ConfigurationCollectionAttribute Class
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
/** @attribute AttributeUsageAttribute(AttributeTargets.Class|AttributeTargets.Property) */ public final class ConfigurationCollectionAttribute extends Attribute
AttributeUsageAttribute(AttributeTargets.Class|AttributeTargets.Property) public final class ConfigurationCollectionAttribute extends Attribute
You use the ConfigurationCollectionAttribute attribute to decorate a ConfigurationElementCollection element. This instructs the .NET Framework to instantiate the collection and to initialize it using your custom ConfigurationElement values.
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| The simplest way of creating 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.
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The attributes instructing the .NET Framework how to instantiate the custom configuration element properties. These types include:
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ConfigurationCollectionAttribute
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The attributes instructing the .NET Framework how to validate the custom configuration element properties. These types include:
The following example shows how to use the ConfigurationCollectionAttribute.
The example contains four classes. The class TestingConfigurationCollectionAttribute creates a custom configuration section containing a collection of elements. The remaining three classes are used to create the custom section. The custom section type UrlsSection contains an Urls property. This property is a custom collection of type UrlsCollection containing custom elements of type UrlConfigElement. Note that the key for this example to work is the Urls property, decorated with the ConfigurationCollectionAttribute.
Imports System Imports System.Configuration ' Define a property section named <urls> ' containing a UrlsCollection collection of ' UrlConfigElement elements. ' This section requires the definition of UrlsCollection and ' UrlsConfigElement types. Public Class UrlsSection Inherits ConfigurationSection ' Declare the collection element. Private url As UrlConfigElement Public Sub New() ' Create a collection element. ' The property values assigned to ' this instance are provided ' by the ConfigurationProperty attributes ' associated wiht the UrlConfigElement ' properties. url = New UrlConfigElement() End Sub 'New ' Declare the urls collection property. ' Note: the "IsDefaultCollection = false" instructs '.NET Framework to build a nested section of 'the kind <urls> ...</urls>. <ConfigurationProperty("urls", _ IsDefaultCollection:=False), _ ConfigurationCollection(GetType(UrlsCollection), _ AddItemName:="addUrl", _ ClearItemsName:="clearUrls", _ RemoveItemName:="RemoveUrl")> _ Public ReadOnly Property Urls() As UrlsCollection Get Dim urlCollection As UrlsCollection = _ CType(MyBase.Item("urls"), UrlsCollection) Return urlCollection End Get End Property End Class 'UrlsSection ' Define the UrlsCollection that will contain the ' UrlsConfigElement elements. Public Class UrlsCollection Inherits ConfigurationElementCollection Public Sub New() Dim url As UrlConfigElement = _ CType(CreateNewElement(), UrlConfigElement) Add(url) End Sub 'New Public Overrides ReadOnly Property CollectionType() _ As ConfigurationElementCollectionType Get Return ConfigurationElementCollectionType.AddRemoveClearMap End Get End Property Protected Overrides Function CreateNewElement() _ As ConfigurationElement Return New UrlConfigElement() End Function 'CreateNewElement Protected Overrides Function GetElementKey(ByVal element _ As ConfigurationElement) As [Object] Return CType(element, UrlConfigElement).Name End Function 'GetElementKey Default Public Shadows Property Item( _ ByVal index As Integer) As UrlConfigElement Get Return CType(BaseGet(index), UrlConfigElement) End Get Set(ByVal value As UrlConfigElement) If Not (BaseGet(index) Is 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 'IndexOf Public Sub Add(url As UrlConfigElement) BaseAdd(url) End Sub 'Add Protected Overrides Sub BaseAdd(ByVal element _ As ConfigurationElement) BaseAdd(element, False) End Sub 'BaseAdd Public Overloads Sub Remove(ByVal url _ As UrlConfigElement) If BaseIndexOf(url) >= 0 Then BaseRemove(url.Name) End If End Sub 'Remove Public Sub RemoveAt(index As Integer) BaseRemoveAt(index) End Sub 'RemoveAt Overloads Public Sub Remove(name As String) BaseRemove(name) End Sub 'Remove Public Sub Clear() BaseClear() End Sub 'Clear End Class 'UrlsCollection ' Define the UrlConfigElement for the ' types contained by the UrlsSection. Public Class UrlConfigElement Inherits ConfigurationElement Public Sub New(name As String, url As String) Me.Name = name Me.Url = url End Sub 'New Public Sub New() End Sub <ConfigurationProperty("name", _ DefaultValue:="Microsoft", _ 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.microsoft.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(Me("port")) End Get Set(ByVal value As Integer) Me("port") = value End Set End Property Class TestingConfigurationCollectionAttribute Shared Sub ShowUrls() Try Dim myUrlsSection As UrlsSection = _ ConfigurationManager.GetSection("MyUrls") If myUrlsSection Is Nothing Then Console.WriteLine("Failed to load UrlsSection.") Else Console.WriteLine("My URLs:") Dim i As Integer For i = 0 To myUrlsSection.Urls.Count - 1 Console.WriteLine(" #{0 {1: {2", i, _ myUrlsSection.Urls(i).Name, _ myUrlsSection.Urls(i).Url + " port " + _ myUrlsSection.Urls(i).Port.ToString()) Next i End If Catch e As Exception Console.WriteLine(e.ToString()) End Try End Sub 'ShowUrls ' Create the custom section. ' It will contain a nested section as ' defined by the UrlsSection (<urls>...</urls>). Shared Sub CreateSection(sectionName As String) ' Get the current configuration (file). Dim config As System.Configuration.Configuration = _ ConfigurationManager.OpenExeConfiguration( _ ConfigurationUserLevel.None) Dim urlsSection As UrlsSection ' Create an entry in the <configSections>. If config.Sections(sectionName) Is Nothing Then urlsSection = New UrlsSection() config.Sections.Add(sectionName, urlsSection) config.Save() End If ' Create the actual target section and write it to ' the configuration file. If config.Sections(("/configuration/" + sectionName)) _ Is Nothing Then urlsSection = config.GetSection(sectionName) ' urlsSection.SectionInformation.ForceSave = True config.Save(ConfigurationSaveMode.Full) End If End Sub 'CreateSection Public Overloads Shared Sub Main(ByVal args() As String) Console.WriteLine("[Current URLs]") CreateSection("MyUrls") ShowUrls() Console.ReadLine() End Sub 'Main End Class 'TestingConfigurationCollectionAttribute
The following is an excerpt of the configuration file containing the custom section as defined in the previous sample.
<configuration>
<configSections>
<section name="MyUrls"
type="Samples.AspNet.UrlsSection,
ConfigurationCollectionAttribute, Version=1.0.0.0,
Culture=neutral, PublicKeyToken=null" />
</configSections>
<MyUrls>
<urls>
<clear />
<add name="Microsoft" url="http://www.microsoft.com" port="0" />
</urls>
</MyUrls>
</configuration>
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.
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