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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.

System.Object
  System.Attribute
    System.Configuration.ConfigurationCollectionAttribute

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

[AttributeUsageAttribute(AttributeTargets.Class|AttributeTargets.Property)]
public sealed class ConfigurationCollectionAttribute : Attribute

The ConfigurationCollectionAttribute type exposes the following members.

  NameDescription
Public methodConfigurationCollectionAttributeInitializes a new instance of the ConfigurationCollectionAttribute class.
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  NameDescription
Public propertyAddItemNameGets or sets the name of the <add> configuration element.
Public propertyClearItemsNameGets or sets the name for the <clear> configuration element.
Public propertyCollectionTypeGets or sets the type of the ConfigurationCollectionAttribute attribute.
Public propertyItemTypeGets the type of the collection element.
Public propertyRemoveItemNameGets or sets the name for the <remove> configuration element.
Public propertyTypeIdWhen implemented in a derived class, gets a unique identifier for this Attribute. (Inherited from Attribute.)
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  NameDescription
Public methodEqualsInfrastructure. Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute.)
Public methodGetHashCodeReturns the hash code for this instance. (Inherited from Attribute.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodIsDefaultAttributeWhen overridden in a derived class, indicates whether the value of this instance is the default value for the derived class. (Inherited from Attribute.)
Public methodMatchWhen overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute.)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
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  NameDescription
Explicit interface implemetationPrivate method_Attribute.GetIDsOfNamesMaps a set of names to a corresponding set of dispatch identifiers. (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.GetTypeInfoRetrieves the type information for an object, which can be used to get the type information for an interface. (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.GetTypeInfoCountRetrieves the number of type information interfaces that an object provides (either 0 or 1). (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.InvokeProvides access to properties and methods exposed by an object. (Inherited from Attribute.)
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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

using System;
using 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 : 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)]
    [ConfigurationCollection(typeof(UrlsCollection),
        AddItemName = "add",
        ClearItemsName = "clear",
        RemoveItemName = "remove")]
    public UrlsCollection Urls
    {
        get
        {
            UrlsCollection urlsCollection =
                (UrlsCollection)base["urls"];
            return urlsCollection;
        }
    }

}

// Define the custom UrlsCollection that contains the  
// custom UrlsConfigElement elements. 
public class UrlsCollection : ConfigurationElementCollection
{
    public UrlsCollection()
    {
        UrlConfigElement url = (UrlConfigElement)CreateNewElement();
        Add(url);
    }

    public override ConfigurationElementCollectionType CollectionType
    {
        get
        {
            return ConfigurationElementCollectionType.AddRemoveClearMap;
        }
    }

    protected override ConfigurationElement CreateNewElement()
    {
        return new UrlConfigElement();
    }

    protected override Object GetElementKey(ConfigurationElement element)
    {
        return ((UrlConfigElement)element).Name;
    }

    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);
    }
    protected override void BaseAdd(ConfigurationElement element)
    {
        BaseAdd(element, false);
    }

    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();
    }
}

// Define the custom UrlsConfigElement elements that are contained  
// by the custom UrlsCollection. 
// Notice that you can change the default values to create new default elements. 
public class UrlConfigElement : ConfigurationElement
{
    public UrlConfigElement(String name, String url)
    {
        this.Name = name;
        this.Url = url;
    }

    public UrlConfigElement()
    {

        this.Name = "Contoso";
        this.Url = "http://www.contoso.com";
        this.Port = 0;
    }

    [ConfigurationProperty("name", DefaultValue = "Contoso",
        IsRequired = true, IsKey = true)]
    public string Name
    {
        get
        {
            return (string)this["name"];
        }
        set
        {
            this["name"] = value;
        }
    }

    [ConfigurationProperty("url", DefaultValue = "http://www.contoso.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;
        }
    }
}
using System;
using System.Configuration;


class UsingConfigurationCollectionAttribute
{

    // Create a custom section and save it in the  
    // application configuration file. 
    static void CreateCustomSection()
    {
        try
        {

            // Create a custom configuration section.
            UrlsSection myUrlsSection = new UrlsSection();

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

            // Add the custom section to the application 
            // configuration file. 
            if (config.Sections["MyUrls"] == null)
            {
                config.Sections.Add("MyUrls", myUrlsSection);
            }


            // 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 (ConfigurationErrorsException err)
        {
            Console.WriteLine("CreateCustomSection: {0}", err.ToString());
        }

    }

    static void ReadCustomSection()
    {
        try
        {
            // Get the application configuration file.
            System.Configuration.Configuration config =
                    ConfigurationManager.OpenExeConfiguration(
                    ConfigurationUserLevel.None) as Configuration;

            // Read and display the custom section.
            UrlsSection myUrlsSection =
               ConfigurationManager.GetSection("MyUrls") as UrlsSection;

            if (myUrlsSection == null)
                Console.WriteLine("Failed to load UrlsSection.");
            else
            {
                Console.WriteLine("URLs defined in the configuration file:");
                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);
                }
            }

        }
        catch (ConfigurationErrorsException err)
        {
            Console.WriteLine("ReadCustomSection(string): {0}", err.ToString());
        }

    }

    static void Main(string[] args)
    {

        // Get the name of the application. 
        string appName =
            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();
    }
}

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
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