Software developer can encrypt an individual page only if a control specifically requests it using ViewStateEncryption-Mode property of the Page directive:
<%@Page ViewStateEncryptionMode=”Auto”>
The developer can set the same attribute in a configuration file:
<configuration xmlns =>     <system.web>         <pages viewStateEncryptionMode=”Auto”>         …     </system.web> </configuration>
Note: Encryption imposes a performance penalty, because the web server will perform the encryption and decryption with each postback.  Don’t encrypt view state if you don’t need to do it.

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