Array.AsReadOnly<T>(T[]) Méthode

Référence

Définition

Espace de noms:: System

Assembly:: System.Runtime.dll

Assembly:: mscorlib.dll

Assembly:: netstandard.dll

Important

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Retourne un wrapper en lecture seule pour le tableau spécifié.

public:
generic <typename T>
 static System::Collections::ObjectModel::ReadOnlyCollection<T> ^ AsReadOnly(cli::array <T> ^ array);

public static System.Collections.ObjectModel.ReadOnlyCollection<T> AsReadOnly<T> (T[] array);

static member AsReadOnly : 'T[] -> System.Collections.ObjectModel.ReadOnlyCollection<'T>

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

Paramètres de type

T

Type des éléments du tableau.

Paramètres

array: T[]

Tableau unidimensionnel, de base zéro pour encapsuler un wrapper ReadOnlyCollection<T> en lecture seule.

Retours

ReadOnlyCollection<T>

Wrapper ReadOnlyCollection<T> en lecture seule pour le tableau spécifié.

Exceptions

ArgumentNullException

array a la valeur null.

Exemples

L’exemple suivant encapsule un tableau dans une lecture seule ReadOnlyCollection<T>.

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

*/

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

*/

open System
open System.Collections.Generic

let printIndexAndValues (myList: IList<'a>) =
    for i = 0 to myList.Count - 1 do
        printfn $"   [{i}] : {myList[i]}"
    printfn ""

// Create and initialize a new string array.
let myArr = [| "The"; "quick"; "brown"; "fox" |]

// Display the values of the array.
printfn "The string array initially contains the following values:"
printIndexAndValues myArr

// Create a read-only IList wrapper around the array.
let myList: IList<_> = Array.AsReadOnly myArr

// Display the values of the read-only IList.
printfn "The read-only IList contains the following values:"
printIndexAndValues myList

// Attempt to change a value through the wrapper.
try 
    myList[3] <- "CAT"

with :? NotSupportedException as e ->
    printfn $"{e.GetType()} - {e.Message}\n"

// Change a value in the original array.
myArr[2] <- "RED"

// Display the values of the array.
printfn "After changing the third element, the string array contains the following values:"
printIndexAndValues myArr

// Display the values of the read-only IList.
printfn "After changing the third element, the read-only IList contains the following values:"
printIndexAndValues myList


// 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

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

    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

    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

End Class


'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

Remarques

Pour éviter les modifications apportées au tableau, exposez le tableau uniquement par le biais de ce wrapper.

Une collection en lecture seule est simplement une collection avec un wrapper qui empêche la modification de la collection; par conséquent, si des modifications sont apportées à la collection sous-jacente, la collection en lecture seule reflète ces modifications.

Cette méthode est une opération O(1).

S’applique à

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