1、 UserControl设置Region和绘制代码：
protected override void OnPaint(PaintEventArgs e)
{
   base.OnPaint(e);
   
   Graphics g = e.Graphics;
   g.SmoothingMode = SmoothingMode.AntiAlias;
   
   using (GraphicsPath path = GraphicsPathHelper.CreatePath(
   ClientRectangle, 8, RoundStyle.All, false))
   {
      using (SolidBrush brush = new SolidBrush(ColorTable.BackColorNormal))
      {
         g.FillPath(brush, path);
      }
      using (Pen pen = new Pen(ColorTable.BorderColor))
      {
         g.DrawPath(pen, path);
         
         using (GraphicsPath innerPath = GraphicsPathHelper.CreatePath(
         ClientRectangle, 8, RoundStyle.All, true))
         {
            g.DrawPath(pen, innerPath);
         }
      }
   }
}

private void SetRegion()
{
   using (GraphicsPath path = GraphicsPathHelper.CreatePath(
   ClientRectangle, 8, RoundStyle.All, false))
   {
      if (base.Region != null)
      {
         base.Region.Dispose();
      }
      base.Region = new Region(path);
   }
}

2、 ToolStripRendererEx重绘代码：
protected override void OnRenderToolStripBackground(
ToolStripRenderEventArgs e)
{
   Graphics g = e.Graphics;
   g.SmoothingMode = SmoothingMode.AntiAlias;
   
   LinearGradientMode mode =
   e.ToolStrip.Orientation == Orientation.Horizontal ?
   LinearGradientMode.Vertical : LinearGradientMode.Horizontal;
   RenderBackgroundInternal(
   g,
   e.AffectedBounds,
   ColorTable.BackColorHover,
   ColorTable.BorderColor,
   ColorTable.BackColorNormal,
   RoundStyle.All,
   false,
   true,
   mode);
}

protected override void OnRenderButtonBackground(
ToolStripItemRenderEventArgs e)
{
   ToolStripButton item = e.Item as ToolStripButton;
   if (item != null)
   {
      LinearGradientMode mode =
      e.ToolStrip.Orientation == Orientation.Horizontal ?
      LinearGradientMode.Vertical : LinearGradientMode.Horizontal;
      Graphics g = e.Graphics;
      g.SmoothingMode = SmoothingMode.AntiAlias;
      Rectangle bounds = new Rectangle(Point.Empty, item.Size);
      
      if (item.BackgroundImage != null)
      {
         Rectangle clipRect = item.Selected ? item.ContentRectangle : bounds;
         ControlPaintEx.DrawBackgroundImage(
         g,
         item.BackgroundImage,
         ColorTable.BackColorNormal,
         item.BackgroundImageLayout,
         bounds,
         clipRect);
      }
      
      if (item.CheckState == CheckState.Unchecked)
      {
         if (item.Selected)
         {
            Color color = ColorTable.BackColorHover;
            if (item.Pressed)
            {
               color = ColorTable.BackColorPressed;
            }
            RenderBackgroundInternal(
            g,
            bounds,
            color,
            ColorTable.BorderColor,
            ColorTable.BackColorNormal,
            RoundStyle.All,
            true,
            true,
            mode);
            return;
         }
         else
         {
            if (e.ToolStrip is ToolStripOverflow)
            {
               using (Brush brush = new SolidBrush(ColorTable.BackColorNormal))
               {
                  g.FillRectangle(brush, bounds);
               }
               return;
            }
         }
      }
      else
      {
         Color color = ControlPaint.Light(ColorTable.BackColorHover);
         if (item.Selected)
         {
            color = ColorTable.BackColorHover;
         }
         if (item.Pressed)
         {
            color = ColorTable.BackColorPressed;
         }
         RenderBackgroundInternal(
         e.Graphics,
         bounds,
         color,
         ColorTable.BorderColor,
         ColorTable.BackColorNormal,
         RoundStyle.All,
         true,
         true,
         mode);
         return;
      }
   }
   
   base.OnRenderButtonBackground(e);
}

protected override void OnRenderSeparator(
ToolStripSeparatorRenderEventArgs e)
{
   Rectangle rect = e.Item.ContentRectangle;
   if (e.ToolStrip is ToolStripDropDown)
   {
      if (e.Item.RightToLeft == RightToLeft.Yes)
      {
         //rect.X -= OffsetMargin + 4;
      }
      else
      {
         rect.X += OffsetMargin + 4;
      }
      rect.Width -= OffsetMargin + 8;
   }
   RenderSeparatorLine(
   e.Graphics,
   rect,
   ColorTable.BackColorPressed,
   ColorTable.BackColorNormal,
   SystemColors.ControlLightLight,
   e.Vertical);
}