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Page.ViewStateUserKey Property

Updated: October 2009

Assigns an identifier to an individual user in the view-state variable associated with the current page.

Namespace:  System.Web.UI
Assembly:  System.Web (in System.Web.dll)

public string ViewStateUserKey { get; set; }
<asp:Page ViewStateUserKey="String" />

Property Value

Type: System.String
The identifier for the individual user.


The ViewStateUserKey property was accessed too late during page processing.

Setting the ViewStateUserKey property can help you prevent attacks on your application from malicious users. It does this by allowing you to assign an identifier to the view-state variable for individual users so that they cannot use the variable to generate an attack. For more information about Web attacks and about what you can do to help prevent them, see Take Advantage of ASP.NET Built-in Features to Fend Off Web Attacks.

You can set this property to any string value, such as the user's authenticated name or the SessionID value.


You must set this property during the Page_Init phase of page processing. Setting this property during the Page_Load phase throws an exception.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1




October 2009

Added a link to information about Web attacks that might be prevented by using this property.

Customer feedback.