winfrom-窗体打开大小和全屏设置

窗体打开满屏（非最大化），点击按钮全屏，ESC键按下时推出全屏：

public Form1()
        {           
            InitializeComponent();

            KeyPreview = true;
            DoubleBuffered = true;
            StartPosition = FormStartPosition.Manual; //窗体的位置由 Forms.Control.Location 属性确定。

            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;
        }