ReadOnlyCollectionBase Class

 

Provides the abstract base class for a strongly typed non-generic read-only collection.

Namespace:   System.Collections
Assembly:  mscorlib (in mscorlib.dll)

System::Object
  System.Collections::ReadOnlyCollectionBase
    System.ComponentModel::ComponentCollection
    System.Configuration::ConfigurationLocationCollection
    System.Diagnostics::ProcessModuleCollection
    System.Diagnostics::ProcessThreadCollection
    System.DirectoryServices.ActiveDirectory::ActiveDirectoryRoleCollection
    System.DirectoryServices.ActiveDirectory::AdamInstanceCollection
    System.DirectoryServices.ActiveDirectory::AdamRoleCollection
    System.DirectoryServices.ActiveDirectory::ApplicationPartitionCollection
    System.DirectoryServices.ActiveDirectory::AttributeMetadataCollection
    System.DirectoryServices.ActiveDirectory::DomainCollection
    System.DirectoryServices.ActiveDirectory::DomainControllerCollection
    System.DirectoryServices.ActiveDirectory::ForestTrustDomainInfoCollection
    System.DirectoryServices.ActiveDirectory::ForestTrustRelationshipCollisionCollection
    System.DirectoryServices.ActiveDirectory::GlobalCatalogCollection
    System.DirectoryServices.ActiveDirectory::ReadOnlyActiveDirectorySchemaClassCollection
    System.DirectoryServices.ActiveDirectory::ReadOnlyActiveDirectorySchemaPropertyCollection
    System.DirectoryServices.ActiveDirectory::ReadOnlyDirectoryServerCollection
    System.DirectoryServices.ActiveDirectory::ReadOnlySiteCollection
    System.DirectoryServices.ActiveDirectory::ReadOnlySiteLinkBridgeCollection
    System.DirectoryServices.ActiveDirectory::ReadOnlySiteLinkCollection
    System.DirectoryServices.ActiveDirectory::ReadOnlyStringCollection
    System.DirectoryServices.ActiveDirectory::ReplicationConnectionCollection
    System.DirectoryServices.ActiveDirectory::ReplicationCursorCollection
    System.DirectoryServices.ActiveDirectory::ReplicationFailureCollection
    System.DirectoryServices.ActiveDirectory::ReplicationNeighborCollection
    System.DirectoryServices.ActiveDirectory::ReplicationOperationCollection
    System.DirectoryServices.ActiveDirectory::TopLevelNameCollection
    System.DirectoryServices.ActiveDirectory::TrustRelationshipInformationCollection
    System.DirectoryServices.Protocols::PartialResultsCollection
    System.DirectoryServices.Protocols::SearchResultEntryCollection
    System.DirectoryServices.Protocols::SearchResultReferenceCollection
    System.DirectoryServices::ResultPropertyValueCollection
    System.Drawing.Design::CategoryNameCollection
    System.Drawing.Design::ToolboxItemCollection
    System.Security.AccessControl::AuthorizationRuleCollection
    System.Security.Authentication.ExtendedProtection::ServiceNameCollection
    System.Web.Management::WebBaseEventCollection
    System.Web.UI.Design::ClientScriptItemCollection
    System.Web.UI.WebControls.WebParts::CatalogPartCollection
    System.Web.UI.WebControls.WebParts::ConnectionInterfaceCollection
    System.Web.UI.WebControls.WebParts::ConsumerConnectionPointCollection
    System.Web.UI.WebControls.WebParts::EditorPartCollection
    System.Web.UI.WebControls.WebParts::ProviderConnectionPointCollection
    System.Web.UI.WebControls.WebParts::TransformerTypeCollection
    System.Web.UI.WebControls.WebParts::WebPartCollection
    System.Web.UI.WebControls.WebParts::WebPartDescriptionCollection
    System.Web.UI.WebControls.WebParts::WebPartVerbCollection
    System.Web.UI.WebControls.WebParts::WebPartZoneCollection
    System.Windows.Forms::FormCollection
    System.Windows.Forms::InputLanguageCollection

[SerializableAttribute]
[ComVisibleAttribute(true)]
public ref class ReadOnlyCollectionBase abstract : ICollection, 
	IEnumerable

NameDescription
System_CAPS_protmethodReadOnlyCollectionBase()

Initializes a new instance of the ReadOnlyCollectionBase class.

NameDescription
System_CAPS_pubpropertyCount

Gets the number of elements contained in the ReadOnlyCollectionBase instance.

System_CAPS_protpropertyInnerList

Gets the list of elements contained in the ReadOnlyCollectionBase instance.

NameDescription
System_CAPS_pubmethodEquals(Object^)

Determines whether the specified object is equal to the current object.(Inherited from Object.)

System_CAPS_protmethodFinalize()

Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)

System_CAPS_pubmethodGetEnumerator()

Returns an enumerator that iterates through the ReadOnlyCollectionBase instance.

System_CAPS_pubmethodGetHashCode()

Serves as the default hash function. (Inherited from Object.)

System_CAPS_pubmethodGetType()

Gets the Type of the current instance.(Inherited from Object.)

System_CAPS_protmethodMemberwiseClone()

Creates a shallow copy of the current Object.(Inherited from Object.)

System_CAPS_pubmethodToString()

Returns a string that represents the current object.(Inherited from Object.)

NameDescription
System_CAPS_pubinterfaceSystem_CAPS_privmethodICollection::CopyTo(Array^, Int32)

Copies the entire ReadOnlyCollectionBase to a compatible one-dimensional Array, starting at the specified index of the target array.

System_CAPS_pubinterfaceSystem_CAPS_privpropertyICollection::IsSynchronized

Gets a value indicating whether access to a ReadOnlyCollectionBase object is synchronized (thread safe).

System_CAPS_pubinterfaceSystem_CAPS_privpropertyICollection::SyncRoot

Gets an object that can be used to synchronize access to a ReadOnlyCollectionBase object.

NameDescription
System_CAPS_pubmethodAsParallel()

Overloaded. Enables parallelization of a query.(Defined by ParallelEnumerable.)

System_CAPS_pubmethodAsQueryable()

Overloaded. Converts an IEnumerable to an IQueryable.(Defined by Queryable.)

System_CAPS_pubmethodCast<TResult>()

Casts the elements of an IEnumerable to the specified type.(Defined by Enumerable.)

System_CAPS_pubmethodOfType<TResult>()

Filters the elements of an IEnumerable based on a specified type.(Defined by Enumerable.)

A ReadOnlyCollectionBase instance is always read-only. See CollectionBase for a modifiable version of this class.

Notes to Implementers:

This base class is provided to make it easier for implementers to create a strongly typed read-only custom collection. Implementers are encouraged to extend this base class instead of creating their own. Members of this base class are protected and are intended to be used through a derived class only.

This class makes the underlying collection available through the InnerList property, which is intended for use only by classes that are derived directly from ReadOnlyCollectionBase. The derived class must ensure that its own users cannot modify the underlying collection.

The following code example implements the ReadOnlyCollectionBase class.

using namespace System;
using namespace System::Collections;
public ref class ROCollection: public ReadOnlyCollectionBase
{
public:
   ROCollection( IList^ sourceList )
   {
      InnerList->AddRange( sourceList );
   }

   property Object^ Item [int]
   {
      Object^ get( int index )
      {
         return (InnerList[ index ]);
      }

   }
   int IndexOf( Object^ value )
   {
      return (InnerList->IndexOf( value ));
   }

   bool Contains( Object^ value )
   {
      return (InnerList->Contains( value ));
   }

};

void PrintIndexAndValues( ROCollection^ myCol );
void PrintValues2( ROCollection^ myCol );
int main()
{
   // Create an ArrayList.
   ArrayList^ myAL = gcnew ArrayList;
   myAL->Add( "red" );
   myAL->Add( "blue" );
   myAL->Add( "yellow" );
   myAL->Add( "green" );
   myAL->Add( "orange" );
   myAL->Add( "purple" );

   // Create a new ROCollection that contains the elements in myAL.
   ROCollection^ myCol = gcnew ROCollection( myAL );

   // Display the contents of the collection using the enumerator.
   Console::WriteLine( "Contents of the collection (using enumerator):" );
   PrintValues2( myCol );

   // Display the contents of the collection using the Count property and the Item property.
   Console::WriteLine( "Contents of the collection (using Count and Item):" );
   PrintIndexAndValues( myCol );

   // Search the collection with Contains and IndexOf.
   Console::WriteLine( "Contains yellow: {0}", myCol->Contains( "yellow" ) );
   Console::WriteLine( "orange is at index {0}.", myCol->IndexOf( "orange" ) );
   Console::WriteLine();
}


// Uses the Count property and the Item property.
void PrintIndexAndValues( ROCollection^ myCol )
{
   for ( int i = 0; i < myCol->Count; i++ )
      Console::WriteLine( "   [{0}]:   {1}", i, myCol->Item[ i ] );
   Console::WriteLine();
}


// Uses the enumerator. 
void PrintValues2( ROCollection^ myCol )
{
   System::Collections::IEnumerator^ myEnumerator = myCol->GetEnumerator();
   while ( myEnumerator->MoveNext() )
      Console::WriteLine( "   {0}", myEnumerator->Current );

   Console::WriteLine();
}

/* 
This code produces the following output.

Contents of the collection (using enumerator):
   red
   blue
   yellow
   green
   orange
   purple

Contents of the collection (using Count and Item):
   [0]:   red
   [1]:   blue
   [2]:   yellow
   [3]:   green
   [4]:   orange
   [5]:   purple

Contains yellow: True
orange is at index 4.

*/

Universal Windows Platform
Available since 10
.NET Framework
Available since 1.1

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

This implementation does not provide a synchronized (thread safe) wrapper for a ReadOnlyCollectionBase, but derived classes can create their own synchronized versions of the ReadOnlyCollectionBase using the SyncRoot property.

Enumerating through a collection is intrinsically not a thread-safe procedure. Even when a collection is synchronized, other threads can still modify the collection, which causes the enumerator to throw an exception. To guarantee thread safety during enumeration, you can either lock the collection during the entire enumeration or catch the exceptions resulting from changes made by other threads.

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