ReadOnlyCollectionBase.Count プロパティとは何？わかりやすく解説 Weblio辞書

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.NET Framework クラスライブラリリファレンス

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ReadOnlyCollectionBase.Count プロパティ

ReadOnlyCollectionBase インスタンスに格納されている要素の数を取得します。

名前空間: System.Collections
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

Public Overridable ReadOnly
 Property Count As Integer

Visual Basic (使用法)

Dim instance As ReadOnlyCollectionBase
Dim value As Integer

value = instance.Count

public virtual int Count { get;
 }

C++

public:
virtual property int Count {
    int get ();
}

/** @property */
public int get_Count ()

JScript

public function get Count
 () : int

プロパティ値
ReadOnlyCollectionBase インスタンスに格納されている要素の数。このプロパティ値を取得することは、O(1) 操作になります。

使用例

ReadOnlyCollectionBase クラスを実装するコード例を次に示します。

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 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.

*/

C++

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.

*/

プラットフォーム

バージョン情報

.NET Framework
サポート対象 : 2.0、1.1、1.0

参照

関連項目
ReadOnlyCollectionBase クラス
ReadOnlyCollectionBase メンバ
System.Collections 名前空間

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ReadOnlyCollectionBase.Count プロパティとは？ わかりやすく解説

ReadOnlyCollectionBase.Count プロパティ

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ReadOnlyCollectionBase.Count プロパティとは？わかりやすく解説