控件DIY：可折叠行的DataGridView

private void Form1_Load(object sender, EventArgs e)

  {
  ht = new Hashtable();
  ht.Add(1, true);

  ht.Add(2, true);//父节点1，2处于展开状态

  //添加测试行  

  dataGridView1.Rows.Add(1, 0);
  dataGridView1.Rows.Add(10, 1);
  dataGridView1.Rows.Add(11, 1);
  dataGridView1.Rows.Add(12, 1);
  dataGridView1.Rows.Add(2, 0);
  dataGridView1.Rows.Add(20, 2);
  dataGridView1.Rows.Add(21, 2);
  dataGridView1.Rows.Add(22, 2);
  }

  Hashtable ht;//存储父节点状态

  private void dataGridView1_RowPostPaint(object sender, DataGridViewRowPostPaintEventArgs e)
  {
  if ((int)dataGridView1.Rows[e.RowIndex].Cells[1].Value == 0)//当前行为父节点时绘制图标
  {
  Rectangle rectangle = new Rectangle(e.RowBounds.Location.X + dataGridView1.RowHeadersWidth - 20,
  e.RowBounds.Location.Y + 4, 14, 14);
  Image img = (bool)ht[(int)dataGridView1.Rows[e.RowIndex].Cells[0].Value]
  ? Properties.Resources.minus : Properties.Resources.plus;
  e.Graphics.DrawImage(img, rectangle);
  }
  else
  {
  dataGridView1.Rows[e.RowIndex].Visible = (bool)ht[(int)dataGridView1.Rows[e.RowIndex].Cells[1].Value];
  }
  }

  private void dataGridView1_RowHeaderMouseClick(object sender, DataGridViewCellMouseEventArgs e)
  {
  int id = (int)dataGridView1.Rows[e.RowIndex].Cells[0].Value;
  int parent = (int)dataGridView1.Rows[e.RowIndex].Cells[1].Value;
  if (parent == 0)
  {
  ht[id] = !(bool)ht[id];
  //重绘之前要显示所有行，否则隐藏行不会再绘制
  foreach (DataGridViewRow gr in dataGridView1.Rows)
  {
  if (!gr.Visible) gr.Visible = true;
  }
  dataGridView1.Refresh();
  }
  }