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New Message on BDOTNET
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From: mygoodwill770521
Message 1 in Discussion
Improving page performance. By trimming the view state where you can live
without it you do yourself and others a favor by reducing payload and improving
page performance. ASP.NET view state is a great feature and an essential tool
for web development of today. It maintains the state of a page as it travels
back and forth. There is no more need to worry about restoring values of page
controls between postbacks. The view state of a page is, by default, placed in
a hidden form field named __VIEWSTATE. This hidden form field can easily get
very large, on the order of tens of kilobytes. Not only does the __VIEWSTATE
form field cause slower downloads, but, whenever the user posts back the Web
page, the contents of this hidden form field must be posted back in the HTTP
request, thereby lengthening the request time, as well. The web is stateless,
For example, you request an ASP.NET page from a web server. Once the page is
processed on the server and returned to you that same server does not remember
the page anymore. Even a slight page postback initiates the same request
sequence and the web server performs the same task again as if it never saw
this page in the first place. This is the grand difference between web
applications and their desktop counterparts. On the desktop you can maintain
state between requests. On the web it�s a much harder task View state is simply
text. It is an aggregate of values of controls on a page. It's a string that
contains values of page controls hashed and encoded in some manner. The view
state contains no information about the server or the client. It only comprises
information about the page itself and its controls. It lives along with the
page in the user's browser.
If you view the source of an ASP.NET web form you will see something like this:
<input type="hidden" name="__VIEWSTATE"
value="CEbzzzEnmmz+Bc8IDFlnpgCLJ/HB00...>
Every server control ultimately derives from the Control class. Be it a
WebControl, HtmlControl or even LiteralControl it has a property called
EnableViewState. When a page is built every control that has this property
enabled contributes to the view state by serializing its contents
State Bag class is used to manage viewstate. This class is like a
dictionary�you may store key/value pairs in it. This is how you store a piece
of useful data in the view state:
ViewState ["SortOrder"] = "email" Susan Warren has kindly put together this
decision chart of view state vs. session:
Session State View State
Holds server resources? Yes No
Times out? Yes � after 20 minutes (default) No
Stores any .NET type? Yes No, limited support for: strings, integers, Booleans,
arrays, ArrayList, hashtable, custom TypeConverters
Increases "HTML payload"? No Yes By default view state is enabled (as of
ASP.NET 1.1)
machine.config reveals this much:
<pages enableViewState="true" enableViewStateMac="true" ... />
The nature of machine.config prescribes general settings for all applications.
In other words since view state is enabled on the machine level it is enabled
on the application, page and control level. Thus each server control has view
state enabled by default
To disable view state of an individual control set its EnableViewState to false:
<asp:Label id=Label1 runat="server" EnableViewState="false" />
As a rule of thumb if a control does not contain any dynamic data, or its value
is hardcoded or assigned on every page request and you're not handling its
events you can disable the control's view state. To disable view state on an
entire page by modifying the Page directive:
<%@ Page ... EnableViewState="false" %> To disable view state on the whole web
application by adding the following line to your web.config:
<pages enableViewState="false" />
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