如何从System.Windows.Forms.Keys转换为关于当前键盘布局的字符？

Question

我使用以下代码从Character获取System.Windows.Forms.Keys。

<DllImport("user32.dll")> _
Private Function MapVirtualKey(uCode As UInteger, uMapType As UInteger) As UInteger
End Function
<Extension> _
Public Function GetVirtualKeyAsChar(ByRef keyData As Keys) As Char
    ' 2 is used to translate into an unshifted character value 
    Return Convert.ToChar(MapVirtualKey(CUInt(keyData), 2))
End Function

但根据键盘布局或移位/控制状态，它不会返回正确的字符。例如，所有返回的字符都是大写的。如果我在文本框中使用其他输入语言，它仍会返回默认的A-Z字母。

我需要这会覆盖PreProcessMessage（）函数中的某些按键行为。我知道我可以使用覆盖OnKeyPress（）函数来实现正确的结果，但我真的需要在PreProcessMessage（）函数中完成我的进程：

Public Overrides Function PreProcessMessage(ByRef m As Message) As Boolean
    Select Case m.Msg
        Case WM_KEYDOWN, WM_SYSKEYDOWN
            ' Extracting keys data that similar to ProcessCmdKey's keyData parameter.
            Dim keyData As Keys = DirectCast(CInt(m.WParam), Keys)
            Select Case keyData
                Case Keys.Back
                    ...
                Case Else
                    Dim ch As Char = GetChar(keyData)
                    ...