How to change SlidingExpiration property of FormsAuthentication programmatically?

To change the SlidingExpiration property of FormsAuthentication programmatically, use following code snippet.

// Get the Web application configuration.
System.Configuration.Configuration configuration = 
    WebConfigurationManager.OpenWebConfiguration("/aspnetTest");

// Get the external Authentication section.
AuthenticationSection authenticationSection = 
    (AuthenticationSection)configuration.GetSection(
    "system.web/authentication");

// Get the external Forms section .
FormsAuthenticationConfiguration formsAuthentication =
    authenticationSection.Forms;

// Get the current SlidingExpiration.
bool currentSlidingExpiration = 
    formsAuthentication.SlidingExpiration;

// Set the SlidingExpiration.
formsAuthentication.SlidingExpiration = false;