System.Windows.Forms.CheckedListBox.SetItemCheckState C# (CSharp) Method

		public void SetItemCheckState (int index, CheckState value)
		{
			if (index < 0 || index >= Items.Count)
				throw new ArgumentOutOfRangeException ("Index of out range");

			if (!Enum.IsDefined (typeof (CheckState), value))
				throw new InvalidEnumArgumentException (string.Format("Enum argument value '{0}' is not valid for CheckState", value));

			CheckState old_value = GetItemCheckState (index);
			
			if (old_value == value)
				return;

			ItemCheckEventArgs icea = new ItemCheckEventArgs (index, value, old_value);
    			OnItemCheck (icea);

			switch (icea.NewValue) {
			case CheckState.Checked:
			case CheckState.Indeterminate:
				check_states[Items[index]] = icea.NewValue;
    				break;
			case CheckState.Unchecked:
				check_states.Remove (Items[index]);
				break;
			default:
				break;
			}

			UpdateCollections ();

    			InvalidateCheckbox (index);
		}

        private void butMoi_Click(object sender, System.EventArgs e)
        {
            int     i = 1;
            DataRow r;

            dtkp = m.get_data("select * from " + user + ".btdkp_bv order by makp").Tables[0];
            for (i = 1; i < 100; i++)
            {
                r = m.getrowbyid(dtkp, "makp='" + i.ToString().PadLeft(2, '0') + "'");
                if (r == null)
                {
                    break;
                }
            }
            ma.Text      = i.ToString().PadLeft(2, '0');
            viettat.Text = ma.Text;
            for (int k = 0; k < dmba.Items.Count; k++)
            {
                dmba.SetItemCheckState(k, CheckState.Unchecked);
            }
            giavtth.Text = s_loaivp = s_mucvp = ten.Text = ""; thucke.Text = "0"; kehoach.Text = "0"; s_loaicd = s_muccd = "";
            ena_object(true);
            ma.Enabled = false;
            viettat.Focus();
        }