ReadOnlyCollection(Of T).CopyTo Method
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Copies the entire ReadOnlyCollection(Of T) to a compatible one-dimensional Array, starting at the specified index of the target array.
Assembly: mscorlib (in mscorlib.dll)
Parameters
- array
- Type:
T
()
The one-dimensional Array that is the destination of the elements copied from ReadOnlyCollection(Of T). The Array must have zero-based indexing.
- index
- Type: System.Int32
The zero-based index in array at which copying begins.
Implements
ICollection(Of T).CopyTo(T(), Int32)| Exception | Condition |
|---|---|
| ArgumentNullException | array is Nothing. |
| ArgumentOutOfRangeException | index is less than zero. |
| ArgumentException | The number of elements in the source ReadOnlyCollection(Of T) is greater than the available space from index to the end of the destination array. |
This method uses Array.Copy to copy the elements.
The elements are copied to the Array in the same order that the enumerator iterates through the ReadOnlyCollection(Of T).
This method is an O(n) operation, where n is Count.
The following code example demonstrates several members of the ReadOnlyCollection(Of T) class. The code example creates a List(Of T) of strings and adds four dinosaur names to it. The code example then wraps the list in a ReadOnlyCollection(Of T).
After demonstrating the Count, Contains, Item, and IList.IndexOf members, the code example shows that the ReadOnlyCollection(Of T) is just a wrapper for the original List(Of T) by adding a new item to the List(Of T) and displaying the contents of the ReadOnlyCollection(Of 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.
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" '""