在嵌套转发器 asp.net vb 中单击按钮时获取标签的值

Question

我有嵌套的转发器，嵌套转发器中的每个项目都有一个标签和一个按钮，我希望能够在单击按钮时访问 label.text，我想我已经快到了，因为我可以返回索引单击的中继器和嵌套中继器，我只是在找到标签本身时遇到了一些麻烦。

无需我发布中继器代码，您也许就能帮助我。这是我单击按钮时的代码。

Protected Sub btnEditUser_Click(ByVal sender As Object, ByVal e As System.EventArgs)

    Dim btnEditUser As Button = DirectCast(sender, Button)
    Dim reClient As RepeaterItem = DirectCast(btnEditUser.NamingContainer.Parent.Parent, RepeaterItem)
    Dim reUser As RepeaterItem = DirectCast(btnEditUser.NamingContainer, RepeaterItem)
    Dim selectedClient As Integer = reClient.ItemIndex
    Dim selectedUser As Integer = reUser.ItemIndex

    Dim UserId As Label = DirectCast(reClients.Items(selectedClient).FindControl("lUserName"), Label)

    Response.Write(selectedClient & " " & selectedUser & " " & UserId.Text)

End Sub

我当前收到此错误“对象引用未设置到对象的实例”。当尝试写入 UserId.Text 的值时，我认为我在这一行中略有错误：

Dim UserId As Label = DirectCast(reClients.Items(selectedClient).FindControl("lUserName"), Label)

Answer 1

这只是一个猜测，但有时，当并非所有行都包含您要查找的控件时，您会遇到这样的错误。通常，代码按顺序循环遍历行，首先命中不包含相关控件的标题行，然后失败。

Answer 2

这是一篇很好的 MSDN 文章 - 在命名层次结构中定位控件 容器< /a>.

Private Function FindControlRecursive(
    ByVal rootControl As Control, ByVal controlID As String) As Control

    If rootControl.ID = controlID Then
        Return rootControl
    End If

    For Each controlToSearch As Control In rootControl.Controls
        Dim controlToReturn As Control = 
            FindControlRecursive(controlToSearch, controlID)
        If controlToReturn IsNot Nothing Then
            Return controlToReturn
        End If
    Next
    Return Nothing
End Function

尝试一下，

Dim UserId As Label =DirectCast(FindControlRecursive(repClient,"lUserName"),Label)