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Programming Visual Basic 2005 by Jesse Liberty

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State

State is the current value of all the controls and variables for the current user in the current session. The Web is inherently a stateless environment, which means that every time a page is posted to the server and then sent back to the browser, the page is recreated from scratch. Unless you explicitly preserve the state of all the controls before the page is posted, the state is lost and all the controls are created with default values. One of the great strengths of ASP.NET is that it automatically maintains state for server controls—both HTML and ASP. This section will explore how that is done and how you can use the ASP.NET state management capabilities.

ASP.NET manages three types of state :

  • View state (which is saved in the state bag)

  • Application state

  • Session state

Table 8-2 compares the different kinds of state.

Table 8-2. State types

Variables

View state

Application state

Session state

Uses server resources

No

Yes

Yes

Uses bandwidth

Yes

No

Depends

Times out

No

No

Yes

Security exposure

Yes

No

Depends

Optimized for nonprimitive types

No

Yes

Yes

Available for arbitrary data

Yes

Yes

Yes

Programmatically accessible

Yes

Yes

Yes

Scope

Page

Application

Session

Survives restart

Yes

No

Depends

The following sections will examine each type of state.

View State

The view state is the state of the page and all its controls. The view state is automatically maintained across posts by the ASP.NET Framework. When a page is posted to the server, the ...

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