Imports System.Windows.Forms
Imports System.Drawing
Imports System.Runtime.InteropServices
 
Public Class FlatComboBox
	Inherits ComboBox
	Public Const WM_PAINT As Integer = &Hf
	<DllImport("user32")> _
	Public Shared Function GetWindowDC(hWnd As IntPtr) As IntPtr
	End Function
 
	<DllImport("user32")> _
	Public Shared Function ReleaseDC(hWnd As IntPtr, hDC As IntPtr) As Integer
	End Function
	Public Sub New()
		MyBase.New()
		Me.SetStyle(ControlStyles.DoubleBuffer, True)
		Me.IntegralHeight = False
		Me.DropDownStyle = ComboBoxStyle.Simple
	End Sub
 
	Protected Overrides Sub WndProc(ByRef m As Message)
		Dim hDC As IntPtr = IntPtr.Zero
		Dim gdc As Graphics = Nothing
		Select Case m.Msg
			Case WM_PAINT
				MyBase.WndProc(m)
				hDC = GetWindowDC(Me.Handle)
				gdc = Graphics.FromHdc(hDC)
				PaintFlatControlBorder(Me, gdc)
				ReleaseDC(m.HWnd, hDC)
				gdc.Dispose()
 
				Exit Select
			Case Else
				MyBase.WndProc(m)
				Exit Select
		End Select
	End Sub
	Private Sub PaintFlatControlBorder(ctrl As Control, g As Graphics)
		Dim rect1 As New Rectangle(0, 0, ctrl.Width, 20)
		Dim rect2 As New Rectangle(0, 21, ctrl.Width, ctrl.Height - 21)
 
		ControlPaint.DrawBorder(g, rect1, Color.Black, ButtonBorderStyle.Solid)
		ControlPaint.DrawBorder(g, rect2, Color.Black, ButtonBorderStyle.Solid)
	End Sub
End Class