筛选代码：
private void comboBox2_SelectedIndexChanged(object sender, EventArgs e)
  {
  DataTable dt = dataGridView1.DataSource as DataTable;
  DataView dv = dt.DefaultView;
  switch(comboBox2.Text)
  {
  case "全部":
  dv.RowFilter = "状态='已配准' or 状态='未配准'" ;
  break;
  case "已配准":
  dv.RowFilter="状态='"+comboBox2.Text+"'";
  break;
  case "未配准":
  dv.RowFilter="状态='"+comboBox2.Text+"'";
  break;
  }
  } 
选中全部时，不行啊

------解决方案--------------------
dv.RowFilter=null 或者dv.RowFilter ="" 试试