vb.net 字符串仅包含 4 位数字(或年份)

Question

如何检查字符串是否只包含 4 位数字(或年份)
我试过这个

 Dim rgx As New Regex("^/d{4}")      
    Dim number As String = "0000"
    Console.WriteLine(rgx.IsMatch(number)) // true
    number = "000a"
    Console.WriteLine(rgx.IsMatch(number)) // false
    number = "000"
    Console.WriteLine(rgx.IsMatch(number)) //false
    number = "00000"
    Console.WriteLine(rgx.IsMatch(number))  // true <<< :(

当少于 4 个或 at 个字符但不超过 4 个时返回 false

谢谢!

Answer 1

我实际上不会为此使用正则表达式。该表达式看似简单 (^\d{4}$)，直到您意识到还需要计算该数值以确定有效的年份范围...除非您想要像 这样的年份>0013 或 9015。无论如何，您最终很可能希望该值是整数。鉴于此，最好的验证可能就是立即尝试将其转换为整数:

Dim numbers() As String = {"0000", "000a", "000", "00000"}
For Each number As String In numbers
    Dim n As Integer
    If Integer.TryParse(number, n) AndAlso number.Length = 4 Then
        'It's a number. Now look at other criteria

    End If 
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