ConfigurationCollectionAttribute Class
Declaratively instructs the .NET Framework to create an instance of a configuration element collection. This class cannot be inherited.
Assembly: System.Configuration (in System.Configuration.dll)
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.
Note: |
|---|
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 attributes that instruct the .NET Framework how to create instances of the custom configuration element properties. These types include:
ConfigurationCollectionAttribute
The attributes that instruct the .NET Framework how to validate the custom configuration element properties. These types include:
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
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.
Note: