Question

在一个类中，我编写了一些方法来检索一些文件，现在为了简化代码编写，我编写了这个私有函数，它需要一个Type：

Private Shared Function GetDeletedItems(Of T)(Optional ByVal DriveLetter As Char = Nothing) As T()

    Return (From Item As ShellObject In RecycleBin
            Where Item.GetType = GetType(T) _
                  AndAlso If(DriveLetter = Nothing,
                             Nothing,
                             Item.Name.StartsWith(DriveLetter,
                                                  StringComparison.InvariantCultureIgnoreCase))).
            Cast(Of T).
            ToArray()

End Function

然后只应该从类中调用这个公共函数，我尝试设置正确的Type来调用私有函数并返回数据：

Public Shared Function GetDeletedItems(ByVal ItemType As ShellItemType,
                                       Optional ByVal DriveLetter As Char = Nothing)

    Dim CurrentType As Type = Nothing

    Select Case ItemType

        Case ShellItemType.All
            CurrentType = GetType(ShellObject)

        Case ShellItemType.Files
            CurrentType = GetType(ShellFile)

        Case ShellItemType.Folders
            CurrentType = GetType(ShellFolder)

    End Select

    Return GetDeletedItems(Of CurrentType)(DriveLetter)

End Function

问题是我在Return指令上遇到错误'因为它说CurrentType没有定义，我做错了什么？

Answer 1

首先，您不需要变量CurrentType，编译器将不乐意编译它。摆脱它。

这是否符合您的要求？

Public Shared Function GetDeletedItems(ByVal ItemType As ShellItemType,
                                       Optional ByVal DriveLetter As Char = Nothing)
    Select Case ItemType

        Case ShellItemType.All
            Return  GetDeletedItems(Of ShellObject)(DriveLetter)
        Case ShellItemType.Files
            Return  GetDeletedItems(Of ShellFile)(DriveLetter)
        Case ShellItemType.Folders
            Return  GetDeletedItems(Of ShellFolder)(DriveLetter)
    End Select

End Function

Answer 2

查看你的代码我没看到分成两个函数的原因。我认为你的外部函数应该是通用函数，你应该完全杀掉ShellItemType。

该方法只是你的内部私有方法，只有你公开：

Public Shared Function GetDeletedItems(Of T)(Optional ByVal DriveLetter As Char = Nothing) As T()

    Return (From Item As ShellObject In RecycleBin
            Where Item.GetType = GetType(T) _
                  AndAlso If(DriveLetter = Nothing,
                             Nothing,
                             Item.Name.StartsWith(DriveLetter,
                                                  StringComparison.InvariantCultureIgnoreCase))).
            Cast(Of T).
            ToArray()

End Function

然后你会这样称呼它：

Dim results = GetDeletedItems(Of ShellObject)(driveLetter)

看来您正在根据类型在方法之外设置ShellItemType变量，因此您实际上可以自己发送该类型。

调用传递Type参数问题的函数

2 个答案: