arrays - 如何遍历容器中的所有对象？

Question

如果我有一个带有未知数量标签的面板，我如何浏览所有标签并更改其中的 .text 值？我试过这样的事情：

for each x as label in mypanel
   x.text = "whatever"
next

但我收到一个错误，即 mypanel 不是集合。

标签是 mypanel 的子标签。

Answer 1

对于获胜形式，请尝试：

for each x as Control in mypanel.Controls
   if TypeOf x Is Label Then
     CType(x, Label).text = "whatever"
   end if
next

Answer 2

取决于Panel这是什么类型的。 赢表格？ WPF ? 错误是对的，Panel不是集合。它只是一个对象。但它的一个属性可能是一个集合。

mypanel.Controls对于 WinForms 或mypanel.ChildrenWPF。如果层次结构多于直接子级，那么您可能需要进一步递归到该层次结构中。

Answer 3

For Each lbl As Label in myPanel.Controls
     lbl.Text = "whatever"
Next

这是假设 myPanel 上的所有内容都是标签。如果还有其他控件，则必须测试它们是否为标签：

For Each ctl as Control in myPanel.Controls
     If Ctl.GetType = Label.GetType Then
        CType(ctl, Label).text = "whatever"
     End if
Next

Answer 4

循环遍历面板中的所有控件，然后确定每个控件是否为Label，如下所示：

For Each theControl As Control In myPanel.Controls
    If TypeOf theControl Is Label Then
        ' Change the text here
        TryCast(theControl, Label).Text = "whatever"
    End If
Next

更新：

要考虑面板中的子控件，请执行以下操作：

Dim listOfLabels As New List(Of Control)

Public Sub GetAllLabelsIn(container As Control)
    For Each theControl As Control In container.Controls
        If TypeOf theControl Is Label Then    
            listOfLabels.Add(theControl)

            If theControl.Controls.Count > 0 Then
                GetAllLabelsIn(theControl)
            End If
        End If
    Next
End Sub

现在你可以这样称呼它：

listOfLabels = new List(Of Control)

GetAllLabelsIn(myPanel)

For Each theControl As Control In listOfLabels
    If TypeOf theControl Is Label Then
        ' Change the text here
        TryCast(theControl, Label).Text = "whatever"
    End If
Next

Answer 5

您首先只能选择Labels。这也返回容器内容器内的标签等......

' Inside a module
<Extension()> _
Public Function ChildControls(Of T As Control)(ByVal parent As Control) As List(Of T)
    Dim result As New ArrayList()
    For Each ctrl As Control In parent.Controls
        If TypeOf ctrl Is T Then result.Add(ctrl)
        result.AddRange(ChildControls(Of T)(ctrl))
    Next
    Return result.ToArray().Select(Of T)(Function(arg1) CType(arg1, T)).ToList()
End Function

用法：

For Each myLabel as Label in myPanel.ChildControls(Of Label)
    myLabel.Text = "I'm a label!"
Next