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Configuration Class

Represents a configuration file applicable to a particular computer, application, or resource. This class cannot be inherited.

Namespace: System.Configuration
Assembly: System.Configuration (in system.configuration.dll)

public sealed class Configuration
public final class Configuration
public final class Configuration
Not applicable.

The Configuration class instance represents the merged view of the configuration settings that apply to a specific physical entity, such as a computer, or to a logical entity, such as an application, or a Web site. The specified logical entity can exist on the local computer or on a remote server.

When no configuration file exists for a specified entity, the Configuration object represents the default configuration settings as defined by the Machine.config file.

You can get a Configuration object using one of the open configuration methods as defined by the following classes:

To generate a configuration file representing the inherited configuration settings for a specified entity, use one of the save-configuration methods:

  • The Save method to create a new configuration file.

  • The SaveAs method to generate a new configuration file at another location.


To enable access to configuration settings on a remote computer, use the Aspnet_regiis command-line tool. For more information about this tool, see ASP.NET IIS Registration Tool (Aspnet_regiis.exe). For information about creating and accessing custom configuration settings other than the intrinsic sections included in the .NET Framework, refer to ConfigurationSection.

Notes to Implementers: The Configuration is the class that allows programmatic access for editing configuration files. You use one of the open methods provided by WebConfigurationManager for Web applications or by ConfigurationManager for client applications. These methods will return a Configuration object, which in turn provides the required methods and properties to handle the underlying configuration files. You can access these files for reading or writing as explained next. You use GetSection or GetSectionGroup to read configuration information. Note that the user or process that reads must have the following permissions:

  • Read permission on the configuration file at the current configuration hierarchy level.

  • Read permissions on all the parent configuration files.

If your application needs read-only access to its own configuration, it is recommended you use the GetSection overloaded methods in case of Web applications. Or the GetSection method in case of client applications. These methods provide access to the cached configuration values for the current application, which has better performance than the Configuration class.

If you use a static GetSection method that takes a path parameter, the path parameter must refer to the application in which the code is running, otherwise the parameter is ignored and configuration information for the currently-running application is returned.

You use one of the Save methods to write configuration information. Note that the user or process that writes must have the following permissions:
  • Write permission on the configuration file and directory at the current configuration hierarchy level.

  • Read permissions on all the configuration files.

The following code example demonstrates how to use the Configuration class to create a configuration file containing a custom section.

// Create a custom section.
static void CreateSection()

        CustomSection customSection;

        // Get the current configuration file.
        System.Configuration.Configuration config =

        // Create the section entry  
        // in <configSections> and the 
        // related target section in <configuration>.
        if (config.Sections["CustomSection"] == null)
            customSection = new CustomSection();
            config.Sections.Add("CustomSection", customSection);
            customSection.SectionInformation.ForceSave = true;

            Console.WriteLine("Section name: {0} created",

    catch (ConfigurationErrorsException err)


The following is the definition of the custom section as used by the previous example.

// Define a custom section.
public sealed class CustomSection :

    public enum Permissions
        FullControl = 0,
        Modify = 1,
        ReadExecute = 2,
        Read = 3,
        Write = 4,
        SpecialPermissions = 5

    public CustomSection()


        DefaultValue = "default.txt")]
    [StringValidator(InvalidCharacters = " ~!@#$%^&*()[]{}/;'\"|\\",
               MinLength = 1, MaxLength = 60)]
    public String FileName
            return (String)this["fileName"];
            this["fileName"] = value;
    [ConfigurationProperty("maxIdleTime", DefaultValue="1:30:30")]
    public TimeSpan MaxIdleTime
            return (TimeSpan)this["maxIdleTime"];
            this["maxIdleTime"] = value;

        DefaultValue = Permissions.Read)]
    public Permissions Permission
            return (Permissions)this["permission"];

            this["permission"] = value;


The following is a configuration excerpt as used by the previous example.

<?xml version="1.0" encoding="utf-8"?>


    <section name="CustomSection" type="Samples.AspNet.CustomSection, 
      Configuration, Version=, Culture=neutral, 
      PublicKeyToken=null" allowDefinition="Everywhere" 
      restartOnExternalChanges="true" />
    <CustomSection fileName="default.txt" maxIdleTime="01:30:30"
      permission="Read" />

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

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0
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