dotnet/corefx

private void SimulateTransparency(PaintEventArgs pevent)
        {
            //simular transparencia
            var graphicsContainer = pevent.Graphics.BeginContainer();
            pevent.Graphics.TranslateTransform(-Left, -Top);
            var paintEvents = new PaintEventArgs(pevent.Graphics, Bounds);
            base.InvokePaintBackground(Parent, paintEvents);
            base.InvokePaint(Parent, paintEvents);
            pevent.Graphics.ResetTransform();
            pevent.Graphics.EndContainer(graphicsContainer);
        }
        protected override void OnPaint(PaintEventArgs pevent)
        {
            int radius = 5;
            SimulateTransparency(pevent);
            pevent.Graphics.SmoothingMode = SmoothingMode.AntiAlias;
            Color fillColor, textColor;
            if (AccessibilityObject.State == AccessibleStates.HotTracked)
            {
                fillColor = ControlPaint.Light(BackColor);
                textColor = ForeColor;
            }
            else if (AccessibilityObject.State == AccessibleStates.Pressed)
            {
                fillColor = ControlPaint.Dark(BackColor);
                textColor = ForeColor;
            }
            else if (!Enabled)
            {
                fillColor = ControlPaint.LightLight(BackColor);
                textColor = ControlPaint.Light(ForeColor);
            }
            else
            {
                fillColor = BackColor;
                textColor = ForeColor;
            }
            using (var path = RoundedRect(ClientRectangle, radius))
            using (var backBrush = new SolidBrush(fillColor))
            using (var frontBrush = new SolidBrush(textColor))
            {
                pevent.Graphics.FillPath(backBrush, path);
                pevent.Graphics.DrawString(Text, Font, frontBrush, ClientRectangle, stringFormat);
                if (Focused && ShowFocusCues)
                {
                    var rect = ClientRectangle;
                    rect.Inflate(-radius, -radius);
                    ControlPaint.DrawFocusRectangle(pevent.Graphics, rect, ForeColor, BackColor);
                }
            }
        }