往两个DropDownList绑定值，并且由第一个drop1的值确定第二个的值

<html>
<asp:label id="label1" Runat="server">选择大类：</asp:label><asp:dropdownlist id="Drop1" Runat="server" AutoPostBack="True" ForeColor="#000033" BackColor="#D6E3FF"
DataValueField="ParentID" DataTextField="ParentName"></asp:dropdownlist></td>
<td><asp:label id="Label2" Runat="server">选择小类：</asp:label><asp:dropdownlist id="Dropdownlist1" Runat="server" ForeColor="#000033" BackColor="#D6E3FF" DataValueField="ParentName"
DataTextField="NodeName"></asp:dropdownlist>
</tr>
<tr>
<td style="WIDTH: 662px" align="right"><asp:label id="Label3" Runat="server">输入关键字：</asp:label><asp:textbox id="textbox1" Runat="server"></asp:textbox></td>
<td><asp:button id="submit" Runat="server" Text="搜索"></asp:button>
vb代码
Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
        theUser = Session("User")
        UserName.Text = theUser
        If Trim(theUser) = "" Then
            Response.Write("<h2 style='Color:red'>")
            Response.Write("对不起，你尚未注册，请重新注册！</h2>")
            Response.End()
        End If
        If Not IsPostBack Then
            Dim Cnn As OleDb.OleDbConnection
            Dim Cmd As OleDb.OleDbDataAdapter
            Dim StrCnn As String
            Dim Ds As New DataSet
            StrCnn = "Provider=Microsoft.Jet.OleDb.4.0;Data Source=" & Server.MapPath("/BBS.mdb")
            StrSQL = "select ParentID, ParentName from TreeNode1 "
            Cnn = New OleDb.OleDbConnection(StrCnn)
            Cnn.Open()
            Cmd = New OleDb.OleDbDataAdapter(StrSQL, Cnn)
            Cmd.Fill(Ds, "TreeNode1")
            Drop1.DataSource = Ds.Tables("TreeNode1").DefaultView
            Drop1.DataTextField = "ParentName"/////////注意这里
            Drop1.DataValueField = "ParentID"///////////注意这里
            Drop1.DataBind()
        End If
    End Sub    Private Sub Drop1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Drop1.SelectedIndexChanged
        Dim Cnn As OleDb.OleDbConnection
        Dim Cmd As OleDb.OleDbCommand
        Dim Dr As OleDb.OleDbDataReader
        Dim Ds As DataSet = New DataSet
        Dim StrCnn As String
        StrCnn = "Provider=Microsoft.Jet.OleDb.4.0;Data Source=" & Server.MapPath("/BBS.mdb")
        Cnn = New OleDb.OleDbConnection(StrCnn)
        Cnn.Open()
        Cmd = New OleDb.OleDbCommand(StrSQL, Cnn)
        StrSQL = "select NodeName from TreeNode1 where ParentName='" + Drop1.SelectedItem.Text.ToString() + "'"
        Dropdownlist1.DataSource = Ds.Tables("TreeNode").DefaultView
        Drop1.DataTextField = "NodeName"////////////////////注意这里
            Drop1.DataValueField = "NodeName"///////////注意这里
        Dropdownlist1.DataBind()
    End Sub
    Private Sub submit_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles submit.Click
        Dim theTag As String
        theTag = Session("tag")
        If Drop1.SelectedItem.Text <> "" And Dropdownlist1.SelectedItem.Text <> "" Then
            Response.Redirect("query.aspx?thetype=thetag")
        End If    End Sub
End Class

我按smilnet（苯苯）的作了修改同样不行，dropdownlist显示“未绑定”，显示同样下拉一片空白，无任何绑定。

作如下修改后，数据能绑定，但运行时，drop1改变时，dropdownlist1依然各项都有，未能跟着改变。请帮看看，到底怎回事？
If Not IsPostBack Then
            Dim Cnn1 As OleDb.OleDbConnection
            Dim Cmd1 As OleDb.OleDbDataAdapter
            Dim StrCnn1 As String
            Dim strSql1 As String
            Dim Ds As New DataSet
            StrCnn1 = "Provider=Microsoft.Jet.OleDb.4.0;Data Source=" & Server.MapPath("/BBS.mdb")
            strSql1 = "select NodeID, ParentName,NodeName from TreeNode1"
            Cnn1 = New OleDb.OleDbConnection(StrCnn1)
            Cnn1.Open()
            Cmd1 = New OleDb.OleDbDataAdapter(strSql1, Cnn1)
            Cmd1.Fill(Ds, "TreeNode1")
            Drop1.DataSource = Ds.Tables("TreeNode1").DefaultView
            Drop1.DataTextField = "ParentName"
            Drop1.DataValueField = "NodeID"
            Drop1.DataBind()
            Dropdownlist1.DataSource = Ds.Tables("TreeNode1").DefaultView
            Dropdownlist1.DataTextField = "NodeName"
            Dropdownlist1.DataValueField = "NodeID"
            Dropdownlist1.DataBind()        End If
    End Sub    Private Sub Drop1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Drop1.SelectedIndexChanged
        Dim Cnn As OleDb.OleDbConnection
        Dim Cmd As OleDb.OleDbCommand
        Dim Dr As OleDb.OleDbDataReader
        Dim Ds As DataSet = New DataSet
        Dim theName As String
        theName = Drop1.SelectedItem.Text.ToString
        Dropdownlist1.Items.Clear()
        Dim StrCnn As String
        StrCnn = "Provider=Microsoft.Jet.OleDb.4.0;Data Source=" & Server.MapPath("/BBS.mdb")
        Cnn = New OleDb.OleDbConnection(StrCnn)
        Cnn.Open()
        Cmd = New OleDb.OleDbCommand(StrSQL, Cnn)
        StrSQL = "select NodeName from TreeNode1 where Parent='" & theName & "'"
        Dropdownlist1.DataSource = Ds.Tables("TreeNode1").DefaultView
        Dropdownlist1.DataTextField = "NodeName"
        Dropdownlist1.DataValueField = "NodeID"
        Dropdownlist1.DataBind()
    End Sub

Dropdownlist1.DataSource = Ds.Tables("TreeNode1").DefaultView 不对，数据要根据重新绑定！
Cmd.Fill(Ds, "TreeNode2")
Dropdownlist1.DataSource = Ds.Tables("TreeNode2").DefaultView

设置drop1的属性AutoPostBack=true;

你先绑定第一个控件，然后调用第一个控件的OnSelectedIndexChanged方法，并设置AutoPostBack="True"，下面是我使用时的代码（OnSelectedIndexChanged="Selection_Change" ）：
---------------------------------------------------------------------------void Selection_Change(Object sender, EventArgs e)
{
// 设置选择字段类型时，字段长度默认值
SCN.Desktop.EmpInfoDB cascade = new SCN.Desktop.EmpInfoDB(dsn); // 提取岗位类别，并绑定到DropDownList上
string str_SuperID = f_EmpDept.SelectedItem.Value;
f_EmpPosition.DataSource = cascade.GetSubDataDicByID(str_SuperID);
f_EmpPosition.DataValueField="f_SubCatID";
f_EmpPosition.DataTextField="f_SubCatName";
f_EmpPosition.DataBind();
}

在If Not IsPostBack Then      end if中绑定第一个控件没问题，在Private Sub Drop1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Drop1.SelectedIndexChanged中绑定第二个控件还是不成功（设置drop1的AutoPostBack="True"）代码如下改动，与drop1绑定在不同table中，二者通过parentName 关联，问题在哪？Private Sub Drop1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Drop1.SelectedIndexChanged
        Dim Cnn As OleDb.OleDbConnection
        Dim Cmd As OleDb.OleDbDataAdapter
        Dim Dr As OleDb.OleDbDataReader
        Dim Ds As DataSet = New DataSet
        Dim theName As String
        theName = Drop1.SelectedItem.Text
        Dropdownlist1.Items.Clear()
        Dim StrCnn As String
        StrCnn = "Provider=Microsoft.Jet.OleDb.4.0;Data Source=" & Server.MapPath("/BBS.mdb")
        Cnn = New OleDb.OleDbConnection(StrCnn)
        Cnn.Open()
        Cmd = New OleDb.OleDbDataAdapter(StrSQL, Cnn)
        StrSQL = "select NodeName from TreeNode2 where ParentName='" & theName & "'"        Cmd.Fill(Ds, "TreeNode2")
        Dropdownlist1.DataSource = Ds.Tables("TreeNode2").DefaultView
        Dropdownlist1.DataTextField = "NodeName"
        Dropdownlist1.DataValueField = "NodeID"
        Dropdownlist1.DataBind()
    End Sub

select NodeName from TreeNode2 where ParentName='" & theName & "' 这句在查询分析器中是否正确？
用 where ParentName=@name,在给@name赋值
注意下列次序：
Cnn = New OleDb.OleDbConnection(StrCnn)
Cnn.Open()
StrSQL = "select NodeName from TreeNode2 where ParentName='" & theName & "'"
Cmd = New OleDb.OleDbDataAdapter(StrSQL, Cnn)

救命啦！！！怪怪怪！！！象csdn的搜索一样分大类搜索和小类搜索，现在不仅不能绑定drop2而且，点击大类搜索（select语句与小类的值无关）出现下列问题，该怎么改？
Private Sub Drop1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Drop1.SelectedIndexChanged

        Dim Cnn As OleDb.OleDbConnection
        Dim Cmd As OleDb.OleDbDataAdapter
        Dim Dr As OleDb.OleDbDataReader
        Dim Ds As DataSet = New DataSet
        Dim theName As String
        theName = Drop1.SelectedItem.Text
        Dropdownlist1.Items.Clear()
        Dim StrCnn As String
        StrCnn = "Provider=Microsoft.Jet.OleDb.4.0;Data Source=" & Server.MapPath("/BBS.mdb")
        Cnn = New OleDb.OleDbConnection(StrCnn)
        Cnn.Open()
        Cmd = New OleDb.OleDbDataAdapter(strSql, Cnn)
        strSql = "select ParentName,NodeName from TreeNode2 where ParentName='" & theName & "'"        Cmd.Fill(Ds, "TreeNode2")
        Dropdownlist1.DataSource = Ds.Tables("TreeNode2").DefaultView
        Dropdownlist1.DataTextField = "NodeName"
        Dropdownlist1.DataValueField = "ParentName"
        Dropdownlist1.DataBind()
    End Sub
“/WebBBS”应用程序中的服务器错误。
--------------------------------------------------------------------------------DataBinder.Eval：“System.Data.DataRowView”不包含名称为 NodeName 的属性。
说明: 执行当前 Web 请求期间，出现未处理的异常。请检查堆栈跟踪信息，以了解有关该错误以及代码中导致错误的出处的详细信息。异常详细信息: System.Web.HttpException: DataBinder.Eval：“System.Data.DataRowView”不包含名称为 NodeName 的属性。源错误:
行 120：        Dropdownlist1.DataTextField = "NodeName"
行 121：        Dropdownlist1.DataValueField = "ParentName"
行 122：        Dropdownlist1.DataBind()
行 123：    End Sub
行 124：
源文件: C:\Inetpub\wwwroot\WebBBS\Searchz.aspx.vb    行: 122 堆栈跟踪:
[HttpException (0x80004005): DataBinder.Eval：“System.Data.DataRowView”不包含名称为 NodeName 的属性。]
   System.Web.UI.DataBinder.GetPropertyValue(Object container, String propName)
   System.Web.UI.DataBinder.GetPropertyValue(Object container, String propName, String format)
   System.Web.UI.WebControls.ListControl.OnDataBinding(EventArgs e)
   System.Web.UI.Control.DataBind()
   WebBBS.Searchz.Drop1_SelectedIndexChanged(Object sender, EventArgs e) in C:\Inetpub\wwwroot\WebBBS\Searchz.aspx.vb:122
   System.Web.UI.WebControls.ListControl.OnSelectedIndexChanged(EventArgs e)
   System.Web.UI.WebControls.DropDownList.System.Web.UI.IPostBackDataHandler.RaisePostDataChangedEvent()
   System.Web.UI.Page.RaiseChangedEvents()
   System.Web.UI.Page.ProcessRequestMain()
--------------------------------------------------------------------------------
版本信息: Microsoft .NET Framework 版本:1.1.4322.573; ASP.NET 版本:1.1.4322.573

先在Page_Load里面绑定第一个DropDownList的值，把第一个DropDownList设置为AutoPostBack=true,在SelectIndexChanged对应的事件里面写代码，根据第一个里面选定的值作为条件来绑定第二个 DropDownList的项

可以把数据绑定在客户端hide域里面，js来操作显示，这样速度快点（感觉上）

我也同意： xueyhfeng(核桃(努力中…看书充电)) 的说法！

这种帮定要注意几个关键的地方：
（1）在page_load里先帮定DropDownList1，并且应该确保它只执行一次，也就是
if(!IsPostBack)
{
//帮定DropDownList1
//如有必要，DropDownList2也在这邦定一下
}
（2）DropDownList1的AutoPostBack的属性要设为true
（3）在DropDownList1的SelectIndexChanged的事件中邦定DropDownList2
建议把DropDownList1和DropDownList2的邦定分别写成一个方法，
邦定时直接调用这个方法就可以了。
还有。楼主用的是Vb语言吗？怎么我看到连接字符串用了+？
我不懂vb，但是好像vb里连接字符串都是用&吧。

调试易

往两个DropDownList绑定值，并且由第一个drop1的值确定第二个的值

解决方案 »