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Tip of the Day
Language: Visual Basic
Expertise: Intermediate
Nov 9, 2001

Clear a Collection


The fastest way to clear a collection is just to set the variable to a new Collection object. However, if it's necessary to free the references the collection is keeping, it's faster to empty the Collection from the beginning than the end.

Here is the test I used:

* Create a new standard EXE Project

* Add three Command Buttontons to Form1

* Insert the following lines of code into Form1
 
Option Explicit

Private Declare Function GetTickCount Lib "kernel32" 
() As Long

Private Function GetCollection(Count As Long) As 
Collection
Dim Index As Long
    Set GetCollection = New Collection
    For Index = 1 To Count
        GetCollection.Add Nothing
    Next
End Function

Private Sub Command1_Click()
Dim Col As Collection
Dim TickCount As Long
    Set Col = GetCollection(10000)
    TickCount = GetTickCount()
    Set Col = New Collection
    MsgBox "TickCount: " & GetTickCount() - TickCount
End Sub

Private Sub Command2_Click()
Dim Col As Collection
Dim TickCount As Long
    Set Col = GetCollection(10000)
    TickCount = GetTickCount()
    Do While Col.Count
        Col.Remove 1
    Loop
    MsgBox "TickCount: " & GetTickCount() - TickCount
End Sub

Private Sub Command3_Click()
Dim Col As Collection
Dim TickCount As Long
    Set Col = GetCollection(10000)
    TickCount = GetTickCount()
    Do While Col.Count
        Col.Remove Col.Count
    Loop
    MsgBox "TickCount: " & GetTickCount() - TickCount
End Sub
Andreas Hillqvist
 
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