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CIS 338: Control Arrays

CIS 338: Control Arrays. Dr. Ralph D. Westfall June, 2011. What Is a Control Array?. it is a group of controls: part of a collection in a .NET form all identified as elements of Me.Controls array each has a different Index e.g., Me.Controls(0) , Me.Controls(1) etc.

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CIS 338: Control Arrays

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  1. CIS 338: Control Arrays Dr. Ralph D. Westfall June, 2011

  2. What Is a Control Array? • it is a group of controls: • part of a collection in a .NET form • all identified as elements of Me.Controls array • each has a different Index • e.g., Me.Controls(0) , Me.Controls(1) etc.

  3. Dropped From, Added To VB.NET • control arrays were in VB 6, but not in earlier versions of .NET • however you can set up controls in earlier .NET code that work like VB6 control arrays • link • link2

  4. VB.NET Control Array Code Dim i As Integer For i = 0 To Me.Controls.Count – 1 MsgBox(Me.Controls(i).ToString) Next

  5. Following Slides Need Updating

  6. Control Array Disadvantages • since all members use the same procedure, may need more complicated logic to handle events Private Sub Command1_Click(Index As _ Integer) Select Case Index Case 0 'user clicked cmdTest(0) button Print "zero" Case 1 'user clicked cmdTest(1) button Print "one" End Select End Sub

  7. Creating a Control Array (VB6) • create first control, and at the very first • change the name • change any other properties that you want to be the same on all elements e.g., Text • select it, then [Ctrl] C or Edit>Copy • [Ctrl] V or Edit>Paste to duplicate • click Yes on dialog box • move copied control where you want it

  8. Programming Control Arrays Dim nI as Integer Private Sub Text1_Change(Index As Integer) For nI = Text1.LBound To Text1.UBound If nI = Index Then Text1(nI).BackColor = "&H000000FF" End If Next nI End Sub • LBound is lowest Index in array (usually 0) • UBound is highest Index in array

  9. Using Parallel Arrays Sub Text1_GotFocus(Index As Integer) Label1(Index).Font.Bold = True End Sub • two arrays: Text1 and Label1 • when Text1(0) gets focus, Label1(0) (same Index) becomes bold • can use LostFocus event to remove bold

  10. Adding Controls with Code nI = Text1.UBound Load Text1(nI + 1) Text1(nI + 1).Visible = True Text1(nI + 1).Top = _ Text1(nI).Top + _ Text1(nI).Height + 120 Text1(nI + 1).Left = _ Text1(nI).Left

  11. Deleting Controls with Code Private Sub Command2_Click() Dim nI As Integer nI = Text1.UBound Unload Text1(nI) End Sub • at run time, can only delete items created by code (previous slide) • can delete any items at design time

  12. Advantages of a Control Array • more efficient – uses less memory • all members work with one procedure • to add controls to program when it is running, must use control arrays • easier to change properties via code • can use loops • gets around the limit of 254 control names per form (but who needs that many??)

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