窗体渐变效果

using System.Runtime.InteropServices;
        [DllImport("user32.dll")]
        private static extern bool AnimateWindow(int hwnd, int dwTime, int dwFlags);

        private const int AW_HOR_POSITIVE = 0x0001;
        private const int AW_HOR_NEGATIVE = 0x0002;
        private const int AW_VER_POSITIVE = 0x0004;
        private const int AW_VER_NEGATIVE = 0x0008;
        private const int AW_CENTER = 0x0010;
        private const int AW_HIDE = 0x10000;
        private const int AW_ACTIVATE = 0x20000;
        private const int AW_SLIDE = 0x40000;
        private const int AW_BLEND = 0x80000;
        private int CloseOpen = 0x20000;


        private void Form1_Load(object sender, EventArgs e)
        {            
            AnimateWindow(this.Handle.ToInt32(), 1000, AW_BLEND | CloseOpen);
        }