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DataList的EditItemTemplate中DropDownList的SelectedIndexChanged事件不响应问题

楼主oceanskytang（唐唐）2002-08-24 09:57:17 在 .NET技术 / ASP.NET 提问

<EditItemTemplate>
......
<asp:DropDownList id="Drop_zipcode2" runat="server" Height="22" Width="103" AutoPostBack="true"></asp:DropDownList>
<asp:TextBox id="TB_areaname2" runat="server" Height="26" Width="102" ReadOnly="True" Text=<%#Container.DataItem("区域名称")%>></asp:TextBox>
......
</EditItemTemplate>

我在update_plantharvest.aspx.vb中这样定义了：

......
Protected WithEvents Drop_zipcode2 As System.Web.UI.WebControls.DropDownList
Protected WithEvents TB_areaname2 As System.Web.UI.WebControls.TextBox
......

Private Sub Drop_zipcode2_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Drop_zipcode2.SelectedIndexChanged
Dim TB_areaname2 As TextBox
TB_areaname2 = CType(DL_plantharvest.FindControl("TB_areaname2"), TextBox)
Dim SelString_Drop_zipcode2 As String = "Select 区域名称 from CD_QYFW where 区域编码='" & Drop_zipcode2.SelectedItem.Text() & "'"
Dim connectStr_Drop_zipcode2 As String = "Provider=MSDAORA;Password=wsj2002;User ID=wsj;Data Source=WsjOrcl"
Dim DbAdapter_Drop_zipcode2 As OleDbDataAdapter = New OleDbDataAdapter(SelString_Drop_zipcode2, connectStr_Drop_zipcode2)
Dim MyDataSet_Drop_zipcode2 As DataSet = New DataSet()
DbAdapter_Drop_zipcode2.Fill(MyDataSet_Drop_zipcode2, "CD_QYFW")
TB_areaname2.Text = MyDataSet_Drop_zipcode2.Tables("CD_QYFW").Rows(0).Item(0)
End Sub

出现的问题是：
TB_areaname2中无响应，并不是如预期得到相对应与"区域编码"的"区域名称",该如何解决？问题点数：20、回复次数：9Top

1 楼icyer（）回复于 2002-08-24 10:33:06 得分 10

<asp:DropDownList id="Drop_zipcode2" runat="server" Height="22" Width="103" AutoPostBack="true" onSelectedIndexChanged="Drop_zipcode2_SelectedIndexChanged"></asp:DropDownList>
然后添加一个函数：
Protected Sub Drop_zipcode2_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs)
...
End Sub
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2 楼oceanskytang（唐唐）回复于 2002-08-24 11:07:42 得分 0

出现了另外一个问题：

行 214： Dim TB_areaname2 As TextBox
行 215： TB_areaname2 = CType(DL_plantharvest.FindControl("TB_areaname2"), TextBox)
行 216： Dim SelString_Drop_zipcode2 As String = "Select 区域名称 from CD_QYFW where 区域编码='" & Drop_zipcode2.SelectedItem.Text() & "'"
行 217： Dim connectStr_Drop_zipcode2 As String = "Provider=MSDAORA;Password=wsj2002;User ID=wsj;Data Source=WsjOrcl"
行 218： Dim DbAdapter_Drop_zipcode2 As OleDbDataAdapter = New OleDbDataAdapter(SelString_Drop_zipcode2, connectStr_Drop_zipcode2)

异常详细信息: System.NullReferenceException: 未将对象引用设置到对象的实例。
源文件: c:\inetpub\wwwroot\AppleDB\update_plantharvest.aspx.vb 行: 216

我在第214行添加定义了Drop_zipcode2为DropDownList，还是出现了以上错误。
Dim Drop_zipcode2 As DropDownList
Drop_zipcode2 = CType(DL_plantharvest.FindControl("Drop_zipcode2"), DropDownList)
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3 楼linlimin（）回复于 2002-08-24 11:43:25 得分 0

首先先邦定数据库到Drop_zipcode2：
Drop_zipcode2.DataSource=mydsBBS.Tables["UsersList"].DefaultView ;
Drop_zipcode2.DataTextField=区域名称字段
Drop_zipcode2.DataValueField=区域编码
Drop_zipcode2.DataBind();
然后将Private Sub Drop_zipcode2_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Drop_zipcode2.SelectedIndexChanged
Dim TB_areaname2 As TextBox
TB_areaname2 = CType(DL_plantharvest.FindControl("TB_areaname2"), TextBox)
Dim SelString_Drop_zipcode2 As String = "Select 区域名称 from CD_QYFW where 区域编码='" & Drop_zipcode2.SelectedItem.Text() & "'"
Dim connectStr_Drop_zipcode2 As String = "Provider=MSDAORA;Password=wsj2002;User ID=wsj;Data Source=WsjOrcl"
Dim DbAdapter_Drop_zipcode2 As OleDbDataAdapter = New OleDbDataAdapter(SelString_Drop_zipcode2, connectStr_Drop_zipcode2)
Dim MyDataSet_Drop_zipcode2 As DataSet = New DataSet()
DbAdapter_Drop_zipcode2.Fill(MyDataSet_Drop_zipcode2, "CD_QYFW")
TB_areaname2.Text = MyDataSet_Drop_zipcode2.Tables("CD_QYFW").Rows(0).Item(0)
End Sub
中的---- Dim SelString_Drop_zipcode2 As String = "Select 区域名称 from CD_QYFW where 区域编码='" & Drop_zipcode2.SelectedItem.Text() & "'"
改为----- Dim SelString_Drop_zipcode2 As String = "Select 区域名称 from CD_QYFW where 区域编码='" & Drop_zipcode2.SelectedItem.Value() & "'"

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4 楼linlimin（）回复于 2002-08-24 11:45:28 得分 0

试一下吧，我主要试用ASP.NET编写，至于VB.NET我不是很熟悉，见笑了！Top

5 楼monkey_zeng（未来报告）回复于 2002-08-24 11:57:13 得分 0

不执行事件,主要是因为AutoPostBack="true",设置为false时就不行.

因为对vb不熟,初步怀疑:
TB_areaname2 = CType(DL_plantharvest.FindControl("TB_areaname2"), TextBox)
出错.Top

6 楼icyer（）回复于 2002-08-24 12:38:57 得分 0

Dim Drop_zipcode2 As DropDownList = CType(sender, DropDownList)
Dim cell As TableCell = CType(Drop_zipcode2.Parent, TableCell)
Dim TB_areaname2 As TextBox = CType(cell.FindControl("TB_areaname2"), TextBox)
Dim SelString_Drop_zipcode2 As String = "Select 区域名称 from CD_QYFW where 区域编码='" & Drop_zipcode2.SelectedItem.Text() & "'"
...
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7 楼monkey_zeng（未来报告）回复于 2002-08-24 12:45:10 得分 0

还没有搞定呀,设置DropDownList的AutoPostBack属性为trueTop

8 楼oceanskytang（唐唐）回复于 2002-08-24 14:05:26 得分 0

Dim cell As TableCell = CType(Drop_zipcode2.Parent, TableCell)

这一行出错：System.InvalidCastException: 指定的转换无效。

我的头都大了，发现对DataList--EditItemTemplate中的控件进行SelectedIndexChanged，TextChanged操作，总报同一个错：
异常详细信息: System.NullReferenceException: 未将对象引用设置到对象的实例。
不知该如何将它们定义？
还忘各位再出出主意！
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