.net 做权限分配时，预览时出现“System.OutOfMemoryException”

Question

<asp:TreeView ID="TreeView1" runat="server"
        ShowCheckBoxes="All" ShowExpandCollapse="False" ShowLines="True">
        <ParentNodeStyle BorderColor="#80FF80" Font-Overline="False" Font-Underline="True"
            ForeColor="#80FF80" Height="20px" />
        <RootNodeStyle Height="20px" />
    </asp:TreeView>
        <br />
       <asp:DropDownList ID="DropDownList1" runat="server" DataSourceID="ObjectDataSource1"
        DataTextField="Rolename" DataValueField="Roleid">
    </asp:DropDownList>
        <br />
        <asp:Button ID="btnUpdate" runat="server" onclick="btnUpdate_Click"  Text="Button" />
       <asp:ObjectDataSource ID="ObjectDataSource1" runat="server" SelectMethod="GetAllRoles"
        TypeName="Maticsoft.BLL.RoleManager" ></asp:ObjectDataSource>
 protected void btnUpdate_Click(object sender, EventArgs e)
    {
        int roleid = int.Parse(DropDownList1.SelectedValue.ToString());
        int a = RolerightManager.delete_by_roleid(roleid);
        int c = 0;        for (int i = 0; i < TreeView1.CheckedNodes.Count; i++)
        {
            int funid = int.Parse(TreeView1.CheckedNodes[i].Value.ToString());
            c = RolerightManager.add_roleRight(roleid, funid);        }
        if (c > 0)
        {
            Response.Write("<script>alert('权限分配成功! ')</script>");
        }
    }
 public static int delete_by_roleid(int roleid)
        {
            return RolerightService.delete_by_roleid(roleid);
        }        public static int add_roleRight(int roleid, int funid)
        {
            Roleright ro = new Roleright();
            ro.Roleid = roleid;
            ro.Funid = funid;
            return RolerightService.add_roleRight(ro);
        }
  public static int delete_by_roleid(int roleid)
        {
            string sql = "delete from Roleright where roleid=" + roleid;
            return DBHelper.ExcuteCommand(sql);
        }        public static int add_roleRight(Roleright roleringht)
        {
            string sql = string.Format("insert into RoleRight (roleid,funid) values ({0},{1})", roleringht.Roleid, roleringht.Funid);
            return DBHelper.ExcuteCommand(sql);
        }  public static IList<Role> GetAllRoles()
        {
            return RoleService.GetAllRole();
        }
 public static IList<Role> GetAllRole()
        {            string sqlstr = "select * from Role where roleid !=3";
            return GetRoleBySql(sqlstr, null);        }
        public static IList<Role> GetRoleBySql(string sqlstr, params SqlParameter[] values)
        {            
            SqlDataReader dr;
            if (values == null)
            {
                dr = DBHelper.GetReader(sqlstr);           
            }
            else
            {
                dr = DBHelper.GetReader(sqlstr, values); 
            }
            try
            {                if (dr != null)
                {
                    List<Role> list = new List<Role>();
                    while (dr.Read())
                    {
                        Role role = new Role();
                        role.Roleid = (int)dr["roleid"];
                        role.Rolename = (string)dr["rolename"];
                        list.Add(role);
                    }
                    dr.Close();
                    return list;
                }
                else
                {
                    dr.Close();
                    return null;
                }            }
            catch (Exception e)
            {
                throw e;
            }
            finally
            {
                dr.Close(); //及时关闭dr,回收资源
            }
大侠们帮看看 是哪出了问题 在网上查了 有的说是程序存在死循环，有的说 内存不足，有的说 读取数据量太多，有的则说 没有及时释放内存，有的则说是递归造成的，不知道如何解决这个问题，请大家 帮看看这代码 哪些地方该如何改 才不会报这样的错误！如果把 <asp:DropDownList ID="DropDownList1" runat="server" DataSourceID="ObjectDataSource1"
        DataTextField="Rolename" DataValueField="Roleid">
    </asp:DropDownList>
        <br />
        <asp:Button ID="btnUpdate" runat="server" onclick="btnUpdate_Click"  Text="Button" />
       <asp:ObjectDataSource ID="ObjectDataSource1" runat="server" SelectMethod="GetAllRoles"
        TypeName="Maticsoft.BLL.RoleManager" ></asp:ObjectDataSource> 和btnUpdate_Click点击事件注释掉后 就显示正常了 权限也显示正常了
不知道错在哪，请大侠们帮帮忙 看一下那代码如何改正