Array.AsReadOnly<T>(T[]) Methode

Definition

Namespace:

System

Assembly:

System.Runtime.dll

Quelle:

Array.cs

Gibt einen schreibgeschützten Wrapper für das angegebene Array zurück.

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)

Typparameter

T

Der Typ der Elemente des Arrays.

Parameter

array

T[]

Das eindimensionale, nullbasierte Array, das mit einem schreibgeschützten ReadOnlyCollection<T>-Wrapper umschlossen werden soll.

Gibt zurück

ReadOnlyCollection<T>

Ein schreibgeschützter ReadOnlyCollection<T>-Wrapper für das angegebene Array.

Ausnahmen

ArgumentNullException

array ist null.

Beispiele

Im folgenden Beispiel wird ein Array in einen schreibgeschützten ReadOnlyCollection<T>umgebrochen.

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

Hinweise

Um Änderungen am Array zu verhindern, machen Sie das Array nur über diesen Wrapper verfügbar.

Eine auflistung, die schreibgeschützt ist, ist einfach eine Auflistung mit einem Wrapper, der das Ändern der Auflistung verhindert. Wenn Änderungen an der zugrunde liegenden Auflistung vorgenommen werden, spiegelt die schreibgeschützte Auflistung diese Änderungen wider.

Bei dieser Methode handelt es sich um einen O(1)-Vorgang.