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ReadOnlyCollectionBase.Count Property

Gets the number of elements contained in the ReadOnlyCollectionBase instance.

[Visual Basic]
Public Overridable ReadOnly Property Count As Integer  Implements _
   ICollection.Count
[C#]
public virtual int Count {get;}
[C++]
public: __property virtual int get_Count();
[JScript]
public function get Count() : int;

Property Value

The number of elements contained in the ReadOnlyCollectionBase instance.

Implements

ICollection.Count

Example

[Visual Basic, C#, C++] The following code example implements the ReadOnlyCollectionBase class.

[Visual Basic] 
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 the enumerator.
      Console.WriteLine("Contents of the collection (using enumerator):")
      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()

      ' Display the contents of the collection using the Count property and the Item property.
      Console.WriteLine("Contents of the collection (using Count and Item):")
      PrintIndexAndValues2(myCol)

   End Sub 'Main

   Public Shared Sub PrintIndexAndValues(myCol As ROCollection)
      Dim i As Integer = 0
      Dim myEnumerator As System.Collections.IEnumerator = myCol.GetEnumerator()
      While myEnumerator.MoveNext()
         Console.WriteLine("   [{0}]:   {1}", i, myEnumerator.Current)
         i += 1
      End While
      Console.WriteLine()
   End Sub 'PrintIndexAndValues

   Public Shared Sub PrintIndexAndValues2(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 'PrintIndexAndValues2

End Class 'SamplesCollectionBase 


'This code produces the following output.
'
'Contents of the collection (using enumerator):
'   [0]:   red
'   [1]:   blue
'   [2]:   yellow
'   [3]:   green
'   [4]:   orange
'   [5]:   purple
'
'Contains yellow: True
'orange is at index 4.
'
'Contents of the collection (using Count and Item):
'   [0]:   red
'   [1]:   blue
'   [2]:   yellow
'   [3]:   green
'   [4]:   orange
'   [5]:   purple


[C#] 
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 the enumerator.
      Console.WriteLine( "Contents of the collection (using enumerator):" );
      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();

      // Display the contents of the collection using the Count property and the Item property.
      Console.WriteLine( "Contents of the collection (using Count and Item):" );
      PrintIndexAndValues2( myCol );

   }
 
   public static void PrintIndexAndValues( ROCollection myCol )  {
      int i = 0;
      System.Collections.IEnumerator myEnumerator = myCol.GetEnumerator();
      while ( myEnumerator.MoveNext() )
         Console.WriteLine( "   [{0}]:   {1}", i++, myEnumerator.Current );
      Console.WriteLine();
   }

   public static void PrintIndexAndValues2( ROCollection myCol )  {
      for ( int i = 0; i < myCol.Count; i++ )
         Console.WriteLine( "   [{0}]:   {1}", i, myCol[i] );
      Console.WriteLine();
   }

}


/* 
This code produces the following output.

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

Contains yellow: True
orange is at index 4.

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

*/


[C++] 
#using <mscorlib.dll>
using namespace System;
using namespace System::Collections;

public __gc class ROCollection : public ReadOnlyCollectionBase  {

public:
    ROCollection( IList* sourceList )  {
        InnerList->AddRange( sourceList );
    }

public:
    __property Object* get_Item( int index )  {
        return( InnerList->Item[index] );
    }

public:
    int IndexOf( Object* value )  {
        return( InnerList->IndexOf( value ) );
    }

public:
    bool Contains( Object* value )  {
        return( InnerList->Contains( value ) );
    }

};

static void PrintIndexAndValues( ROCollection* myCol )  {
    int i = 0;
    System::Collections::IEnumerator* myEnumerator = myCol->GetEnumerator();
    while ( myEnumerator->MoveNext() )
        Console::WriteLine( S"   [{0}]:   {1}", __box(i++), myEnumerator->Current );
    Console::WriteLine();
}

static void PrintIndexAndValues2( ROCollection* myCol )  {
    for ( int i = 0; i < myCol->Count; i++ )
        Console::WriteLine( S"   [{0}]:   {1}", __box(i), myCol->Item[i] );
    Console::WriteLine();
}

int main()  {

    // Create an ArrayList.
    ArrayList* myAL = new ArrayList();
    myAL->Add( S"red" );
    myAL->Add( S"blue" );
    myAL->Add( S"yellow" );
    myAL->Add( S"green" );
    myAL->Add( S"orange" );
    myAL->Add( S"purple" );

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

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

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

    // Display the contents of the collection using the Count property and the Item property.
    Console::WriteLine( S"Contents of the collection (using Count and Item):" );
    PrintIndexAndValues2( myCol );

}

/* 
This code produces the following output.

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

Contains yellow: True
orange is at index 4.

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

*/

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

See Also

ReadOnlyCollectionBase Class | ReadOnlyCollectionBase Members | System.Collections Namespace

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