List(Of T).Clear Method ()

 

Removes all elements from the List(Of T).

Namespace:   System.Collections.Generic
Assembly:  mscorlib (in mscorlib.dll)

Count is set to 0, and references to other objects from elements of the collection are also released.

Capacity remains unchanged. To reset the capacity of the List(Of T), call the TrimExcess method or set the Capacity property directly. Decreasing the capacity reallocates memory and copies all the elements in the List(Of T). Trimming an empty List(Of T) sets the capacity of the List(Of T) to the default capacity.

This method is an O(n) operation, where n is Count.

The following example demonstrates the Clear method and various other properties and methods of the List(Of T) generic class. The Clear method is used at the end of the program, to remove all items from the list, and the Capacity and Count properties are then displayed.

Imports System
Imports System.Collections.Generic

Public Class Example

    Public Shared Sub Main()
        Dim dinosaurs As New List(Of String)

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

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

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

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

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

        Console.WriteLine(vbLf & "Insert(2, ""Compsognathus"")")
        dinosaurs.Insert(2, "Compsognathus")

        Console.WriteLine()
        For Each dinosaur As String In dinosaurs
            Console.WriteLine(dinosaur)
        Next
        ' Shows how to access the list using the Item property.
        Console.WriteLine(vbLf & "dinosaurs(3): {0}", dinosaurs(3))
        Console.WriteLine(vbLf & "Remove(""Compsognathus"")")
        dinosaurs.Remove("Compsognathus")

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

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

        dinosaurs.Clear()
        Console.WriteLine(vbLf & "Clear()")
        Console.WriteLine("Capacity: {0}", dinosaurs.Capacity)
        Console.WriteLine("Count: {0}", dinosaurs.Count)
    End Sub
End Class

' This code example produces the following output:
'
'Capacity: 0
'
'Tyrannosaurus
'Amargasaurus
'Mamenchisaurus
'Deinonychus
'Compsognathus
'
'Capacity: 8
'Count: 5
'
'Contains("Deinonychus"): True
'
'Insert(2, "Compsognathus")
'
'Tyrannosaurus
'Amargasaurus
'Compsognathus
'Mamenchisaurus
'Deinonychus
'Compsognathus
'
'dinosaurs(3): Mamenchisaurus
'
'Remove("Compsognathus")
'
'Tyrannosaurus
'Amargasaurus
'Mamenchisaurus
'Deinonychus
'Compsognathus
'
'TrimExcess()
'Capacity: 5
'Count: 5
'
'Clear()
'Capacity: 5
'Count: 0

Universal Windows Platform
Available since 8
.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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