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ConfigurationCollectionAttribute Class

Declaratively instructs the .NET Framework to create an instance of a configuration element collection. This class cannot be inherited.

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

'Declaration
<AttributeUsageAttribute(AttributeTargets.Class Or AttributeTargets.Property)> _
Public NotInheritable Class ConfigurationCollectionAttribute _
	Inherits Attribute
'Usage
Dim instance As ConfigurationCollectionAttribute

You use the ConfigurationCollectionAttribute attribute to decorate a ConfigurationElementCollection element. This instructs the .NET Framework to create an instance of the collection and to initialize it using your custom ConfigurationElement values.

NoteNote:

The simplest way to create a custom configuration element is to use the attributed (declarative) model. You declare the elements and decorate them with the ConfigurationCollectionAttribute attribute. For each element marked with this attribute, the .NET Framework uses reflection to read the decorating parameters and create a related ConfigurationElementCollection instance. You can also use the programmatic model. In this case it is your responsibility to declare the custom public collection but also to override the ConfigurationElementCollection member and return the properties collection.

The .NET Framework configuration system provides attribute types that you can use during the creation of custom configuration elements. There are two kinds of attributes:

The following example shows how to use the ConfigurationCollectionAttribute.

This example consists of three classes: UrlsSection, UrlsCollection and UrlConfigElement.The UrlsSection class uses the ConfigurationCollectionAttribute to define a custom configuration section. This section contains a URL collection (defined by the UrlsCollection class) of URL elements (defined by the UrlConfigElement class). When you run the example, an instance of the UrlsSection class is created and the following configuration elements are generated in the application configuration file:

<configuration>
    <configSections>
        <section name="MyUrls" type="UrlsSection, 
          ConfigurationCollectionAttribute, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" />
    </configSections>
    <MyUrls>
        <urls>
            <remove name="Contoso" />
            <add name="Contoso" url="http://www.contoso.com" port="0" />
        </urls>
    </MyUrls>
</configuration
Imports System
Imports System.Configuration




' Define a custom section that contains a custom 
' UrlsCollection collection of custom UrlConfigElement elements. 
' This class shows how to use the ConfigurationCollectionAttribute. 
Public Class UrlsSection
	Inherits ConfigurationSection
    ' Declare the Urls collection property using the 
    ' ConfigurationCollectionAttribute. 
    ' This allows to build a nested section that contains 
    ' a collection of elements.
    <ConfigurationProperty("urls", IsDefaultCollection:=False),
        System.Configuration.ConfigurationCollection(GetType(UrlsCollection),
        AddItemName:="add", ClearItemsName:="clear", RemoveItemName:="remove")> _
    Public ReadOnly Property Urls() As UrlsCollection
        Get 
            Dim urlsCollection As UrlsCollection = CType(MyBase.Item("urls"), UrlsCollection)
            Return urlsCollection
        End Get 
    End Property 

End Class 

' Define the custom UrlsCollection that contains the  
' custom UrlsConfigElement elements. 
Public Class UrlsCollection
    Inherits ConfigurationElementCollection
    Public Sub New()
        Dim url As UrlConfigElement = CType(CreateNewElement(), UrlConfigElement)
        Add(url)
    End Sub 

    Public Overrides ReadOnly Property CollectionType() As ConfigurationElementCollectionType
        Get 
            Return ConfigurationElementCollectionType.AddRemoveClearMap
        End Get 
    End Property 

    Protected Overloads Overrides Function CreateNewElement() As ConfigurationElement
        Return New UrlConfigElement()
    End Function 

    Protected Overrides Function GetElementKey(ByVal element As ConfigurationElement) As Object
        Return (CType(element, UrlConfigElement)).Name
    End Function

    Default Shadows Property Item(ByVal index As Integer) As UrlConfigElement
        Get 
            Return CType(BaseGet(index), UrlConfigElement)
        End Get 
        Set(ByVal value As UrlConfigElement)
            If BaseGet(index) IsNot Nothing Then
                BaseRemoveAt(index)
            End If
            BaseAdd(index, value)
        End Set 
    End Property

    Default Public Shadows ReadOnly Property Item(ByVal Name As String) As UrlConfigElement
        Get 
            Return CType(BaseGet(Name), UrlConfigElement)
        End Get 
    End Property 

    Public Function IndexOf(ByVal url As UrlConfigElement) As Integer 
        Return BaseIndexOf(url)
    End Function 

    Public Sub Add(ByVal url As UrlConfigElement)
        BaseAdd(url)
    End Sub 
    Protected Overloads Overrides Sub BaseAdd(ByVal element As ConfigurationElement)
        BaseAdd(element, False)
    End Sub 

    Public Sub Remove(ByVal url As UrlConfigElement)
        If BaseIndexOf(url) >= 0 Then
            BaseRemove(url.Name)
        End If 
    End Sub 

    Public Sub RemoveAt(ByVal index As Integer)
        BaseRemoveAt(index)
    End Sub 

    Public Sub Remove(ByVal name As String)
        BaseRemove(name)
    End Sub 

    Public Sub Clear()
        BaseClear()
    End Sub 
End Class 

' Define the custom UrlsConfigElement elements that are contained  
' by the custom UrlsCollection. 
Public Class UrlConfigElement
    Inherits ConfigurationElement
    Public Sub New(ByVal name As String, ByVal url As String)
        Me.Name = name
        Me.Url = url
    End Sub 

    Public Sub New()
        Me.Name = "Contoso" 
        Me.Url = "http://www.contoso.com" 
        Me.Port = 0
    End Sub

    <ConfigurationProperty("name", DefaultValue:="Contoso", IsRequired:=True, IsKey:=True)> _
    Public Property Name() As String 
        Get 
            Return CStr(Me("name"))
        End Get 
        Set(ByVal value As String)
            Me("name") = value
        End Set 
    End Property

    <ConfigurationProperty("url", DefaultValue:="http://www.contoso.com", IsRequired:=True),
        RegexStringValidator("\w+:\/\/[\w.]+\S*")> _
    Public Property Url() As String 
        Get 
            Return CStr(Me("url"))
        End Get 
        Set(ByVal value As String)
            Me("url") = value
        End Set 
    End Property

    <ConfigurationProperty("port", DefaultValue:=0, IsRequired:=False),
        IntegerValidator(MinValue:=0, MaxValue:=8080, ExcludeRange:=False)> _
    Public Property Port() As Integer 
        Get 
            Return CInt(Fix(Me("port")))
        End Get 
        Set(ByVal value As Integer)
            Me("port") = value
        End Set 
    End Property 
End Class
Imports System.Configuration


Friend Class UsingConfigurationCollectionAttribute

	' Create a custom section and save it in the  
	' application configuration file. 
	Private Shared Sub CreateCustomSection()
		Try 

			' Create a custom configuration section. 
			Dim myUrlsSection As New UrlsSection()

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

			' Add the custom section to the application 
			' configuration file. 
			If config.Sections("MyUrls") Is Nothing Then
				config.Sections.Add("MyUrls", myUrlsSection)
			End If 


			' Save the application configuration file.
			myUrlsSection.SectionInformation.ForceSave = True
			config.Save(ConfigurationSaveMode.Modified)

			Console.WriteLine("Created custom section in the application configuration file: {0}", config.FilePath)
			Console.WriteLine()

		Catch err As ConfigurationErrorsException
			Console.WriteLine("CreateCustomSection: {0}", err.ToString())
		End Try 

	End Sub 

	Private Shared Sub ReadCustomSection()
		Try 
			' Get the application configuration file. 
			Dim config As System.Configuration.Configuration = TryCast(ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None), Configuration)

			' Read and display the custom section. 
			Dim myUrlsSection As UrlsSection = TryCast(ConfigurationManager.GetSection("MyUrls"), UrlsSection)

			If myUrlsSection Is Nothing Then
				Console.WriteLine("Failed to load UrlsSection.")
			Else
				Console.WriteLine("URLs defined in app.config:")
				For i As Integer = 0 To myUrlsSection.Urls.Count - 1
					Console.WriteLine("  Name={0} URL={1} Port={2}", myUrlsSection.Urls(i).Name, myUrlsSection.Urls(i).Url, myUrlsSection.Urls(i).Port)
				Next i
			End If 
        Catch err As ConfigurationErrorsException
            Console.WriteLine("ReadCustomSection(string): {0}", err.ToString())
		End Try 

	End Sub 

	Shared Sub Main(ByVal args() As String)

		' Get the name of the application. 
		Dim appName As String = Environment.GetCommandLineArgs()(0)

		' Create a custom section and save it in the  
		' application configuration file.
		CreateCustomSection()

		' Read the custom section saved in the 
		' application configuration file.
		ReadCustomSection()

        Console.WriteLine()
        Console.WriteLine("Enter any key to exit.")

		Console.ReadLine()
	End Sub 
End Class

System.Object
  System.Attribute
    System.Configuration.ConfigurationCollectionAttribute

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

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