BlockInput C# Winform

put this in the middle of the public partial class
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[return: MarshalAs(UnmanagedType.Bool)]
        [DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
        public static extern void BlockInput([In, MarshalAs(UnmanagedType.Bool)] bool fBlockIt);
        [DllImport("Gdi32.dll", EntryPoint = "CreateRoundRectRgn")]

        private static extern IntPtr CreateRoundRectRgn

(
    int nLeftRect,     // x-coordinate of upper-left corner
    int nTopRect,      // y-coordinate of upper-left corner
    int nRightRect,    // x-coordinate of lower-right corner
    int nBottomRect,   // y-coordinate of lower-right corner
    int nWidthEllipse, // height of ellipse
    int nHeightEllipse // width of ellipse
);
        int w = Screen.PrimaryScreen.Bounds.Width;
        int h = Screen.PrimaryScreen.Bounds.Height;

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And then type this
            this.Location = new Point(0, 0);
            Size = new Size(w, h);
            TopMost = true;
            Cursor.Hide();
            BlockInput(true);