Mencegah Aplikasi yang sama berjalan lebih dari 1

Selamat berkreatifitas sobat pecinta visual basic 6

Trik kali ini adalah mencegah aplikasi yang sama dijalankan lebih dari 1x. Kegunaan fitur ini untuk mencegah user menjalankan aplikasi lebih dari 1 dalam satu waktu.

Langsung saja ke sourcenya

1. Buat satu project
2. Buat Form dengan 1 textbox didalamnya
3. Masih di Form1. Masukkan Kode berikut ini

Dim PreviewsInstanceExists As Boolean
Private Sub Form_Load()
On Error GoTo ErrorHandler
     PreviewsInstanceExists = True
     Text1.LinkTopic = App.Title & "|" & Me.Name
     Text1.LinkItem = "Text1"
     Text1.LinkMode = 1 'If no Application is listening it will cause an error no DDE responce
     'If the code continues without error means ths is not the first instance
     'and we have connected with the first via DDE.
     Text1.Text = "NEW INSTANCE OPENED " & Interaction.Command
     Text1.LinkPoke
     Unload Me
ErrorHandler:
  If Err.Number = 282 Then
     'Seems no application is listening in DDE this means its the first instance.
     'Me.LinkMode = 1 'Done manualy
     Me.LinkTopic = Me.Name
     Me.Caption = "This is the first instance"
     PreviewsInstanceExists = False
  End If
End Sub


Private Sub Text1_Change()
  'NOTE: Do not have any modal forms or textboxes popping up in the _Change event
  'because after the commands in this event are executed a DDE transfer ok is sent
  If (PreviewsInstanceExists = False) And Left(Text1.Text, 19) = "NEW INSTANCE OPENED" Then
     Me.Visible = True
     Me.WindowState = vbNormal
     Me.SetFocus
     If Len(Text1.Text) > 20 Then Label2.Caption = "Command line parameters of the other instance:" & vbCrLf & Mid(Text1.Text, 20)
     Text1.Text = ""
  End If
End Sub

Sumber: Planet Source Code