using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
 
namespace WindowsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
 
        private void CheckCheck(object sender, EventArgs e) 
        {
            bool flag = true;
            foreach (Control ctrl in Form1.ActiveForm.Controls)
            {
                if (ctrl is CheckBox && ctrl.Name != “chkNone” && ctrl.Name != “chkAll”)
                {
                    CheckBox chk = (CheckBox)ctrl;
                    if (chk.Checked) flag = false;
                }
            }
            chkNone.Checked = flag;
        }
 
 
        private void chkNone_MouseClick(object sender, MouseEventArgs e)
        {
            CheckAll(false);
        }
 
        private void chkAll_MouseClick(object sender, MouseEventArgs e)
        {
            CheckAll(true);
        }
        private void CheckAll(bool b)
        {
            foreach (Control ctrl in Form1.ActiveForm.Controls)
            {
                if (ctrl is CheckBox && ctrl.Name != “chkNone” && ctrl.Name != “chkAll”)
                {
                    CheckBox chk = (CheckBox)ctrl;
                    chk.Checked = b;
                }
            }
        }
 
     }
}