Imports System
Imports System.Configuration
Imports System.Collections
Imports System.ComponentModel

' Define a custom section.
' Shows how to use the ConfigurationProperty
' class when defining a custom section.
Public NotInheritable Class CustomSection
    Inherits ConfigurationSection

    ' The collection (property bag) that contains 
    ' the section properties.
    Private Shared _Properties As ConfigurationPropertyCollection

    ' The FileName property.
    Private Shared _FileName As ConfigurationProperty

    ' The Alias property.
    Private Shared _Alias As ConfigurationProperty

    ' The MasUsers property.
    Private Shared _MaxUsers As ConfigurationProperty

    ' The MaxIdleTime property.
    Private Shared _MaxIdleTime As ConfigurationProperty

    ' CustomSection constructor.
    Shared Sub New()

        ' Initialize the _FileName property
        _FileName = New ConfigurationProperty( _
            "fileName", GetType(String), "default.txt")

        ' Initialize the _MaxUsers property
        _MaxUsers = New ConfigurationProperty( _
            "maxUsers", GetType(Long), 1000L, _
            ConfigurationPropertyOptions.None)

        ' Initialize the _MaxIdleTime property
        Dim minTime As TimeSpan = TimeSpan.FromSeconds(30)
        Dim maxTime As TimeSpan = TimeSpan.FromMinutes(5)
        Dim _TimeSpanValidator = _
            New TimeSpanValidator(minTime, maxTime, False)

        _MaxIdleTime = New ConfigurationProperty( _
            "maxIdleTime", GetType(TimeSpan), _
            TimeSpan.FromMinutes(5), _
            TypeDescriptor.GetConverter(GetType(TimeSpan)), _
            _TimeSpanValidator, _
            ConfigurationPropertyOptions.IsRequired, _
            "[Description:This is the max idle time.]")

        ' Initialize the _Alias property
        _Alias = New ConfigurationProperty( _
            "alias", GetType(String), "alias.txt")

        ' Property collection initialization.
        ' The collection (property bag) that contains 
        ' the properties is declared as:
        ' ConfigurationPropertyCollection _Properties;
        _Properties = New ConfigurationPropertyCollection()
        _Properties.Add(_FileName)
        _Properties.Add(_Alias)
        _Properties.Add(_MaxUsers)
        _Properties.Add(_MaxIdleTime)

    End Sub

    ' Return the initialized property bag
    ' for the configuration element.
    Protected Overrides ReadOnly Property Properties() _
    As ConfigurationPropertyCollection
        Get
            Return _Properties
        End Get
    End Property

    <StringValidator(InvalidCharacters:= _
    " ~!@#$%^&*()[]{}/;'""|\", MinLength:=1, _
    MaxLength:=60)> _
    Public Property FileName() As String
        Get
            Return CStr(Me("fileName"))
        End Get
        Set(ByVal value As String)
            Me("fileName") = value
        End Set
    End Property

    <StringValidator(InvalidCharacters:= _
    " ~!@#$%^&*()[]{}/;'""|\", MinLength:=1, _
    MaxLength:=60)> _
    Public Property [Alias]() As String
        Get
            Return CStr(Me("alias"))
        End Get
        Set(ByVal value As String)
            Me("alias") = value
        End Set
    End Property

    <LongValidator(MinValue:=1, _
    MaxValue:=1000000, ExcludeRange:=False)> _
    Public Property MaxUsers() As Long
        Get
            Return Fix(Me("maxUsers"))
        End Get
        Set(ByVal value As Long)
            Me("maxUsers") = value
        End Set
    End Property

    Public Property MaxIdleTime() As TimeSpan
        Get
            Return CType(Me("maxIdleTime"), TimeSpan)
        End Get
        Set(ByVal value As TimeSpan)
            Me("maxIdleTime") = value
        End Set
    End Property
End Class

using System;
using System.Configuration;
using System.Collections;
using System.ComponentModel;

namespace ConfigurationPropertyExample
{
    // Define a custom section.
    // Shows how to use the ConfigurationProperty
    // class when defining a custom section.
    public sealed class CustomSection : ConfigurationSection
    {
        // The collection (property bag) that contains 
        // the section properties.
        private static ConfigurationPropertyCollection _Properties;

        // The FileName property.
        private static ConfigurationProperty _FileName;

        // The Alias property.
        private static ConfigurationProperty _Alias;

        // The MaxUsers property.
        private static ConfigurationProperty _MaxUsers;

        // The MaxIdleTime property.
        private static ConfigurationProperty _MaxIdleTime;

        // CustomSection constructor.
        static CustomSection()
        {
            // Initialize the _FileName property
            _FileName =
                new ConfigurationProperty("fileName",
                typeof(string), "default.txt");

            // Initialize the _MaxUsers property
            _MaxUsers =
                new ConfigurationProperty("maxUsers",
                typeof(long), (long)1000,
                ConfigurationPropertyOptions.None);

            // Initialize the _MaxIdleTime property
            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),
                TypeDescriptor.GetConverter(typeof(TimeSpan)),
                _TimeSpanValidator,
                ConfigurationPropertyOptions.IsRequired,
                "[Description:This is the max idle time.]");

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

            // Initialize the Property collection.
            _Properties = new ConfigurationPropertyCollection();
            _Properties.Add(_FileName);
            _Properties.Add(_Alias);
            _Properties.Add(_MaxUsers);
            _Properties.Add(_MaxIdleTime);
        }

        // Return the initialized property bag
        // for the configuration element.
        protected override ConfigurationPropertyCollection Properties
        {
            get
            {
                return _Properties;
            }
        }

        // Clear the property.
        public void ClearCollection()
        {
            Properties.Clear();
        }

        // Remove an element from the property collection.
        public void RemoveCollectionElement(string elName)
        {
            Properties.Remove(elName);
        }

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

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

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

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

        public TimeSpan MaxIdleTime
        {
            get
            {
                return (TimeSpan)this["maxIdleTime"];
            }
            set
            {
                this["maxIdleTime"] = value;
            }
        }
    }
}

<configuration>
  <configSections>
    <section name="CustomSection" type="ConfigurationPropertyExample.CustomSection, ConfigurationPropertyExample" 
      allowDefinition="Everywhere" allowExeDefinition="MachineToApplication" 
      restartOnExternalChanges="true" />
  </configSections>
  <CustomSection fileName="override.txt" alias="alias.txt" 
    maxUsers="1000" maxIdleTime="00:05:00" />
</configuration>

' Create a custom section.
Shared Sub CreateSection()
    Try
        Dim customSection As CustomSection

        ' Get the current configuration file.
        Dim config As System.Configuration.Configuration = _
            ConfigurationManager.OpenExeConfiguration( _
            ConfigurationUserLevel.None)

        ' Create the section entry  
        ' in the <configSections> and the 
        ' related target section in <configuration>.
        ' Since the config file already has "CustomSection",
        ' call this one "CustomSection2".
        If config.Sections("CustomSection") Is Nothing Then
            customSection = New CustomSection()
            config.Sections.Add("CustomSection", customSection)
            customSection.SectionInformation.ForceSave = True
            config.Save(ConfigurationSaveMode.Full)
        End If
    Catch err As ConfigurationErrorsException
        Console.WriteLine(err.ToString())
    End Try
End Sub

// Define a custom section programmatically.
static void CreateSection()
{
    try
    {
        CustomSection customSection;

        // Get the current configuration file.
        System.Configuration.Configuration config =
                ConfigurationManager.OpenExeConfiguration(
                ConfigurationUserLevel.None);

        // Create the section entry  
        // in the <configSections> and the 
        // related target section in <configuration>.
        // Call it "CustomSection2" since the file in this 
        // example already has "CustomSection".
        if (config.Sections["CustomSection"] == null)
        {
            customSection = new CustomSection();
            config.Sections.Add("CustomSection2", customSection);
            customSection.SectionInformation.ForceSave = true;
            config.Save(ConfigurationSaveMode.Full);
        }
    }
    catch (ConfigurationErrorsException err)
    {
        Console.WriteLine(err.ToString());
    }
}