两次while Dr.read()问题

Question

<%
        Dim Str As String
        Dim Sql As String
        Dim Dr As OleDbDataReader
        Dim Cnn As OleDbConnection
        Dim Cmd As OleDbCommand
        Dim Sql1 As String
        Dim Cmd1 As OleDbCommand
        Dim Dr1 As OleDbDataReader
        Str = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & Server.MapPath("dbhql/bbs.mdb")
        Cnn = New OleDbConnection(Str)
        Cnn.Open()
        Sql = "select LB from LB"
        Cmd = New OleDbCommand(Sql, Cnn)
        Dr = Cmd.ExecuteReader()
        %>
    <table align=left width="760" border="1" bordercolordark="#33ccff" bgcolor="#ffcccc">
        <%While Dr.read() %>
        <tr>
            <td background="images/tb.gif" align="left" style="height: 27px">
        <a href="bbs.aspx?LB=<%=Dr.GetString(0)%>"><font color="#861E1E" style="font-size:12px">&#9618;<%=Dr.GetString(0)%>&#9618;</font></a>
            </td>
        </tr>        <tr>
            <td style="height: 50px">
                <table width="760" align="left" border="0" bordercolordark="#ff0033" bordercolor="#99cc99">
                    <tr bgcolor=floralwhite>
                        <td style="width: 63px; height: 16px">
                        </td>
                        <td style="width: 245px; height: 16px">
                            论坛</td>
                        <td style="width: 69px; height: 16px">
                            主题</td>
                        <td style="width: 70px; height: 16px">
                            文章</td>
                        <td style="width: 200px; height: 16px">
                            最后发表</td>
                        <td style="height: 16px">
                            版主</td>
                    </tr>
            <% 
                Sql1 = "select LB,LB1,(select count(title) from Coment),(select count(*) from Coment),Title,BanZhu,FlagPic,Time from Coment where LB='Dr.GetString(0)' "
                Cmd1 = New OleDbCommand(Sql1, Cnn)
                Dr1 = Cmd1.ExecuteReader()%> 
                    <%While Dr1.Read()%>
                    <tr>
                        <td style="width: 63px; height: 16px">
                        <img src="images/forum_nonews.gif"/></td>
                        <td style="width: 245px; height: 16px">
                        <%=Dr1.GetString(1)%>
                        </td>
                        <td style="width: 69px; height: 16px">
                        <%=Dr1.GetInt32(2)%>
                        </td>
                        <td style="width: 70px; height: 16px">
                        <%=Dr1.GetInt32(3)%>
                        </td>
                        <td style="width: 200px; height: 16px">
                        <%=Dr1.GetString(4)%>
                        </td>
                        <td style="height: 16px">
                            <asp:DropDownList ID="Drop1" runat="server">
                                <asp:ListItem Selected="True">版主列表</asp:ListItem>
                            </asp:DropDownList>
                            <%Drop1.Items.Add(IIf(IsDBNull(Dr1("BanZhu")), "", Dr1("BanZhu")))%>
                    </tr>
                    <%End While%>
                    <% Dr1.Close()%>
                </table>
            </td>
         </tr>   
            <%End While%>
            <%  Dr.Close()%>
    </table>
这当中Sql1 = "select LB,LB1,(select count(title) from Coment),(select count(*) from Coment),Title,BanZhu,FlagPic,Time from Coment where LB='Dr.GetString(0)' "
查询会没有呢？？？？？也就是说Dr.GetString(0)没有接收到？？

Answer 1

OleDbDataReader是单向只向前取数据，循环一次就不能再取数据了

Answer 2

那不是读一次数据，Sql1 = "select LB,LB1,(select count(title) from Coment),(select count(*) from Coment),Title,BanZhu,FlagPic,Time from Coment where LB='Dr.GetString(0)' "
这个查询语句都会有结果吗？？？？？

Answer 3

datareader可以理解是一个向前只读指针

Answer 4

Cmd = New OleDbCommand(Sql, Cnn)
Cmd1 = New OleDbCommand(Sql1, Cnn)问题在这里,你两条查询语句都使用同一个Cnn

Answer 5

where LB='Dr.GetString(0)' 
==>
where LB='"+ Dr.GetString(0) +"'"

Answer 6

Cmd = New OleDbCommand(Sql, Cnn)
Cmd1 = New OleDbCommand(Sql1, Cnn)问题在这里,你两条查询语句都使用同一个Cnn
连接字符串每次都一样的，所以问题不是在这里！

Answer 7

where LB='Dr.GetString(0)' 
==>
where LB='"+ Dr.GetString(0) +"'"
汗...

Answer 8

连接字符串每次都一样的，所以问题不是在这里！where LB='"+ Dr.GetString(0) +"'"===========================================
果然如你所说,俺错了

Answer 9

cpp2017(慕白兄) 
hy_lihuan() 原来真的是这样，字符串的连接。。谢谢拉。
还有感谢回答问题的朋友们
OleDbDataReader是单向只向前取数据 。。说的一点都没错。。呵呵。。
谢谢

Answer 10

hehe...一句谢谢比10000分都重要。

Answer 11

学习一下 也得50分
cpp2017(慕白兄)  我开个新贴 把分还给你吧