ReadOnlyCollection<T> Class

Definition

generic <typename T>
public ref class ReadOnlyCollection : System::Collections::Generic::ICollection<T>, System::Collections::Generic::IEnumerable<T>, System::Collections::Generic::IList<T>, System::Collections::Generic::IReadOnlyCollection<T>, System::Collections::Generic::IReadOnlyList<T>, System::Collections::IList

generic <typename T>
public ref class ReadOnlyCollection : System::Collections::Generic::ICollection<T>, System::Collections::Generic::IEnumerable<T>, System::Collections::Generic::IList<T>, System::Collections::IList

public class ReadOnlyCollection<T> : System.Collections.Generic.ICollection<T>, System.Collections.Generic.IEnumerable<T>, System.Collections.Generic.IList<T>, System.Collections.Generic.IReadOnlyCollection<T>, System.Collections.Generic.IReadOnlyList<T>, System.Collections.IList

[System.Runtime.InteropServices.ComVisible(false)]
[System.Serializable]
public class ReadOnlyCollection<T> : System.Collections.Generic.ICollection<T>, System.Collections.Generic.IEnumerable<T>, System.Collections.Generic.IList<T>, System.Collections.IList

[System.Runtime.InteropServices.ComVisible(false)]
[System.Serializable]
public class ReadOnlyCollection<T> : System.Collections.Generic.ICollection<T>, System.Collections.Generic.IEnumerable<T>, System.Collections.Generic.IList<T>, System.Collections.Generic.IReadOnlyCollection<T>, System.Collections.Generic.IReadOnlyList<T>, System.Collections.IList

type ReadOnlyCollection<'T> = class
    interface ICollection<'T>
    interface seq<'T>
    interface IEnumerable
    interface IList<'T>
    interface IReadOnlyCollection<'T>
    interface IReadOnlyList<'T>
    interface ICollection
    interface IList

[<System.Runtime.InteropServices.ComVisible(false)>]
[<System.Serializable>]
type ReadOnlyCollection<'T> = class
    interface IList<'T>
    interface ICollection<'T>
    interface seq<'T>
    interface IList
    interface ICollection
    interface IEnumerable

[<System.Runtime.InteropServices.ComVisible(false)>]
[<System.Serializable>]
type ReadOnlyCollection<'T> = class
    interface IList<'T>
    interface ICollection<'T>
    interface IList
    interface ICollection
    interface IReadOnlyList<'T>
    interface IReadOnlyCollection<'T>
    interface seq<'T>
    interface IEnumerable

[<System.Runtime.InteropServices.ComVisible(false)>]
[<System.Serializable>]
type ReadOnlyCollection<'T> = class
    interface IList<'T>
    interface ICollection<'T>
    interface seq<'T>
    interface IEnumerable
    interface IList
    interface ICollection
    interface IReadOnlyList<'T>
    interface IReadOnlyCollection<'T>

type ReadOnlyCollection<'T> = class
    interface IList<'T>
    interface ICollection<'T>
    interface IReadOnlyList<'T>
    interface IReadOnlyCollection<'T>
    interface seq<'T>
    interface IList
    interface ICollection
    interface IEnumerable

Public Class ReadOnlyCollection(Of T)
Implements ICollection(Of T), IEnumerable(Of T), IList, IList(Of T), IReadOnlyCollection(Of T), IReadOnlyList(Of T)

Public Class ReadOnlyCollection(Of T)
Implements ICollection(Of T), IEnumerable(Of T), IList, IList(Of T)

Type Parameters

Inheritance

Object

ReadOnlyCollection<T>

Derived

System.Collections.ObjectModel.ReadOnlyObservableCollection<T>

System.Data.Metadata.Edm.ReadOnlyMetadataCollection<T>

System.Security.Cryptography.ManifestSignatureInformationCollection

System.ServiceModel.Channels.AddressHeaderCollection

System.Windows.Input.StylusButtonCollection

More…

Attributes

ComVisibleAttribute SerializableAttribute

Implements

ICollection<T> IEnumerable<T> IList<T> IReadOnlyCollection<T> IReadOnlyList<T> ICollection IEnumerable IList

Examples

The following code example demonstrates several members of the ReadOnlyCollection<T> class. The code example creates a List<T> of strings and adds four dinosaur names to it. The code example then wraps the list in a ReadOnlyCollection<T>.

After demonstrating the Count, Contains, Item[], and IList.IndexOf members, the code example shows that the ReadOnlyCollection<T> is just a wrapper for the original List<T> by adding a new item to the List<T> and displaying the contents of the ReadOnlyCollection<T>.

Finally, the code example creates an array larger than the collection and uses the CopyTo method to insert the elements of the collection into the middle of the array.

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;

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

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

        ReadOnlyCollection<string> readOnlyDinosaurs =
            new ReadOnlyCollection<string>(dinosaurs);

        Console.WriteLine();
        foreach( string dinosaur in readOnlyDinosaurs )
        {
            Console.WriteLine(dinosaur);
        }

        Console.WriteLine("\nCount: {0}", readOnlyDinosaurs.Count);

        Console.WriteLine("\nContains(\"Deinonychus\"): {0}",
            readOnlyDinosaurs.Contains("Deinonychus"));

        Console.WriteLine("\nreadOnlyDinosaurs[3]: {0}",
            readOnlyDinosaurs[3]);

        Console.WriteLine("\nIndexOf(\"Compsognathus\"): {0}",
            readOnlyDinosaurs.IndexOf("Compsognathus"));

        Console.WriteLine("\nInsert into the wrapped List:");
        Console.WriteLine("Insert(2, \"Oviraptor\")");
        dinosaurs.Insert(2, "Oviraptor");

        Console.WriteLine();
        foreach( string dinosaur in readOnlyDinosaurs )
        {
            Console.WriteLine(dinosaur);
        }

        string[] dinoArray = new string[readOnlyDinosaurs.Count + 2];
        readOnlyDinosaurs.CopyTo(dinoArray, 1);

        Console.WriteLine("\nCopied array has {0} elements:",
            dinoArray.Length);
        foreach( string dinosaur in dinoArray )
        {
            Console.WriteLine("\"{0}\"", dinosaur);
        }
    }
}

/* This code example produces the following output:

Tyrannosaurus
Amargasaurus
Deinonychus
Compsognathus

Count: 4

Contains("Deinonychus"): True

readOnlyDinosaurs[3]: Compsognathus

IndexOf("Compsognathus"): 3

Insert into the wrapped List:
Insert(2, "Oviraptor")

Tyrannosaurus
Amargasaurus
Oviraptor
Deinonychus
Compsognathus

Copied array has 7 elements:
""
"Tyrannosaurus"
"Amargasaurus"
"Oviraptor"
"Deinonychus"
"Compsognathus"
""
 */

Imports System.Collections.Generic
Imports System.Collections.ObjectModel

Public Class Example

    Public Shared Sub Main()

        Dim dinosaurs As New List(Of String)

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

        Dim readOnlyDinosaurs As _
            New ReadOnlyCollection(Of String)(dinosaurs)

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

        Console.WriteLine(vbLf & "Count: {0}", _
            readOnlyDinosaurs.Count)

        Console.WriteLine(vbLf & "Contains(""Deinonychus""): {0}", _
            readOnlyDinosaurs.Contains("Deinonychus"))

        Console.WriteLine(vbLf & _
            "readOnlyDinosaurs(3): {0}", readOnlyDinosaurs(3))

        Console.WriteLine(vbLf & "IndexOf(""Compsognathus""): {0}", _
            readOnlyDinosaurs.IndexOf("Compsognathus"))

        Console.WriteLine(vbLf & "Insert into the wrapped List:")
        Console.WriteLine("Insert(2, ""Oviraptor"")")
        dinosaurs.Insert(2, "Oviraptor")

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

        Dim dinoArray(readOnlyDinosaurs.Count + 1) As String
        readOnlyDinosaurs.CopyTo(dinoArray, 1)

        Console.WriteLine(vbLf & "Copied array has {0} elements:", _
            dinoArray.Length)
        For Each dinosaur As String In dinoArray
            Console.WriteLine("""{0}""", dinosaur)
        Next

   End Sub
End Class

' This code example produces the following output:
'
'Tyrannosaurus
'Amargasaurus
'Deinonychus
'Compsognathus
'
'Count: 4
'
'Contains("Deinonychus"): True
'
'readOnlyDinosaurs(3): Compsognathus
'
'IndexOf("Compsognathus"): 3
'
'Insert into the wrapped List:
'Insert(2, "Oviraptor")
'
'Tyrannosaurus
'Amargasaurus
'Oviraptor
'Deinonychus
'Compsognathus
'
'Copied array has 7 elements:
'""
'"Tyrannosaurus"
'"Amargasaurus"
'"Oviraptor"
'"Deinonychus"
'"Compsognathus"
'""

Remarks

An instance of the ReadOnlyCollection<T> generic class is always read-only. A collection that is read-only is simply a collection with a wrapper that prevents modifying the collection; therefore, if changes are made to the underlying collection, the read-only collection reflects those changes. See Collection<T> for a modifiable version of this class.

Notes to Inheritors

This base class is provided to make it easier for implementers to create a generic read-only custom collection. Implementers are encouraged to extend this base class instead of creating their own.