学了点GDI+ 做了一个滑动的效果

代码很简单，写成控件，定义一个角度的属性，然后改动属性重绘。

 public UserControl1()
        {
            InitializeComponent();
            this.SetStyle(ControlStyles.AllPaintingInWmPaint, true);
            this.SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
            this.SetStyle(ControlStyles.ResizeRedraw, true);
            this.SetStyle(ControlStyles.UserPaint, true);
            this.SetStyle(ControlStyles.SupportsTransparentBackColor, true);
            this.SetStyle(ControlStyles.Selectable, true);
        }
       int arcAngle;
        public int  ArcAngle
        {
            get { return arcAngle; }
            set { arcAngle = value; this.Invalidate(); }
        }
      
        protected override void OnPaint(PaintEventArgs e)
        {
            Graphics g = e.Graphics;
            Rectangle rec = new Rectangle(0, 0, this.Width, this.Height);
            SolidBrush solidBrush1 = new SolidBrush(Color.Red);
            SolidBrush solidBrush2 = new SolidBrush(Color.Blue);
            g.FillPie(solidBrush1, rec, 180+arcAngle,180-arcAngle);
            g.FillPie(solidBrush2, rec, 180, arcAngle);
            base.OnPaint(e);
        }