Collection(Of T).Clear Method
Removes all elements from the Collection(Of T).
Namespace: System.Collections.ObjectModel
Assembly: mscorlib (in mscorlib.dll)
Count is set to zero, and references to other objects from elements of the collection are also released.
This method is an O(n) operation, where n is Count.
Notes to InheritorsDerived classes can override ClearItems to change the behavior of this method.
The following code example demonstrates many of the properties and methods of Collection(Of T). The code example creates a collection of strings, uses the Add method to add several strings, displays the Count, and lists the strings. The example uses the IndexOf method to find the index of a string and the Contains method to determine whether a string is in the collection. The example inserts a string using the Insert method and retrieves and sets strings using the default Item property (the indexer in C#). The example removes strings by string identity using the Remove method and by index using the RemoveAt method. Finally, the Clear method is used to clear all strings from 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 Collection(Of String) dinosaurs.Add("Psitticosaurus") dinosaurs.Add("Caudipteryx") dinosaurs.Add("Compsognathus") dinosaurs.Add("Muttaburrasaurus") outputBlock.Text += String.Format("{0} dinosaurs:", dinosaurs.Count) & vbCrLf Display(outputBlock, dinosaurs) outputBlock.Text &= vbLf & String.Format("IndexOf(""Muttaburrasaurus"") {0}", _ dinosaurs.IndexOf("Muttaburrasaurus")) & vbCrLf outputBlock.Text &= vbLf & String.Format("Contains(""Caudipteryx"") {0}", _ dinosaurs.Contains("Caudipteryx")) & vbCrLf outputBlock.Text += String.Format(vbLf & "Insert(2, ""Nanotyrannus"")") & vbCrLf dinosaurs.Insert(2, "Nanotyrannus") Display(outputBlock, dinosaurs) outputBlock.Text += String.Format(vbLf & "dinosaurs(2): {0}", dinosaurs(2)) & vbCrLf outputBlock.Text &= vbLf & "dinosaurs(2) = ""Microraptor""" & vbCrLf dinosaurs(2) = "Microraptor" Display(outputBlock, dinosaurs) outputBlock.Text &= vbLf & "Remove(""Microraptor"")" & vbCrLf dinosaurs.Remove("Microraptor") Display(outputBlock, dinosaurs) outputBlock.Text &= vbLf & "RemoveAt(0)" & vbCrLf dinosaurs.RemoveAt(0) Display(outputBlock, dinosaurs) outputBlock.Text &= vbLf & "dinosaurs.Clear()" & vbCrLf dinosaurs.Clear() outputBlock.Text += String.Format("Count: {0}", dinosaurs.Count) & vbCrLf End Sub Private Shared Sub Display(ByVal outputBlock As System.Windows.Controls.TextBlock, ByVal cs As Collection(Of String)) outputBlock.Text &= vbCrLf For Each item As String In cs outputBlock.Text &= item & vbCrLf Next item End Sub End Class ' This code example produces the following output: ' '4 dinosaurs: ' 'Psitticosaurus 'Caudipteryx 'Compsognathus 'Muttaburrasaurus ' 'IndexOf("Muttaburrasaurus"): 3 ' 'Contains("Caudipteryx"): True ' 'Insert(2, "Nanotyrannus") ' 'Psitticosaurus 'Caudipteryx 'Nanotyrannus 'Compsognathus 'Muttaburrasaurus ' 'dinosaurs(2): Nanotyrannus ' 'dinosaurs(2) = "Microraptor" ' 'Psitticosaurus 'Caudipteryx 'Microraptor 'Compsognathus 'Muttaburrasaurus ' 'Remove("Microraptor") ' 'Psitticosaurus 'Caudipteryx 'Compsognathus 'Muttaburrasaurus ' 'RemoveAt(0) ' 'Caudipteryx 'Compsognathus 'Muttaburrasaurus ' 'dinosaurs.Clear() 'Count: 0
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