VB.NET如何用Decimal.TryParse同时兼容解析带点号或逗号的十进制字符串

完全不需要修改原始输入字符串，有两种常用实现方式：

方案1：顺序尝试双文化解析（最简实现，推荐） #

先尝试解析荷兰比利时地区的逗号分隔格式，解析失败则尝试解析点分隔的通用格式，短路运算不会产生额外性能开销：

Imports System.Globalization

' 变量声明
Dim amountVal As Decimal
' 合并后的解析逻辑
Dim isParseSuccess As Boolean = 
    Decimal.TryParse(amountStr, NumberStyles.AllowDecimalPoint, CultureInfo.CreateSpecificCulture("nl-BE"), amountVal) 
    OrElse 
    Decimal.TryParse(amountStr, NumberStyles.AllowDecimalPoint, CultureInfo.InvariantCulture, amountVal)

如果需要支持千位分隔符，将NumberStyles.AllowDecimalPoint替换为NumberStyles.Number即可。

方案2：自定义格式提供器（单次解析实现） #

如果希望只执行一次解析逻辑，可以自定义兼容两种分隔符的格式处理类：

Imports System.Globalization
Imports System.Linq

Public Class BeneluxDecimalParser
    Implements IFormatProvider

    Public Function GetFormat(formatType As Type) As Object Implements IFormatProvider.GetFormat
        If formatType Is GetType(NumberFormatInfo) Then
            Dim numInfo As New NumberFormatInfo()
            ' 根据输入字符串动态判断小数分隔符
            If _input.Count(Function(c) c = "."c) = 1 AndAlso _input.Count(Function(c) c = ","c) = 0 Then
                numInfo.NumberDecimalSeparator = "."
            Else
                numInfo.NumberDecimalSeparator = ","
            End If
            Return numInfo
        End If
        Return Nothing
    End Function

    Private _input As String
    Public Sub New(input As String)
        _input = input
    End Sub

    ' 封装TryParse方法
    Public Shared Function TryParse(input As String, ByRef result As Decimal) As Boolean
        Return Decimal.TryParse(input, NumberStyles.AllowDecimalPoint, New BeneluxDecimalParser(input), result)
    End Function
End Class

调用方式非常简洁：

Dim amountVal As Decimal
Dim isParseSuccess As Boolean = BeneluxDecimalParser.TryParse(amountStr, amountVal)

内容的提问来源于stack exchange，提问作者SimonD