List<T>.AsReadOnly List<T>.AsReadOnly List<T>.AsReadOnly List<T>.AsReadOnly Method

Definición

Devuelve un contenedor de ReadOnlyCollection<T> de solo lectura para la colección actual.Returns a read-only ReadOnlyCollection<T> wrapper for the current collection.

public:
 System::Collections::ObjectModel::ReadOnlyCollection<T> ^ AsReadOnly();
public System.Collections.ObjectModel.ReadOnlyCollection<T> AsReadOnly ();
member this.AsReadOnly : unit -> System.Collections.ObjectModel.ReadOnlyCollection<'T>
Public Function AsReadOnly () As ReadOnlyCollection(Of T)

Devoluciones

Objeto que actúa como contenedor de solo lectura para la List<T> actual.An object that acts as a read-only wrapper around the current List<T>.

Ejemplos

En el siguiente ejemplo se AsReadOnly muestra el método.The following example demonstrates the AsReadOnly method. Se List<T> crea un de cadenas con una capacidad de 4, ya que se sabe que el tamaño final de la lista es exactamente 4.A List<T> of strings with a capacity of 4 is created, because the ultimate size of the list is known to be exactly 4. La lista se rellena con cuatro cadenas y el AsReadOnly método se usa para obtener una implementación de interfaz genérica de solo IList<T> lectura que contiene la lista original.The list is populated with four strings, and the AsReadOnly method is used to get a read-only IList<T> generic interface implementation that wraps the original list.

Un elemento de la lista original se establece en "Coelophysis" mediante la Item[Int32] propiedad (el indizador en C#) y el contenido de la lista de solo lectura se muestra de nuevo para mostrar que es simplemente un contenedor para la lista original.An element of the original list is set to "Coelophysis" using the Item[Int32] property (the indexer in C#), and the contents of the read-only list are displayed again to demonstrate that it is just a wrapper for the original list.

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

void main()
{
    List<String^>^ dinosaurs = gcnew List<String^>(4);

    Console::WriteLine("\nCapacity: {0}", dinosaurs->Capacity);

    dinosaurs->Add("Tyrannosaurus");
    dinosaurs->Add("Amargasaurus");
    dinosaurs->Add("Mamenchisaurus");
    dinosaurs->Add("Deinonychus");

    Console::WriteLine();
    for each(String^ dinosaur in dinosaurs)
    {
        Console::WriteLine(dinosaur);
    }

    Console::WriteLine("\nIList<String^>^ roDinosaurs = dinosaurs->AsReadOnly()");
    IList<String^>^ roDinosaurs = dinosaurs->AsReadOnly();

    Console::WriteLine("\nElements in the read-only IList:");
    for each(String^ dinosaur in roDinosaurs)
    {
        Console::WriteLine(dinosaur);
    }

    Console::WriteLine("\ndinosaurs[2] = \"Coelophysis\"");
    dinosaurs[2] = "Coelophysis";

    Console::WriteLine("\nElements in the read-only IList:");
    for each(String^ dinosaur in roDinosaurs)
    {
        Console::WriteLine(dinosaur);
    }
}

/* This code example produces the following output:

Capacity: 4

Tyrannosaurus
Amargasaurus
Mamenchisaurus
Deinonychus

IList<String^>^ roDinosaurs = dinosaurs->AsReadOnly()

Elements in the read-only IList:
Tyrannosaurus
Amargasaurus
Mamenchisaurus
Deinonychus

dinosaurs[2] = "Coelophysis"

Elements in the read-only IList:
Tyrannosaurus
Amargasaurus
Coelophysis
Deinonychus
 */
using System;
using System.Collections.Generic;

public class Example
{
    public static void Main()
    {
        List<string> dinosaurs = new List<string>(4);

        Console.WriteLine("\nCapacity: {0}", dinosaurs.Capacity);

        dinosaurs.Add("Tyrannosaurus");
        dinosaurs.Add("Amargasaurus");
        dinosaurs.Add("Mamenchisaurus");
        dinosaurs.Add("Deinonychus");

        Console.WriteLine();
        foreach(string s in dinosaurs)
        {
            Console.WriteLine(s);
        }

        Console.WriteLine("\nIList<string> roDinosaurs = dinosaurs.AsReadOnly()");
        IList<string> roDinosaurs = dinosaurs.AsReadOnly();

        Console.WriteLine("\nElements in the read-only IList:");
        foreach(string dinosaur in roDinosaurs)
        {
            Console.WriteLine(dinosaur);
        }

        Console.WriteLine("\ndinosaurs[2] = \"Coelophysis\"");
        dinosaurs[2] = "Coelophysis";

        Console.WriteLine("\nElements in the read-only IList:");
        foreach(string dinosaur in roDinosaurs)
        {
            Console.WriteLine(dinosaur);
        }
    }
}

/* This code example produces the following output:

Capacity: 4

Tyrannosaurus
Amargasaurus
Mamenchisaurus
Deinonychus

IList<string> roDinosaurs = dinosaurs.AsReadOnly()

Elements in the read-only IList:
Tyrannosaurus
Amargasaurus
Mamenchisaurus
Deinonychus

dinosaurs[2] = "Coelophysis"

Elements in the read-only IList:
Tyrannosaurus
Amargasaurus
Coelophysis
Deinonychus
 */
Imports System.Collections.Generic

Public Class Example

    Public Shared Sub Main()

        Dim dinosaurs As New List(Of String)(4)

        Console.WriteLine(vbLf & "Capacity: {0}", dinosaurs.Capacity)

        dinosaurs.Add("Tyrannosaurus")
        dinosaurs.Add("Amargasaurus")
        dinosaurs.Add("Mamenchisaurus")
        dinosaurs.Add("Deinonychus")

        Console.WriteLine()
        For Each dinosaur As String In dinosaurs
            Console.WriteLine(dinosaur)
        Next

        Console.WriteLine(vbLf & _
            "Dim roDinosaurs As IList(Of String) = dinosaurs.AsReadOnly")
        Dim roDinosaurs As IList(Of String) = dinosaurs.AsReadOnly

        Console.WriteLine(vbLf & "Elements in the read-only IList:")
        For Each dinosaur As String In roDinosaurs
            Console.WriteLine(dinosaur)
        Next

        Console.WriteLine(vbLf & "dinosaurs(2) = ""Coelophysis""")
        dinosaurs(2) = "Coelophysis"

        Console.WriteLine(vbLf & "Elements in the read-only IList:")
        For Each dinosaur As String In roDinosaurs
            Console.WriteLine(dinosaur)
        Next

    End Sub
End Class

' This code example produces the following output:
'
'Capacity: 4
'
'Tyrannosaurus
'Amargasaurus
'Mamenchisaurus
'Deinonychus
'
'Dim roDinosaurs As IList(Of String) = dinosaurs.AsReadOnly
'
'Elements in the read-only IList:
'Tyrannosaurus
'Amargasaurus
'Mamenchisaurus
'Deinonychus
'
'dinosaurs(2) = "Coelophysis"
'
'Elements in the read-only IList:
'Tyrannosaurus
'Amargasaurus
'Coelophysis
'Deinonychus

Comentarios

Para evitar modificaciones en el List<T> objeto, expóngalo solo a través de este contenedor.To prevent any modifications to the List<T> object, expose it only through this wrapper. Un ReadOnlyCollection<T> objeto no expone los métodos que modifican la colección.A ReadOnlyCollection<T> object does not expose methods that modify the collection. Sin embargo, si se realizan cambios en el List<T> objeto subyacente, la colección de solo lectura refleja esos cambios.However, if changes are made to the underlying List<T> object, the read-only collection reflects those changes.

Este método es una operación O (1).This method is an O(1) operation.

Se aplica a