VB.NET - 迭代容器对象中的控件

我有一个带有“清除”按钮的表单。

当用户单击“清除”时，我想清除表单上所有可见元素的值。对于日期控件，我想将它们重置为当前日期。

我的所有控件都包含在面板上。

现在，我正在使用以下代码执行此操作。有没有比手动检查每种控件类型更简单的方法？这种方法似乎过于笨拙。

更糟糕的是，为了递归地清除子容器内的控件（即面板内的组框），我必须使用重载的“GroupBox”版本来重复整个怪物。

编辑：感谢您的建议，下面的代码大大简化了。

Private Sub btnClear_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClear.Click
    'User clicks Clear, so clear all the controls within this panel
    ClearAllControls(panMid, True) 'True indicates that yes, i want to recurse through sub-containers
End Sub

ClearAllControls(ByRef container As Panel, Optional Recurse As Boolean = True)   
  'Clear all of the controls within the container object
  'If "Recurse" is true, then also clear controls within any sub-containers
  Dim ctrl As Control
  For Each ctrl In container.Controls
      If (ctrl.GetType() Is GetType(TextBox)) Then
          Dim txt As TextBox = CType(ctrl, TextBox)
          txt.Text = ""
      End If
      If (ctrl.GetType() Is GetType(CheckBox)) Then
          Dim chkbx As CheckBox = CType(ctrl, CheckBox)
          chkbx.Checked = False
      End If
      If (ctrl.GetType() Is GetType(ComboBox)) Then
          Dim cbobx As ComboBox = CType(ctrl, ComboBox)
          cbobx.SelectedIndex = -1
      End If
      If (ctrl.GetType() Is GetType(DateTimePicker)) Then
          Dim dtp As DateTimePicker = CType(ctrl, DateTimePicker)
          dtp.Value = Now()
      End If

      If Recurse Then
          If (ctrl.GetType() Is GetType(Panel)) Then
              Dim pnl As Panel = CType(ctrl, Panel)
              ClearAllControls(pnl, Recurse)
          End If
          If ctrl.GetType() Is GetType(GroupBox) Then
              Dim grbx As GroupBox = CType(ctrl, GroupBox)
              ClearAllControls(grbx, Recurse)
          End If
      End If
  Next
End Sub

@Theracoonbear：我喜欢你的建议，但是当我将声明更改为：

Private Sub ClearAllControls(ByRef controls As ControlCollection, Optional ByVal Recurse As Boolean = True)

然后这一行给我“无法将类型'ControlCollection'的对象转换为类型'ControlCollection'。”：

  ClearAllControls(panMid.Controls)

您可以跳过 GetType 和 CType 之舞TryCast http://msdn.microsoft.com/en-us/library/zyy863x8(VS.80).aspx:

Dim dtp as DateTimePicker = TryCast(ctrl, DateTimePicker)
If dtp IsNot Nothing then dtp.Value = Now()

这将为您节省大约 10 行代码。

An 扩展方法 http://msdn.microsoft.com/en-us/library/bb384936.aspx离开 Control 类应该保持它非常整洁：

<Extension()> _
Public Shared Sub ClearValue(c as Control, recursive as Boolean)
   Dim dtp as DateTimePicker = TryCast(c, DateTimePicker)
   If dtp IsNot Nothing Then dtp.Value = Now()
   ' Blah, Blah, Blah
End Sub

编辑：如果忽略 NullReferenceExceptions 的邪恶扩展方法的想法不会让您感到畏缩：

<Extension()> _
Public Shared Sub ClearValue(c as CheckBox)
   If c IsNot Nothing Then c.Checked = False
End Sub

TryCast(ctrl, CheckBox).ClearValue()