1、获取树节点的值，用事件AfterSelect加载（id值的获取，用name来获取）
2、双击treeview控件得到
private void treeView1_AfterSelect(object sender, TreeViewEventArgs e)
{
string sql = "select * from emp";
)//Level控件中树视图的深度
sql = "select * from emp where dept_id=" + e.Node.Tag;//
DataTable dt = DbAccess.MySqlHelper.getDataTable(sql);
this.dataGridView1.DataSource = dt;
}