HOWTO: Create an Incremental Search ComboBox

• Microsoft Visual Basic Professional and Enterprise Editions for Windows, version 5.0
• Standard, Professional, and Enterprise Editions of Microsoft Visual Basic, 16-bit and 32-bit, for Windows, version 4.0

SUMMARY

The ComboBox that ships with Visual Basic has simplistic functionality whereas many third-party controls offer additional extra features. One of these third-party features is the ability of the ComboBox to search for text and find entries starting with that text as you type text into the ComboBox.

For example, if you type the letters "He," the ComboBox will search for the first text entry starting with "He," and will display the full text, such as "Hello World."

Below is a code sample that demonstrates how to achieve this functionality with the ComboBox that ships with Visual Basic.

MORE INFORMATION

Step by Step Example

1. Start a new project in Visual Basic. Form1 is created by default.

2. Place a ComboBox control on the form.

3. Add the following code to the Form1 code window:

   Option Explicit

   Private Const WM_SETREDRAW = &HB Private Const KEY_A = 65 Private Const KEY_Z = 90 #If Win32 Then

      Private Declare Function SendMessage Lib "user32" Alias _
          "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, _
          ByVal wParam As Long, lParam As Long) As Long
   
      #Else
   
      Private Declare Function SendMessage Lib "User" ( _
          ByVal hwnd As Integer, ByVal wMsg As Integer, _
          ByVal wParam As Integer, lParam As Any) As Long
   
      #End If
      Private Sub Combo1_KeyUp(KeyCode As Integer, Shift As Integer)
        Dim sComboText As String
        Dim iLoop As Integer
        Dim sTempString As String
        Dim lReturn As Long
        If KeyCode >= KEY_A And KeyCode <= KEY_Z Then
          'only look at letters A-Z
          sTempString = Combo1.Text
          If Len(sTempString) = 1 Then sComboText = sTempString
          lReturn = SendMessage(Combo1.hWnd, WM_SETREDRAW, False, 0&)
          For iLoop = 0 To (Combo1.ListCount - 1)
            If UCase((sTempString & Mid$(Combo1.List(iLoop), _
              Len(sTempString) + 1))) = UCase(Combo1.List(iLoop)) Then
              Combo1.ListIndex = iLoop
              Combo1.Text = Combo1.List(iLoop)
              Combo1.SelStart = Len(sTempString)
              Combo1.SelLength = Len(Combo1.Text) - (Len(sTempString))
              sComboText = sComboText & Mid$(sTempString, Len(sComboText) + 1)
              Exit For
            Else
              If InStr(UCase(sTempString), UCase(sComboText)) Then
                sComboText = sComboText & Mid$(sTempString, Len(sComboText) _
                + 1)
                Combo1.Text = sComboText
                Combo1.SelStart = Len(Combo1.Text)
              Else
                sComboText = sTempString
                End If
            End If
          Next iLoop
          lReturn = SendMessage(Combo1.hWnd, _
          WM_SETREDRAW, True, 0&)
        End If
      End Sub
   
      Sub Form_load()
        Combo1.AddItem "Alpha"
        Combo1.AddItem "Beta"
        Combo1.AddItem "Charlie"
        Combo1.AddItem "Delta"
        Combo1.AddItem "Dingo"
      End Sub
   
   

4. On the Run menu, click Start, or press the F5 key to run the program.

NOTE: The style property of the ComboBox must be "0 - Dropdown Combo" for this to work correctly.

Keywords          : GnrlVb kbprg
Technology        : kbvba
Version           : WINDOWS:4.0 5.0
Platform          : WINDOWS
Issue type        : kbhowto