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CollectionBase Class

Provides the abstract base class for a strongly typed collection.

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

[SerializableAttribute] 
[ComVisibleAttribute(true)] 
public abstract class CollectionBase : IList, ICollection, IEnumerable
/** @attribute SerializableAttribute() */ 
/** @attribute ComVisibleAttribute(true) */ 
public abstract class CollectionBase implements IList, ICollection, 
	IEnumerable
SerializableAttribute 
ComVisibleAttribute(true) 
public abstract class CollectionBase implements IList, ICollection, 
	IEnumerable
Not applicable.

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

The capacity of a CollectionBase is the number of elements the CollectionBase can hold. As elements are added to a CollectionBase, the capacity is automatically increased as required through reallocation. The capacity can be decreased by setting the Capacity property explicitly.

Notes to Implementers: This base class is provided to make it easier for implementers to create a strongly typed custom collection. Implementers are encouraged to extend this base class instead of creating their own.

The following code example implements the CollectionBase class and uses that implementation to create a collection of Int16 objects.

using System;
using System.Collections;

public class Int16Collection : CollectionBase  {

   public Int16 this[ int index ]  {
      get  {
         return( (Int16) List[index] );
      }
      set  {
         List[index] = value;
      }
   }

   public int Add( Int16 value )  {
      return( List.Add( value ) );
   }

   public int IndexOf( Int16 value )  {
      return( List.IndexOf( value ) );
   }

   public void Insert( int index, Int16 value )  {
      List.Insert( index, value );
   }

   public void Remove( Int16 value )  {
      List.Remove( value );
   }

   public bool Contains( Int16 value )  {
      // If value is not of type Int16, this will return false.
      return( List.Contains( value ) );
   }

   protected override void OnInsert( int index, Object value )  {
      // Insert additional code to be run only when inserting values.
   }

   protected override void OnRemove( int index, Object value )  {
      // Insert additional code to be run only when removing values.
   }

   protected override void OnSet( int index, Object oldValue, Object newValue )  {
      // Insert additional code to be run only when setting values.
   }

   protected override void OnValidate( Object value )  {
      if ( value.GetType() != typeof(System.Int16) )
         throw new ArgumentException( "value must be of type Int16.", "value" );
   }

}


public class SamplesCollectionBase  {

   public static void Main()  {
 
      // Create and initialize a new CollectionBase.
      Int16Collection myI16 = new Int16Collection();

      // Add elements to the collection.
      myI16.Add( (Int16) 1 );
      myI16.Add( (Int16) 2 );
      myI16.Add( (Int16) 3 );
      myI16.Add( (Int16) 5 );
      myI16.Add( (Int16) 7 );

      // Display the contents of the collection using foreach. This is the preferred method.
      Console.WriteLine( "Contents of the collection (using foreach):" );
      PrintValues1( myI16 );

      // Display the contents of the collection using the enumerator.
      Console.WriteLine( "Contents of the collection (using enumerator):" );
      PrintValues2( myI16 );

      // Display the contents of the collection using the Count property and the Item property.
      Console.WriteLine( "Initial contents of the collection (using Count and Item):" );
      PrintIndexAndValues( myI16 );

      // Search the collection with Contains and IndexOf.
      Console.WriteLine( "Contains 3: {0}", myI16.Contains( 3 ) );
      Console.WriteLine( "2 is at index {0}.", myI16.IndexOf( 2 ) );
      Console.WriteLine();

      // Insert an element into the collection at index 3.
      myI16.Insert( 3, (Int16) 13 );
      Console.WriteLine( "Contents of the collection after inserting at index 3:" );
      PrintIndexAndValues( myI16 );

      // Get and set an element using the index.
      myI16[4] = 123;
      Console.WriteLine( "Contents of the collection after setting the element at index 4 to 123:" );
      PrintIndexAndValues( myI16 );

      // Remove an element from the collection.
      myI16.Remove( (Int16) 2 );

      // Display the contents of the collection using the Count property and the Item property.
      Console.WriteLine( "Contents of the collection after removing the element 2:" );
      PrintIndexAndValues( myI16 );

   }
 
   // Uses the Count property and the Item property.
   public static void PrintIndexAndValues( Int16Collection 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( Int16Collection myCol )  {
      foreach ( Int16 i16 in myCol )
         Console.WriteLine( "   {0}", i16 );
      Console.WriteLine();
   }

   // Uses the enumerator. 
   // NOTE: The foreach statement is the preferred way of enumerating the contents of a collection.
   public static void PrintValues2( Int16Collection 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):
   1
   2
   3
   5
   7

Contents of the collection (using enumerator):
   1
   2
   3
   5
   7

Initial contents of the collection (using Count and Item):
   [0]:   1
   [1]:   2
   [2]:   3
   [3]:   5
   [4]:   7

Contains 3: True
2 is at index 1.

Contents of the collection after inserting at index 3:
   [0]:   1
   [1]:   2
   [2]:   3
   [3]:   13
   [4]:   5
   [5]:   7

Contents of the collection after setting the element at index 4 to 123:
   [0]:   1
   [1]:   2
   [2]:   3
   [3]:   13
   [4]:   123
   [5]:   7

Contents of the collection after removing the element 2:
   [0]:   1
   [1]:   3
   [2]:   13
   [3]:   123
   [4]:   7

*/


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

public class Int16Collection extends CollectionBase
{
    /** @property 
     */
    public short get_Value(int index)
    {
        short s = System.Convert.ToInt16(get_List().get_Item(index));
        return(s) ; 
    } //get_Value

    /** @property 
     */
    public void set_Value(int index,short value)
    {
        get_List().set_Item(index, (Int16)value);
    } //set_Value
   
    public int Add(short value) 
    {
        return get_List().Add((Int16)value);
    } //Add
   
    public int IndexOf(short value)
    {
        return get_List().IndexOf((Int16)value);
    } //IndexOf
     
    public void Insert(int index, short value) 
    {
        get_List().Insert(index, (Int16)value);
    } //Insert
   
    public void Remove(short value) 
    {
        get_List().Remove((Int16)value);
    } //Remove
   
    public boolean Contains(short value) 
    {
        // If value is not of type Int16, this will return false.
        return get_List().Contains((Int16)value);
    } //Contains
   
    protected   void OnInsert(int index, Object value) 
    {
        // Insert additional code to be run only when inserting values.
    } //OnInsert
    
       protected   void OnRemove(int index, Object value) 
    {
        // Insert additional code to be run only when removing values.
    } //OnRemove
    
       protected   void OnSet(int index, Object oldValue, Object newValue) 
    {
        // Insert additional code to be run only when setting values.
    } //OnSet
    
    protected   void OnValidate(Object value) 
    {
        if ( value.GetType() != Type.GetType("System.Int16")  ) {
            throw new ArgumentException("value must be of type Int16.", 
                "value");
        }
    } //OnValidate
} //Int16Collection

public class SamplesCollectionBase
{
    public static void main(String[] args)
    {
        // Create and initialize a new CollectionBase.
        Int16Collection myI16 =  new Int16Collection();
      
        // Add elements to the collection.
        myI16.Add((Int16)1);
        myI16.Add((Int16)2);
        myI16.Add((Int16)3);
        myI16.Add((Int16)5);
        myI16.Add((Int16)7);
          
        // Display the contents of the collection using for.
        Console.WriteLine("Contents of the collection (using for):");
        PrintValues1(myI16);
          
        // Display the contents of the collection using the enumerator.
        Console.WriteLine("Contents of the collection (using enumerator):");
        PrintValues2(myI16);
          
        // Display the contents of the collection using the Count property and 
        // the Item property.
        Console.WriteLine("Initial contents of the collection "
            + "(using Count and Item):");
        PrintIndexAndValues(myI16);
          
        // Search the collection with Contains and IndexOf.
        Console.WriteLine("Contains 3: {0}", 
            (System.Boolean)myI16.Contains((Int16)3));
        Console.WriteLine("2 is at index {0}.", 
            (Int16)myI16.IndexOf((Int16)2));
        Console.WriteLine();
          
        // Insert an element into the collection at index 3.
        myI16.Insert(3, (Int16)13);
        Console.WriteLine("Contents of the collection after inserting at"
            + " index 3:");
        PrintIndexAndValues(myI16);
          
        // Get and set an element using the index.
        myI16 .set_Item( 4 ,(Int16)123 );
        Console.WriteLine("Contents of the collection after setting the"
            + " element at index 4 to 123:");
        PrintIndexAndValues(myI16);
          
        // Remove an element from the collection.
        myI16.Remove((Int16)2);
          
        // Display the contents of the collection using the Count property and
        // the Item property.
        Console.WriteLine("Contents of the collection after removing the"
            + " element 2:");
        PrintIndexAndValues(myI16);
   } //main
    
   // Uses the Count property and the Item property.
    public static void PrintIndexAndValues(Int16Collection 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(Int16Collection myCol) 
    {
        for (int iCtr = 0; iCtr < myCol.get_Count(); iCtr++) {
            Console.WriteLine("   {0}", myCol.get_Item(iCtr));
        }
        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(Int16Collection myCol) 
    {
        System.Collections.IEnumerator myEnumerator = myCol.GetEnumerator();
        while(myEnumerator.MoveNext()) {
            Console.WriteLine("   {0}", myEnumerator.get_Current());
        }
        Console.WriteLine();
    } //PrintValues2
} //SamplesCollectionBase

/* 
Contents of the collection (using for):
   1
   2
   3
   5
   7

Contents of the collection (using enumerator):
   1
   2
   3
   5
   7

Initial contents of the collection (using Count and Item):
   [0]:   1
   [1]:   2
   [2]:   3
   [3]:   5
   [4]:   7

Contains 3: True
2 is at index 1.

Contents of the collection after inserting at index 3:
   [0]:   1
   [1]:   2
   [2]:   3
   [3]:   13
   [4]:   5
   [5]:   7

Contents of the collection after setting the element at index 4 to 123:
   [0]:   1
   [1]:   2
   [2]:   3
   [3]:   13
   [4]:   123
   [5]:   7

Contents of the collection after removing the element 2:
   [0]:   1
   [1]:   3
   [2]:   13
   [3]:   123
   [4]:   7

*/


System.Object
  System.Collections.CollectionBase
     Derived Classes

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 CollectionBase, but derived classes can create their own synchronized versions of the CollectionBase 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.

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0
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