Win 7 glass background

gistfile1.cs

    [DllImport("gdi32")]
    private static extern IntPtr CreateEllipticRgn(int nLeftRect, int nTopRect, int nRightRect, int nBottomRect);
    [DllImport("dwmapi")]
    private static extern int DwmEnableBlurBehindWindow(IntPtr hWnd, ref DwmBlurbehind pBlurBehind);
    public struct DwmBlurbehind
    {
        public int DwFlags;
        public bool FEnable;
        public IntPtr HRgnBlur;
        public bool FTransitionOnMaximized;
    }
    public Form1()
    {
        InitializeComponent();
    }
    private void Form1_Load(object sender, EventArgs e)
    {
        var hr = CreateEllipticRgn(0, 0, Width, Height);
        var dbb = new DwmBlurbehind {FEnable = true, DwFlags = 1, HRgnBlur = hr, FTransitionOnMaximized = false};
        DwmEnableBlurBehindWindow(Handle, ref dbb);
    }
    protected override void OnPaint(PaintEventArgs e)
    {
        e.Graphics.FillRectangle(new SolidBrush(Color.Black), new Rectangle(0, 0, Width, Height));
    }