. ViewState <inputtype="hidden"name="__VIEWSTATE"id="__VIEWSTATE"value="/wEPDwUKMTc0NTQxNTAwMWQYAQUeX19Db250cm9sc1JlcXVpcmVQb3N0QmFja0tleV9fFgMFKWN0bDAwJENvbnRlbnRQbGFjZUhvbGRlcjEkQ2hlY2tCb3hMaXN0MSQwBSljdGwwMCRDb250ZW50UGxhY2VIb2xkZXIxJENoZWNrQm94TGlzdDEkMQUpY3RsMDAkQ29udGVudFBsYWNlSG9sZGVyMSRDaGVja0JveExpc3QxJDFN/3diiSeYfuwsveCFZkB8GZhziyh9fxFB4N3DEHI9Ow=="/>

8. Application • Lifetime: • The life of the application • Persists until the service restarts • Scope: • The entire application • All users in all sessions have access to this object • Usage: • Application wide settings • Configuration settings

9. Cache • Lifetime: • Until the cached object expires • Scope: • Application wide • All users in all sessions have access to this object • Usage: • Stored commonly accessed data

10. Cookies?

11. Cookies • Lifetime: • Lifetime of the cookie • Be kind to your users. Don’t forget to set an expiration date on your cookies • Scope: • The browser • Can be accessed on any page in the cookie’s domain (determined by browser security settings) • Usage: • Quenching random hunger cravings

12. Don’t do this:

13. Strongly Typed State • Remember: a collection of objects • Collection<string, object> • You can store any object in these collections • What if you want to restrict the types objects stored in the State? • Enforce type in a typeless environment • Removes confusion about what’s stored in the object

14. Strongly Typed State publicintUserId { get { if (!(Session["UserId"] isint)) Session["UserId"] = -1; return (int)Session["UserId"]; } set { Session["UserId"] = value; } }