请看这段返回OleDbDataReader的代码究竟有哪些错误？

[fywindy]

       this.TreeView2.Clear();//清TreeView的节点
       public OleDbDataReader ExecuteQueryReturnReader(string sql, string connStr)
        {
            OleDbConnection conn = new OleDbConnection();
            OleDbDataReader reader = null;
            try
            {
                conn = new OleDbConnection(connStr);
                conn.Open();

                OleDbCommand command = conn.CreateCommand();
                command.CommandText = sql;
                reader = command.ExecuteReader();
                
            }
            catch(Exception ex)
            {
               
            }
            finally
            {
                //if (conn != null)
                    //conn.Close();
            }
            return reader;
        }      

这是类里面封装的一种方法，我这么用以上的代码：

 string TableName = "";
                string strConnection = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + DataBase;
                ExecSql con = new ExecSql();
                string ID = string.Format("select NodeID from config where Name='{0}'",e.Node.Text);
                OleDbDataReader p = con.ExecuteQueryReturnReader(ID, strConnection);
                if(p == null)
                {

                    MessageBox.Show("222");
                }
                if (p != null)
                {
                    while (p.Read())
                    {
                        TableName = p[0].ToString();

                    }
                    p.Close();
                }
                else
                {
                    
                }
                
                string sql = string.Format("select FaID from {0}",TableName);
                OleDbDataReader p2 = con.ExecuteQueryReturnReader(sql, strConnection);
                if(p2 != null)
                {
                      while(p2.Read())
                     {
                        for(int i=0;i<p2.FieldCount;i++)
                        {
                            if (string.Compare(p2[i].ToString(),"0",true) == 0)
                            {
                                string Name = string.Format("select Name from {0} where FaID={1}", TableName, "0");
                        
                                OleDbDataReader N = con.ExecuteQueryReturnReader(Name, strConnection);
                                if(N != null)
                                {
                                    while (N.Read())
                                    {
                                        string NodeName = N[0].ToString();
                                        EvebtTree2AddData(NodeName);


                                    }
                                    N.Close();

                                }
                               
                            }
                            else if (string.Compare(p2[i].ToString(),"101",true) == 0)
                            {
                                string Name = string.Format("select Name from {0} where FaID={1}", TableName, "101");
                                OleDbDataReader N = con.ExecuteQueryReturnReader(Name, strConnection);
                                while (N.Read())
                                {
                                    string NodeName = N[0].ToString();
                                    SerialNodes = new TreeNode();
                                    SerialNodes.Text = NodeName;
                                    rootnode2.Nodes.Add(SerialNodes);
                                }
                                N.Close();
                            }
                            else if (string.Compare(p2[i].ToString(),"102",true) == 0)
                            {
                                string Name = string.Format("select Name from {0} where FaID={1}", TableName, "102");
                                OleDbDataReader N = con.ExecuteQueryReturnReader(Name, strConnection);
                                while (N.Read())
                                {
                                    string NodeName = N[0].ToString();
                                    TreeNode NewNodes = new TreeNode();
                                    NewNodes.Text = NodeName;
                                    SerialNodes.Nodes.Add(NewNodes);
                                }
                                N.Close();
                            }
                            else
                            {
                                
                            }
                        }
                     }
                     p2.Close();
                }
               
                this.treeView2.ExpandAll();
            }

大致的意思就是我单机TreeView1的节点然后根据数据库里面的数据建立ViewTree2的节点（如图），但是当我单击多次TreeView的时候就会出现数据库读取错误，经常会出现 OleDbDataReader 变量返回为空的情况，从而导致程序崩溃，另外不知道什么原因Treeview2的节点有时候会重复建立，请哪位大侠帮帮忙解答一下！！！PS：
注：（例如当我每次单击2的时候就会从数据库读出数据从而建立另一边树的节点，但是不知道为什么节点会重复建立，而且当多次单击的时候 OleDbDataReader 就会返回为空，从而导致程序崩溃）