Question

这是字符串的简单编码器，在正则表达式中是可接受的。适用于Option Infer On，但在Option Infer Off生成的朗姆酒中崩溃 MissingMemberException: No default member found for type VB$AnonymousDelegate_1(Of Char, String)。

即使使用Option Infer Off，LINQ表达式是否可以重写？我想保留它，因为我认为在大型遗留项目/库中存在转换Option Infer On的风险。（或者我错了？）

这是方法的代码：

Shared Function EscapeLiteralForRegexPattern(inputString As String) As String

  '*** Based on Escape(). Keep them in sync.
  Const dontEscapeFrom = &H20
  Const dontEscapeTo = &H7E
  If String.IsNullOrEmpty(inputString) Then Return inputString

  Const escaper As String = "\"
  Const escapePattern As String = escaper & escaper
  Const tabPattern As String = escaper & "t"
  Const crPattern As String = escaper & "r"
  Const lfPattern As String = escaper & "n"
  Const unicodePattern As String = escaper & "u{0:X4}"
  Const asciiPattern As String = escaper & "x{0:X2}"

  Dim ConvertChar = Function(c As Char) As String
             If c = escaper Then Return escapePattern
             Dim ac As Integer = AscW(c)
             If ac >= dontEscapeFrom AndAlso ac <= dontEscapeTo Then
               Return Regex.Escape(c)
             End If
             Dim result As String = String.Format(If(ac < &H80, asciiPattern, unicodePattern), ac)
             If dontEscapeFrom = 0 Then Return result
             Select Case c
               Case vbTab
                 Return tabPattern
               Case vbCr
                 Return crPattern
               Case vbLf
                 Return lfPattern
               Case Else
                 Return result
             End Select
           End Function

  Return String.Join(String.Empty, inputString.Select(Function(c) ConvertChar(c)).ToArray())

End Function

这是我试过的LINQ更改（但问题仍然存在）：

  Return String.Join(String.Empty, inputString.Select(Function(c As Char) As String
                              Return ConvertChar(c)
                            End Function).ToArray())

Answer 1

信用转到 Hans Passant - 请参阅他的评论。

我将代码添加到遗留的庞大库中，需要Option Explicit Off，Option Strict Off直到重写。

我忘记了它们已关闭，因此在编码期间错过了一些显式类型声明。在Option Explicit On和Option Strict On以及所有请求的更正后，MissingMemberException的整个问题都消失了。

可以重写LINQ以避免MissingMemberException与＆＃39; Option Infer Off＆＃39;？

1 个答案: