using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace _0011 {
 public partial class Form1 : Form {
  public Form1() {
   InitializeComponent();
   /*по умолчанию делаем режим Full Screen*/
   //убираем границы формы
   FormBorderStyle = FormBorderStyle.None;
   //разворачиваем форму на весь экран
   WindowState = FormWindowState.Maximized;
  }
  //кнопка Обычный режим
  private void button1_Click(object sender, EventArgs e) {
   FormBorderStyle = FormBorderStyle.Sizable;
   WindowState = FormWindowState.Normal;
  }
  //кнопка Full Screen
  private void button2_Click(object sender, EventArgs e) {
   FormBorderStyle = FormBorderStyle.None;
   WindowState = FormWindowState.Maximized;
  }
 }
}