提示和注释
ConfigurationElement 是一个用于表示配置文件（如 Web.config）中 XML 元素的抽象类。 配置文件中的元素可以包含零个、一个或多个子元素。
因为 ConfigurationElement 类定义为抽象类，所以无法创建它的实例。 只能从它派生类。 .NET Framework 包括从 ConfigurationElement 类派生出的类，为了能够表示标准的 XML 配置元素，如 ConfigurationSection。 也可以扩展 ConfigurationElement 类，以访问自定义配置元素和节。 在本主题后面的示例演示如何通过使用从 ConfigurationElement 派生的自定义类来访问自定义配置元素和部分。
还可以扩展标准配置类型，例如 ConfigurationElement、ConfigurationElementCollection、ConfigurationProperty 和 ConfigurationSection。 有关更多信息，请参见那些类的文档。
有关如何访问配置文件中信息的更多信息，请参见 ConfigurationManager 类和 WebConfigurationManager 类。
对继承者的说明
每个 ConfigurationElement 对象都为表示其元素特性或子元素集合的 ConfigurationProperty 对象创建一个内部的 ConfigurationPropertyCollection 集合。
无法自定义的信息和功能都包含在 ElementInformation 属性所提供的 ElementInformation 对象中。
可以使用编程或声明性（特性化）代码编写模型创建自定义配置元素：
编程模型要求为每个元素特性创建一个用于获取或设置其值的属性，并将其添加到基础 ConfigurationElement 基类的内部属性包中。 请参见 ConfigurationSection 类，以获得有关如何使用此模型的示例。
此声明性模型（也称为特性化模型）相对简单，它允许您使用属性定义一个元素特性，然后再用特性对该元素特性进行修饰。 这些特性将属性类型及其默认值通知给 ASP.NET 配置系统。 利用通过反射获取的此信息，ASP.NET 配置系统将创建元素属性对象，并执行所需的初始化。 本主题稍后显示的示例介绍如何使用此模型。
System.Configuration.ConfigurationElement 类例子
None
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VB
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' Set Assembly name to ConfigurationElement
' and set Root namespace to Samples.AspNet
Imports System
Imports System.Configuration
Imports System.Collections
Class TestConfigurationElement
' Entry point for console application that reads the
' app.config file and writes to the console the
' URLs in the custom section.
Shared Sub Main(ByVal args() As String)
' Get the current configuration file.
Dim config As System.Configuration.Configuration = _
ConfigurationManager.OpenExeConfiguration( _
ConfigurationUserLevel.None)
' Get the MyUrls section.
Dim myUrlsSection As UrlsSection = _
config.GetSection("MyUrls")
If myUrlsSection Is Nothing Then
Console.WriteLine("Failed to load UrlsSection.")
Else
Console.WriteLine("The 'simple' element of app.config:")
Console.WriteLine(" Name={0} URL={1} Port={2}", _
myUrlsSection.Simple.Name, _
myUrlsSection.Simple.Url, _
myUrlsSection.Simple.Port)
Console.WriteLine("The urls collection of app.config:")
Dim i As Integer
For i = 0 To myUrlsSection.Urls.Count - 1
Console.WriteLine(" Name={0} URL={1} Port={2}", _
i, myUrlsSection.Urls(i).Name, _
myUrlsSection.Urls(i).Url, _
myUrlsSection.Urls(i).Port)
Next i
End If
Console.ReadLine()
End Sub
End Class
C#
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// Set Assembly name to ConfigurationElement
using System;
using System.Configuration;
using System.Collections;
namespace Samples.AspNet
{
// Entry point for console application that reads the
// app.config file and writes to the console the
// URLs in the custom section.
class TestConfigurationElement
{
static void Main(string[] args)
{
// Get current configuration file.
System.Configuration.Configuration config =
ConfigurationManager.OpenExeConfiguration(
ConfigurationUserLevel.None);
// Get the MyUrls section.
UrlsSection myUrlsSection =
config.GetSection("MyUrls") as UrlsSection;
if (myUrlsSection == null)
Console.WriteLine("Failed to load UrlsSection.");
else
{
Console.WriteLine("The 'simple' element of app.config:");
Console.WriteLine(" Name={0} URL={1} Port={2}",
myUrlsSection.Simple.Name,
myUrlsSection.Simple.Url,
myUrlsSection.Simple.Port);
Console.WriteLine("The urls collection of app.config:");
for (int i = 0; i < myUrlsSection.Urls.Count; i++)
{
Console.WriteLine(" Name={0} URL={1} Port={2}",
myUrlsSection.Urls[i].Name,
myUrlsSection.Urls[i].Url,
myUrlsSection.Urls[i].Port);
}
}
Console.ReadLine();
}
}
}
VB
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Imports System
Imports System.Configuration
Imports System.Collections
' Define a custom section containing an individual
' element and a collection of elements.
Public Class UrlsSection
Inherits ConfigurationSection
_
Public Property Name() As String
Get
Return CStr(Me("name"))
End Get
Set(ByVal value As String)
Me("name") = value
End Set
End Property
' Declare an element (not in a collection) of the type
' UrlConfigElement. In the configuration
' file it corresponds to .
_
Public ReadOnly Property Simple() _
As UrlConfigElement
Get
Dim url As UrlConfigElement = _
CType(Me("simple"), _
UrlConfigElement)
Return url
End Get
End Property
' Declare a collection element represented
' in the configuration file by the sub-section
'
' Note: the "IsDefaultCollection = false"
' instructs the .NET Framework to build a nested
' section like ....
_
Public ReadOnly Property Urls() _
As UrlsCollection
Get
Dim urlsCollection _
As UrlsCollection = _
CType(Me("urls"), UrlsCollection)
Return urlsCollection
End Get
End Property
Protected Overrides Sub DeserializeSection( _
ByVal reader As System.Xml.XmlReader)
MyBase.DeserializeSection(reader)
' Enter your custom processing code here.
End Sub 'DeserializeSection
Protected Overrides Function SerializeSection( _
ByVal parentElement As ConfigurationElement, _
ByVal name As String, _
ByVal saveMode As ConfigurationSaveMode) As String
Dim s As String = _
MyBase.SerializeSection(parentElement, _
name, saveMode)
' Enter your custom processing code here.
Return s
End Function 'SerializeSection
End Class 'UrlsSection
C#
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using System;
using System.Configuration;
using System.Collections;
namespace Samples.AspNet
{
// Define a custom section containing an individual
// element and a collection of elements.
public class UrlsSection : ConfigurationSection
{
[ConfigurationProperty("name",
DefaultValue = "MyFavorites",
IsRequired = true,
IsKey = false)]
[StringValidator(InvalidCharacters =
" ~!@#$%^&*()[]{}/;'\"|\\",
MinLength = 1, MaxLength = 60)]
public string Name
{
get
{
return (string)this["name"];
}
set
{
this["name"] = value;
}
}
// Declare an element (not in a collection) of the type
// UrlConfigElement. In the configuration
// file it corresponds to .
[ConfigurationProperty("simple")]
public UrlConfigElement Simple
{
get
{
UrlConfigElement url =
(UrlConfigElement)base["simple"];
return url;
}
}
// Declare a collection element represented
// in the configuration file by the sub-section
//
// Note: the "IsDefaultCollection = false"
// instructs the .NET Framework to build a nested
// section like ....
[ConfigurationProperty("urls",
IsDefaultCollection = false)]
public UrlsCollection Urls
{
get
{
UrlsCollection urlsCollection =
(UrlsCollection)base["urls"];
return urlsCollection;
}
}
protected override void DeserializeSection(
System.Xml.XmlReader reader)
{
base.DeserializeSection(reader);
// You can add custom processing code here.
}
protected override string SerializeSection(
ConfigurationElement parentElement,
string name, ConfigurationSaveMode saveMode)
{
string s =
base.SerializeSection(parentElement,
name, saveMode);
// You can add custom processing code here.
return s;
}
}
}
VB
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Imports System
Imports System.Configuration
Imports System.Collections
Public Class UrlsCollection
Inherits ConfigurationElementCollection
Public Sub New()
' Add one url to the collection. This is
' not necessary; could leave the collection
' empty until items are added to it outside
' the constructor.
Dim url As UrlConfigElement = _
CType(CreateNewElement(), UrlConfigElement)
' Add the element to the collection.
Add(url)
End Sub 'New
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 'CreateNewElement
Protected Overloads Overrides Function CreateNewElement( _
ByVal elementName As String) _
As ConfigurationElement
Return New UrlConfigElement(elementName)
End Function 'CreateNewElement
Protected Overrides Function GetElementKey( _
ByVal element As ConfigurationElement) As [Object]
Return CType(element, UrlConfigElement).Name
End Function 'GetElementKey
Public Shadows Property AddElementName() As String
Get
Return MyBase.AddElementName
End Get
Set(ByVal value As String)
MyBase.AddElementName = value
End Set
End Property
Public Shadows Property ClearElementName() As String
Get
Return MyBase.ClearElementName
End Get
Set(ByVal value As String)
MyBase.AddElementName = value
End Set
End Property
Public Shadows ReadOnly Property RemoveElementName() As String
Get
Return MyBase.RemoveElementName
End Get
End Property
Public Shadows ReadOnly Property Count() As Integer
Get
Return MyBase.Count
End Get
End Property
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(ByVal url As UrlConfigElement)
BaseAdd(url)
' Add custom code here.
End Sub 'Add
Protected Overrides Sub BaseAdd( _
ByVal element As ConfigurationElement)
BaseAdd(element, False)
' Add custom code here.
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(ByVal index As Integer)
BaseRemoveAt(index)
End Sub 'RemoveAt
Public Overloads Sub Remove(ByVal name As String)
BaseRemove(name)
End Sub 'Remove
Public Sub Clear()
BaseClear()
End Sub 'Clear '
End Class 'UrlsCollection
C#
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using System;
using System.Configuration;
using System.Collections;
namespace Samples.AspNet
{
public class UrlsCollection : ConfigurationElementCollection
{
public UrlsCollection()
{
// Add one url to the collection. This is
// not necessary; could leave the collection
// empty until items are added to it outside
// the constructor.
UrlConfigElement url =
(UrlConfigElement)CreateNewElement();
Add(url);
}
public override
ConfigurationElementCollectionType CollectionType
{
get
{
return
ConfigurationElementCollectionType.AddRemoveClearMap;
}
}
protected override
ConfigurationElement CreateNewElement()
{
return new UrlConfigElement();
}
protected override
ConfigurationElement CreateNewElement(
string elementName)
{
return new UrlConfigElement(elementName);
}
protected override Object
GetElementKey(ConfigurationElement element)
{
return ((UrlConfigElement)element).Name;
}
public new string AddElementName
{
get
{ return base.AddElementName; }
set
{ base.AddElementName = value; }
}
public new string ClearElementName
{
get
{ return base.ClearElementName; }
set
{ base.AddElementName = value; }
}
public new string RemoveElementName
{
get
{ return base.RemoveElementName; }
}
public new int Count
{
get { return base.Count; }
}
public UrlConfigElement this[int index]
{
get
{
return (UrlConfigElement)BaseGet(index);
}
set
{
if (BaseGet(index) != null)
{
BaseRemoveAt(index);
}
BaseAdd(index, value);
}
}
new public UrlConfigElement this[string Name]
{
get
{
return (UrlConfigElement)BaseGet(Name);
}
}
public int IndexOf(UrlConfigElement url)
{
return BaseIndexOf(url);
}
public void Add(UrlConfigElement url)
{
BaseAdd(url);
// Add custom code here.
}
protected override void
BaseAdd(ConfigurationElement element)
{
BaseAdd(element, false);
// Add custom code here.
}
public void Remove(UrlConfigElement url)
{
if (BaseIndexOf(url) >= 0)
BaseRemove(url.Name);
}
public void RemoveAt(int index)
{
BaseRemoveAt(index);
}
public void Remove(string name)
{
BaseRemove(name);
}
public void Clear()
{
BaseClear();
// Add custom code here.
}
}
}
VB
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Imports System
Imports System.Configuration
Imports System.Collections
Public Class UrlConfigElement
Inherits ConfigurationElement
' Constructor allowing name, url, and port to be specified.
Public Sub New(ByVal newName As String, _
ByVal newUrl As String, _
ByVal newPort As Integer)
Name = newName
Url = newUrl
Port = newPort
End Sub 'New
' Default constructor, will use default values as defined
Public Sub New()
End Sub 'New
' Constructor allowing name to be specified, will take the
' default values for url and port.
Public Sub New(ByVal elementName As String)
Name = elementName
End Sub 'New
_
Public Property Name() As String
Get
Return CStr(Me("name"))
End Get
Set(ByVal value As String)
Me("name") = value
End Set
End Property
_
Public Property Url() As String
Get
Return CStr(Me("url"))
End Get
Set(ByVal value As String)
Me("url") = value
End Set
End Property
_
Public Property Port() As Integer
Get
Return Fix(Me("port"))
End Get
Set(ByVal value As Integer)
Me("port") = value
End Set
End Property
Protected Overrides Sub DeserializeElement(ByVal reader _
As System.Xml.XmlReader, _
ByVal serializeCollectionKey As Boolean)
MyBase.DeserializeElement(reader, _
serializeCollectionKey)
' Enter your custom processing code here.
End Sub 'DeserializeElement
Protected Overrides Function SerializeElement(ByVal writer _
As System.Xml.XmlWriter, _
ByVal serializeCollectionKey As Boolean) As Boolean
Dim ret As Boolean = _
MyBase.SerializeElement(writer, serializeCollectionKey)
' Enter your custom processing code here.
Return ret
End Function 'SerializeElement
Protected Overrides Function IsModified() As Boolean
Dim ret As Boolean = MyBase.IsModified()
' Enter your custom processing code here.
Return ret
End Function 'IsModified
End Class 'UrlConfigElement
C#
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using System;
using System.Configuration;
using System.Collections;
namespace Samples.AspNet
{
public class UrlConfigElement : ConfigurationElement
{
// Constructor allowing name, url, and port to be specified.
public UrlConfigElement(String newName,
String newUrl, int newPort)
{
Name = newName;
Url = newUrl;
Port = newPort;
}
// Default constructor, will use default values as defined
// below.
public UrlConfigElement()
{
}
// Constructor allowing name to be specified, will take the
// default values for url and port.
public UrlConfigElement(string elementName)
{
Name = elementName;
}
[ConfigurationProperty("name",
DefaultValue = "Microsoft",
IsRequired = true,
IsKey = true)]
public string Name
{
get
{
return (string)this["name"];
}
set
{
this["name"] = value;
}
}
[ConfigurationProperty("url",
DefaultValue = "http://www.microsoft.com",
IsRequired = true)]
[RegexStringValidator(@"\w+:\/\/[\w.]+\S*")]
public string Url
{
get
{
return (string)this["url"];
}
set
{
this["url"] = value;
}
}
[ConfigurationProperty("port",
DefaultValue = (int)0,
IsRequired = false)]
[IntegerValidator(MinValue = 0,
MaxValue = 8080, ExcludeRange = false)]
public int Port
{
get
{
return (int)this["port"];
}
set
{
this["port"] = value;
}
}
protected override void DeserializeElement(
System.Xml.XmlReader reader,
bool serializeCollectionKey)
{
base.DeserializeElement(reader,
serializeCollectionKey);
// You can your custom processing code here.
}
protected override bool SerializeElement(
System.Xml.XmlWriter writer,
bool serializeCollectionKey)
{
bool ret = base.SerializeElement(writer,
serializeCollectionKey);
// You can enter your custom processing code here.
return ret;
}
protected override bool IsModified()
{
bool ret = base.IsModified();
// You can enter your custom processing code here.
return ret;
}
}
}
using System;
using System.Configuration;
using System.Collections;
namespace Samples.AspNet
{
public class UrlConfigElement : ConfigurationElement
{
// Constructor allowing name, url, and port to be specified.
public UrlConfigElement(String newName,
String newUrl, int newPort)
{
Name = newName;
Url = newUrl;
Port = newPort;
}
// Default constructor, will use default values as defined
// below.
public UrlConfigElement()
{
}
// Constructor allowing name to be specified, will take the
// default values for url and port.
public UrlConfigElement(string elementName)
{
Name = elementName;
}
[ConfigurationProperty("name",
DefaultValue = "Microsoft",
IsRequired = true,
IsKey = true)]
public string Name
{
get
{
return (string)this["name"];
}
set
{
this["name"] = value;
}
}
[ConfigurationProperty("url",
DefaultValue = "http://www.microsoft.com",
IsRequired = true)]
[RegexStringValidator(@"\w+:\/\/[\w.]+\S*")]
public string Url
{
get
{
return (string)this["url"];
}
set
{
this["url"] = value;
}
}
[ConfigurationProperty("port",
DefaultValue = (int)0,
IsRequired = false)]
[IntegerValidator(MinValue = 0,
MaxValue = 8080, ExcludeRange = false)]
public int Port
{
get
{
return (int)this["port"];
}
set
{
this["port"] = value;
}
}
protected override void DeserializeElement(
System.Xml.XmlReader reader,
bool serializeCollectionKey)
{
base.DeserializeElement(reader,
serializeCollectionKey);
// You can your custom processing code here.
}
protected override bool SerializeElement(
System.Xml.XmlWriter writer,
bool serializeCollectionKey)
{
bool ret = base.SerializeElement(writer,
serializeCollectionKey);
// You can enter your custom processing code here.
return ret;
}
protected override bool IsModified()
{
bool ret = base.IsModified();
// You can enter your custom processing code here.
return ret;
}
}
}