Array.AsReadOnly ジェネリック メソッド

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Array.AsReadOnly ジェネリック メソッド

メモ : このメソッドは、.NET Framework version 2.0 で新しく追加されたものです。

指定した配列をラップする読み取り専用のラッパーを作成します。

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

Visual Basic (宣言)

Public Shared Function AsReadOnly(Of
 T) ( _
    array As T() _
) As ReadOnlyCollection(Of T)

Visual Basic (使用法)

Dim array As T()
Dim returnValue As ReadOnlyCollection(Of
 T)

returnValue = Array.AsReadOnly(array)

C#

public static ReadOnlyCollection<T> AsReadOnly<T>
 (
    T[] array
)

C++

public:
generic<typename T>
static ReadOnlyCollection<T>^ AsReadOnly (
    array<T>^ array
)

J#

J# では、ジェネリックな型およびメソッドは使用できますが、新規に宣言することはできません。

JScript

JScript では、ジェネリックな型およびメソッドは使用できません。

型パラメータ

T

配列要素の型。

パラメータ

array

読み取り専用の ReadOnlyCollection ラッパーでラップする、インデックス番号が 0 から始まる 1 次元配列。

戻り値
指定した配列をラップする読み取り専用の ReadOnlyCollection ラッパー。

例外

例外の種類	条件
ArgumentNullException	array が null 参照 (Visual Basic では Nothing) です。

解説

配列が変更されないようにするには、配列を公開するときに必ずこのラッパーを使用するようにします。

読み取り専用のコレクションは、コレクションの変更を防ぐラッパーがコレクションに組み込まれているに過ぎません。したがって、基になっているコレクションで変更が加えられた場合、読み取り専用のコレクションでもその内容が反映されます。

このメソッドは O(1) 操作です。

使用例

次の例では、配列を読み取り専用の ReadOnlyCollection でラップしています。

Visual Basic

Imports System
Imports System.Collections.Generic

Public Class SamplesArray

    Public Shared Sub Main()

        ' Create and initialize a new string array.
        Dim myArr As String()
 =  {"The", "quick",
 "brown", "fox"}

        ' Display the values of the array.
        Console.WriteLine("The string array initially contains
 the following values:")
        PrintIndexAndValues(myArr)

        ' Create a read-only IList wrapper around the array.
        Dim myList As IList(Of
 String) = Array.AsReadOnly(myArr) '

        ' Display the values of the read-only IList.
        Console.WriteLine("The read-only IList contains the following
 values:")
        PrintIndexAndValues(myList)

        ' Attempt to change a value through the wrapper.
        Try
            myList(3) = "CAT"
        Catch e As NotSupportedException
            Console.WriteLine("{0} - {1}", e.GetType(),
 e.Message)
            Console.WriteLine()
        End Try

        ' Change a value in the original array.
        myArr(2) = "RED"

        ' Display the values of the array.
        Console.WriteLine("After changing the third element, the
 string array contains the following values:")
        PrintIndexAndValues(myArr)

        ' Display the values of the read-only IList.
        Console.WriteLine("After changing the third element, the
 read-only IList contains the following values:")
        PrintIndexAndValues(myList)

    End Sub 'Main

    Overloads Public Shared
 Sub PrintIndexAndValues(myArr() As String)
        Dim i As Integer
        For i = 0 To myArr.Length - 1
            Console.WriteLine("   [{0}] : {1}", i,
 myArr(i))
        Next i
        Console.WriteLine()
    End Sub 'PrintIndexAndValues

    Overloads Public Shared
 Sub PrintIndexAndValues(myList As IList(Of
 String))
        Dim i As Integer
        For i = 0 To myList.Count - 1
            Console.WriteLine("   [{0}] : {1}", i,
 myList(i))
        Next i
        Console.WriteLine()
    End Sub 'PrintIndexAndValues
 

End Class 'SamplesArray


'This code produces the following output.
'
'The string array initially contains the following values:
'   [0] : The
'   [1] : quick
'   [2] : brown
'   [3] : fox
'
'The read-only IList contains the following values:
'   [0] : The
'   [1] : quick
'   [2] : brown
'   [3] : fox
'
'System.NotSupportedException - Collection is read-only.
'
'After changing the third element, the string array contains the following
 values:
'   [0] : The
'   [1] : quick
'   [2] : RED
'   [3] : fox
'
'After changing the third element, the read-only IList contains the
 following values:
'   [0] : The
'   [1] : quick
'   [2] : RED
'   [3] : fox

C#

using System;
using System.Collections.Generic;

public class SamplesArray  {
 
   public static void Main()
  {
 
      // Create and initialize a new string array.
      String[] myArr = { "The", "quick", "brown", "fox"
 };
 
      // Display the values of the array.
      Console.WriteLine( "The string array initially contains
 the following values:" );
      PrintIndexAndValues( myArr );

      // Create a read-only IList wrapper around the array.
      IList<String> myList = Array.AsReadOnly( myArr );
      
      // Display the values of the read-only IList.
      Console.WriteLine( "The read-only IList contains the following values:"
 );
      PrintIndexAndValues( myList );

      // Attempt to change a value through the wrapper.
      try  {
         myList[3] = "CAT";
      }
      catch ( NotSupportedException e )  {
         Console.WriteLine( "{0} - {1}", e.GetType(), e.Message );
         Console.WriteLine();
      }

      // Change a value in the original array.
      myArr[2] = "RED";

      // Display the values of the array.
      Console.WriteLine( "After changing the third element, the string
 array contains the following values:" );
      PrintIndexAndValues( myArr );

      // Display the values of the read-only IList.
      Console.WriteLine( "After changing the third element, the read-only IList
 contains the following values:" );
      PrintIndexAndValues( myList );

   }
 
   public static void PrintIndexAndValues(
 String[] myArr )  {
      for ( int i = 0; i < myArr.Length;
 i++ )  {
         Console.WriteLine( "   [{0}] : {1}", i, myArr[i] );
      }
      Console.WriteLine();
   }

   public static void PrintIndexAndValues(
 IList<String> myList )  {
      for ( int i = 0; i < myList.Count;
 i++ )  {
         Console.WriteLine( "   [{0}] : {1}", i, myList[i] );
      }
      Console.WriteLine();
   }

}


/* 
This code produces the following output.

The string array initially contains the following values:
   [0] : The
   [1] : quick
   [2] : brown
   [3] : fox

The read-only IList contains the following values:
   [0] : The
   [1] : quick
   [2] : brown
   [3] : fox

System.NotSupportedException - Collection is read-only.

After changing the third element, the string array contains the
 following values:
   [0] : The
   [1] : quick
   [2] : RED
   [3] : fox

After changing the third element, the read-only IList contains the following values:
   [0] : The
   [1] : quick
   [2] : RED
   [3] : fox

*/

C++

using namespace System;
using namespace System::Collections::Generic;

namespace Samples
{
    public ref class SamplesArray
    {
    public:
        static void Work()
        {

            // Create and initialize a new string array.
            array <String^>^ textArray = 
                {"The", "quick", "brown", "fox"};

            // Display the values of the array.
            Console::WriteLine("The string array initially
 contains "
                "the following values:");
            PrintIndexAndValues(textArray);

            // Create a read-only IList wrapper around the array.
            IList <String^>^ textList = Array::AsReadOnly(textArray);

            // Display the values of the read-only IList.
            Console::WriteLine("The read-only IList contains " 
                "the following values:");
            PrintIndexAndValues(textList);

            // Attempt to change a value through the wrapper.
            try
            {
                textList[3] = "CAT";
            }
            catch (NotSupportedException^ ex) 
            {
                Console::WriteLine("{0} - {1}", ex->GetType(), 
                    ex->Message);
                Console::WriteLine();
            }


            // Change a value in the original array.
            textArray[2] = "RED";

            // Display the values of the array.
            Console::WriteLine("After changing the third element," 
                "the string array contains the following
 values:");
            PrintIndexAndValues(textArray);

            // Display the values of the read-only IList.
            Console::WriteLine("After changing the third element, the"
 
                " read-only IList contains the following values:");
            PrintIndexAndValues(textList);
        }

        static void PrintIndexAndValues(array<String^>^
 textArray)
        {
            for (int i = 0; i < textArray->Length;
 i++)
            {
                Console::WriteLine("   [{0}] : {1}", i, textArray[i]);
            }
            Console::WriteLine();
        }

        static void PrintIndexAndValues(IList<String^>^
 textList)
        {
            for (int i = 0; i < textList->Count;
 i++)
            {
                Console::WriteLine("   [{0}] : {1}", i, textList[i]);
            }
            Console::WriteLine();
        }
    };
}

int main()
{
    Samples::SamplesArray::Work();

}

/* 
This code produces the following output.

The string array initially contains the following values:
[0] : The
[1] : quick
[2] : brown
[3] : fox

The read-only IList contains the following values:
[0] : The
[1] : quick
[2] : brown
[3] : fox

System.NotSupportedException - Collection is read-only.

After changing the third element, the string array contains the
 following values:
[0] : The
[1] : quick
[2] : RED
[3] : fox

After changing the third element, the read-only IList contains the following values:
[0] : The
[1] : quick
[2] : RED
[3] : fox

*/

プラットフォーム

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

開発プラットフォームの中には、.NET Framework によってサポートされていないバージョンがあります。サポートされているバージョンについては、「システム要件」を参照してください。

バージョン情報

.NET Framework
サポート対象 : 2.0

参照

関連項目
Array クラス
Array メンバ
System 名前空間