VB.NET 如何去掉 GroupBox 控件的边框？

工程里面添加一个类，命名为myGroupBox，代码如下：
Imports System.ComponentModel
Imports System.Drawing.Drawing2D
Public Class myGroupBox
Inherits GroupBox
Public Sub New()
MyBase.BackColor = Color.Transparent
End Sub
_
Public Overrides Property BackColor() As Color
Get
Return MyBase.BackColor
End Get
Set(value As Color)
MyBase.BackColor = value
End Set
End Property
Private m_backColor As Color = Color.Transparent
Public Property ActualBackColor() As Color
Get
Return Me.m_backColor
End Get
Set(value As Color)
Me.m_backColor = value
End Set
End Property
Protected Overrides Sub OnPaint(e As PaintEventArgs)
Dim tSize As Size = TextRenderer.MeasureText(Me.Text, Me.Font)
Dim borderRect As Rectangle = e.ClipRectangle
borderRect.Y += tSize.Height / 2
borderRect.Height -= tSize.Height / 2
Dim gPath As GraphicsPath = CreatePath(0, borderRect.Y, CSng(Me.Width - 1), borderRect.Height - 1, 5, True, _
True, True, True)
e.Graphics.FillPath(New SolidBrush(ActualBackColor), gPath)
e.Graphics.DrawPath(New Pen(Me.BackColor), gPath)
borderRect.X += 6
borderRect.Y -= 7
e.Graphics.DrawString(Me.Text, Me.Font, New SolidBrush(Me.ForeColor), borderRect)
End Sub
Public Function CreatePath(x As Single, y As Single, width As Single, height As Single, radius As Single, _
RoundTopLeft As Boolean, RoundTopRight As Boolean, RoundBottomRight As Boolean, RoundBottomLeft As Boolean) As GraphicsPath
Dim xw As Single = x + width
Dim yh As Single = y + height
Dim xwr As Single = xw - radius
Dim yhr As Single = yh - radius
Dim xr As Single = x + radius
Dim yr As Single = y + radius
Dim r2 As Single = radius * 2
Dim xwr2 As Single = xw - r2
Dim yhr2 As Single = yh - r2
Dim p As New GraphicsPath()
p.StartFigure()
'Top Left Corner
If RoundTopLeft Then
p.AddArc(x, y, r2, r2, 180, 90)
Else
p.AddLine(x, yr, x, y)
p.AddLine(x, y, xr, y)
End If
'Top Edge
p.AddLine(xr, y, xwr, y)
'Top Right Corner
If RoundTopRight Then
p.AddArc(xwr2, y, r2, r2, 270, 90)
Else
p.AddLine(xwr, y, xw, y)
p.AddLine(xw, y, xw, yr)
End If
'Right Edge
p.AddLine(xw, yr, xw, yhr)
'Bottom Right Corner
If RoundBottomRight Then
p.AddArc(xwr2, yhr2, r2, r2, 0, 90)
Else
p.AddLine(xw, yhr, xw, yh)
p.AddLine(xw, yh, xwr, yh)
End If
'Bottom Edge
p.AddLine(xwr, yh, xr, yh)
'Bottom Left Corner
If RoundBottomLeft Then
p.AddArc(x, yhr2, r2, r2, 90, 90)
Else
p.AddLine(xr, yh, x, yh)
p.AddLine(x, yh, x, yhr)
End If
'Left Edge
p.AddLine(x, yhr, x, yr)
p.CloseFigure()
Return p
End Function
End Class

工具栏会出现一个myGroupBox控件，放入窗体，你会发现边框没了。

把背景色设置为透明，不就行了么？不就融入背景了

去掉干嘛？