How to Quickly Search a List Box

• Standard, Professional, and Enterprise Editions of Microsoft Visual Basic, 16-bit and 32-bit, for Windows, version 4.0

SUMMARY

A popular item in a user interface is to "link" a text box to a list box so that as the user types text into the text box, the nearest match in the list box is selected. Although this technique can be implemented fairly easily using pure Visual Basic code, the Windows API provides a quick and easy way of doing this.

MORE INFORMATION

The following technique uses the LB_FINDSTRING message for a list box to locate a partial match for a string in a list box. To do this, call the Windows API SendMessage function. The SendMessage function requires the following parameters to list the files:

SendMessage   (hWnd,LB_FINDSTRING, wParam, lparam)

hWnd    is the hWnd of the list box.

          Use -1 to search the whole list box.
Lparam   is a long pointer to the string to find.

Example to Demonstrate Searching a List Box

1. Start a new project in Visual Basic. Add a text box (Text1) and a list box (list1) to Form1.

2. On the Visual Basic Insert menu, choose module to add a new code module to the project. Add the following code to the General declarations section of module1:

         #If Win32 Then
            Declare Function SendMessage Lib "user32" Alias "SendMessageA" _
            (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As _
            Integer, ByVal lParam As Any) As Long
         #Else
            Declare Function SendMessage Lib "user" (ByVal hwnd As Integer, _
            ByVal wMsg As Integer, ByVal wp As Integer, lp As Any) As Long
         #End If
   
         Public Const LB_FINDSTRING = &H18F
   
   

3. In the Form_Load method for the form, add the following items to the list box using the following code:

         Sub Form_Load()
            List1.Clear
            List1.AddItem "Apples"
            List1.AddItem "Banana"
            List1.AddItem "Bread"
            List1.AddItem "Break"
         End Sub
   
   

4. In the Change method of the text box, add the following code:

         Sub Text1_Change()
            List1.ListIndex = SendMessage(List1.hWnd, LB_FINDSTRING, -1, _
            ByVal Cstr(Text1.Text))
         End Sub