TreeView 数据绑顶

全部合起来TreeView1.ExpandAll();
全部合展开TreeView1.CollapseAll();
设置TreeNode的这个属性 TreeNodeSelectAction.Expand;设置好了就OK

public void BindTView()
    {
        sql = "select * from P_class where depth=0";
        OleDbConnection con = new OleDbConnection(SqlCon);
        con.Open();
        OleDbCommand com = new OleDbCommand(sql, con);
        OleDbDataReader dr = com.ExecuteReader();
        while (dr.Read())
        {
            TreeNode tn = new TreeNode();
            tn.Text = dr["classen"].ToString();
            tn.Value = dr["classid"].ToString();
            this.TreeView1.Nodes.Add(tn);
            BindTViewExten(tn);
        }
        dr.Close();
        con.Close();

    }