C# WinForm窗体最大化

效果图:

核心代码:
1. 控制类

using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;

namespace WindowsApplication2
{
    public class Pb_C_MaxFrm
    {
        Form _MaxFrom;
        ESCMsgFrm _ESCFrm;

        FormBorderStyle _oriFrmBorderStyle;
        FormWindowState _oriFrmWindowState;

        bool _bIsMax = false;
        public Pb_C_MaxFrm()
        {

        }
        public Pb_C_MaxFrm(Form maxForm)
        {
            setMaxForm(maxForm);
        }
        public bool IsMax
        {
            get { return _bIsMax; }
        }
        public void setMaxForm(Form maxForm)
        {
            _MaxFrom = maxForm;
            //记录窗体的原始状态
            _oriFrmBorderStyle = maxForm.FormBorderStyle;
            _oriFrmWindowState = maxForm.WindowState;
            _MaxFrom.KeyDown+=new KeyEventHandler(_MaxFrom_KeyDown);
 
        }
        bool CheckData()
        {
            return _MaxFrom == null ? false : true;
        }
        void  _MaxFrom_KeyDown(object sender, KeyEventArgs e)
        {
            //按下[F11]键执行全屏化
            if (e.KeyCode == Keys.F11)
                Show();
            else if (e.KeyCode == Keys.Escape)//按下[Esc]键返回原始窗体
                unShow();
        }

        public void Show()
        {
            if (!CheckData())
                return;

            #region 窗体最大化
            if (_MaxFrom.WindowState != FormWindowState.Maximized || _MaxFrom.FormBorderStyle!= FormBorderStyle.None)
            {
                _MaxFrom.FormBorderStyle = FormBorderStyle.None;
                _MaxFrom.WindowState = FormWindowState.Maximized;

                #region 启动闪屏
                if (_ESCFrm == null)
                {
                    _ESCFrm = new ESCMsgFrm();
                    _ESCFrm.FormClosed += new FormClosedEventHandler(_ESCFrm_FormClosed);
                    _ESCFrm.Owner = _MaxFrom;
                }
                _ESCFrm.Show();
                #endregion
            }
            #endregion  

            _bIsMax = true;
        }

        public void unShow()
        {
            if (!CheckData())
                return;

            if (_ESCFrm != null)
                _ESCFrm.Close();
            //返回到初始状态
            _MaxFrom.FormBorderStyle = _oriFrmBorderStyle;
            _MaxFrom.WindowState = _oriFrmWindowState;

            _bIsMax = false;
        }

        void _ESCFrm_FormClosed(object sender, FormClosedEventArgs e)
        {
            _ESCFrm = null;
        }
    }
}

2.[按ESC返回]信息窗口类

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Text;
using System.Windows.Forms;

namespace WindowsApplication2
{
    public partial class ESCMsgFrm : Form
    {
        public ESCMsgFrm()
        {
            InitializeComponent();
        }

        #region 窗体效果(暂时未用)
        /// <summary>
        /// 设置窗体的四角为圆角
        /// </summary>
        void setCircleCorner()
        {
            #region 圆角蒙板

            System.Drawing.Drawing2D.GraphicsPath GraphicsPath = new System.Drawing.Drawing2D.GraphicsPath();

            #region 左上
            GraphicsPath.AddRectangle(new Rectangle(0, 0, 5, 5));
            GraphicsPath.AddRectangle(new Rectangle(10, 0, 2, 1));
            GraphicsPath.AddRectangle(new Rectangle(9, 0, 1, 2));
            GraphicsPath.AddRectangle(new Rectangle(8, 0, 1, 2));
            GraphicsPath.AddRectangle(new Rectangle(7, 0, 1, 3));
            GraphicsPath.AddRectangle(new Rectangle(6, 0, 1, 4));
            GraphicsPath.AddRectangle(new Rectangle(5, 0, 1, 5));
            GraphicsPath.AddRectangle(new Rectangle(0, 5, 5, 1));
            GraphicsPath.AddRectangle(new Rectangle(0, 6, 4, 1));
            GraphicsPath.AddRectangle(new Rectangle(0, 7, 3, 1));
            GraphicsPath.AddRectangle(new Rectangle(0, 8, 2, 1));
            GraphicsPath.AddRectangle(new Rectangle(0, 9, 2, 1));
            GraphicsPath.AddRectangle(new Rectangle(0, 10, 1, 1));
            GraphicsPath.AddRectangle(new Rectangle(0, 11, 1, 1));
            #endregion

            #region 右上
            GraphicsPath.AddRectangle(new Rectangle(Width - 11, 0, 2, 1));
            GraphicsPath.AddRectangle(new Rectangle(Width - 9, 0, 2, 2));
            GraphicsPath.AddRectangle(new Rectangle(Width - 7, 0, 1, 3));
            GraphicsPath.AddRectangle(new Rectangle(Width - 6, 0, 1, 4));
            GraphicsPath.AddRectangle(new Rectangle(Width - 5, 0, 5, 5));
            GraphicsPath.AddRectangle(new Rectangle(Width - 4, 5, 4, 1));
            GraphicsPath.AddRectangle(new Rectangle(Width - 3, 6, 5, 1));
            GraphicsPath.AddRectangle(new Rectangle(Width - 2, 7, 2, 2));
            GraphicsPath.AddRectangle(new Rectangle(Width - 1, 9, 1, 2));
            #endregion

            #region 左下
            GraphicsPath.AddRectangle(new Rectangle(0, Height - 5, 5, 1));
            GraphicsPath.AddRectangle(new Rectangle(0, Height - 6, 4, 1));
            GraphicsPath.AddRectangle(new Rectangle(0, Height - 7, 3, 1));
            GraphicsPath.AddRectangle(new Rectangle(0, Height - 9, 2, 2));
            GraphicsPath.AddRectangle(new Rectangle(0, Height - 12, 1, 3));
            GraphicsPath.AddRectangle(new Rectangle(0, Height - 4, 5, 4));
            GraphicsPath.AddRectangle(new Rectangle(5, Height - 4, 1, 4));
            GraphicsPath.AddRectangle(new Rectangle(6, Height - 3, 1, 3));
            GraphicsPath.AddRectangle(new Rectangle(7, Height - 2, 2, 2));
            GraphicsPath.AddRectangle(new Rectangle(9, Height - 1, 3, 1));
            #endregion

            #region 右下
            GraphicsPath.AddRectangle(new Rectangle(Width - 9, Height - 1, 2, 1));
            GraphicsPath.AddRectangle(new Rectangle(Width - 7, Height - 2, 1, 2));
            GraphicsPath.AddRectangle(new Rectangle(Width - 6, Height - 3, 1, 3));
            GraphicsPath.AddRectangle(new Rectangle(Width - 5, Height - 4, 1, 4));
            GraphicsPath.AddRectangle(new Rectangle(Width - 4, Height - 4, 4, 4));
            GraphicsPath.AddRectangle(new Rectangle(Width - 4, Height - 5, 5, 1));
            GraphicsPath.AddRectangle(new Rectangle(Width - 3, Height - 6, 3, 1));
            GraphicsPath.AddRectangle(new Rectangle(Width - 2, Height - 8, 2, 2));
            GraphicsPath.AddRectangle(new Rectangle(Width - 1, Height - 11, 1, 3));
            #endregion

            System.Drawing.Region RegionX = new Region();
            RegionX.Xor(GraphicsPath);
            this.Region = RegionX;

            #endregion
        }
        /// <summary>
        /// 圆角透明
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="p_1"></param>
        /// <param name="p_2"></param>
        private void Type(Control sender, int p_1, double p_2)
        {
            GraphicsPath oPath = new GraphicsPath();
            oPath.AddClosedCurve(new Point[] { new Point(0, sender.Height / p_1),
                new Point(sender.Width / p_1, 0), 
                new Point(sender.Width - sender.Width / p_1, 0), 
                new Point(sender.Width, sender.Height / p_1), 
                new Point(sender.Width, sender.Height - sender.Height / p_1), 
                new Point(sender.Width - sender.Width / p_1, sender.Height), 
                new Point(sender.Width / p_1, sender.Height), 
                new Point(0, sender.Height - sender.Height / p_1) }, 
                (float)p_2);
            sender.Region = new Region(oPath);
        }

        #endregion

        private void ESCMsgFrm_Load(object sender, EventArgs e)
        {
            this.ShowInTaskbar = false;//不在任务栏里显示
            this.StartPosition = FormStartPosition.CenterScreen;
            this.Opacity = 1;

            //以下两句话可以保证窗体显示时只显示字体,因为背景色已被设置为透明
            //设置窗体背景色为银色
            this.BackColor = Color.Silver;
            this.TransparencyKey = Color.Silver;//将窗体中银色部分设置为透明

            timer1.Interval = 300;
            timer1.Start();
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            if (this.Opacity > 0)
            {
                this.Opacity -= 0.17;
            }
            else
            {
                this.Opacity = 0;
                this.Close();
            }
        }

        private void ESCMsgFrm_FormClosing(object sender, FormClosingEventArgs e)
        {
            timer1.Stop();
        }

    }
}

3.如何调用

public partial class Form2 : Form
    {
        Pb_C_MaxFrm m;
        public Form2()
        {
            InitializeComponent();
            m = new Pb_C_MaxFrm();
            m.setMaxForm(this);
        }

        private void Form2_Load(object sender, EventArgs e)
        {
            
        }
    }