C#DataGrdviewl加入checkBox全选删除

        #region 加入checkBox
        /// <summary>
        /// 加入checkBox
        /// </summary>
        /// <param name="datagridview"></param>
        private void chekBox(DataGridView datagridview)
        {
            DataGridViewCheckBoxColumn newColumn = new DataGridViewCheckBoxColumn();//添加CHECKBOX
            newColumn.HeaderText = "选择";
            datagridview.Columns.Insert(, newColumn);
            datagridview.MultiSelect = true;
            newColumn.InheritedStyle.Alignment = DataGridViewContentAlignment.TopCenter;
            newColumn.Width = ;
            datagridview.VirtualMode = false;
        }
        #endregion

   //dataGrvieCheckBox是否全选
        private void dataGrviesCheckBoxIsFT(CheckBox checkbox, DataGridView datagridview)
        {
            if (checkbox.Checked == true)
            {
                if (datagridview.Rows.Count > )
                {
                    for (int i = ; i < datagridview.Rows.Count; i++)
                    {

                        ((DataGridViewCheckBoxCell)datagridview.Rows[i].Cells[]).Value = true;
                    }
                }
            }
            else
            {
                if (datagridview.Rows.Count > )
                {
                    for (int i = ; i < datagridview.Rows.Count; i++)
                    {
                        ((DataGridViewCheckBoxCell)datagridview.Rows[i].Cells[]).Value = false;
                    }
                }
            }
        }

        //选中删除的记录
        private void button15_Click(object sender, EventArgs e)
        {
            if (dataFssb.Rows.Count > )
            {
                for (int i = ; i < dataFssb.Rows.Count; i++)
                {
                    string _selectValue = dataFssb.Rows[i].Cells[].EditedFormattedValue.ToString();
                    if (_selectValue == "True")
                    {
                        //MessageBox.Show(dataGridView2.Rows[i].Cells["fsmx_no"].Value.ToString());
                        sqlhelpers.ExecuteNonQuery("delete from dxpt_Fsmx where fsmx_no=" + dataFssb.Rows[i].Cells["fsmx_no1"].Value.ToString() + "");

                    }
                }
            }

            this.dataFssb.DataSource = sqlhelpers.datatable("select rwlb,wczt,zdsjhm,fsnr,cjsj,cgsj,fsmx_no from dxpt_fsmx where wczt='发送失败'");
        }