ConfigurationProperty Class

Note: This class is new in the .NET Framework version 2.0.

This class supports the .NET Framework infrastructure and is not intended to be used directly from your code.

Represents an attribute or a child of a configuration element. This class cannot be inherited.

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

public sealed class ConfigurationProperty
public final class ConfigurationProperty
public final class ConfigurationProperty

In the case of a simple ConfigurationElement, such as the CustomSection shown in the next example, the ConfigurationProperty objects represent attributes such as fileName.

In the case of more complex configuration elements such as a section containing subsections, for instance authentication, the ConfigurationProperty objects can represent ConfigurationElement objects as well as attributes.

The ConfigurationPropertyCollection class represents the collection of the ConfigurationProperty objects that can be either attributes or ConfigurationElement objects of a configuration element.

The ConfigurationProperty class represents an individual configuration setting. This class allows you to get or set the name, type, and default value for a particular configuration entity (attribute or element) and specify whether the attribute is required, is an element key, or represents a default element collection.

Notes to Implementers Every ConfigurationElement object creates an internal ConfigurationPropertyCollection collection of ConfigurationProperty objects that represents either the element attributes or a collection of child elements. Non-customizable information and functionality is contained by an ElementInformation object provided by the ElementInformation property. You can use a programmatic or a declarative (attributed) coding model to create a custom configuration element.

  • Programmatic Model. This model requires that you create a property for each element attribute to get and/or set its value and add it to the internal property bag of the underlying ConfigurationElement base class.

  • Declarative Model. This simpler model, also called attributed model, allows you to define an element attribute by using a property and decorate it with attributes. These attributes instruct the ASP.NET configuration system about the property types and their default values. With this information, obtained through reflection, the ASP.NET configuration system creates the element property objects for you and performs the required initialization.

  1. The following code example shows how to use the ConfigurationProperty when creating a custom section.

// Define a custom section.
// It shows how to use the ConfigurationProperty
// class when defining a custom section
// programmatically. 
// The variables prefixed with the
// _ sign are ConfigurationProperty types.
public sealed class CustomSection :

    // CustomSection constructor.
    static CustomSection()

        // Initialize the _FileName
        _FileName =
            new ConfigurationProperty("fileName",
            typeof(string), "default.txt");

        // Initialize the _MaxUsers
        _MaxUsers =
            new ConfigurationProperty("maxUsers",
            typeof(long), (long)1000,

        // Initialize the _MaxIdleTime
        TimeSpan minTime = TimeSpan.FromSeconds(30);
        TimeSpan maxTime = TimeSpan.FromMinutes(5);

        ConfigurationValidatorBase _TimeSpanValidator =
            new TimeSpanValidator(minTime, maxTime, false);

        _MaxIdleTime =
           new ConfigurationProperty("maxIdleTime",
       typeof(TimeSpan), TimeSpan.FromMinutes(5),
       "[Description:This is the max idle time.]");

        // Initialize the _Alias
        _Alias =
            new ConfigurationProperty("alias",
            typeof(string), "alias.txt");

        // Property collection initialization.
        // The collection (property bag) that contains 
        // the properties is declared as:
        // ConfigurationPropertyCollection _Properties;
        _Properties =
            new ConfigurationPropertyCollection();

        // The collection (property bag) that contains 
        // the properties is declared as:
        // ConfigurationPropertyCollection _Properties;


    // Return the initialized property bag
    // for the configuration element.
    // The collection (property bag) that contains 
    // the properties is declared as:
    // ConfigurationPropertyCollection _Properties;
    protected override ConfigurationPropertyCollection Properties
            return _Properties;

    // Clear the property.
    // It deletes all the attributes of the
    // configuration element represented by
    // the property.
    public void ClearCollection()

    // Remove an element from the property collection.
    // It deletes the specified attribute from the
    // configuration element represented by
    // the property.
    public void RemoveCollectionElement(string elName)

    // Get the property collection enumerator.
    public IEnumerator GetCollectionEnumerator()
        return (Properties.GetEnumerator());


    [StringValidator(InvalidCharacters = " ~!@#$%^&*()[]{/;'\"|\\",
        MinLength = 1, MaxLength = 60)]
    public string FileName
            return (string)this["fileName"];
            this["fileName"] = value;

    [StringValidator(InvalidCharacters = " ~!@#$%^&*()[]{/;'\"|\\",
        MinLength = 1, MaxLength = 60)]
    public string Alias
            return (string)this["alias"];
            this["alias"] = value;

    [LongValidator(MinValue = 1, MaxValue = 1000000,
        ExcludeRange = false)]
    public long MaxUsers
            return (long)this["maxUsers"];
            this["maxUsers"] = value;

    public TimeSpan MaxIdleTime
            return (TimeSpan)this["maxIdleTime"];
            this["maxIdleTime"] = value;

The following is an excerpt of the configuration used by the code in the example above.

<?xml version="1.0" encoding="utf-8"?>
    <section name="CustomSection" type="Samples.AspNet, ConfigurationProperty, Version=, Culture=neutral, PublicKeyToken=null" allowDefinition="Everywhere" allowExeDefinition="MachineToApplication" restartOnExternalChanges="true" />
  <CustomSection fileName="default.txt" alias="alias.txt" maxUsers="1000"
    maxIdleTime="00:05:00" />

The following example shows how to create the above section.

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

        CustomSection customSection;

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

        // Create the section entry  
        // in the <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;
    catch (ConfigurationErrorsException err)


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 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 .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0