VB.net中的性能损失相当于从十六进制到字节的轻量级转换

Performance loss in VB.net equivalent of light weight conversion from hex to byte

我已经阅读了这里的答案https://stackoverflow.com/a/14332574/44080

我还尝试生成等效的vb.net代码：

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Option Strict ON

Public Function ParseHex(hexString As String) As Byte()
If (hexString.Length And 1) <> 0 Then
Throw New ArgumentException("Input must have even number of characters")
End If
Dim length As Integer = hexString.Length \ 2
Dim ret(length - 1) As Byte
Dim i As Integer = 0
Dim j As Integer = 0
Do While i < length
Dim high As Integer = ParseNybble(hexString.Chars(j))
j += 1
Dim low As Integer = ParseNybble(hexString.Chars(j))
j += 1
ret(i) = CByte((high << 4) Or low)
i += 1
Loop

Return ret
End Function

Private Function ParseNybble(c As Char) As Integer
If c >="0"C AndAlso c <="9"C Then
Return c -"0"C
End If
c = ChrW(c And Not &H20)
If c >="A"C AndAlso c <="F"C Then
Return c - ("A"C - 10)
End If
Throw New ArgumentException("Invalid nybble:" & c)
End Function

我们能在不引入数据转换的情况下删除parsnybble中的编译错误吗？

没有为类型'char'和'char'定义Return c -"0"c运算符'-'

没有为类型'char'和'integer'定义c = ChrW(c And Not &H20)运算符'and'