I'm implementing a function. While choosing any of datagridviewcheckboxcolumn in form1 and show form2 when click button to close, datagridviewcheckboxcolumn in the form1 will is false ?
Please help on this.

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

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        Form2 Frm2 = new Form2();
        public Form1()
        {
            InitializeComponent();
            DataGridViewCheckColumn();

            Frm2.newEvent += new FrmCheckbox(Frm2_Event);

        }
        public void DataGridViewCheckColumn()
        {

            dataGridView1.ColumnCount = 6;

            dataGridView1.AllowUserToAddRows = false;

            DataGridViewCheckBoxColumn colCB = new 

DataGridViewCheckBoxColumn();
            colCB.Name = "chkcol";
            colCB.HeaderText = "Select";
            colCB.Width = 40;
            dataGridView1.Columns.Add(colCB);


            dataGridView1.Columns[0].Name = "C0";
            dataGridView1.Columns[1].Name = "C1";
            dataGridView1.Columns[2].Name = "C2";
            dataGridView1.Columns[3].Name = "C3";
            dataGridView1.Columns[4].Name = "C4";
            dataGridView1.Columns[5].Name = "C5";

            dataGridView1.Columns[0].HeaderText = "C0";
            dataGridView1.Columns[1].HeaderText = "C1";
            dataGridView1.Columns[2].HeaderText = "C2";
            dataGridView1.Columns[3].HeaderText = "C3";
            dataGridView1.Columns[4].HeaderText = "C4";
            dataGridView1.Columns[5].HeaderText = "C5";

            dataGridView1.Columns[0].Width = 40;
            dataGridView1.Columns[1].Width = 40;
            dataGridView1.Columns[2].Width = 40;
            dataGridView1.Columns[3].Width = 40;
            dataGridView1.Columns[4].Width = 40;
            dataGridView1.Columns[5].Width = 40;


            dataGridView1.Rows.Add(new string[] { "A1", "B1", "C1", 

"D1", "E1", "F1" });
            dataGridView1.Rows.Add(new string[] { "A2", "B2", "C2", 

"D2", "E2", "F2" });
            dataGridView1.Rows.Add(new string[] { "A3", "B3", "C3", 

"D3", "E3", "F3" });
            dataGridView1.Rows.Add(new string[] { "A4", "B4", "C4", 

"D4", "E4", "F4" });
            dataGridView1.Rows.Add(new string[] { "A5", "B5", "C5", 

"D5", "E5", "F5" });
            dataGridView1.Rows.Add(new string[] { "A6", "B6", "C6", 

"D6", "E6", "F6" });
            dataGridView1.Rows.Add(new string[] { "A7", "B7", "C7", 

"D7", "E7", "F7" });




            dataGridView1.AutoResizeColumns();
        }

        void Frm2_Event()
        {

            //for (int i = 0; i <= dataGridView1.Rows.Count - 1; i++)
            //{

            //    if (Convert.ToBoolean(dataGridView1.Rows[i].Cells

["chkcol"].Value) == true )
            //    {
            //        dataGridView1.Rows[i].Cells["chkcol"].Value = false ;
            //    }

            //}
            foreach (DataGridViewRow row in dataGridView1.Rows)
            {
                if (Convert.ToBoolean(row.Cells["chkcol"].Value) == true)
                {
                    row.Cells["chkcol"].Value = false;
                }
            }

        }

        private void dataGridView1_CellContentClick(object sender, 

DataGridViewCellEventArgs e)
        {
             for (int i = 0; i <= dataGridView1.RowCount - 1; i++)
            {
                if (Convert.ToBoolean(dataGridView1.Rows

[e.RowIndex].Cells["chkcol"].Value = true))
                {
                    Frm2.ShowDialog();
                    break;
                }
            }

        }

    }
}



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

 namespace WindowsFormsApplication1
 {
     public delegate void FrmCheckbox();
     public partial class Form2 : Form
     {
         public event FrmCheckbox newEvent;
         public Form2()
         {
             InitializeComponent();
            //button1.Click +=new EventHandler (button1_Click );
         }

         private void button1_Click(object sender, EventArgs e)
         {
             if (newEvent != null)
             {
                 newEvent();

             }
         }




     }
 }

the delegates, events etc... are fine , erase your dataGridView1_CellContentClick event
and try this

 private void dataGridView1_CellClick(object sender, DataGridViewCellEventArgs e)
        {
            if (e.ColumnIndex!=dataGridView1.Columns.Count-1)
            {
                for (int i = 0; i <= dataGridView1.RowCount - 1; i++)
                {
                    if (Convert.ToBoolean(dataGridView1.Rows
    [i].Cells["chkcol"].Value = true))
                    {
                        Frm2.ShowDialog();
                        break;

                    }
                }
            }
        }

if(Convert.ToBoolean(dataGridView1.Rows[i].Cells["chkcol"].Value = true))

This statement will always return true as you are setting the Value to true in your statement. Was this was your intended result?