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MachineKeySection Class

Defines the configuration settings that control the key generation and algorithms that are used in encryption, decryption, and media access control (MAC) operations in Windows Forms authentication, view-state validation, and session-state application isolation. This class cannot be inherited.

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

public sealed class MachineKeySection : ConfigurationSection

The MachineKeySection class provides a way to programmatically access and modify the content of the <MachineKey> section in the configuration file. The <MachineKey> section can be configured at the machine (Machine.config) or application (Web.config) level and controls the keys and algorithms that are used for Windows Forms authentication, view-state validation, and session-state application isolation. For any of these features to work across a network of Web servers (a Web farm), the <MachineKey> attributes must be configured explicitly and identically with valid key values. The "AutoGenerate" value does not work for Web farms, because it relies on a cryptographically random secret, which is persisted using machine-local protection and will not be coherent across more than one computer.

Notes to Implementers:

If it is required to specify keys in this configuration section, as is often required in Web-farm scenarios, it is recommended that you encrypt this section by using protected configuration.

The example in this section demonstrates how to specify values declaratively for several attributes of the machineKey Element (ASP.NET Settings Schema) section, which can also be accessed as members of the MachineKeySection class.

The following example from a configuration file shows how to specify values declaratively for the machineKey Element (ASP.NET Settings Schema) section.

  <machineKey validationKey="AutoGenerate,IsolateApps" 

The following example demonstrates how to use the MachineKeySection class.

#region Using directives

using System;
using System.Collections.Generic;
using System.Text;
using System.Configuration;
using System.Web;
using System.Web.Configuration;


namespace Samples.Aspnet.SystemWebConfiguration
  class UsingMachineKeySection
    static void Main(string[] args)
        // Set the path of the config file.
        string configPath = "";

        // Get the Web application configuration object.
        Configuration config = WebConfigurationManager.OpenWebConfiguration(configPath);

        // Get the section related object.
        MachineKeySection configSection = 

        // Display title and info.
        Console.WriteLine("ASP.NET Configuration Info");

        // Display Config details.
        Console.WriteLine("File Path: {0}",
        Console.WriteLine("Section Path: {0}",

        // Display ValidationKey property.
        Console.WriteLine("ValidationKey: {0}",

        // Set ValidationKey property.
        configSection.ValidationKey = "AutoGenerate,IsolateApps";

        // Display DecryptionKey property.
        Console.WriteLine("DecryptionKey: {0}",

        // Set DecryptionKey property.
        configSection.DecryptionKey = "AutoGenerate,IsolateApps";

        // Display Validation property.
        Console.WriteLine("Validation: {0}",

        // Set Validation property.
        configSection.Validation = MachineKeyValidation.SHA1;

        // Update if not locked. 
        if (!configSection.SectionInformation.IsLocked)
          Console.WriteLine("** Configuration updated.");
          Console.WriteLine("** Could not update, section is locked.");

      catch (Exception e)
        // Unknown error.

      // Display and wait

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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