ReadOnlyCollectionBase-Klasse

Stellt die abstract-Basisklasse für eine stark typisierte nicht generische schreibgeschützte Auflistung bereit.

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

Syntax

'Declaration
<SerializableAttribute> _
<ComVisibleAttribute(True)> _
Public MustInherit Class ReadOnlyCollectionBase
    Implements ICollection, IEnumerable
'Usage
Dim instance As ReadOnlyCollectionBase

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

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

/** @attribute SerializableAttribute() */ 
/** @attribute ComVisibleAttribute(true) */ 
public abstract class ReadOnlyCollectionBase implements ICollection, IEnumerable

SerializableAttribute 
ComVisibleAttribute(true) 
public abstract class ReadOnlyCollectionBase implements ICollection, IEnumerable

Hinweise

Eine ReadOnlyCollectionBase-Instanz ist immer schreibgeschützt. Eine nicht schreibgeschützte Version dieser Klasse finden Sie unter CollectionBase.

Hinweise für Implementierer Diese Basisklasse wird bereitgestellt, um das Erstellen einer benutzerdefinierten, schreibgeschützten streng typisierten Auflistung bei der Implementierung zu vereinfachen. Es wird empfohlen, bei der Implementierung diese Basisklasse zu erweitern, anstatt eine eigene zu erstellen. Die Member dieser Basisklasse sind geschützt und dürfen nur durch eine abgeleitete Klasse verwendet werden. Diese Klasse stellt die zugrunde liegende Auflistung über die InnerList-Eigenschaft zur Verfügung, die nur für die Verwendung durch direkt von ReadOnlyCollectionBase abgeleiteten Klassen vorgesehen ist. Für die abgeleitete Klasse muss sichergestellt sein, dass ihre eigenen Benutzer die zugrunde liegende Auflistung nicht ändern können.

Beispiel

Im folgenden Codebeispiel wird die ReadOnlyCollectionBase-Klasse implementiert.

Imports System
Imports System.Collections

Public Class ROCollection
    Inherits ReadOnlyCollectionBase


    Public Sub New(sourceList As IList)
        InnerList.AddRange(sourceList)
    End Sub 'New


    Default Public ReadOnly Property Item(index As Integer) As [Object]
        Get
            Return InnerList(index)
        End Get
    End Property


    Public Function IndexOf(value As [Object]) As Integer
        Return InnerList.IndexOf(value)
    End Function 'IndexOf


    Public Function Contains(value As [Object]) As Boolean
        Return InnerList.Contains(value)
    End Function 'Contains

End Class 'ROCollection 


Public Class SamplesCollectionBase

    Public Shared Sub Main()

        ' Create an ArrayList.
        Dim myAL As New 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.
        Dim myCol As New ROCollection(myAL)

        ' Display the contents of the collection using For Each. This is the preferred method.
        Console.WriteLine("Contents of the collection (using For Each):")
        PrintValues1(myCol)

        ' 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()

    End Sub 'Main


    ' Uses the Count property and the Item property.
    Public Shared Sub PrintIndexAndValues(myCol As ROCollection)
        Dim i As Integer
        For i = 0 To myCol.Count - 1
            Console.WriteLine("   [{0}]:   {1}", i, myCol(i))
        Next i
        Console.WriteLine()
    End Sub 'PrintIndexAndValues


    ' Uses the For Each statement which hides the complexity of the enumerator.
    ' NOTE: The For Each statement is the preferred way of enumerating the contents of a collection.
    Public Shared Sub PrintValues1(myCol As ROCollection)
        Dim obj As [Object]
        For Each obj In  myCol
            Console.WriteLine("   {0}", obj)
        Next obj
        Console.WriteLine()
    End Sub 'PrintValues1


    ' Uses the enumerator. 
    ' NOTE: The For Each statement is the preferred way of enumerating the contents of a collection.
    Public Shared Sub PrintValues2(myCol As ROCollection)
        Dim myEnumerator As System.Collections.IEnumerator = myCol.GetEnumerator()
        While myEnumerator.MoveNext()
            Console.WriteLine("   {0}", myEnumerator.Current)
        End While
        Console.WriteLine()
    End Sub 'PrintValues2

End Class 'SamplesCollectionBase 


'This code produces the following output.
'
'Contents of the collection (using For Each):
'   red
'   blue
'   yellow
'   green
'   orange
'   purple
'
'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.

using System;
using System.Collections;

public class ROCollection : ReadOnlyCollectionBase  {

   public ROCollection( IList sourceList )  {
      InnerList.AddRange( sourceList );
   }

   public Object this[ int index ]  {
      get  {
         return( InnerList[index] );
      }
   }

   public int IndexOf( Object value )  {
      return( InnerList.IndexOf( value ) );
   }

   public bool Contains( Object value )  {
      return( InnerList.Contains( value ) );
   }

}


public class SamplesCollectionBase  {

   public static void Main()  {

      // Create an ArrayList.
      ArrayList myAL = new 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 = new ROCollection( myAL );

      // Display the contents of the collection using foreach. This is the preferred method.
      Console.WriteLine( "Contents of the collection (using foreach):" );
      PrintValues1( myCol );

      // 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.
   public static void PrintIndexAndValues( ROCollection myCol )  {
      for ( int i = 0; i < myCol.Count; i++ )
         Console.WriteLine( "   [{0}]:   {1}", i, myCol[i] );
      Console.WriteLine();
   }

   // Uses the foreach statement which hides the complexity of the enumerator.
   // NOTE: The foreach statement is the preferred way of enumerating the contents of a collection.
   public static void PrintValues1( ROCollection myCol )  {
      foreach ( Object obj in myCol )
         Console.WriteLine( "   {0}", obj );
      Console.WriteLine();
   }

   // Uses the enumerator. 
   // NOTE: The foreach statement is the preferred way of enumerating the contents of a collection.
   public static 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 foreach):
   red
   blue
   yellow
   green
   orange
   purple

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.

*/

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.

*/

import System.*;
import System.Collections.*;

public class ROCollection extends ReadOnlyCollectionBase
{
    public ROCollection(IList sourceList) 
    {
        get_InnerList().AddRange(sourceList);
    } //ROCollection
   
    /** @property 
     */
    public Object get_Item(int index)
    {
        return get_InnerList().get_Item(index);
    } //get_Item
     
    public int IndexOf(Object value) 
    {
        return get_InnerList().IndexOf(value);
    } //IndexOf
   
    public boolean Contains(Object value) 
    {
        return get_InnerList().Contains(value);
    } //Contains
} //ROCollection

public class SamplesCollectionBase
{
    public static void main(String[] args)
    {
        // Create an ArrayList.
        ArrayList myAL = new 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 = new ROCollection(myAL);
          
        // Display the contents of the collection using for. This is the 
        // preferred method.
        Console.WriteLine("Contents of the collection (using for):");
        PrintValues1(myCol);
          
        // 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}",
            (System.Boolean)myCol.Contains("yellow"));
        Console.WriteLine("orange is at index {0}.", 
            (Int32)myCol.IndexOf("orange"));
        Console.WriteLine();
    } //main
    
    // Uses the Count property and the Item property.
    public static void PrintIndexAndValues(ROCollection myCol) 
    {
        for(int i = 0; i < myCol.get_Count(); i++) {
            Console.WriteLine("   [{0}]:   {1}",(Int32)i, myCol.get_Item(i));
        } 
        Console.WriteLine();
    } //PrintIndexAndValues
   
    // Uses the for statement which hides the complexity of the enumerator.
    // NOTE: The for statement is the preferred way of enumerating the contents
    // of a collection.
    public static void PrintValues1(ROCollection myCol) 
    {
        for (int iCtr = 0; iCtr < myCol.get_Count(); iCtr++ ) {
            Object obj = myCol.get_Item(iCtr);
            Console.WriteLine("   {0}", obj);
        }
        Console.WriteLine();
    } //PrintValues1
     
    // Uses the enumerator. 
    // NOTE: The for statement is the preferred way of enumerating the
    // contents of a collection.
    public static void PrintValues2(ROCollection myCol) 
    {
        System.Collections.IEnumerator myEnumerator = myCol.GetEnumerator();
        while(myEnumerator.MoveNext()) {
            Console.WriteLine("   {0}", myEnumerator.get_Current());
        }
        Console.WriteLine();
    } //PrintValues2
} //SamplesCollectionBase
 
/* 
This code produces the following output.

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

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.

*/

Vererbungshierarchie

System.Object
  System.Collections.ReadOnlyCollectionBase
     Abgeleitete Klassen

Threadsicherheit

Öffentliche statische (Shared in Visual Basic) Member dieses Typs sind threadsicher. Bei Instanzmembern ist die Threadsicherheit nicht gewährleistet.

Diese Implementierung stellt keinen synchronisierten (threadsicheren) Wrapper für die ReadOnlyCollectionBase bereit, abgeleitete Klassen können jedoch mithilfe der SyncRoot-Eigenschaft eigene synchronisierte Versionen der ReadOnlyCollectionBase erstellen.

Die Enumeration einer Auflistung ist systemintern keine threadsichere Prozedur. Selbst wenn eine Auflistung synchronisiert wird, besteht die Möglichkeit, dass andere Threads sie ändern. Dies führt dazu, dass der Enumerator eine Ausnahme auslöst. Um während der Enumeration Threadsicherheit zu gewährleisten, können Sie entweder die Auflistung während der gesamten Enumeration sperren, oder Sie können die durch andere Threads aufgrund von Änderungen ausgelösten Ausnahmen abfangen.

Plattformen

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

.NET Framework unterstützt nicht alle Versionen sämtlicher Plattformen. Eine Liste der unterstützten Versionen finden Sie unter Systemanforderungen.

Versionsinformationen

.NET Framework

Unterstützt in: 2.0, 1.1, 1.0

Siehe auch

Referenz

ReadOnlyCollectionBase-Member
System.Collections-Namespace
ArrayList-Klasse
CollectionBase-Klasse
System.Collections.Generic