C#自定义控件VS用户控件

private void timer1_Tick(object sender, EventArgs e)
  {


   this.Time = DateTime.Now;  

   Refresh();   
  }

#region draw clock
  private void UserClock_Paint(object sender, PaintEventArgs e)
  {
   Graphics dc = e.Graphics;
   Pen pn = new Pen(ForeColor);
   SolidBrush br = new SolidBrush(ForeColor);
   initCoordinates(dc); 
   DrawDots(dc, br);
   DrawHourHand(dc, pn);
   DrawSecondHand(dc, pn);
   DrawMinuteHand(dc, pn);
  }
  
  public void initCoordinates(Graphics dc)
  {
   if (this.Width == 0 || this.Height == 0) return;
   dc.TranslateTransform(this.Width / 2, this.Height / 2);
   dc.ScaleTransform(this.Height / 250F, this.Width / 250F);
  }
  public void DrawDots(Graphics dc, Brush brush)
  {
   int iSize;
   for (int i = 0; i <= 59; i++)
   {
    if (i % 5 == 0)
    {
     iSize = 15;
    }
    else
    {
     iSize = 5;
    }
    dc.FillEllipse(brush, -iSize / 2, -100 - iSize / 2, iSize, iSize);
    dc.RotateTransform(6);
   }
  }
  public virtual void DrawHourHand(Graphics grfx, Pen pn)
  {
   GraphicsState gs = grfx.Save();
   grfx.RotateTransform(360.0F * Time.Hour / 12 + 30.0F * Time.Minute / 60);
   grfx.DrawLine(pn, 0, 0, 0, -50);
   grfx.Restore(gs);
  }
  public virtual void DrawMinuteHand(Graphics grfx, Pen pn)
  {
   GraphicsState gs = grfx.Save();
   grfx.RotateTransform(360.0F * Time.Minute / 60 + 6.0F * Time.Second / 60);
   grfx.DrawLine(pn, 0, 0, 0, -70);
   grfx.Restore(gs);
  }
  public virtual void DrawSecondHand(Graphics grfx, Pen pn)
  {
   GraphicsState gs = grfx.Save();
   grfx.RotateTransform(360.0F * Time.Second / 60);
   grfx.DrawLine(pn, 0, 0, 0, -100);
   grfx.Restore(gs);
  }
  #endregion