请教大虾们一个问题，谢谢

 public void ShowPc(string str)

        {



            SqlConnection myconn = new SqlConnection();

            myconn.ConnectionString = Main.mystr;

            myconn.Open();

            DataSet myds = new DataSet();

            SqlDataAdapter myadp = new SqlDataAdapter(str, myconn);

            myadp.Fill(myds, "ksb");

            dataGridView1.DataSource = myds.Tables["ksb"];         

            myconn.Close();



        }



        public void LoadCheckBox()

        {

            DataGridViewCheckBoxColumn checkbox = new DataGridViewCheckBoxColumn();

            //列显示名称

            checkbox.HeaderText = "出场";

            checkbox.Name = "IsChecked";

            checkbox.TrueValue = true;

            checkbox.FalseValue = false;



            checkbox.DataPropertyName = "IsChecked";

            //列宽

            checkbox.Width = 50;

            //列大小不改变

            checkbox.Resizable = DataGridViewTriState.False;

            //添加的checkbox在dgv第一列

            this.dataGridView1.Columns.Insert(0, checkbox);

            

            for (int i = 0; i < dataGridView1.Rows.Count; i++)

            {

                dataGridView1.Rows[i].Cells[0].Value =true;                

            }

            

        }



        private void Modify_Load(object sender, EventArgs e)

        {

            currentpc = 1;

            str = "select * from ksb where pc='" + currentpc + "' and examdate=(select val from setting where items='currentexam') order by seat";

            ShowPc(str);

            LoadCheckBox();          



        }