窗體打開滿屏（非最大化），點擊按鈕全屏，ESC鍵按下時推出全屏：

public Form1()        {                       InitializeComponent();            KeyPReview = true;            DoubleBuffered = true;            StartPosition = FormStartPosition.Manual; //窗體的位置由 Forms.Control.Location 屬性確定。            Rectangle rect = Screen.GetWorkingArea(this);            this.Width = rect.Width;            this.Height = rect.Height;        }        private void fullscreen_Click(object sender, EventArgs e)        {            this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;            this.WindowState = System.Windows.Forms.FormWindowState.Maximized;        }        private void Form1_KeyDown(object sender, KeyEventArgs e)        {            switch (e.KeyCode)            {                case Keys.Escape:                    returnback();                    break;                default:                    break;            }        }        private void returnback()        {            this.WindowState = FormWindowState.Normal;            this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.Sizable;        }