ReadOnlyCollection<T> Class

Type Parameters

• T
  The type of elements in the collection.

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

Public Class Example

   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)

      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)

      outputBlock.Text &= vbCrLf
      For Each dinosaur As String In readOnlyDinosaurs
         outputBlock.Text &= dinosaur & vbCrLf
      Next

      outputBlock.Text &= String.Format(vbLf & "Count: {0}", _
          readOnlyDinosaurs.Count) & vbCrLf

      outputBlock.Text &= String.Format(vbLf & "Contains(""Deinonychus"" & vbCrLf: {0}", _
          readOnlyDinosaurs.Contains("Deinonychus"))

      outputBlock.Text &= String.Format(vbLf & _
          "readOnlyDinosaurs(3): {0}", readOnlyDinosaurs(3)) & vbCrLf

      outputBlock.Text &= String.Format(vbLf & "IndexOf(""Compsognathus"" & vbCrLf: {0}", _
          readOnlyDinosaurs.IndexOf("Compsognathus"))

      outputBlock.Text &= vbLf & "Insert into the wrapped List:" & vbCrLf
      outputBlock.Text &= String.Format("Insert(2, ""Oviraptor"")") & vbCrLf
      dinosaurs.Insert(2, "Oviraptor")

      outputBlock.Text &= vbCrLf
      For Each dinosaur As String In readOnlyDinosaurs
         outputBlock.Text &= dinosaur & vbCrLf
      Next

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

      outputBlock.Text &= String.Format(vbLf & "Copied array has {0} elements:", _
          dinoArray.Length) & vbCrLf
      For Each dinosaur As String In dinoArray
         outputBlock.Text &= String.Format("""{0}""", dinosaur) & vbCrLf
      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"
'""

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

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      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);

      outputBlock.Text += "\n";
      foreach (string dinosaur in readOnlyDinosaurs)
      {
         outputBlock.Text += dinosaur + "\n";
      }

      outputBlock.Text += String.Format("\nCount: {0}", readOnlyDinosaurs.Count) + "\n";

      outputBlock.Text += String.Format("\nContains(\"Deinonychus\"): {0}",
          readOnlyDinosaurs.Contains("Deinonychus")) + "\n";

      outputBlock.Text += String.Format("\nreadOnlyDinosaurs[3]: {0}",
          readOnlyDinosaurs[3]) + "\n";

      outputBlock.Text += String.Format("\nIndexOf(\"Compsognathus\"): {0}",
          readOnlyDinosaurs.IndexOf("Compsognathus")) + "\n";

      outputBlock.Text += "\nInsert into the wrapped List:" + "\n";
      outputBlock.Text += String.Format("Insert(2, \"Oviraptor\")") + "\n";
      dinosaurs.Insert(2, "Oviraptor");

      outputBlock.Text += "\n";
      foreach (string dinosaur in readOnlyDinosaurs)
      {
         outputBlock.Text += dinosaur + "\n";
      }

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

      outputBlock.Text += String.Format("\nCopied array has {0} elements:",
          dinoArray.Length) + "\n";
      foreach (string dinosaur in dinoArray)
      {
         outputBlock.Text += String.Format("\"{0}\"", dinosaur) + "\n";
      }
   }
}

/* 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"
""
 */