Making a combobox autofill

[TheWizardofInt]

I am trying to make a VB.Net form autofill from the contents of its drop down, so in this case if you type H and Hartford is in the drop down, then it autofills 'Hartford'

 

 ' Constant
Public Const CB_SELECTSTRING = &H14D
 ' API Declarations
   Public Declare Function SendMessage Lib "user32" Alias "SendMessageA" _
       (ByVal hwnd As IntPtr, ByVal wMsg As Integer, ByVal wParam As Integer, _
           ByVal lParam As String) As Integer

Private Sub cmbCity_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles cmbCity.KeyPress
       Dim APIRetVal As Integer
       Dim sText As String

       Dim KeyAscii As String = e.KeyChar
       With cmbCity
           If Not (KeyAscii = Chr(8) Or KeyAscii = Chr(27) Or KeyAscii = Chr(13)) Then
               If .SelectionLength > 0 Then
                   sText = Mid(.Text, 1, .SelectionStart) & KeyAscii
               Else
                   sText = .Text & KeyAscii
               End If

               APIRetVal = SendMessage(.Handle, CB_SELECTSTRING, -1, sText)

               If APIRetVal <> -1 Then
                   .SelectionStart = Len(sText)
                   .SelectionLength = Len(.Text) - .SelectionStart + 1
               Else
                   .Text = sText
                   .SelectionStart = Len(sText) + 1
               End If

               KeyAscii = ""
           End If
       End With
   End Sub

 

It finds the selection as you F-11 through the program, then when the sub closes it retypes the Hh and selects it

 

Any idea where I am messing up here?

[PlausiblyDamp]

change the KeyAscii = "" to e.handled =true.

[PlausiblyDamp]

also noticed there is a lot of VB6 code in there - was this converted by the upgrade wizard? If you want to drop the compatability stuff the following is a more .Net way of doing things. (Although replacing the chr function can make it a bit long but more readable)

 

Public Const CB_SELECTSTRING = &H14D
' API Declarations
Public Declare Function SendMessage Lib "user32" Alias "SendMessageA" _
	(ByVal hwnd As IntPtr, ByVal wMsg As Integer, ByVal wParam As Integer, _
		ByVal lParam As String) As Integer

Private Sub cmbCity_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles cmbCity.KeyPress
	Dim APIRetVal As Integer
	Dim sText As String


	With cmbCity

If Not (e.KeyChar = Convert.ToChar(Keys.Back) Or e.KeyChar = Convert.ToChar(Keys.Escape) Or e.KeyChar = Convert.ToChar(Keys.Enter)) Then
			If .SelectionLength > 0 Then
				sText = .Text.Substring(0, .SelectionStart) & e.KeyChar

			Else
				sText = .Text & e.KeyChar
			End If

			APIRetVal = SendMessage(.Handle, CB_SELECTSTRING, -1, sText)

			If APIRetVal <> -1 Then
				.SelectionStart = sText.Length
				.SelectionLength = .Text.Length - .SelectionStart + 1
			Else
				.Text = sText
				.SelectionStart = sText.Length + 1
			End If

			e.Handled = True
		End If
	End With
End Sub

[TheWizardofInt]

That was it - e.handled or it doesn't save the results

 

Thanks for the free lesson on the other stuff!

[PlausiblyDamp]

Feeling bored so you might want to try this.

I've created a basic Combobox control with the functionality built in, not a complete control by any standards but a good starting point.

Create a new WindowsControl Project and paste this into a new class module and have a play.

 

Public Class AutoCompleteComboBox
   Inherits System.Windows.Forms.ComboBox


   Protected Overrides Sub OnKeyPress(ByVal e As System.Windows.Forms.KeyPressEventArgs)

       Dim sText As String = Text
       Dim i As Integer

       If e.KeyChar = Convert.ToChar(Keys.Back) Then
           Text = Text.Substring(0, SelectionStart - 1)
           sText = Text
       End If

       i = FindString(sText)

       If i >= 0 Then
           SelectedIndex = i
           [select](sText.Length, Text.Length)
       End If
       MyBase.OnKeyPress(e)
   End Sub
End Class

[PlausiblyDamp]

Found a small bug and also added a property to allow the autocomplete to be turned on or off.

 

Public Class AutoCompleteComboBox
   Inherits System.Windows.Forms.ComboBox


   Protected _AutoCompleteEnabled As Boolean = True

    _
   Public Property AutoCompleteEnabled() As Boolean
       Get
           Return _AutoCompleteEnabled
       End Get
       Set(ByVal Value As Boolean)
           _AutoCompleteEnabled = Value
       End Set
   End Property

   Protected Overrides Sub OnKeyPress(ByVal e As System.Windows.Forms.KeyPressEventArgs)

       If _AutoCompleteEnabled = True Then  'Only do something if autocomplete is enabled
           Dim sText As String = Text
           Dim i As Integer

           If e.KeyChar = Convert.ToChar(Keys.Back) Then
               If Text.Length = 0 Then Return 'Don't backspace when nothing there
               Text = Text.Substring(0, SelectionStart - 1)
               sText = Text
           End If

           i = FindString(sText)

           If i >= 0 Then
               SelectedIndex = i
               [select](sText.Length, Text.Length)
           End If
       End If
       MyBase.OnKeyPress(e)
   End Sub
End Class

[rkf]

can you convert that to c# for me??

 

Please??

[blacrain]

Hello, I'm new here.. and found this very usefull. The only problem I found was when there was text in the box, you put the cursor at the beginning of the text, and hit backspace. We'd get a nice error. I fixed it with

 

If SelectionStart = 0 And SelectionLength = 0 Then Return

 

So the whole thing looks like:

 

Public Class AutoCompleteComboBox
   Inherits System.Windows.Forms.ComboBox


   Protected _AutoCompleteEnabled As Boolean = True

   <System.ComponentModel.Category("Behavior"), System.ComponentModel.Description("Enables or disables the autocompletion functionality")> _
   Public Property AutoCompleteEnabled() As Boolean
       Get
           Return _AutoCompleteEnabled
       End Get
       Set(ByVal Value As Boolean)
           _AutoCompleteEnabled = Value
       End Set
   End Property

   Protected Overrides Sub OnKeyPress(ByVal e As System.Windows.Forms.KeyPressEventArgs)

       If _AutoCompleteEnabled = True Then  'Only do something if autocomplete is enabled
           Dim sText As String = Text
           Dim i As Integer

           If e.KeyChar = Convert.ToChar(Keys.Back) Then
               If Text.Length = 0 Then Return 'Don't backspace when nothing there
               If SelectionStart = 0 And SelectionLength = 0 Then Return 'There's nothing to delete
               Text = Text.Substring(0, SelectionStart - 1)
               sText = Text
           End If

           i = FindString(sText)

           If i >= 0 Then
               SelectedIndex = i
               [select](sText.Length, Text.Length)
           End If
       End If
       MyBase.OnKeyPress(e)
   End Sub
End Class