List(Of T).Reverse Method (Int32, Int32)
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Reverses the order of the elements in the specified range.
Assembly: mscorlib (in mscorlib.dll)
Parameters
- index
- Type: System.Int32
The zero-based starting index of the range to reverse.
- count
- Type: System.Int32
The number of elements in the range to reverse.
| Exception | Condition |
|---|---|
| ArgumentOutOfRangeException | index is less than 0. -or- count is less than 0. |
| ArgumentException | index and count do not denote a valid range of elements in the List(Of T). |
This method uses Array.Reverse to reverse the order of the elements, such that the element at List(Of T)[i], where i is any index within the range, moves to List(Of T)[j], where j equals index plus index plus count minus i minus 1.
This method is an O(n) operation, where n is Count.
The following code example demonstrates both overloads of the Reverse method. The code example creates a List(Of T) of strings and adds six strings. The Reverse method overload is used to reverse the list, and then the Reverse(Int32, Int32) method overload is used to reverse the middle of the list, beginning with element 1 and encompassing four elements.
Imports System.Collections.Generic Public Class Example Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock) Dim dinosaurs As New List(Of String) dinosaurs.Add("Pachycephalosaurus") dinosaurs.Add("Parasauralophus") dinosaurs.Add("Mamenchisaurus") dinosaurs.Add("Amargasaurus") dinosaurs.Add("Coelophysis") dinosaurs.Add("Oviraptor") outputBlock.Text &= vbCrLf For Each dinosaur As String In dinosaurs outputBlock.Text &= dinosaur & vbCrLf Next dinosaurs.Reverse() outputBlock.Text &= vbCrLf For Each dinosaur As String In dinosaurs outputBlock.Text &= dinosaur & vbCrLf Next dinosaurs.Reverse(1, 4) outputBlock.Text &= vbCrLf For Each dinosaur As String In dinosaurs outputBlock.Text &= dinosaur & vbCrLf Next End Sub End Class ' This code example produces the following output: ' 'Pachycephalosaurus 'Parasauralophus 'Mamenchisaurus 'Amargasaurus 'Coelophysis 'Oviraptor ' 'Oviraptor 'Coelophysis 'Amargasaurus 'Mamenchisaurus 'Parasauralophus 'Pachycephalosaurus ' 'Oviraptor 'Parasauralophus 'Mamenchisaurus 'Amargasaurus 'Coelophysis 'Pachycephalosaurus