[VB.NET] เทคนิคการเร่งความเร็วในการเพิ่มไอเท็มให้กับ ComboBox Control

thongkorn

มาดูโค้ดกันเถอะ ...

1. Public Class frmFastAddItem
   
2.     '/ Start-Stop Timer
   
3.     Private mTimeDouble As Double
   
4.     Private sWatch As New Stopwatch()
   
5. 
   
6.     '/ Technique
   
7.     Private Sub FastAddItem(ByVal MaxItem As Integer)
   
8.         Dim lst As List(Of Object) = New List(Of Object)(MaxItem)
   
9.         For i As Integer = 1 To MaxItem
   
10.             lst.Add(i)
    
11.         Next
    
12.         cmbTest.Items.AddRange(lst.ToArray())
    
13.         '//
    
14.         cmbTest.SelectedIndex = cmbTest.Items.Count - 1
    
15.     End Sub
    
16. 
    
17.     '/ Normal.
    
18.     Private Sub AddItemVB(ByVal MaxItem As Integer)
    
19.         For i = 1 To MaxItem
    
20.             cmbTest.Items.Add(i)
    
21.         Next
    
22.         cmbTest.SelectedIndex = cmbTest.Items.Count - 1
    
23.     End Sub
    
24. 
    
25.     Private Sub btnAddItemFast_Click(sender As System.Object, e As System.EventArgs) Handles btnAddItemFast.Click
    
26.         cmbTest.Items.Clear()
    
27.         lblTimer.Text = "Timer List: "
    
28.         GroupBox1.Text = " Test with List "
    
29.         sWatch.Reset()
    
30.         sWatch.Start()
    
31.         Cursor = Cursors.WaitCursor
    
32.         '//
    
33.         Call FastAddItem(20000)
    
34.         '//
    
35.         Cursor = Cursors.Default
    
36.         sWatch.Stop()
    
37.         mTimeDouble = sWatch.ElapsedMilliseconds * 0.001
    
38.         lblTimer.Text = lblTimer.Text & mTimeDouble.ToString & " sec."
    
39.     End Sub
    
40. 
    
41.     Private Sub btnAddItem_Click(sender As System.Object, e As System.EventArgs) Handles btnAddItem.Click
    
42.         cmbTest.Items.Clear()
    
43.         lblTimer.Text = "Timer normal code: "
    
44.         GroupBox1.Text = " Test with normal code "
    
45.         sWatch.Reset()
    
46.         sWatch.Start()
    
47.         Cursor = Cursors.WaitCursor
    
48.         '//
    
49.         Call AddItemVB(20000)
    
50.         '//
    
51.         Cursor = Cursors.Default
    
52.         sWatch.Stop()
    
53.         mTimeDouble = sWatch.ElapsedMilliseconds * 0.001
    
54.         lblTimer.Text = lblTimer.Text & mTimeDouble.ToString & " sec."
    
55.     End Sub
    
56. 
    
57.     Private Sub frmFastAddItem_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
    
58.         lblTimer.Text = ""
    
59.     End Sub
    
60. 
    
61. End Class

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