Center ComboBox Text

[Niya]

Nice Edge!! Here is the revised code with Edge's contribution:-

Imports System.ComponentModel
Imports System.Runtime.InteropServices
 
Public Class ComboBoxEx
    Inherits ComboBox
 
    Sub New()
        MyBase.DrawMode = Windows.Forms.DrawMode.OwnerDrawFixed
 
    End Sub
 
    Protected Overrides Sub OnHandleCreated(ByVal e As System.EventArgs)
        MyBase.OnHandleCreated(e)
        Helpers.CenterComboText(Me)
    End Sub
 
    Protected Overrides Sub OnTextChanged(ByVal e As System.EventArgs)
        Helpers.CenterComboText(Me)
        MyBase.OnTextChanged(e)
    End Sub
 
    'We hide this property from the intellisense and property grid
    'to prevent anyone from changing it.
    <Browsable(False), DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden), EditorBrowsable(EditorBrowsableState.Never)> _
    Public Shadows ReadOnly Property DrawMode() As DrawMode
        Get
            'This property is declared merely so we can
            'hide it
            Return MyBase.DrawMode
        End Get
    End Property
 
    Protected Overrides Sub OnDrawItem(ByVal e As System.Windows.Forms.DrawItemEventArgs)
        Dim txt As String = MyBase.Items(e.Index).ToString
        Dim sf As New StringFormat
 
        e.DrawBackground()
 
        sf.Alignment = StringAlignment.Center
 
        e.Graphics.DrawString(txt, e.Font, New SolidBrush(e.ForeColor), e.Bounds, sf)
 
        e.DrawFocusRectangle()
 
    End Sub
End Class
 
Friend Class Win32API
    <StructLayout(LayoutKind.Sequential)> _
    Public Structure RECT
        Public Left As Integer
        Public Top As Integer
        Public Right As Integer
        Public Bottom As Integer
    End Structure
 
    Public Const EM_SETMARGINS As Integer = &HD3
    Public Const EC_LEFTMARGIN = &H1
 
    Public Declare Function FindWindowEx Lib "User32.dll" Alias "FindWindowExA" (ByVal hWnd As IntPtr, ByVal hwndChildAfter As IntPtr, ByVal lpszClass As String, ByVal lpszWindow As String) As IntPtr
    Public Declare Function GetWindowRect Lib "User32.dll" (ByVal hWnd As IntPtr, ByRef lpRect As RECT) As Boolean
    Public Declare Function SendMessage Lib "User32.dll" Alias "SendMessageA" (ByVal hWnd As IntPtr, ByVal Msg As UInteger, ByVal wParam As Integer, ByVal lParam As Integer) As Integer
 
End Class
 
Friend Class Helpers
    Public Shared Sub CenterComboText(ByVal cbo As ComboBox)
        ' combo must be set to DropDown style!
        If Not cbo.DropDownStyle = ComboBoxStyle.DropDown Then Return
        ' get handle to Edit box in combo
        Dim cboEdit_hWnd As IntPtr = Win32API.FindWindowEx(cbo.Handle, IntPtr.Zero, "Edit", Nothing)
        ' if handle found set combo edit box text left margin
        If Not cboEdit_hWnd = IntPtr.Zero Then
            ' Determine width of string displayed
            Dim textWidth As Integer
            Using g As System.Drawing.Graphics = cbo.CreateGraphics()
                textWidth = CInt(g.MeasureString(cbo.Text, cbo.Font).Width)
            End Using
            ' get combo's Edit window size
            Dim rct As Win32API.RECT
            Win32API.GetWindowRect(cboEdit_hWnd, rct)
            ' figure left margin so text appears centered in combo's edit box area.
            Dim leftMargin As Integer = ((rct.Right - rct.Left) - textWidth) \ 2
            ' set left margin of combo's Edit box 
            Win32API.SendMessage(cboEdit_hWnd, Win32API.EM_SETMARGINS, Win32API.EC_LEFTMARGIN, leftMargin)
        End If
    End Sub
End Class