Microsoft KB Archive/115712

= VB3 How to Fill a List Box from a Snapshot Generically =

Article ID: 115712

Article Last Modified on 1/9/2003

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APPLIES TO


 * Microsoft Visual Basic 3.0 Professional Edition

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This article was previously published under Q115712



SUMMARY
This article shows by example how to fill a list box with a snapshot when the contents of the snapshot are unknown at design time. The example uses TAB characters to create a columnar display, and it adds a horizontal scroll bar so the user can view the entire record.



MORE INFORMATION
When handling result sets from database queries that produce variable result sets, you may find it useful to have a generic function display the contents in a list box.

The following example defines a Sub (Fill_List) that accepts a list-box control and snapshot as parameters and fills the list box with the contents of the snapshot. The function can be easily modified to accept a table or dynaset object as well.

For additional information, please see the following article in the Microsoft Knowledge Base:

71067 How to Set Tab Stops in a List Box in Visual Basic

Step-by-Step Instructions for Creating the Program
 Start a new project in Visual Basic. Form1 is created by default. Add a command button (Command1) and a list box (List1) to the form. Set the caption property of Command1 to "Fill list".  Add the following code to the form's general declarations section: Option Explicit Declare Function SendMessage Lib "User" (ByVal hWnd As Integer, ByVal  wMsg   As    Integer, ByVal wParam As Integer, lparam As Any) As Long Const WM_USER = &H400 Const LB_SETTABSTOPS = WM_USER + 19 Const LB_SETHORIZONTALEXTENT = WM_USER + 21

Sub Fill_List (lb As ListBox, sn As Snapshot) Const NUMCHARS = 2 ' Amount of white space between columns.

' Temporary variables to preserve form font settings: Dim hold_fontname As String, hold_fontsize As Integer Dim hold_fontbold As Integer, hold_fontitalic As Integer Dim hold_fontstrikethru As Integer, hold_fontunderline As Integer

Dim whiteSpace As Integer, accumtabstops As Integer, dialogUnits As  Integer Dim fieldVal As String, listline As String Dim avgWidth As Single

Dim retval As Long, i As Integer Dim biggest_value As Single Dim tabstops As Integer

' Save form's font settings so we can use the form to calculate the ' TextWidth / Height of the strings to go into the list box. hold_fontname = Me.FontName hold_fontsize = Me.FontSize hold_fontbold = Me.FontBold hold_fontitalic = Me.FontItalic hold_fontstrikethru = Me.FontStrikethru hold_fontunderline = Me.FontUnderline

' Set form font settings to be identical to list box. Me.FontName = lb.FontName Me.FontSize = lb.FontSize Me.FontBold = lb.FontBold Me.FontItalic = lb.FontItalic Me.FontStrikethru = lb.FontStrikethru Me.FontUnderline = lb.FontUnderline

' Get the average character width of the current list box font ' (in pixels) using the form's TextWidth width method. avgWidth = Me.TextWidth("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ") avgWidth = avgWidth / Screen.TwipsPerPixelX / 52

' Set the white space you want between columns. whiteSpace = avgWidth * NUMCHARS

ReDim biggest_value(0 To sn.Fields.Count - 1) ReDim tabstops(1 To sn.Fields.Count)

lb.Clear

' Loop through the field values for each record in the snapshot. ' Calculate the width required for that field value to fit in the list ' box. Also, build each line of the list box and add it to the list as    ' you go. While Not sn.EOF For i = 0 To sn.Fields.Count - 1 fieldVal = sn(i) & ""      ' Append "" in case of a null field.

' The LB_SETTABSTOP message requires coordinates in dialog units ' (roughly 4 *, the average character width in pixels). dialogUnits = ((Me.TextWidth(fieldVal) / Screen.TwipsPerPixelX + whiteSpace) \ avgWidth) * 4 If dialogUnits > biggest_value(i) Then biggest_value(i) = dialogUnits End If

listline = listline & sn(i) & Chr$(9) Next i

lb.AddItem listline listline = "" sn.MoveNext Wend

' Fill the tabstops array with the position of each tab stop. For i = 0 To sn.Fields.Count - 1 accumtabstops = accumtabstops + biggest_value(i) tabstops(i + 1) = accumtabstops Next i

' Send LB_SETTABSTOP to the list box to set the position of each column. retval& = SendMessage(lb.hWnd, LB_SETTABSTOPS, i, tabstops(1))

' Set the horizontal extent just wider than the first tab stop. ' This will produce a horizontal scroll bar on the list box. ' This message requires coordinates in pixels, so we convert the tab ' stop coordinate back from dialog units to pixels. retval& = SendMessage(lb.hWnd, LB_SETHORIZONTALEXTENT, (tabstops(i) \ 4)  *   avgWidth, 0&)

' Restore form's original font property settings. Me.FontName = hold_fontname Me.FontSize = hold_fontsize Me.FontBold = hold_fontbold Me.FontItalic = hold_fontitalic Me.FontStrikethru = hold_fontstrikethru Me.FontUnderline = hold_fontunderline End Sub   Add the following code to the Command1_Click event: Sub Command1_Click Dim db As database Dim sn As Snapshot

Set db = OpenDatabase("BIBLIO.MDB") Set sn = db.CreateSnapshot("select * from [title author publisher]") Fill_List list1, sn

Set sn = Nothing db.Close End Sub  Run the program by pressing the F5 key. Now, the list box contains neat columns displaying the contents of the [Title Author Publisher] query. The scroll bar enables you to see the entire line. Alter the NUMCHARS constant to allow more white space between columns if you want.

Additional query words: 3.00

Keywords: KB115712

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