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我想知道是否存在使用 Type 作为表达式的技巧，例如在此代码中：

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load

    Dim ControlType = CheckBox ' CheckBox is a type and cannot be used as an expression

    Dim ControlArray(5) As ControlType ' (5) The number of controls to create.

    For num As Int64 = 0 To ControlArray.LongLength - 1
        ControlArray(num) = New ControlType ' Expected: New CheckBox
        ControlArray(num).Text = (ControlType.ToString & num.ToString) ' Expected string: "CheckBox 0"
        Me.Controls.Add(ControlArray(num))
    Next

End Sub

我不是在问我如何做一个控件数组，我是在问我是否可以做一个通用控件数组，例如在 var (ControlType) 中指定类型并像上面的代码示例一样使用它。

更新

这是我现在尝试使用的代码

尝试附加处理程序时，我无法识别 CheckBox 的“CheckedChanged”事件

尝试检查其值时也无法识别“.Checked”属性。

Public Class Form1

    Dim ControlType As Type = GetType(CheckBox) ' The type of Control to create.
    Dim ControlArray(5) As Control              ' (5) The number of controls to create.

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load

        For num As Int64 = 0 To ControlArray.LongLength - 1
            ControlArray(num) = Activator.CreateInstance(ControlType) ' Create the control instance (New CheckBox)
            ControlArray(num).Name = ControlType.Name & num.ToString ' Name example  : CheckBox 0
            ControlArray(num).Text = ControlType.Name & num.ToString ' String example: CheckBox 0
            ControlArray(num).Top = 20 * num ' Adjust the location of each control.
            Me.Controls.Add(ControlArray(num)) ' Add the control to a container.

            ' This does not work:
            AddHandler ControlArray(num).CheckedChanged, AddressOf CheckBoxSub ' Add a event handler to a procedure.

        Next

    End Sub

    Public Sub CheckBoxSub(ByVal sender As Object, ByVal e As System.EventArgs) ' Sub which is handling the controls.

        If sender.Checked = True Then MsgBox(sender.name & " is checked") Else MsgBox(sender.name & " is unchecked")

        ' Just an example of how to use the controls,
        ' This does not work:
        ControlArray(2).checked = True ' CheckBox 2.Checked = True

    End Sub

End Class
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2 回答 2

1

您可以使用 System.Type 来保存对象的类型。

您还可以使用 Activator.CreateInstance(MyType) 创建 MyType 类型对象的实例。

例如

Dim ControlType As System.Type = GetType(CheckBox)
Dim ControlArray(5) As Control

For num As Int64 = 0 To 5
    ControlArray(num) = Activator.CreateInstance(ControlType)
    ControlArray(num).Left = num * 100
    ControlArray(num).Name = "CheckBox " & num
    ControlArray(num).Text = ControlArray(num).Name
    Me.Controls.Add(ControlArray(num))
Next

编辑：

要添加事件处理程序，您需要将控件 DirectCast() 到对象类型，例如：

AddHandler DirectCast(ControlArray(Num), CheckBox).CheckedChanged, AddressOf MyHandler
于 2013-06-11T10:36:30.087 回答
1

关于您更新的问题：您需要将对象转换为正确的类型才能使用 CheckBox 特定的属性或事件。例如，而不是

AddHandler ControlArray(num).CheckedChanged, AddressOf CheckBoxSub

你写

Dim cbx As CheckBox = TryCast(ControlArray(num), CheckBox)
If cbx IsNot Nothing Then
    AddHandler cbx.CheckedChanged, AddressOf CheckBoxSub
End If

你的第二个例子也一样：

Dim cbx As CheckBox = TryCast(ControlArray(2), CheckBox)
If cbx IsNot Nothing Then         ' If the second control is a check box 
   cbx.Checked = True 
End If

TryCast将给定对象转换为给定类型，Nothing如果对象具有不同类型则返回。

于 2013-06-11T11:12:29.750 回答